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85 GT Vibration issue

997 Views 3 Replies 3 Participants Last post by  Chief2Horses
Gonna try my best to describe what's going on.

There is nothing noticeable until I reach any speed over 50 MPH. Once I'm over 50 there's a vibration coming from the drive train. If I push the clutch in it's even more pronounced. If I put the car in neutral it's even MORE pronounced. As soon as I put the car back into gear (any gear) the vibration goes 90% away.

The engine and trans are mostly stock. All I have done is a carb and full exhaust. The trans mount and harmonic balancer were just replaced.

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What I've always been told, not by experience myself, this could be a couple 3 three things.

1.) Pilot bearing on the Trans Snout, where it sits inside the Crank. It can be broken but still work, you will get vibration at certain times, usually in neutral or vice versa. It has needle bearings that fail. Older Cars, before the needle bearing style they used a solid "bushing" style(vs. bearing), which is what I put in when I do clutch job overhauls. No bearings, it will last 3 clutch jobs and never fail. Its made of Oilite Bronze, oil impregnated bronze. Doorman makes one PN#690-033.1, what I have now. McCleod makes them too but they're literally 8X the price and the same thing.

2.) Crank Damper(Harmonic Balancer) itself. Look at the "ring" of rubber your damper. There is a rubber isolater(thin layer) that keeps these two together. If its buldging or looks cracked or seperated its no good. Mine is currency bulding and Im getting a vibration in neutral above 4k. Same when in gear above 4k also. Try to find a balancer thats new, then look at yours, you'll see the rubber is flush and straight on the new one compared to one second gear hero drove. --------I would suspect this is your problem, I hope, otherwise you gotta pull the trans and everything, flywheel to get to the other $7 part.

3.) I've heard a flywheel can do this by one person, but I don't see how, mite be possible but I've always concluded with the first two scenarios.
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Drive shaft out of balance? Crappy U joints?
Drive shaft out of balance? Crappy U joints?
Ahh.. Yes he's right, your symptoms sound more like what 90lx mentions, my symptoms are in neutral and revving at a stop.
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