700R4 vs. 700R4

[8284shortbed]

Hey guys,

I've been lurking for a little while and finally figured I'd post some questions. The first question I have is concerning two different trucks with the 700r4 trans. I have an 82 1/2 ton 2wd and an 84 1/2 ton 4wd. They both have the overdrive auto, though the 4wd is a 350 v8 and the 2wd is the 305. Here's the annoyance:

I drive both around in drive until I need the highway, and even then I only manually shift both trucks into OD after 45 or 50 mph. The 2wd rig stays in OD no matter what at that point unless my speed drops to below 45 mph. I love this. The 4wd, however, appears to be extremely sensitive to throttle pressure. I can accelerate lightly or hold the pedal steady for a steady speed, but as soon as I ease up on the throttle, even very slightly, the thing downshifts out of OD. Hold the throttle steady or put a little pressure back on and it shifts back into OD. It doesn't matter if I'm going 50 or 75, it behaves this way no matter what. Extremely annoying.

Common sense would tell me there's an adjustment somewhere that can help alleviate this, but reality says it's probably not that simple. I'm hoping there's an expert in the house that can shed some light on this. I imagine there are differences in the technology in both trucks from 82 to 84, as well as differences in trans between 2wd and 4wd, but I just don't know enough about them and am betting someone on here does. Thanks for any insight you guys can provide!

- Don

[vic_V8]

adjust the TV detent cable

http://www.thirdgen.org/detent

[8284shortbed]

Thank you very much! If it's that easy that will be awesome! Thanks again!

[vic_V8]

it's a place to start, that's for sure. then try all the normal stuff, filter changes, etc.

[Jameslleary]

Sounds to me like your torque converter is unlocking on the 4wd...check the vacuum line going to the lockup switch on your firewall. the TV cable only controls line pressure, not shifting. Check the adjustment for the heck of it though. Just noticed you are in Oregon...is it possible that your 84 has the computer controlled q-jet? if so, it may be a sensor issue.

[8284shortbed]

I'm not sure on the computer controlled Q-jet. How would I ID the computer controlled part? I do believe it is a q-jet carb. I'm just not sure how I'd determine if it's computer controlled. I'll be digging around under the hood this weekend, so I'll learn a lot more. The truck is new to me, and as I understand it spent all but the last 5 years in california. While I've done an oil change, I've yet to do the tune up, air cleaner etc. The trans has a recent fluid/filter change and all looks clean. will check the TV cable and see if I can find locate the vacuum line to the lockup switch on teh firewall. It's completely bone stock under there will all emissions, vacuum lines, etc in place, so it may be a chore to locate. But I'll have fun trying! Thanks for the input. Any other ideas out there are certainly welcome!

[Jameslleary]

I'm not sure on the computer controlled Q-jet. How would I ID the computer controlled part? I do believe it is a q-jet carb. I'm just not sure how I'd determine if it's computer controlled. I'll be digging around under the hood this weekend, so I'll learn a lot more. The truck is new to me, and as I understand it spent all but the last 5 years in california. While I've done an oil change, I've yet to do the tune up, air cleaner etc. The trans has a recent fluid/filter change and all looks clean. will check the TV cable and see if I can find locate the vacuum line to the lockup switch on teh firewall. It's completely bone stock under there will all emissions, vacuum lines, etc in place, so it may be a chore to locate. But I'll have fun trying! Thanks for the input. Any other ideas out there are certainly welcome!

I think you may have the Computer controlled setup. go ahead and take your air cleaner off, and snap a pic of the engine...close up. We will be able to help you better that way. My 86 came from the factory with that setup, and i have quite a bit of experience with it.

[8284shortbed]

I'll do that. I should have some time set aside tomorrow to handle the tune up and take a look around at everything else. Thanks for all of the help.

[8284shortbed]

Hey Guys, I need one more post before I can post links to my pics. So that's what this is. Next post with links to pics in just a moment.

Thanks,
don

[8284shortbed]

Ok, here are pics of the carb. Are we looking at the computer controlled setup? I completed the tune-up after taking these pics. I have not yet looked into adjustments for trans that were mentioned above. I also have a coolant leak that I was unable to locate. Still working on that too. Anyway, here are the pics.

http://i290.photobucket.com/albums/l...ucks/Carb3.jpg
http://i290.photobucket.com/albums/l...ucks/Carb2.jpg
http://i290.photobucket.com/albums/l...ucks/Carb1.jpg

Thanks,
Don

[mainechev]

Fixed

[Jameslleary]

Yup, thats a california truck. Ok...here we go. You do have the Computer controlled system. this particular system does not control the lockup. its been a long time, but if i remember correctly, there should be a pressure switch on the right side of the transmission, aft of where the tv cable is mounted, that controls lockup hydraulically. check to see if you have it, and it has not come unplugged...it did on mine several times.

[8284shortbed]

Thanks. I will try to get under there and look today. Right side of the transmission = passenger side? After driving it some more and paying closer attention to how it drives, i think you're on to something with the lockup, as it actually behaves the same when in drive. Would the torque converter have to lockup in drive as well? it appears to have what I would call an "extra shift" (i'm assuming this is the lockup) around 40 mph, maybe 45. But if left in drive it behaves the same as it does in OD when easing pressure on the throttle. I will try to get underneath it today and take a look.

[Fast305]

Yup, thats a california truck. Ok...here we go. You do have the Computer controlled system. this particular system does not control the lockup. its been a long time, but if i remember correctly, there should be a pressure switch on the right side of the transmission, aft of where the tv cable is mounted, that controls lockup hydraulically. check to see if you have it, and it has not come unplugged...it did on mine several times.

Atleast on my 83 G20 if my van had came with the CCC Q-Jet it would have had the TCC controled by the ECM.

As for the downshift at part throttle on the 700r4. Personally I never liked how my 83 700r4 held OD at high levels of throttle. I would rather have had it downshift at less throttle, especially climbing hills. The Governor calibration,TV Sleeve and Plunger, and shift valves varied model to model, giving different upshift and downshift timing.

700r4s could lock in 2nd, 3rd, and 4th gear.

[Jameslleary]

Atleast on my 83 G20 if my van had came with the CCC Q-Jet it would have had the TCC controled by the ECM.

As for the downshift at part throttle on the 700r4. Personally I never liked how my 83 700r4 held OD at high levels of throttle. I would rather have had it downshift at less throttle, especially climbing hills. The Governor calibration,TV Sleeve and Plunger, and shift valves varied model to model, giving different upshift and downshift timing.

700r4s could lock in 2nd, 3rd, and 4th gear.

According to the digram I had, there was no wire for lockup on the diagram for my old cc q-jet setup, indo remember there was a pressur switch mounted on the pass side of the trans, that looked lik the same type of switch for an aftermarket lockup kit, but it was a all GM, and the lockup wires wer not hacked at all. I have to see if i can find a better diagram.

8284...lockup does feel like a 4th shift, and it usually is supposed to happen at around 38 mph.
Fast...your right, mine locks up in 3rd as well...and, BTW, I have swapped out the TPI for TBI.

[Jameslleary]

Ok, it is computer controlled, there is a 4th gear lockup wire coming from pinout "p"on the small ecm plug, wire #382 lt blue and black,that sends the lockup signal, and then there is a 4th gear inpute pinout, which I would assume comes from that pass side pressure switch i am talking about. its wire #446 lt blue wire, pinout "n" on the small ecm connector.
Now that I have this digram, and you mention that you are feeling that 4th shift into lockup, i would check the throttle position sensor setting. The TPS sensor is operated by the accellerator pump rod, on the drivers side of the carburetor. you can check this with a digital volt meter, with the key in the on position. the sensor output wire is the dark blue, poke it with the positive meter probe, and poke the black sensor wire with the neg meter probe, and you should see .54volts at idle position, and 4 volts at full throttle. if I remember correctly, there is a very small screw on the casting, where the accelerator pump arm pivots, and you can adjust the TPS by turning the screw.
I do remember lockup being pretty darn sensitive...it may just be nature of this particular beast.
contrary to what others may say about it, the system is good if it is maintained which yours looks like it has. you should be able to get around 15 to 17 mpg empty.

[8284shortbed]

Very cool. I wasn't able to get around to looking at it yesterday. I'll double check the things you mention above this weekend. Appreciate the help!

[lenoardmike]

that's an nice stuff it would help me also thanks for the post.



Performance Tuning