Oldguard 7

Yesterday one of my friends came by in his 77 to ask me if I can hear a faint "thump" under acceleration. I asked him when does it occur; he said at 45 mph. So I ride with him and he steps on the gas (in drive range), you feel the upshift but then I heard a faint thump as the car accelerated his vehicle (continued to pull steadily as RPM increases)

Today I got in my corvette (79) and hit the gas I feel the upshift, no thump and my vehicle continues to pull steadily as RPM increases. We both have th350 trans. What could be the issue with his vehicle... modulator, kick down cable?

riverracer au

maybe the front diff rubber mount is worn??

hugie82

Did 77 have a lock up converter?

garygnu

have your friend check all mounts ,and suspension parts for any play .

jnealg

check the engine mounts, tranny mount, u joints, diff mounting bolts.

I think I had a prob of some type with every component. once I tightened them up or replaced missing/worn bolts i lost my thump. the biggest change was replacing the tranny mount. take it off and look at it. dont look at it while its mounted and assume its good.

scrappy76

Same here, had a thump that got worse, ended up being the tranny mount. I replaced it along with the diff snubber. All is good.