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.
Pretty good list but I will add to check your engine vibration damper. If you have the 68 or later style with the rubber ring sandwiched in between and if the outer metal ring has slipped and clocked in a different position. if it's way off you won't find your timing marks even near where they are supposed to be but if it only slipped a little can be hard to detect with a timing light and you will manually have to find tdc on # 1 and check for alignment. The second suspect of the top of my head is the torque converter and if they properly re balanced it after separation and reweld.
Always big thanks for your replies. Mine is a 67 so I am not sure whether vibration damper applies. However, in search of this particular part within the pubs I have been less than successful. I do not see it in either the parts guide or the service manual in engine sections. Am I looking in the right spot? I have a video of the motor dynoed and the guy is all over it with a timing light. I will run my timing light on it to see if I can get a good reading.
Is dropping the trans by itself a hard procedure? That bell housing seems hard to reach.
They all use a balancer/damper but 67 did not originally use the rubber ring type but over the years who knows what has been done to the motor. It is the round thing with the timing mark on it and bolts on to the front of the crank. Just do a search and you will find some good pictures of it to help you understand. As far as the trans. I've done many on my back without a lift and with everything being new and clean will be a breeze. Whatever bellhousing bolts you can't reach from the top just use a long half inch drive extension and a impact universal from underneath. Before you pull anything though you need to talk to the shop who did the trans and find out the story with the converter.
Sounds like a balance issue to me given the rpm specific excitement. I would disconnect the torque converter from the flywheel, making sure converter is clear of flywheel and crank pilot and start the motor. If problem remains it is the motor. If problem disappears it the trans. Since it does it in park or neutral I suspect the converter. Remember, it spins with the motor.
