Having a problem with a vibration on my 67 firebird. Engine was quarantined in a reputable machine shop for 14 mos for rebuild. Motor was dynoed and shipped back to me Covid free back in Oct. I had the transmission rebuilt with a reman torque converter installed. Rebuilt P/S pump and gearbox, alternator, new AC compressor installed but not operational. U joints installed by me. My son and I installed the motor/trans together. Used Mity Mounts for engine and new mount for Transmission. During engine/trans install, passenger side mount stripped. Removed the mity mount and installed a napa mount for $9. Mity mount sent me a replacement which arrived after installing napa mount, so 1 NAPA $9 and one Mity Mount is what’s holding up Betty. No muffler, just an exhaust pipe right now, so very loud. OEM with 2 resonator and transverse muffler dual exhaust in box to be installed, which was decided from a previous post, but hesitating installion because of vibration. Exhaust pipe is the old one, and it is attached at exhaust manifold, and then held up by a hose clamp which is attached to the old exhaust pipe hanger (rubber btw pipe and body) behind driver rear wheel.
I am getting a vibration felt through the steering wheel, and floor board(body). I noticed it first while driving right before the transmission shifts at 25-35 MPH, then again at 40-50 MPH. At 60 MPH it’s smooth. Thought it was U joints at first, because when going into neutral the vibration went away. Went to a local trans shop and owner told me after driving it that he thought it was in the engine, but not in tranny. He noticed that in neutral, AND park, the vibration occurred at a specific RPM. No tach, but tried it at home with a diagnostic tach and it seemed 2500 was the number.A vibration like this would be noticed during dyno, but could have developed a problem since. Still I think it was something I did, or added. When I picked the trans up from the shop after being rebuilt, he included a reman torque converter. I didn’t like the looks of it. According to him It was cut open with a torch or grinder, cleaned out then welded shut. It wasn’t what I would want to pair with a newly rebuilt trans, but shop owner said that he could not find a new one.
Here is what some people have told me it could be:
It’s happening in park, which removes the tires from the equation. Remove PS pump, alternator, AC, water pump (new) belts—Already tried this Something is loose. Check all drive train connections Check spark plug wires for correct order. Check spark plug wires for arcing, remove from loom. Check motor mount, install new mount on passenger side Check oil pan, associated engine parts, and transmission are not contacting frame Check torque converter: Remove flywheel cover, take off three bolts holding torque converter to flywheel. Move converter away from flywheel, and do engine run up and see if vibration occurs.
Is there anything else that you would recommend I check that is not contained on this list? I am really stumped by this. When I run out of things to do on this list I will have to check the motor, so I hope it doesn’t come to this.
