Vibration only when downshifting.....

[waterboy1976]

Ok well here we go.....baby is done and back on the road...now whenn cruising coming up to a stop sign I depress clutch...downshift from 4th to 3rd let out clutch and get a semi serious low vibration....same from 3rd to 2nd..........now....when I upshift...1-2, 2-3,3-4 no vibrations what so ever even through heavy RPM's. Everything is new, u joints, clutch, tranny rebuilt, engine, everything....balanced and good...no vibrations at speeds....5mph to 75 mph...is this a clutch adjustment issue? or what?....Im thinking I have the clutch adjusted out too far and it engaing to the flywheel too slow.....any ideas????

 

[wishuwerehere82]

The only thing that comes to mind at this time that would be negative torque related is motor mounts. If one side is broken, the engine would rock up on decelleration but not on acceleration. But I would assune you replaced them with the rebuilt engine. Hmmmm......

 

[JohnZ]

Did you replace the diff nose mounting bracket-to-frame bushings?

 

[waterboy1976]

motor mounts: Energy Susp Poly

Rear end snubber bushing all new too....

Tranny mount new too.....

Im gonna go drive her today and see if there isnt a Vibration on acceleration that Im not paying attention to...that will open up more options....

 

[waterboy1976]

UPDATE..........


What if when I put it back together, I put the driveshaft in backwards?? Like front to back???? I discovered yesterday after looking at the driveshaft I have the front mounted in the back and the back mounted in the front......The vibration is when I upshift AND downshift.........not just downshifting like I spoke of earlier, but its more present when I downshift though......

 

[Vettehead Mikey]

You may want to get the driveshaft check balanced, if not already done. Your poly engine mounts are not doing you any favours here either.

 

[waterboy1976]

You may want to get the driveshaft check balanced, if not already done. Your poly engine mounts are not doing you any favours here either.

Poly mounts....Really? Ive never heard that......Why? Im learning here help me out.......THey are the red mounts from Energy Suspension...I thought those were the best.......Ive talked to two driveline guys and most recommend flipping the driveshaft and have it balanced.......what about those mounts though??? Thanks...!!!!!

 

[Bill75]

You might want to try the balancing as Mickey suggested, I had mine done about 3 weeks ago after noticing the exact same symptoms you mention. It made a VERY noticable difference. They moved the weights on mine about 1 1/2 inches from their factory position.

Bill

 

[ruby76]

flip the driveshaft first before you go and waste money on balancing it. If just flipping it makes the difference youre not out any money. I've had bad vibrations in my old truck before and solved it by rotating how the tq converter mounted on the flywheel by one bolt (120 degrees) The flywheel/tq converter must have been matched or something. If you flip the driveshaft and still have the vibration, then you can pursue the other options.

 

[JohnZ]

Poly mounts....Really? Ive never heard that......Why? Im learning here help me out.......THey are the red mounts from Energy Suspension...I thought those were the best.......Ive talked to two driveline guys and most recommend flipping the driveshaft and have it balanced.......what about those mounts though??? Thanks...!!!!!

Engine mounts are engine mounts, (as are trans mounts) and have nothing to do with performance; OEM and poly both attach the engine to the frame, but the OEM rubber mounts isolate engine noise and vibration from the frame, and poly mounts transmit driveline noise and vibration into the frame.