Okay so today my dad an I finished rebuilding the transmission. This was a complete teardown, and it appears as though it will be once again. We installed the transmission into the car and not even 30minutes into operation the thing dies.

Here is a little background info, but you'll have to excuse me, my terminology may be a little off, I deal with engines, not trannys
1. The forward input clutch assembly had smoked clutches and steels
2. The band was moderately cooked
3. The accumulators were worn, had slop in the hole through which the guide pin passes
4. It is a 1991 chevrolet camaro with a 3.1l v6

So we looked on the project as though we could improve the tranny a little bit, and here is what we did.
1. Replaced all steels and clutches with stuff from a stock rebuild kit
2. Installed corvette servo
3. Replaced the part that people replace with "the beast," with the factory piece
4. Replaced accumulator pistons

We went out on one run and got this
1. At first it would shift at part throttle at around 2000 rpm
2. The tranny would float at 5200 rpm before it decided to shift into second
3. After the 5 minute run around it would shift at part throttle at about 3000 rpm
I did adjust the T.V. cable before we went out, per the specs in the gm manual, but I readjusted it before I went out on the second run

By myself on this one, here is what it did
1. It did shift at a more reasonable 2200 rpm under part throttle
2. It would still float at 5200 rpm before shifting into second
3. Going down the expressway I noticed a funny smell and saw smoke coming out from behind me, had the smell of transmission fluid
3. On the return home I babied it
4. Still had the reasonable 1-2 shift at 2200rpm
5. same with the 2-3
6. But the 3-4 shift never came
7. So the engine was turning at 2500rpm at 50mph with 215/65/r15 tires and a 3.23 rear end
8. I even verified that it was still in 3rd by putting the selector into 3rd and felt for that distinct bump of a down shift, never came
9. On the off ramp I was coasting at 35mph, I downshifted into 3 then second so I could check the operation of the overdriven clutch
10. It felt like it never engaged and there was little if no engine brakeing
11. Got to a light and decided to take a left to take the back roads home
12. By this point it sounded bad, as in there was a distinct mettalic sound to the operation of the transmission and all I had was 1st gear
13. Stopped it and pushed/towed it home the rest of the way
14. I still have reverse and 1st, the fluid smelled burnt but was not metallic, and I haven't drop the pan. I may do that but it all depends on my mood tomorrow

So this project really turned into a depressing ordeal, the car has been a bit unreliable, I mean it has its fits every now and then, but this is quite a big fit. If any one could tell me what they think happened to the transmission it would be very appreciated.

 

Sounds like the overrun sprag (the thing with all the "s" shaped things in it) installed backwards... you'll need new overrun clutches and steels (2 each). also it will need a really good cleaning since all that crap is spread all through the tranny now. So a new filter and fresh fluid too.

 

Okay, today on a test run the transmission decided to act a little differently. I do infact have an engine braking upon downshift. But here is what I have so far today
1.It does have a 1-2 shift but you have to wind the engine up to 5200 rpm or so, get out of it, then go to part throttle and the tranny will shift
2. When up at that higher engine speed there is fluid coming out of the vent
3. It was not overfilled
4. It still has reverse as well as engine braking when you put the gear selector into 1st
5. The fluid is in fact not burnt, I just never took the time to smell new tranny fluid for a good comparison, so it smells exactly the same
6. I still have reverse and forward, but when I shift it makes a bit of a clunk sound

At this point I'm going to put my money on the problem being in the valve body. If anyone else has any ideas feel free to chime in.

Thanks,
Scott

 

Oh and I forgot to mention that there is no metallic luster to the fluid at all, so I don't think that there is any hard parts broken. When I checked the fluid this morning there was just tiny little bit on the end of the stick, and I checked it with the enigine running and in park. With that low of a fluid level that might have explained the sound because the pump might have been moderately starved.

 

Still no 4th? I still think the overrun sprag is backwards

 

If I had no metallic luster in the fluid, no metal on the magnet in the pan (just dropped it earlier) and I had 4th gear on the 1st run before all this messed up. Then why would the sprag be installed backwards. If it worked the first time then it should be in the right direction. Do you have any clue as to what would cause fluid to come out of the vent, and don't say being overfull.

 

The tranny could be running hot and pushing the fluid out.

 

Put the transmission lever in 4th (OD) position, if the car moves the sprag is in correctly, if it does not move, then it is in there backwards.

 

After a while of just looking at the transmission my dad noticed that the snap ring that holds in the 2-4 servo was not completely seated. So it caused the servo to **** itself in the case. It appeared as though the fluid was coming out of the vent when in actuality it was coming from the servo, which explains how the car would only smoke when it was in any other gear but reverse and 1st, becuase the servo has no deal with those two gears. So is it possible that the servo being kinda stuck would cause the odd shifting and force the engine to have to turn at 5000+ rpm before it woulds shift?

 

that's bogus. if the forward sprag is in backwards it will have no third or fourth gear. pro built is wrong. I know this because a builder(not me) at one of the shops used a sprag rotation chart that transtar used to give out had a sprag rotation for the 4l60e and 4t60e next to eachother and he mixed it up. the transmission had no third and fourth gear but first and second and reverse worked. he highlighted the correct one on the poster just to make sure that he didn't do it again. my boss was pissed. I made him pull the trans back out as he was just a temporary builder. just changing the forward sprag back to the correct direction fixed the problem.

 

If the servo was not fully/correctly seated, that would explain a 2nd and 4th gear issue, both during the shift and while "engauged". Depending on the mileage and % that it did engauge may mean the band is already hurt, and/or the drum is hurt. Since it sounds as though it created enough heat to push out some fluid, you may be in for another tear down. Also, if you so decide to continue running it(providing the servo corrects the issues) you should go ahead and change the fluid and filter as a precaution.

What were your clutch pack tolerances and what was the shaft end-play? I'm guessing no apply seals were changed?

 

Here's the final verdict on the thing. The car is now running and operating better than ever. As it turns out the servo not being fully retained by the snap ring caused all of the issues. Shagwell, we did change out the fluid in the transmission just as a precaution but there wasn't any metal in the fluid so we didn't worry about the filter. Oh and the tolerance on the shaft end-play was 0.022in. Also, the tranny had only 4 miles at most on it before we repaired the issue. So no worries there. Thanks for all yall's help.

-Scott

 

shagwell must've consulted CLEO, because his crystal ball was almost spot on!!!!! wow.
glad to hear it worked out. It's a rewarding feeling eh?

 

If the forward sprag is in backwards, it will not takeoff in the "OD" position, but it will take off in the "D" postion. I have seen this many times and it is always the same. The overrun clutch is on in the 1, 2, 3 positions, not in the "OD" position on the 700R4. Whatever chart he was using is wrong.

 

Well, I've not yet installed a sprag backwards, so I had no diagnosis for that. Just seemed the only thing in comon with all issues was the band. - Just proves that even the peanut gallery gets one from time to time!

If you didn't find any metal in the fluid, then the filter should be fine. I was just reccomending the fluid change due to the likely-hood that it was over-heated due to the band slippage.

Good luck with it, hopefully in that short of driving nothing was damaged. At most the band recieved some extra wear, along with the rev drum.

 

sometimes heating a new band if it's the brown one isn't such a bad thing. if a new band slips a little sometimes you can rack the vehicle, and pry the servo cover to make the band a little hot (called curing the band) and it will give a firmer apply. an old school trick/ but not recommended for all. I like when I see the trans tore down and there is a slight brown on the band but not burnt-meaning it cured properly and didn't slip. note:sometimes replacing a "cured" band with a new one and it'll slip more, but that's if the drum wasn't prepped properly.

 

I'll have to install a forward sprag backwards sometime just to verify. Didn't look at a range reference chart yet/ just tried to remember the symptom from years ago with a bad builder experience. can't dig back in my head files that far as it was probably 1995 since that one.

 

Curing the 2-4 band (2nd design) is tricky, but it can be done, either that or wait about 10,000 miles. Do not do this to the early design (single tang) or the Hi-Energy bands.