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View Full Version : Driveline Clunk??



litespeed
01-11-2007, 04:36 PM
I have got a pretty serious drive line clunk going on. I cannot tell where in the heck it is coming from? Coming from any speed to a complete stop, I get the "Clunk". Then when I go to take off again "Clunk". Any Ideas? How would you tell if it is the rear end, transfer case or transmission? All the fluids are new (only 5,000 miles) and at the proper level. The rear drive shaft has new U-joints and I have greased the crap out of the splines on the slip yoke.

Also.... If I come to a stop really slow there is no "Clunk" but an audible loud "Tick" as the transmission shifts to 1st.

bigreave
01-11-2007, 07:56 PM
could be the yoke or u joint s, doe sit clunk when you put in gear from park to drive ?

litespeed
01-11-2007, 08:58 PM
could be the yoke or u joint s, doe sit clunk when you put in gear from park to drive ?

Yes. A little. It is pretty bad when I am cruising down the road and then stop and take off again. I just replaced the u-joints less than 2000 miles ago. When I did the u-joints I greased the slip yoke like everyone has posted here. Still clunks.

Is it possible the yoke or output shaft on the transfer case is shot?

IH8FORD
01-11-2007, 09:20 PM
how much and what kind of greese did you use. i just pulled my driveshaft out and greesed the hell out of the slip yoke and mine dosent clunk at all anymore. the clunk i had was really bad when stoping and starting just like yours.

litespeed
01-11-2007, 09:32 PM
how much and what kind of greese did you use. i just pulled my driveshaft out and greesed the hell out of the slip yoke and mine dosent clunk at all anymore. the clunk i had was really bad when stoping and starting just like yours.

I'll have to pull the tube out of the grease gun and look. It is some kind of high temp. synthetic chasis lube. I actually pulled the shaft a couple weeks ago to grease the thing again. Maybe I did not use enough? I put so much grease on the splines that it was actually hard to get back in. Is it possible to use too much grease? I pumped a bunch in the hole (where the splines are). Then I smeared the rest into all the grooves with my finger. :stir: Do you think this was sufficient or not enough?

BIGRED2000
01-11-2007, 11:51 PM
If You Keep The Brake All The Way Down When You Shift Into Drive Or Reverse..does It Still Clunk???usually Drivetrane Noises Are U Joints(probably Like 85%)..if Not Then Its Either Slop In The Tranny Or The Rear Diff Needs To Be Re-shimmed..you Should Be Able To Put The Truck In Park And Crawl Under It..turn It Manually And Tell If Its A U Joint Or Rear Diff..you Should Not Have Harly Any Play In Park..if So You Should Be Able To See The Play Between The Shaft And The Rear Diif If Its A U-joint

litespeed
01-12-2007, 06:53 AM
If You Keep The Brake All The Way Down When You Shift Into Drive Or Reverse..does It Still Clunk???usually Drivetrane Noises Are U Joints(probably Like 85%)..if Not Then Its Either Slop In The Tranny Or The Rear Diff Needs To Be Re-shimmed..you Should Be Able To Put The Truck In Park And Crawl Under It..turn It Manually And Tell If Its A U Joint Or Rear Diff..you Should Not Have Harly Any Play In Park..if So You Should Be Able To See The Play Between The Shaft And The Rear Diif If Its A U-joint

Yes...... With the brake all the way down while shifting it does Clunk going into Drive or Reverse. It is worse while coming to a stop or taking off. I have noticed at the boat ramp and sometimes on a bit of an incline that when I put the truck into Park without the E-brake that the truck will roll quite a bit before it stops (probably about 4 to 6 inches). Also, if I get underneath and twist the drive shaft by hand (engine off), I can twist it quite a bit in either direction. There is no play in the U-joints and there is a click or clank coming from either the transfer case or transmission when I rack the shaft back and forth. Hard to pin point.

But if I can twist the drive shaft at all..... That would mean that there is a bunch of play in the rear end? Right?

I know where there is a 1500 HD down the road. I already got the springs off it. Now I'm wondering if I should grab the 14 bolt and the drive shaft out of it?

IH8FORD
01-12-2007, 11:07 AM
yeah that was plenty of greese. your problem must be somewhere else

tpichevy
01-12-2007, 11:26 AM
what year is your truck. i am havin the same thing with mine its a 04 z71. the noise its real bad when i shift fron p ro r and start to move. i was told its the the name of the game and it wont hurt anything. http://www.fullsizechevy.com/forums/showthread.php?t=247797

swiss
01-12-2007, 03:27 PM
I went through the same thing shortly after i bought mine. Had a new drive shaft installed and the click and clunk are gone.

aggiedave98
01-12-2007, 11:01 PM
A few points...

Before you talked about the play in your driveshaft, I was going to say check your engine mounts... that was a big problem in my '89 burb and when I replaced them, my problem went away... or at least got a lot better. And check your tranny mount on the crossmember.

Now, after your comments on the play in the driveshaft, that doesn't sound right... 4-6 in... I would jack the rear end up and see if you rotate a tire, how much play you have.


If you have that much play it sounds like something is not right

500ski
01-23-2007, 06:41 PM
I have an 01 Z71. I get the clunk on take off's and sometimes on hard stops. I really thought it was the rear end. After taking it to a local tranny shop,they told me it was my transfer case chain. To much play,the sound travels down the driveshaft,to make it sound like it's the rear end. Any truth to this?

tpichevy
01-23-2007, 06:48 PM
"transfer case chain" what is this do? never herd of this befor....all i want to know if i should be worried about it and get it fixed....

AyerForce
01-23-2007, 06:56 PM
The transfer case chain is what transfers the power to the front shaft inside the case. Its the actual link to get power to the front axle.

tpichevy
01-23-2007, 07:03 PM
oh got ya....well who out there can tell us if this could be the problem....and if we should get it fixed? :stir:

94m5
01-27-2007, 02:48 AM
Not sure on the transfer case.....But I would like to know if anyone has the procedure for shimming the differential as stated earlier in this thread.


I'm getting a clunk from my 14 bolt, and feel this may be the culprit. U-joints have been swapped, and everything else seems tight.


Thanks in advance.


Mike

70chevrolet
01-27-2007, 06:32 AM
putting grease on it will only work for a few weeks and it will turn your t-case fluid brown. Trust me on this... Change your t-case fluid and use gm auto-trac 2 transfer case fluid (the blue $hit). I never would have believed it unless it worked for me.
Shifting from drive to reverse clunk... GONE
stomping on the gas clunk from a stand still....GONE
shifting from park to drive clunk...GONE.
And mine was clunking real bad.

litespeed
01-27-2007, 10:04 AM
putting grease on it will only work for a few weeks and it will turn your t-case fluid brown. Trust me on this... Change your t-case fluid and use gm auto-trac 2 transfer case fluid (the blue $hit). I never would have believed it unless it worked for me.
Shifting from drive to reverse clunk... GONE
stomping on the gas clunk from a stand still....GONE
shifting from park to drive clunk...GONE.
And mine was clunking real bad.


OK.... I have read about this stuff before. I just changed the fluid over to RP synthetic about 1 month ago. Greasing the slip yoke did nothing. Hard to belive that a different fluid could cure this problem? And in the transfer case? Is it a thicker oil?

I thought this stuff was for the push button system? Mine has the lever in the floor. Or does it matter?

Edit: Where do you buy the stuff and how much? Any place besides the dealer to get it?

94m5
01-27-2007, 10:23 AM
*nudges in closer to hear the answer.....*

Meshmez
01-28-2007, 12:20 AM
im having this problem too. when i get on the gas of let off i can hear a little clunk. sometimes its pretty loud (especially when i have just been in reverse and i start to go forward or vice versa)

i was thinking it might be a loose or worn out tranny/transfer case mount that was moving. but im going to try changing the fluid. my fluid may very well be low too, the front shaft seal is leaking (going to replace it asap) so maybe the fluid is the cause of all the clunking?! maybe the slip yoke?

MudMonster
01-28-2007, 01:08 AM
come on, where to get the stuff? i have a lil clunk...but my 2005 did also..and i bought it new....

bajakid2
01-28-2007, 03:05 AM
You can buy the Bluefluid at Chevy thats were i got it from..it helped the 1st time i changed it out..then my transfercase blew up and i had it rebuilt then they put ATF in it now my clunks back soo ill have to change it out again soon..

97_Sierra
01-28-2007, 09:31 AM
why did your t-case blow?

litespeed
01-28-2007, 01:18 PM
come on, where to get the stuff? i have a lil clunk...but my 2005 did also..and i bought it new....

I just talked to 70chevrolet again. Dealer only apparnetly. He put it in his 94 and cured the problem. His problems sound identical to mine. I'm going to give it a try this coming week.

I'll post how it turns out. I'm skeptical but willing to do just about anything to get rid of the clunk. VERY annoying.

MudMonster
01-28-2007, 07:27 PM
did the tranny blow up because of the auto trak II fluid????

is the ac delco auto trak II the same as the gm auto trak II stuff yall are talkin about? I found ac delco auto trak II for sale on a web site, but the gm stuff..

bajakid2
01-28-2007, 08:31 PM
my t-case blew becuase one of the breather lines werent connected and it got sand in it and the chain snapped or something..i dont remember exacly..

94m5
02-03-2007, 10:38 AM
I'm on my way down to the GM dealer right now. I have an appointment to have the engine oil, tranny fluid, front and rear diff, and transfer case oil swapped out.


I'll let ya know what happens with the clunk.....

litespeed
02-03-2007, 12:29 PM
I'm on my way down to the GM dealer right now. I have an appointment to have the engine oil, tranny fluid, front and rear diff, and transfer case oil swapped out.


I'll let ya know what happens with the clunk.....

I have the fluid. I just have not put it in yet. Been raining for most of the week and there is no end in sight. I will post the results after I install the GM fluid.

I would like to know if the Auto Trac fluid helps yours too. Post your results when you get it changed.

Meshmez
02-08-2007, 12:53 PM
so i had leaky seals front and rear on my t-case, and the clunk when getting on/off the throttle. so last weekend i replaced the seals and put the auto trak 2 in.

well the new seals dont leak... but the clunk hasnt changed a bit. im starting to wonder if it might the the u-joints on the driveshaft...

Tbi-MAX
02-08-2007, 05:21 PM
TPS sensor. It will do this!

Cheez
02-20-2007, 02:06 PM
Meshmez, was it very difficult to remove the old seals from the transfer case? My Haynes says I need a slide hammer to remove the front seal (mine is leaking). Did you have to use the same? By the way, I am replacing the u-joints as well....the rear one on the front shaft is sloppy, and I am pretty sure that the slop is what caused the seal to go bad.

AL05Chevy
02-20-2007, 04:23 PM
My 99 GMC Z-71 would clunk when you put it in reverse. I traded the truck in with 140,000 on the odometer with no problems all newer Chevy and GMC will eventually due it if you drive them long enough.:(

WideOpen
02-21-2007, 02:44 AM
I have a friend that had the same problem. What was happening was the shocks were worn out in the rear. When he came to an abrupt stop or a some what quick launch, the overload leafs in the spring pack would slap the upper leafs causing a clunk. Basicly axle wrap. Installed new shocks and clunk is gone.

elyk54
03-02-2007, 03:15 PM
Well i dont have a 4WD but i did have the same clunking noise coming from my truck. i thought that it was the u joints but turned out to be that both u BOLTS were loose. tightened them up and now no more noise. i had checked everything everyone on this thread did with no luck. i got under my truck and started kicking the frame and noticed that the u bolts were loose. hope this helps, and if not then oh well.

JWolfe75
03-02-2007, 05:31 PM
I had this same clunk when you come to a stop or take off from a dead stop on my '98 burban. At first I thought it was the u-joints, then maybe the brake shoes catching on the drums(had a deep groove in one)....turned out to be my leaf springs. no more teflon between the springs....popped in new ones...no more clunk. Good luck.

97_Sierra
03-02-2007, 07:59 PM
im going to get a complete bushing set from summitracing that includes leafspring bushings. While I ahve them out im going to take'em in and get them resprung and a helper spring put on....see if that helps. I'm also installing a new slip yoke this week.

mattr1983
03-05-2007, 07:10 PM
so i have this identical problem but now when i put it in gear truck wont move. i give it gas but it wont move and not like a sliping feeling more like its something in the drivetrain isnt turning. even in nuetral wont roll but if i but the t case in nuetral it will roll. any ideas?

Rook's
03-06-2007, 07:09 PM
I had this same clunk when you come to a stop or take off from a dead stop on my '98 burban. At first I thought it was the u-joints, then maybe the brake shoes catching on the drums(had a deep groove in one)....turned out to be my leaf springs. no more teflon between the springs....popped in new ones...no more clunk. Good luck.


i've had a 93 2wd 1500 and now i have a 90 4wd 1500, and they both have the clunk on take off or stop. sometimes i will stop, and just be sitting at the light, then "clunk" its almost like somebody kicked your bumper. its the leaf spring bushings, like the guy above said, theres no more teflon, and the sound is them binding, and releasing.

litespeed
03-07-2007, 02:06 PM
i've had a 93 2wd 1500 and now i have a 90 4wd 1500, and they both have the clunk on take off or stop. sometimes i will stop, and just be sitting at the light, then "clunk" its almost like somebody kicked your bumper. its the leaf spring bushings, like the guy above said, theres no more teflon, and the sound is them binding, and releasing.

Are you referring to the "spring eye" bushings or the small flat plastic spacers between the springs?

Meshmez
03-22-2007, 02:10 PM
Meshmez, was it very difficult to remove the old seals from the transfer case? My Haynes says I need a slide hammer to remove the front seal (mine is leaking). Did you have to use the same? By the way, I am replacing the u-joints as well....the rear one on the front shaft is sloppy, and I am pretty sure that the slop is what caused the seal to go bad.
sorry i didnt see this sooner. im sure you have already finished your seal replacement.

the front seal is a huge pain. might not be so bad if you have the right slide hammer.. but there wasnt a store in town that had a slide hammer with a hook small enough to get in the little holes to pull the seal out. the rear seal is easy, you can pop it out with a screwdriver.

so_real
03-23-2007, 02:11 AM
did u ever check your tranny mount...it could just be gone and need replacing by now.

ryanmhale
06-12-2007, 08:11 PM
nickel plated slip yoke will solve this problem for good (if you haven't solved it by now) greasing the slip yoke is another solution, but it's just a bandage for the problem

firestorm
06-13-2007, 08:01 AM
My truck has had both clunks described in this thread. The slip-yoke clunk (aka sqwuak) went away with enough driving. The other "clunk", coming from the transfer case, is sometimes a click (i.e. shifting from park to reverse) and sounds like a u-joint. Other times, it is a clunk or series of clunks, which generally happens during light throttle 1-2 shifts for me. It's almost a hollow sounding clunk, and sounds like a driveshaft shaking back and forth; I believe it's precisely that. I've been under my truck numerous times, and I can twist the front driveshaft back and forth and feel a good amount of play. That leads me to believe that the chain is stretched. I only use my 4WD in dirt, mud, and snow, so I'm not too concerned about it at the moment. It's been like that for 3 years. Also, it does have the blue autotrac 2 fluid in the transfer case, and it is an autotrac, push button "Auto4WD" t-case.

swiss
06-14-2007, 08:18 PM
Drive shaft.

tundrarx1
06-17-2007, 06:56 PM
Firestorm, i have exactly the same clunck in the transfer case, doing the same thing, park to reverse, and 1-2 shift. I have some play when i move it by Hand, exactly like chaincase in my snowmobile when i move the secondary by hand. But, my truck only have 65 000 km.

How this affect the life of the chaincase ?

firestorm
06-18-2007, 12:22 PM
Unfortunately, I don't know what is considered too much play. Like I said, mine has been like this for 3 years. I had the front diff. carrier bearings replaced by the dealer, and they said nothing about the slop; I didn't ask them to look at it either though. They noted that the t-case fluid was a little dark, and I did have them change it. No change in the noise.

AFAIK, in 2WD, the front driveshaft always turns and with no load or connection to the front end. When the truck shifts gears, there's a moment when there a disruption in the transfer, unlike the rear shaft, which will be spinning in relation to the rear wheels. I imagine the chain is loading and unloading, and the slop allows the shaft to chance speed or direction momentarily. And I believe this is amplified by torque management, where the computer lets up on the throttle during gear changes. I'm only guessing, but it seems to fit.

tundrarx1
06-19-2007, 01:48 PM
i found that the Transfert Case mount is Game over, i need to replace it, i can lift all the transfer case and tranny about 1/2 inch. by hand.

navihawk
06-19-2007, 02:13 PM
G80 rear end? I get a clunk or a bang now and then. I've dismissed it as the locker locking up.When the tire slipps on a takoff the locker kick in.Feels like someone rear ended you.

SleaStak
06-20-2007, 12:58 AM
the clunk on stop and start up is coming from the rear. gm 8.5 diff have a problem with the side gear shaft wear. the shaft gets sloppy and that is the clunk. i fixed one last week. solved the problem. you can replace the shaft and gears or replace the whole posi unit. i would replace the later since gm put those crappy posi units with that governor in it. replacing the shaft and gears will not change the back lash or pinion shims.

benz_004
06-22-2007, 04:40 PM
My truck is at the dealer right now for this reason. I talked with one of the service guys & he says they want to look into the t-case. He claims the transmission bands get worn & contribute to the "clunking noise." Also, the transmission "re-learns" with driving & increases line pressure in order to make up for worn bands. I have about 48K right now, so i haven't even changed the tranny fluid yet & my u-joints appear to be solid.

I'll update everyone when i get my truck back -

litespeed
06-23-2007, 03:26 PM
Update: I still have the clunk. I've learned to live with it. It is more of an annoyance than anything. I still have not switched over to AutoTrac fluid. It still has Royal Purple in there. I have been working too much to screw with it. I will be playing with it again the next couple weeks. Someone posted a post in here about leaf springs. That is not it either. I just upgraded to 3/4 ton springs and all the slides and bushings are new (along with the u-joints). The transmission mount is a possibility. I will definitely look into that. It is not the G80 either. I know the sound of that thing operating. It does get stuck (locked) sometimes and I need to drive a few blocks to get it to unlock. It is obviously coming from right under the middle of the cab. It sounds like there is too much "lash" between the trans. and trans. case and or just a sloppy trans. case.

Now I have the damn disapearing coolant fiasco. I'm hoping it is a hose or pump. I dread the thought of doing an intake gasket change in the 96 degree heat and 95% humidity.

SleaStak
06-23-2007, 05:12 PM
rear end noises will be transmitted to the t-case via the drive shaft. so it can be a little misleading. i would pull the rear end cover off and check the pin and gear lash. that is the cheapest was to go ( just a gasket and oil to put it back together). trans case will get expensive to pull apart when you are not even sure of the problem.

litespeed
06-24-2007, 01:04 AM
rear end noises will be transmitted to the t-case via the drive shaft. so it can be a little misleading. i would pull the rear end cover off and check the pin and gear lash. that is the cheapest was to go ( just a gasket and oil to put it back together). trans case will get expensive to pull apart when you are not even sure of the problem.

The fluid was changed last year when I bought the truck and before this thread was started. The Diff. looked like brand new inside. I should have posted this in the first post (sorry).

Thanks for the tip though... Is there a "seat of the pants" way to check the backlash by jacking up the rear and rotating the tires? I can push the truck back and forth a couple inches on level ground and in Park with the parking brake off. Seems like a lot to me. This is why I am refering to "drive line" lash when I talk about the problem. It is obviously between the engine and rear end. The question is where?

Edit: The disappearing coolant fiasco turned out to be a bad water pump (thank god). Fixing that Monday. The truck is parked until then.

SleaStak
06-24-2007, 04:53 AM
nope, you need to pull the case off and check it with a dial indicator. but you really need to look at the butt of the pin for movement, i will bet real money that is the problem. from a dead start you will hear a clunk on start up. its the pin moving in the case. i have photos of a worn out pin. i can post if you want.

benz_004
06-26-2007, 03:22 PM
My svc rep at the dealer just called & told me they replaced the shift forks in the t-case, & front/rear seals. We'll see how much this helps, more later -

EDIT: This t-case overhaul of sorts ended up costing almost $900 from the stealership. I'm under extended warranty, so i took it there & bent over: $540 labor, $390 parts

Dealership notes from repair ticket: "6.9hr total - NP8 transfer case clanking when put into gear..Removed & disassembled transfer case. Shift fork worn where E-shift shaft rides. Worn tabs. Wear on rear bearing. Recondition transfer case. Replaced shift fork assembly. Replaced rear bearing. Replaced front input seal & rear output seal. Replaced sealant. Installed new style pump to case savor clip. Replaced gasket & fluids."

arcticcatmatt
06-26-2007, 05:26 PM
For those saying it could be the chain, I can't agree with that. The HYVO chain is extremely stong and is not the weak point of the system.

When I purchased my truck (04 Z71), 2 weeks later I got the "tick" sound. tick,tick,tick. They said it was something to do with the drive shaft and how its welded. Put a new one in it and good to go. 3 months later, tick returned. New driveshaft again, tick gone. A year later, tick returned, driveshaft 3 now, no more tick. Its been gone ever since.

As for the clunk. When pulling away from a stop sign, it felt like I had a rear brake hanging up. I would hit the gas, feel a hesitation, clunk, then go. That one turned out to be a bearing in the transfer case. They removed it and it was "dirty" feeling (30k on truck). They ordered a new one and that one came in dirty feeling. They ordered another one and that one felt perfect, installed it, my problem was gone.

I have driven alot of 04 silverado's (3 in the family and 2 as rental trucks). They all had that clunk in the rear. I test drove a 2007 silverado the other day, no clunk.

benz_004
06-26-2007, 05:37 PM
One more thing: just now driving back from the dealership, i noticed my truck still makes noise when it shifts. However, it is much more positive a shift & the noise is entirely different. No "clunk!" more like a click now...

I think that could be the slip yoke or rear diff as you guys previously mentioned. I am going to wait & see on this one, it doesn't bother me---yet..

02Slvrado
06-27-2007, 08:43 PM
I have a drivline line clunk in my 02 Z71 and when I took it to the dealer they showed me this:


Driveline TSB's

--------------------------


Clunk, Bump or Squawk when Vehicle Comes to Complete Stop or Accelerating from Complete Stop or Accelerating from Complete Stop (Replace Rear Drive Shaft Nickel-Plated Slip Yoke) #01-04-17-004B - (Jan 5, 2005)

1999-2000 Cadillac Escalade (Old Style)

2002-2004 Cadillac Escalade, Escalade EXT

2003-2004 Cadillac Escalade ESV

1996-1999 Chevrolet 1500 Series Extended Cab Short Box Pickup (Old Style)

1996-1999 Chevrolet 1500 Series Regular Cab Pickup and Utility Models (Old Style)

1999-2002 Chevrolet Silverado Extended Cab Short Box (New Style)

1999-2004 Chevrolet Silverado 1500 Series Regular Cab (New Style)

2000-2004 Chevrolet 1500 Series Avalanche, Suburban and Tahoe

2001-2004 Chevrolet Silverado 2500/3500 Series Regular Cab with Long Bed or Extended Cab (New Style)

2001-2004 Chevrolet Silverado 2500 Series Crew Cab, Short Box (New Style)

1996-1999 GMC 1500 Series Extended Cab Short Box Pickup (Old Style)

1996-1999 GMC 1500 Series Regular Cab Pickup and Utility Models (Old Style)

1999-2002 GMC Sierra Extended Cab Short Box (New Style)

1999-2004 GMC Sierra 1500 Series Regular Cab (New Style)

2000-2004 GMC 1500 Series Yukon, Yukon XL

2001-2004 GMC Sierra 2500/3500 Series Regular Cab with Long Bed or Extended Cab (New Style)

2001-2004 GMC Sierra 2500 Series Crew Cab, Short Box (New Style)

2003-2005 HUMMER H2

with Four Wheel Drive (4WD) or All Wheel Drive (AWD) and One-Piece Propeller Shaft ONLY

This bulletin is being revised to add Cadillac Escalade (Old Style) and HUMMER H2 to the Models section. Please discard Corporate Bulletin Number 01-04-17-004A (Section 04 -- Driveline/Axle).

Condition

Some customers may comment on a clunk, bump or squawk noise when the vehicle comes to a stop or when accelerating from a complete stop.

Cause

A slip/stick condition between the transfer case output shaft and the driveshaft slip yoke may cause this condition.

TEE
06-28-2007, 12:04 PM
My 94 does it bad and has had U joints, carrier bearing and rebalanced the drive shaft and it's still there and getting worse. I'm looking into the nickel plated yoke....

myboost2
07-03-2007, 02:59 PM
Long Post
My 93 step side 2wd automatic has the symptoms as above posts. I have found that if I move into neutral before coming to a stop that the truck stops perfectly without any clunk or "hunching up" in the rear,like I had been rear ended.Just a nice smooth stop as well as a nice clean take off.Rear end is an open gear with normal lash, drive shaft is good as well. I did find and change out a separated trans mount, but this made no difference.
I am looking into a couple different items. One is whether or not the clutch pack is releasing on decel and the brake torque back through the trans is binding everything up(remember neutral stop/start is clean).I saw mentioned in previous post that TPS(throttle position sensor) is a cause. If I get a flaky signal out will this fool the cpu into not sending the proper converter or servo signal to the trans???? Manually performed neutral stopping seems to prove this out.. Can any GM trans logic guys shed some light here???
Thanks

litespeed
08-16-2007, 09:56 AM
rear end noises will be transmitted to the t-case via the drive shaft. so it can be a little misleading. i would pull the rear end cover off and check the pin and gear lash. that is the cheapest was to go ( just a gasket and oil to put it back together). trans case will get expensive to pull apart when you are not even sure of the problem.

Ok... Here is another update. I stand corrected and now I believe that you are correct. I got into the bed and had someone else drive the truck. There is Definitely a loud clunk coming from the rear. There is a "lash" problem. If you stab the pedal and let off while driving slowly is is very noticeable.

So, back to this G80 thing. Is it the G80 that is going, the gears, the bearings or a combination of things? How long do you think I have before this thing grenades and leaves me stranded?

I DO NOT want to fix it. I already have my eyes on a 14 bolt in a local salvage yard. I am too busy and too strapped to try to fix it right now. I'm hoping that this rear end will hold up until I can swap it out.

SleaStak
08-16-2007, 12:11 PM
it will last for a long time, it will just get louder. when it does wear to the point of breaking something, it will probably break a tooth off the gear. dont worry about it breaking any time soon.

Trolin
08-17-2007, 07:53 PM
Having the same clunk shifting to reverse. Dealer showed me TSB on problem. The noise is coming from inside the "propshaft" and requires yet another new improved GM part. They said it wont cause damage just annoying noise. Mine is so bad it rattle every time I hit a bump. Guess I'll keep driving for now.

Meshmez
09-02-2007, 11:47 AM
i was having problems with clunks too. whenever i got on the gas or brakes it would clunk. i finally figured out that my transmission mount was a little loose. the bolts that go to the transmission, not the crosmember, were slightly loose and it was allowing the mount to pop back and forth. i was about ready to replace u joints and everything! but luckly i found it. so check your mounts!

jetdr
09-30-2007, 08:37 PM
I had the exact same clunking in my 2000 z71. Tried everything and nothing helped. Researched the GM service bulletins and found that GM issued a bulletin that replaced the transfer case oil with a different oil to fix the problem. That bulletin was later rescended and a new one was issued to replace the rear drive shaft fwd yoke with a nickel plated spline yoke. Seems that the clunk is caused from the spline sticking on the output shaft and when you start and stop, the splines jerk rather than slip smoothly. I went to the GM dealer to see what fluid was now recommended in the electric auto transfer cases. I was told to put GM Autotrac II fluid in it. Costs 5-6 bucks a quart at the chevy dealer and it took just over 2 quarts if I remember right. After the new fluid went in, no more clunking and its been 25000 miles since with not a peep of a clunk.