Help With Violent Vibration

viberation

i would look again at ds...yes you say you changed u-joints

many guys dont install them right,,,here are some common problems

pin fell over in cap and joint isnt completly in,,,snap ring should be in groove,,

u joint is too tight,or loose,,,i have even seen 1310 installed in 1330

using a press the wrong way will bend ears on yoke,,

i also find that on alum shafts when ujoint is removed the cross will leave 4 burrs that need to be filed down before re installing ujoint,,it will cause a binding feeling with joint

important,,,the shaft must be rebalanced after change of u-joints,,,it is just like a tire

driveshafts by spicer

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Dana Holding Corporation The Expert Librarian - Information for driveshafts, u-joints, axles, heavy axles, light axles, Drivelines


scroll down to j3311-1 driveshaft installation manual

Just wondering if the pinion dog bone has been removed. Could this be an easy solution for the vibration? I wonder....

Also, how may ppl out there actually have their drive shafts balanced after a U-joint replacement? How many shops (short of an all out race shop) actually have the equipment to balance a drive shaft?

Heck even the Ford service manual doesn't have a step "balance drive shaft" under U-joint replacement.

Question? How long has it been since your rear differential has been serviced? How hard are you on it?

From my personal experience I have had a number of issues with the service life from Ford 8.8 rear ends. I don't race and I don't abuse it (well not too much). I do perform more frequent service than Ford recommends. Yet both of my Mustangs have rebuilt rear ends (80k and 145K miles).

If this were my car would put it on axle stands and run at idle. If the car has traction control, disable it. This will also make the dash warning light come on. Don't worry about it. It will clear on it own after a short while of normal driving.

Use a mechanic’s stethoscope and probe around the differential housing near the pinion. Listen for the roar of bad bearings. Next carefully probe around each axle tube. Again listening for the roar of bad bearings.

Consider inspecting the rear diff gear oil. Examine the sump for metal. For a serious inspection, pull the half shafts and carrier. Inspect the load bearing surfaces of the half shaft. If not smooth, replace. Inspect the carrier bearing race surfaces. They should be mirror smooth.

If the half shafts are damaged, it is possible to get a "service replacement" wheel bearings. The service replacement relocate the bearings outboard of the factory location. This may allow a worn half to be saved thus saving $$.

If no problem found, disconnect the drive shaft and check the pinion for excessive in/out up/down play. If done while the carrier has been removed, it is possible to get a better "feel" of the pinion bearing's condition.

The pinion bearings are much tougher to replace. Wheel bearings and carrier bearings are much easier.

Checking motor mounts and transmission mounts have already been mentioned. Don't forget, if the factory mounts have been replaced with after market units, sometimes more NVH should be an expected result. After all, there's no free lunch.

There is a procedure in the Ford service manual to isolate suspected drive shaft imbalance. It involves using hose clamps installed around the DS. The clamps are rotated in a pattern to try and determine the best balance point. It's a detailed labor intensive trial and error process. Taking good notes is important to get better results.

The importance of tires, shocks, and bushings should not be overlooked as possible vibration sources.

For drive line NVH issues it can be a real PIA to track down. Sometimes taking the car's history into consideration can help narrow down the possible sources. Again, there often is no "easy" answer.

Well said burns. I didn't notice the driveline vibration until after a clutch replacement a few months ago. Factory clutch grenaded after a missed shift into 3rd (car had about 130K miles on it so it was due anyways). Hard to say if the vibration was before the clutch replacement as I was able to limp it home by matching revs and shifting without using the clutch. Later I was able to get it into first after some help pushing it down the street to get it to the shop.

The rear was rebuilt w/ 3.73's (including all new bearings, and a trac-loc rebuild) at around 100K miles, and last summer I installed the FRPP aluminum D/S.