Jacob Vaughan

I have a 97 camaro with lt1 and 4l60e.

The drive shell failed, so I pulled the trans and rebuilt it myself.

After reinstalling the trans everything worked except I have no lockup. Only trouble code is p1870. I confirmed lockup is being commanded by computer using tech2. Confirmed solenoid actuates when lockup is commanded.

I replaced the valve body and solenoids, didnt solve problem. Replaced torque converter, also didn't solve problem.

Now I'm completely out of ideas, did a pressure test and everything is perfect.

Car is bone stock with no modifications.

KChevy75

Any other codes even though not trans related? Engine misfires can cause tcc to not apply.

If you have a tech2, put it in bi-directional mode and manually apply tcc. If you can feel the torque converter actually locking up, check for misfires.

I was going to say tcc valve components installed incorrectly but you replaced the entire valve body already.

What did you use for the trans fluid?

Did you rebuild everything? New bushings, o-rings, ptfe seals, etc?

A missing, slipped or damaged o-ring on the stator input shaft can cause this.

You can try modifying the pwm solenoid so it's basically just an on/off. This involves notching the last two pieces of plastic and removing the o-ring. Don't go into the o-ring area as you can reinstall the o-ring and go back to pwm mode. If the TC still doesn't lockup, o-ring is missing/damaged/moved, electrical issue or something was missed during the rebuild.

Jacob Vaughan

Thanks for your response!

Just used a generic dex3 full synthetic fluid.

Yes I rebuilt everything, all new seals, bushings etc.

When i did the initial rebuild I installed sonnax oversized tcc regulator valve as a precaution. After vacuum testing the valve body I ended up just throwing 'hail mary' parts at it as I've exhausted all troubleshooting steps in the manuals.

I have a spare PWM solenoid so I could try that method in the video you mentioned, interesting idea, although both valve bodies have the sonnax valve installed so not sure if it will work with that.

Looks like i'll be pulling the trans for a third time, will replace the pump. Thats the only other thing that I can think of that could be causing the problem. There is obviously a massive leak in the apply circuit, or the exhaust isn't exhausting properly.

I also applied compressed air into the input shaft and actuated the tcc apply valve manually, can hear a sizable exhaust sound change when actuating the apply valve, which is what it is supposed to do. This is so bizzare.

KChevy75

The pwm mod should work fine with the Sonnax oversize tcc kit. I did the TCC Regulator & Isolator Valve Kit (77754-04K) on mine along with the mod and it works as expected.

Some history of what I did with my 4l60e for a similar issue but no code and tcc slip was within specs. My suburban was having a shudder under load upon tcc lockup starting around 285,000 miles. I wasn't sure if it was trans, torque converter or engine. Code reader showed only a large evap leak which I had put off fixing since it's a bit of a pain (I've done it 4 times now). Advanced module code read showed nothing engine or trans related. I needed a way to prove it was the trans or torque converter and not the engine as I don't want to swap parts without actually diagnosing first. I had previously replaced the plugs 11,000 miles ago so I didn't bother checking them. After finding no engine related issues, I finally pulled #1 out and the supposed iridium tip was nothing but a nub. Pulled #3, same thing. Pulled the rest and they were all nubs. All counterfeit, probably wires as well. There were no misfires registering, however. I thought I found the problem. Replaced them and the wires with genuine parts. Nope. Problem persisted.

There was no doubt this was occurring upon TC lockup only but engine related issues can cause tcc lockup issues. With the engine eliminated at the cause, I focused on the trans. Before I even did any engine diags, the trans was due for a full flush so I fully flushed it, changed the filter and swapped the pan with one that had a drain as I knew I'd probably be opening it up several times. Absolutely no change in the shudder.

For diagnostic purposes, I added 2 tubes of LubeGard Instant Shudder Fix. No change. I added a third, no change.

I took the valve body out and went through it fully. New gaskets and separator plate as one hole was enlarged a bit by the ball. Replaced the PWM solenoid and reinstalled it. No change.

I then did the Sonnax 77754-04K kit as it had 290,000 miles on it and was showing some wear but not much. No change.

Line pressure in all gears was within specs so pump appears to be good. My understanding is it takes very little pressure to apply the tcc clutch anyway.

All I could come up with to prove it is most likely torque converter related was to perform the pwm mod. After putting everything back together, the shudder was completely gone. The torque convert fully locks up no, no issues. We even pulled a fully loaded trailer (about 3,500 lbs) up a few mountains with no slippage. The only thing, however, is you can feel it lock up and unlock. I don't have a lift so getting the trans out it a real pain and I'm not looking forward to taking it out a fourth time so it's going to stay as is unless something changes.

The torque converter has 90,000 miles on it as I replace it when the sprag broke. I have a feeling the reman unit was rebuilt with cheaper clutch material instead of the proper carbon fiber clutches. If I ever do have to replace it, I'm going to cut it open to see what the problem actually is.