NBM-WU8

iTrader: (2)

Hey guys, hoping for some insight on what might be going on here. My dad has an 88 Monte Carlo SS that we swapped a Chevrolet Performance Crate carbed LS3/515 and Supermatic 4L70E run by a Compushift Trans Controller.

We have put a couple thousand miles on the car and had a "slight" issue making the trip back from LSFest 2015. Something started to "bang" violently. We pulled over, looked the car over didn't find anything. When we took off again, as soon as it locked up in 4th gear, it started doing the same thing. We ended up trailering the car home and it sat until this winter when we finally started checking it over.

With the car on jack stands, we ran it through all the gears and everything went well until it locked up in 4th. The banging started again. I then disabled TCC lockup and ran it through all the gears to find that everything went smoothly. We drained the fluid and didn't find any signs of it being burnt and no extraordinary amount of metal that we were expecting, no large chunks etc.

Assuming it was a torque converter issue, we sent it out to be checked out and they were not able to find anything wrong. I've done a bunch of searching and haven't really come across anything that sounds like our issue.

Does anyone have any ideas on what we should be looking into or looking for?

wht/73

Did you try calling Mike Hoy at Compushift 1st?
That would have been my 1st call before posting here.
Especially since you disabled the lock up.
Mike is VERY helpful.
My triple disc locks up pretty hard in my 80E
It could be something else besides the trans and you can only feel it when it's locked up.
Maybe u joints going south or u joint straps not tight.

mOtOrHeAd MiKe

iTrader: (8)

If the controller cannot manage TCC lock-up with PWM functionality the TCC solenoid is going to come on at 100% and effectively dump the clutch. Truthfully, this is normal.

NBM-WU8

iTrader: (2)

I should have been a little more specific in regards to the "banging". It is not just One bang when it locks up. It was a constant, repetitive banging. While we had it on standings running, it sounded as if it were coming from the bellhousing area as best as we could tell

I didn't even think to call compushift before we pulled it apart. I called and spoke with him the other day and he gave me some things to look into, most of which shouldn't be the issue. U-joint straps were tight when we pulled it out, motor and trans mounts were all tight. The convertor should be showing up tomorrow so we'll have to put everything back together and give it a shot again.