View Full Version : help! 700r4, no 4th after minor disassembly (pump swap,etc...)
Trying to fix TCC lockup, I just swapped my pump from a donor 700r4. After installing it, I noticed I was missing the turbine shaft o-ring. Installed one, but forgot about the pump retainer clip during reassembly because the pump that came out didn't have a retainer clip (p/n 94 in ATSG fig 215)
Now I have no engine braking in OD 1-3 (rpm falls to idle when throttle is closed), and I have no 3-4 shift at all.
Is the retainer clip important? I don't see what it might do besides prevent seal failure, but seal failure would be catastrophic, no?
Edit; I also added the gold shim ring from transgo jr kit to my 2-4 servo (couldn't get cover on with shim in & trans mounted last week,so I omitted it at the time. I'm now thinking this might be it, I'll give it a shot.
['89 suburban 4x4. Donor 700r4 is an '88 burb 4x4.]
03-19-2011, 07:34 PM
you may have a bad turbine shaft seals the teflons they may not ba sealing no engine breaking means that the ovverun clutches are not applying the overun passage on the turbine shaft is the first seal then the forward circuit is the next seal, and the direct is the last seal toward the drum. when the pump was installed it could have damaged them..as for the 4th problem did you install the 4th servo piston correctly with the deep side of the piston towards the cover also did you put new seals on the servo.
Perhaps nothing is wrong at all... I did not use new servo seals, but they look fine, and installing my spare servo did not change anything.
I currently have overrun braking in D, it's only when OD is selected that rpm returns to idle. I'm finding various threads (elsewhere) that say that's how it's supposed to be. I thought the overrun clutch behavior I had was fine before my tinkering, so now I have no idea what's correct =)
As for 4th, I did another test drive and my shift points feel higher, so I'm thinking the other pump (from diesel 700r4) has changed my line pressures and that's why I'm not hitting 4th. 3-2 downshift is now very firm, too. I'm not sure this is bad at all.
I feel like I should loosen the TV cable to bring my shift points down a bit and see if I can get to 4th, except I'm thinking perhaps I should get a gauge and hydraulic line for the test port to see if I'm out of spec instead of trial-by-fire.
03-20-2011, 11:32 AM
no you shouldnt have engine breaking in 4th in 4th the forward sprag os overunning. did the valve body come from a diesle also? the pump should have much to do with that as your TV cable regualtes the line pressure to the downshift side of the shift valve. the cable may jusy not be adjusted correctlty (too tight)
03-20-2011, 11:34 AM
if you think its a pump pressure issue change the PR spring from your pump
Oye, good insight. I bet my reverse/intermediate boost valve fell out and is causing some weirdness (I installed the PR valve while tranny was out (case was vertical instead of normal orientation).
I'm using the transgo PR spring. One thing I'm not sure of is if the TV boost valve is matched to the pump, or if the size isn't really all that critical.
The tv boost valve stem in my 700r4 was .422. The diesel 700r4 was a .395. I currently have the .422 boost valve in the pump from the diesel, which should create a higher line pressure, but I don't think it would be anything outrageous like what I'm experiencing.
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