Hitting the rev limiter on the 2-3 shift at WOT...

[waveoff]

Well the last time the tranny in my '98 Camaro Z28 started doing this it lasted for a couple of weeks and then I lost 3rd and 4th gear. I had it rebuilt and it was working great for the past 11k miles and 50+ 1/4 mile passes. All good things must come to an end though. A few weeks ago it started bumping the rev limiter on the 2-3 shift at WOT. It's been getting worse over the past few weeks. It used to do the 2-3 WOT shift fine when the car had just gotten up to operating temperature and then after driving for a 1/2 hour or so it would bump the rev limiter on the 2-3 shift at WOT for the rest of the drive. Now it bumps the rev limiter all of the time on the 2-3 shift at WOT. Partial throttle 2-3 shifts are fine. I took it back to the tranny shop and they said it looked like a computer issue to them. So I tried what joecar recommended in this thread http://forum.efilive.com/showthread.php?t=4672&highlight=2-3 but I still hit the limiter. Could someone please look at the tune and log from one of my runs and let me know if I'm doing something wrong? The tune has the upshift rpm's set to 5000 since the WOT MPH adjustment method didn't seem to work for me. Thanks!

[waveoff]

Disregard this post folks. It looks like it was a mechanical issue. My tranny has died yet again! :(

[joecar]

After rebuilding, hook up a pressure 0-300 psi gauge to the test port (just above shift lever on LHS of your 4L60E; see that the guage indicates sufficient line pressure to match engine output while driving (something like 90-130 psi at low torque, 230-250 psi at high torque, and proportionally increasing in-between)...

(requires poking the guage hose thru the cabin, or taping it to the car body, and placing the guage so you can see it safely while driving).

You maybe should increase the shift pressure tables D0701, D0702, D0703
(say increase by 10-15%; also start sloping up right from zero so there's no flat part).

[waveoff]

Thanks for the advice! I'm going to have the shop put a 3400 stall TC in before they button it all back up. What parameters will I need to adjust when going with a high stall TC? I'll try and search for an answer here in the meantime. :)

[joecar]

Just might have to lower the WOT shift RPM.

When the shop installs the rebuilt trans, get them to check line pressure while engine is at load.

[98ls1blackbird]

Just might have to lower the WOT shift RPM.

When the shop installs the rebuilt trans, get them to check line pressure while engine is at load.


I dont want to hijack this thread, but I am having the same problem with my 98 T/A, I've tried to lower the shift point rpm and it does not have an effect, I already lowered the shift speed so the shift should be controlled by the rpm. I had to raise my rev limiter to 6500 rpm. My logs show the 2-3 shift at around 6448 rpm's, with the shift point set to 5900. I'm starting to think this is a mechanical issue. Sorry for the hijack.
Thanks

[HTMtrSprt]

We just went through this on a customer car.... shifted perfectly on the chassis dyno but flared and hit the limiter on the road during the 2-3 shift. Solution.... believe it or not.... we added 3/4 qt of fluid and it shifted like a champ. The car's acceleration pulled the fluid away from the pickup just enough to drop pressure so it couldn't shift correctly. The level was just above the bottom of the "hot" zone and yet wasn't enough. It needs to be ABSOLUTELY full or slightly over to prevent problems OR install a deep pan w/ extended pickup.

Hope this helps.

HiTech

[Mr. P.]

I dont want to hijack this thread, but I am having the same problem with my 98 T/A, I've tried to lower the shift point rpm and it does not have an effect, I already lowered the shift speed so the shift should be controlled by the rpm. I had to raise my rev limiter to 6500 rpm. My logs show the 2-3 shift at around 6448 rpm's, with the shift point set to 5900. I'm starting to think this is a mechanical issue. Sorry for the hijack.
Thanks
The 3-4 clutch is the real weak point in the 4L60 - you've got to have the *right* clutch setup plus do all the tricks necessary to get the other clutches to release as fast as mechanically possible because this transmission 'drags' clutches bad. Shift kits only make the problem worse, they speed the application of 3rd (it grabs great) but does not help 2nd release fast enough and for that split second you have both clutches simultaneously applied, and both take it in the shorts. It costs about another $100 in internal hydraulic mods but do what you can to make clutch release as fast as possible. Clutch - personally I would use the Blue Plate specials or the B/W carbons (tan, 8 friction elements) with the thickest steels you can find, use the steels specified for the friction materials don't just grab for the hardened/kohlene steels especially with the B/W carbons; hot tip - use the 700R4 pedestal to give you more room for the 3-4 clutch stackup.


...Solution.... believe it or not.... we added 3/4 qt of fluid and it shifted like a champ. ...
Another tip - spend $140 and switch to the C5 pan, it holds the same capacity as the deep truck pan but is formed to have a 2" sump in the middle of the pan; you will also have to run the C5 filter with the 2" tall pickup. I felt an immediate improvement, this part works. GM Part nums, 24208593 pan kit, 24208574 filter kit.

Mr. P. :)