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Old 10-16-2010, 06:28 PM   #1
MOPWR2U
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Diagnosing Driveline Vibrations?

I've got a slight driveline vibration in my Jeep Wrangler. The Jeep has a 2.5" lift with CV driveshafts at both ends. To try and eliminate the vibration I have adjusted my control arms so that the angles are correct both front and rear. The pinion is exactly 1/2 degree down from pointing directly at the transfercase.

Doing this did not change the vibration, which is a just barely noticeable lower frequency thrumming vibration that occurs at 40 mph, and then goes away. Vibration recurrs at 80 mph and is twice as noticeable, and at a higher frequency at that speed. The dual frequency character of the vibration made me think it was due to a harmonic vibration from a driveshaft angle issue, but the angles are correct. I've also tried moving the pinion up and down a few degrees, in ~1 degree increments in each direction, and it does not change the vibration.

I then took the front driveshaft off and took the Jeep for a drive, ... vibration was the same.

I then put the front driveshaft on, took the rear driveshaft off, and went for a drive, ... vibration was the same.

I can't talk my wife into driving the Ram 3500 with my Jeep hooked to a strap, and towing my Jeep at 80 mph with no driveshafts on the Jeep. If I still had vibration with both driveshafts gone I would know the vibration is in an axle, and not a driveshaft.

What I'm trying to determine is if I have a vibration in BOTH driveshafts. Perhaps when I remove the front driveshaft I feel the vibration in the rear driveshaft. When I remove the rear driveshaft I feel the vibration in the front driveshaft. Both driveshafts are essentially new (4000 miles use, never damaged, and supposedly balanced when they were built). The rear driveshaft is a Tom Wood driveshaft, and has no balanced weights on it, and I can't see a weld where a balance weight has been. The front driveshaft is a Six States driveshaft with Terflex yokes, and has a balance weight in place.

So, how would you go about diagnosing this vibration? Would you A) get someone else to tow you in your Jeep at 80 mph? B) take both driveshafts to the local driveshaft shop and have them re-rebalanced? C) buy a set of bias ply super swampers so I cant feel the vibration? (ie. don't worry about it) D) something else altogether?

Thanks.
__________________
2014 Wrangler Sport: Teraflex 3" suspension lift, Fox 2.0 reservoir shocks, Tom Wood 1350 driveshafts, Dynatrac Dana 60s w/ 4.56 gears and Eaton electric lockers, Warn front locking hubs, Currie Anti-rock front swaybar, Fox ATS, 35" Toyo MTs on 17x8.5 Fuel Anza's, Poison Spyder bumpers and rocker guards, Warn M8000s winch, Teraflex tailgate hinge & spare tire carrier

Last edited by MOPWR2U; 10-16-2010 at 06:35 PM.
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