S/C'd 383, full internals. brand new tranny, wont engage 3 or 4. someone told me it was a vacuum related issue, but why? the 4L60e doesnt use vacuum right? i work at a honda shop, dont do camaros a whole lot, just wonderin if anyone has an answer for me. thanks.

 

3rd and 4th are the same clutch pack, Id guess a nipped seal or teflon ring or maybe the bonded piston. At any rate, sounds internal. Is it just neutraling out when it goes for 3rd?

 

it shifts to third and fourth (needs to get to highway speed to engage 4th), but thats about it, really really light throttle, you can tell its in gear, but gag it at all, and it'll hit the rev limiter. some jackass told me i need some random vacuum solenoid or somethin stupid. now as far as i know, the "E" at the end of 4L60 means electronic. so im stumped. just trying to make sure its tranny, not somethin else. any help would be great...

 

The 4L60e is all electronic. If you have not programmed the trans for the additional power, that is your problem. Easy way to deal with it, is the TCI, TCU (Transmission Control Unit). The 3rd / 4th clutch pack is fried if it is slipping. There are several aftermarket clutch packs that add discs and are built to take more heat. If the trans is stock, you might want to check out some of the other components available to beef it up.

 

the tranny as far as i know is built up pretty well. something about 9 disc clutch packs. anyway, will the 4L80e TCU handle any more power, or what do i have to do here. but you all think 3rd and 4th are now MIA?

 

The 4L60e will easily take 600 hp if it is controlled properly. Some guys claim they can take care of it in the OEM computer. I am not convinced.

The 4L80e is much stonger, but a nightmare to install in a 4th gen. The TCU allows contolling the oil pressure enough to make the clutch discs live. I have my 4L60e holding 230 psi through the 2-3 shift @ wot. Partial throttle, cruising, the pressures are like stock with silky smooth shifts.

It doesn't matter what components are put into a trans. If the pressure is not held high enough, the clutch pack will not last.

Go to TCI's site and check out their software for the TCU.

 

The vacuum modulator can be added and it rises the pressure when the engine vacuum drops and says the tranny needs it. It replaces the electronically controlled force motor which now controlls pressure by software. You also need a check valve to release the pressure to the vacuum modulator when you are in boost. So now the vacuum controlls the pressure rise, but the PCM controlls the shifts.

 

do you know where i can get this modulator and check valve? and 100% sure its needed?

 

Yer 3-4 clutch pack isnt right. Its not holding under torque/load. They've either got a ripped seal, bad drum (leaking) or just plain way too much clearance in the 3-4 pack. Hows the 1-2 shift, under load and normal speeds?

 

Transgo makes it.

Have you ever met ANYONE who can give a decent explanation of the pressure offset tables in an A4 PCM??? My trans seemed to be doing fine with my computer tuned pressures, but I was never comfortable with them. Jury's still out on the modulator/check valve mod, but I got that clue from some guy who built trannys and raced alot - he was on the LT1 Edit list along with some really knowledgable pioneers of LT1 PCM hacking.

 

the 1-2 shift is like a kick in the head. and nice smooth shifts at normal speeds. looking at switching drum and putting in a 15 disc clutch pack. i dont know where else to turn, the original owner said the ECM/TCU have both been re-flashed to compensate.

 

also, this car is for sale, on low boost (4lbs), it pulled 622whp. its a 95 Z28, nice burgandy color. C5 chrome vette wheels. $28,000 in parts. the labor was free. so if interested, make a GOOD offer. email me for pics, cwixlow2@yahoo.com

 

trans will be rebuilt this week, all problems will hopefully be taken care of prior to sale, if not, youre all camaro guys right...

 

come on here, somebody needs this car.

 

a 383 LT1 made 622 rwhp with 4 lbs. of boost???? How in the hell is that possible.
Anyways, since yer 1-2 shift is good that rules out the EPC being bad. You could however have a bad accumulator thats just leaking pressure off. Unfortunately its the accumulator under the valve body. If you feel confident, take the V.B. down and check out the accum. in the case side. Sometimes stupid people use plastic accumulators which break. Im leaning more towards the 3-4 piston seal is ripped. Prolly snagged it during assembly or they re-used a bonded piston they "thought" was good.