Under acceleration, vibes in my butt!!

Hello, still working on all these issues with my recently purchased 98 classic. Under heavy throttle i get alot of vibes comming up through my seat from underneath.could this be bad ujoints?? i hope its not the engine! the engine is smooth otherwise..........hmmmm
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witstick said:

Hello, still working on all these issues with my recently purchased 98 classic. Under heavy throttle i get alot of vibes comming up through my seat from underneath.could this be bad ujoints?? i hope its not the engine! the engine is smooth otherwise..........hmmmm
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Yes, it could be U-Joints or motor/transmission mounts.

Yes - unless everything is balanced/just right, you will get 'some' vibration in the driveline. ( - part of my day job is driveline analysis)

If U-joints are worn, you might also hear or feel a 'clunk' whenever you suddenly accelerate or let off the gas. Just get underneath and check them.

If the motor or trans mounts are worn, whatever natural vibration there is will be worse. Again, just take a look. If they are mashed or cracked and split, that might part of the problem.

If your rear springs are worn/sagging, you could be getting some axle wind-up, which would throw off the alignment and give you some pretty strong driveline vibrations.

You didn't mention any suspension mods, so assuming everything stock. Raise the suspension and things get worse.

Vibrations in the butt?! Thats an easy one. Just try to enjoy it and carry some baby wipes to clean up the mess.

yes i can feel a clunk when i quick get on or off the gas, indication of bad ujoints? i got undeneath and tryed to see if any play but i couldnt feel anything by hand..........

Yep, more thank likely the U-joints. I drove my Toyota through some deep water and (shame on me) did not grease the joints afterwards. Took about six months and the rust just chews up the needle bearings.

It could also be wear on the ring and pinion, but that seems unlikely for a '98, unless its got a ton of miles on it, and it wouldn't (or shouldn't) contribute to vibration when you hit the gas.