chevrev

iTrader: (2)

Just got my LS1/4l60e into my 57. Runs great, smooth, powerful ,etc...BUT, when I really get on it and accelerate hard, there is an aweful grinding noise. It sounds like its under my feet (tranny area). My first suspicion would be the transmission. It was a fresh rebuild, but maybe not a good one??
Otherwise, it seems to shift fine and run out well, but that grinding noise has me worried!

Any ideas????

55chevy

iTrader: (6)

I would look around the driveshaft and other areas to see if you have any clearance issues when the engine is under torque. Also, if you can see the flexplate, look for rubbing or loose bolts on it that could be rubbing.

BadVRod

Might check your rear end. Mine made a nice grinding noise right before it locked up.

55chevy

iTrader: (6)

I was just thinking about the rearend and driveshaft length when I read this other post.. https://ls1tech.com/forums/conversio...sion-case.html .

Jimbo1367

good idea.

chevrev

iTrader: (2)

I jacked the rear end up and noticed that the floor pan tunnel just above the universal joint where the drive shaft meets the c4 differential has some gouging/scraping in it. The drive shaft/rear end joint must be flexing enough to touch it when put under a heavier load (ie, hard acceleration) to touch it. Hopefully this is the problem and the tranny is fine! We'll see...I'll make some adjustments/modifications so the universal joint can't make contact with the undercarriage and see if that solves it.

gofastwclass

iTrader: (2)

Sounds like the car must be lowered. I've had that problem when the pinion angle was screwy or the car was lowered too much for the available transmission tunnel clearance.

55chevy

iTrader: (6)

I'm not familiar with the c4 diff but I would think that there is some type of torque arm or stabilizer that helps to hold the pinion down during high torque. I still have my leaf springs but I have Caltracs that prevents the rotation of the axle during takeoff. It sounds like you are on the right track, good luck.

chevrev

iTrader: (2)

Just wanted to post an update on this issue. Redesigned the rear diff mount to give it more stability.

No more grinding noise when I accelerate!

rtsland1

what was the remedy? having same issue w lowered ss