Sorry in advance for the novel....

I’m really at a loss here. I’m working on getting my Chevelle running right and I’m having transmission problems.

I’m running a LQ9 6.0L mated to a 4L80E trans controlled with the stock pcm using a file for a 2002 Chevy truck with a 6.0L/4L80E combo, programmed with EFILive.

Here’s the problem, I can’t get this thing to shift right. It will only shift from 1st to 2nd and it will only do so when shifting manually rather than putting it in D4 or D3.

I have two transmissions and they’re exhibiting the same symptoms. Here’s what I’ve done so far.

Installed transmission 1 with new filter and fluid. Not shifting into 3rd or 4th. Checked fluid level, ok. Took the 2-3 shift solenoid, 1-2 shift solenoid, TCC PWM solenoid, and Transmission Fluid Pressure (TFP) Manual Valve Position Switch from transmission 2 and put them in transmission 1 to see if this fixed the problem…it didn’t. The only electrical solenoid that I did not swap was the Pressure Control (PC) Solenoid Valve due to having a different connector.

I thought it might be an internal problem so I swapped in transmission 2 hoping the problem would go away…and I’m having the exact same symptoms.

I checked all the electrical connections between the pcm and the tranny and everything seems to be in the right place, and there are no shorts…I plan on rechecking this though. I manually triggered all the solenoids in both transmissions and they all clicked and seemed to work fine, but I’m just judging based off of the sound.

I added enough transmission fluid into transmission 2 that it started puking it out, so I know it’s not low on fluid.

I tried putting in a different file in the pcm (full reflash) and this had no effect.

I’m at a loss now. I plan on rechecking all electrical connections and am going to datalog some transmission parameters to see if the pcm is even triggering solenoids when it should.

Can anyone shed some light on what I might be able to look for?

Seriously frustrated and have done a lot of work for nothing so far.

Max

 

Ummmm....Not sure what's going on there, but 2 transmissions with the same problem says to me that the transmissions aren't the problem.

What did the wiring harness come out of? I don't know of any LQ9 applications that ran an 80E, I thought they all ran 60E's.

If it is formerly a 60E harness, did you re-pin it for the 80E? There are a couple of pins that move around (I know on the trans end, and I think the PCM end too).

'JustDreamin'

 

I'm thinking the same thing that it's not the trans which is good. You are correct on the harness, it was for a 4L60E and I repinned one pin at the pcm for the big connector and added the VSS connector, but I have to recheck all that stuff for a third time today. Thanks for the reply

 

Did you add a VSS or the ISS sensor (vehicle speed or Input shaft speed)? Both the 60 & 80 run a VSS signal, but only the 80 runs the ISS.

I know the 80E and 60E use some of the pins in the big gray (trans end) connector differently. For mine, I had to move a couple pins because I didn't get TC lockup.

Not sure what's going on with yours. Sounds like you must have power and ground, because its making a shift.

'JustDreamin'

 

Check out this thread

 

I added the ISS sensor connector to the pcm. I moved a couple of pins at the pcm for the big gray connector, but I'll have to check the specifics of what went where and I can't find that diagram at the moment. I'm thinking it's just a pcm pin problem. Agreed on the power/ground situation.

 

Thanks for the link

 

Did you remove the unused pin from the 4L60E connector? Do you have access to a scanner to see which codes are showing up? If you get a code, there is very good information available for diagnosing the issue.

 

Yes sir, removed two unused pins for the 4L60E and moved one to the correct position for TCC PWM. I was just getting ready to do some datalogging and check for codes when I found this...

 

Well, I think I found the problem. I was checking all my wires that go into the trans from the pcm for continuity and found a problem with the connector going into the VSS sensor (output). I pulled the wiring for this sensor which still had what I believed was the stock looming on it, opened it up and found that both wires were totally chopped to ****, i.e. disconnected. I didn't think to check this to begin with because it was part of the stock harness and I believed was untouched. Just goes to show you need to check EVERY electrical connection for continuity. Hopefully this fixes the problem I'll update when I get this fixed. I'm sure glad I broke my back the last couple of days swapping transmissions

Max

 

Thats truly sucks! But no VSS will definitely keep the tranny from shifting...

 

Yay! I've got 4 gears now. Time for tuning, and I'll be adding a running video to my build thread. Thanks for the input guys.

 

It certainly does, I can't figure out how the wires could be chopped up and still be inside the stock looming, though it apparently couldn't be stock anyways. I'm just happy it's working now