4L60e won't drive forward

[twinturbotony]

Note: I am typing this for my husband, so please forgive me if I mess up any of the terminology. Building cars is his dream and this is his first build. He is quite discouraged at this point, but he is a brilliant mechanic and I know he can do this! He is also stubborn and rarely asks for help. I am just getting the thread started for him. We have scoured the forum for ideas and have tried what we've found. I am hoping some of the more experienced folks here might have some new leads to follow. He will be the one managing replies. Thanks in advance, Danielle

I am doing an LS swap on a '94 Camaro. I am using an LM7 out of a 2000 Chevy Silverado 4x4 and a 4L60e transmission. I am using the PCM from the donor truck and have used the much of the original wiring harnesses for the engine and trans. The engine runs great (twin turbos and all), but the dang thing won't drive forward. I have ruled out any mechanical problems, going as far as buying a whole new transmission. It really seems to be an issue with the tune, but I'm new to tuning, so I'm not sure what.

After installing the transmission (both times), the car will go in reverse. Nothing in D or shifting through gears manually. Nothing when you unplug the trans to force it into limp mode. Last night, I did a segment swap for the trans. After that, still no forward drive. However, the wheels rotated slowly backward when put in low. (Odd.) I thought maybe the problem had to do with tuning being different for a 2wd vs. 4wd transmission. I couldn't find a 2wd vehicle with 4L60e with the same OS so I could do another segment swap. I carefully compared a tune for a 2wd Silverado and changed the setting on my tune to match. After writing the new tune to the car, reverse still works, but we're back to nothing in Drive or manually shifting through the gears. However, we now when the trans is unplugged it can be manually shifted into 2 & 3.

Any ideas about what could be going on? (Other than a mechanical problem with the transmission.) I am running out of ideas of things to check. Is there something wrong with the tune still? Could it be an issue with wiring? I am attaching the tune I am currently using in case it helps to look at it.

-Tony

[Alvin]

Hey

There is no difference between 2wd and 4wd transmission tunes. The same file will run both and you want to be careful doing segment swaps back and forth. At this point I'd go back to the original file you saved from the PCM and write entire. Carefully.

The trans should have forward movement completely unplugged. Since it doesn't that eliminates something in the PCM as the biggest problem anyway.

I'm sure you've put a pressure gauge on the trans?

This sounds really dumb but I went back and forth with a customer for over half a year about this.... Nothing wrong with the rear end? For sure? Different situation but my guy's problem was his half shafts weren't engaging the rear end. Can't be the case really in a solid axle car like yours.. but he did 2 transmissions and literally like a half year back and forth before he found it.

[twinturbotony]

OK. The trans does have forward movement now when completely unplugged. I have manual 2nd and 3rd and reverse. I can use HP Tuner to command 2nd and 3rd, but I can't get 1st or 4th. When plugged in it won't drive in any selected forward gears without HP Tuner.

There is for sure nothing wrong with the rear end. Thoughts?

Hey

There is no difference between 2wd and 4wd transmission tunes. The same file will run both and you want to be careful doing segment swaps back and forth. At this point I'd go back to the original file you saved from the PCM and write entire. Carefully.

The trans should have forward movement completely unplugged. Since it doesn't that eliminates something in the PCM as the biggest problem anyway.

I'm sure you've put a pressure gauge on the trans?

This sounds really dumb but I went back and forth with a customer for over half a year about this.... Nothing wrong with the rear end? For sure? Different situation but my guy's problem was his half shafts weren't engaging the rear end. Can't be the case really in a solid axle car like yours.. but he did 2 transmissions and literally like a half year back and forth before he found it.

[dhoagland]

Couple of things
Did you know the donor vehicle? Was it driving correctly when it was retired?

Completely new Trans, did it include valve body?

Can you post a log with this happening and logging everything possible for the transmission

I can see your frustration not being able to tie all this together.

Like Alvin suggested have you verified pressures?
Do you have a schematic that you can trace all wire (signals coming to/from ECM to Transmission)

[dhoagland]

If I'm understand correctly commanding with Scanner you don't have 1 & 4
Could possibly be solenoid A.
But unplugged solenoid shouldn't matter? (Yes question mark, I'm not 4L60 guru) Lets say it doesn't, that takes me to looking at the spools in the schematic seeing what 1 & 4 have in common, possibly a dump valve or a check ball.
But if ya have a new VB that's pretty out there that the exact issues exist

EDIT... File too big. PM me an e-mail and I'll shoot it to ya
I didn't look very close but this manual seems to have hydraulic circuits draw out pretty well to start looking for common components that match your conditions.