tonight my '91 Auto was slipping when driving conservatively, when at speed if i gave it gas the motor would rev but he car would not accelerate. And it would sometimes not shift to 3rd or OD, i would be cruising at 40MPH in second gear. when shifting the motor would rev up about 500RPMs before comming down to the next gear.

sounds like the tranny is going, but when i drive it hard it shifts nice and firm as usual, when i would give it a lot of gas the trans would hook up again.

so what could be the problem?

oh yea, she only has 52,000 miles

thanks in advance

 

almost forgot, i had the trans and torque converter flush 4 thousand miles ago, i dont know if that would have something to do with it or not.

 

If it pulls well in 1st & 2nd but slips going into or in 3rd & 4th the problem is the 3-4 clutch pack and indeed it's time for a rebuild before you need a flat bed to get it to the rebuilder.

My A4 was behaving like yours a few months ago, when suddenly I only had 1st & 2nd.

 

thats exactly what it does, it drives fine in 1st and 2nd, but 3rd and 4th are acting up, thanks

 

I was just about to start a thread like this but thank you yellow dragon! I'm kinda in the same boat as you.

For some reason I have a very firm, tire chirping 1-2 and 2-3 is less firm, 3-4 is the least firm and at WOT, it will only seem to stay on 3rd, even if I am at 5800 rpms. Then when I let off, it will shift to 4 aka OD.

So 65Z01, do you think my 2-3 and 3-4 clutch pack is also going? Why would you think my Vette doesn't wanna upshift to 4 on a WOT run like it used to? Does the TPS have anything to do with this? My TPS is still set at stock .54 volts. If I set it up to .70 like you did, would it make a huge, earth shaking difference? Thanks!

 

i thought the A4 was designed not to shift to 4th at WOT,

 

F-body A4 doesn't but Vette A4 does. That is one of the differences between Vette 700R4 and transmissions used in lesser cars.

 

Yes, a real corvette trans shifts from 3 to overdrive at WOT.
-Beppe-

 

Replace the tc when the trans is rebuilt. Trash cannot be flushed from a lock up converter. Also be sure shop flushes the cooler and lines.

 

What you are describing is normal... IF you have a non-vette tranny or the upshift sleeve has been removed from your tranny during a rebuild.
If non tranny work has been done, and it was doing it fine before, then your tranny is starting to slowly go.. Mine did that for 2 years (No OD at WOT) before it started slipping badly and needing a rebuild..

 

With our A4s (700R/4) the ECM ONLY controls TCC lockup; the weights and springs withing the A4's governor control WOT upshifts.

If your WOT shifts are hanging up more over time it could be due to dirt or sticking in the valve body. This was a symptom with my OEM A4, i.e. the WOT 2-3 shift was way slow.

On the recent rebuild, after the 3-4 pack went out, the shop replaced the TC and gave the coolant lines a thorough flush.

As stated our A4 came with the "Corvette 3-4 upshift sleeve", which is the "in mod" to the A4 in an F-body car. This is what allows our Vettes to upshift at WOT. If your A4 was rebuilt and no longer upshifts at WOT you need to have that sleeve installed.

To test for the WOT 3-4 upshift note the 1-2 and 2-3 upshift RPM shift points and extrapolate to where the 3-4 "should" be. Though the upshift is governed by tail shaft speed the tach change is a good indicator of the spread in shift points.

Changing the small weights in the governor will change the overall shift points and changing the springs will change the shift point RPM spread.

For example, my 1-2 shift is at 5,100rpm and the 2-3 at 5,700rpm so I can expect my 3-4 to be above my power band which is pretty much dead by 6k rpm. If I want to bring these shifts into line I need to muck around with my governor recal kit.

 

Perhaps with the 700R4 and 4L60 equipped with the TV cable. But with the 4L60E electronically controlled transmissions the PCM contains shift tables that control the shift points and it depends on the rear end (differential) gear ratio installed at the factory. If the car has the 3.07:1 (G94 G44) performance gear ratio the PCM wil command a shift from 3rd to 4th (OD) at 136mph from 75% TPS to 100% TPS (WOT). But if the car has the GM1 standard 2.59 ratio the PCM will not command a shift to 4th and will leave the car in 3rd all the way to top speed (161 mph or whatever it is) at WOT. This is why if a guy has a car with the 4L60E (94 - 96 models) and 2.59 original rear end and he changes rear ratio to, say, 3.54:1, he's going to be limiting his top speed because the PCM will keep the car in 3rd at WOT even with the new 3.54 rear installed, UNLESS he goes into the PCM and edits the shift tables accordingly (using Tunercat or LT1Edit, etc). For reference here are the shift tables as shown by Tunercat software:

3.07 car:




2.59 car:

 

My 94 auto did the same exact thing.......tranny went ... $1590 to rebuilt....lots of metal found in the pan

 

Man, I have been looking for this. super info. thanks.

 

thanks for all the help

she's heading to the trans shop on monday, is there anything i should remind them of while rebuilding the trans because its a vette tranny? any special parts only in the vette tranny that they may miss?

-mark

 

A vette trans has a wot upshift valve as discussed earlier. Corvette has a different servo. Corvette has a different governor. Vette uses (usually) green accumulator springs. Accumulator works like a shock absorber to cushion shifts. The boost valve in the pump is .471 stock. Non vettes are about .400 .Pump pressure spring(I believe) is different. Valve body is different. Output shaft is slightly different. Very expensive to completely convert a non vette trans to a vette trans. Most people do not change everything out. I recommend the vette servo, governor, and a .500 boost valve. These are cheap and easily available in the aftermarket. I like the B&M shift kits, others do not. The B&M kit supplies a high pressure pump spring and sleves to lock out the accumulators. This eliminates the springs. The wot upshift valve is available (with a .471 boost valve) for approx $28 from gm. Hope this helps.

 

So if I ever needed a tranny rebuild, I'd have to go to a real Corvette mechanic, NOT a general transmission rebuilder, EVEN if he claims to have been working on transmissions for 30 years. I bet at that length of time, he might have worked on 10 Vette trannies, probably all of them done wrong or a halfass job. Sorry if this offends anyone but I now see an A4 Corvette transmission is not just your old regular transmission.

 

The best advise "I" can give is keep your vette trans and rebuild it if possible. Most transmission guys, myself included, can easily rip down and build up a 4 speed auto box. Very few truly understand how, exactly, they work. This is sad but true. If you have a good tranny guy, hang on to him. No substitute for professionalism.

 

thanks for all the help,

i was checking the trans fluid again today because im obsessive about taking my car anywhere, and i saw it was about 4 inches too high on the dipstick, would this affect anything, or be the cause of the tranny going out?

 

I assume you were checking the fluid level with the trans in park and the engine warm. If so, 4 inches too high is BAD. Trans is a hydraulic unit and will foam the fluid if overfilled. Too much fluid is about as bad as not enough. All kinds of heartburn can occur from inproper fluid levels. Suck out some fluid and get the level correct, then test drive.