Driveline vibe fighting - a little summary and a pic

[jms]

Here's a summary of my experiences regarding driveline vibrations that might help others...

2002: K5, 350/700R4/208 w/ stock suspension: no vibrations.

Spring 2003: a little buildup: 3"TC springs front, 1" d-shaft spacer on the front t'case output, 2.5" ORD shackle flip + 1" ORD Zero rate in rear, D60 ff rear axle swapped for the old 10-bolt. Spring pads welded for best fit by local shop, no precise measurements on my part but nothing looks out of the ordinary:
Horrible vibes on coast at 35-40mph.

Shim axle 5* down: bad vibes, same speed.

Shim axle 5* up (against better knowledge): bad vibes, same speed.

Move axle 1" forward: bad vibes, same speed.

Axle back to stock location, no shims, drop t'case down 1" by using the factory spacers: vibes gone, maybe a little at over 65 mph, bingo, everything fine. Put a third bolt between x-member and frame for good measure and called it good. Success. went 'wheeling.

Fast forward to BlazerBash'04: Hard hit on White Knuckle Hill where t'case skidplate and t'case x-member meet (if you hit somewhere, that's the place to hit...); result: whole x-member pushed upwards by about 1/2", bottom of frame rearranged from|_ to |/: vibrations are back, annoyingly so between 50 and 60mph, mostly on coast but depending on air pressure also while on the gas.

Winter '05: Replace transmission mount (old/marinated in ATF): vibes are little better, but still very annoying.

Replace broken u-joint cap at pinion yoke, put a fresh u-joint in at pinion as wellas at slip yoke: much better (having all the needle bearings does help), still very noticeable.

Spring '05: New pinion yoke (Mark Williams, upgraded to 1350): vibrations more pronounced.

Finally, three weeks ago: Got a 90* angle bracket out of 1/4" high-carbon steel to fit on the outside and underside of the frame for an even mounting surface and mounted it to the side of the frame with 3 7/16 G8 bolts. Used the rest of a 1/4" steel piece to cut 3 rectangles for each side which I stacked and drilled for the holes to fit the x-member; place the x-member 1" below the frame again (as in before the hit): vibratons almost completely gone, voila!

Perfectionism: while replacing t'case mounting bolts with new longer G8 hardware, I added one more 1/2" G8 washer (1/8"??): victory! Vibrations completely gone, smooth driving up to 75mph (above that it's really noisy with the MTRs and 4.56 gears), no vibes on coast whether I let off quick or whether I go to quarter throttle. Highway tested on a recent trip to Tuttle Creek ORV area in KS, 180 miles one way: smooth sailing, almost didn't make it back, but that's another story...

Here's a (admittedly lousy but taken with the el cheapo under-da-truck camera) pic of my contraption (just as a disclaimer: this is not fabrication - this is whittling...)

Thought about a rear CV d-shaft, but that is postponed until doubler decision is finalized...

Anyways, hope this helps someone, michael

 

[pauly383]

I only had to drive my truck to work once before I wimped out and put the CV shaft on Mr. Visa Card

Mine vibed at all speeds . I have had the shackle flipped rear since day one of the lift . Didn't want to mess with anything , I still drive mine to work daily .

If you do go CV , basically the pinion points almost directly at the transfer case , perhaps just a little down to allow for axle windup .

Since ya got it squared away , maybe copy the size of that shim stack you made , and either copy it to a thick one piece spacer , or have a crossmember fabbed up that same amount of drop .

Probably cost a lot less than a shaft

 

[jms]

The driveshaft issue will come up when (if?) I get a doubler (funny thing is everytime I think I'm close to doing this, some other financial obligation pops up and spoils the fun...)

But the plan is to get doubled up eventually, and then get a 1350 CV for the fixed output in the rear. That ought to do it for my sort-of 3/4 ton setup (or would it be 5/8 since the rear is a D60?). For the front axle, methinks 1310 (or whatever it is called) is fine as long as there's the 10-bolt in there. That reminds me to look the axle over anways; I had more than a couple of very hard bounces last Sunday. I usually don't do this, but if this comes up again, I may have to rethink that Sheetmetal Gang thing....

 

[gone huntin]

Well, I tried everything but that, 5* shims and all. My cv shaft should be here any day now.

 

[mouse]

The 1350 joint (by itself, not CV) has a smaller working angle than the 1310 u-joint, which probably made the problem worse when you switched. It seems your u-joint angles are out of phase and you have suceeded in fixing it by the excessive T-case lowering. I would want to gain the clearance back, but that would mean buying a CV shaft.

 

[jms]

Not sure the max. working angle of 1350 vs. 1310 is an issue on the highway, I'm not close to that at all.

I wouldn't call lowering the t'case by 1 1/8" excessive. Usually, nobody wants to hear that lowering the case is a valid means to fix a vibration issue. Actually, that's exactly why I posted this - in a search, all the recommendations usually are 'buy a CV shaft' - which may not be the solution for everyone. Neither may be my approach, which admittedly is a $36 'hack' around a $200 problem.

For me, high-centering in the middle has not been a frequent or problematic issue, and in fact, the ground clearance has not been affected much by lowering the t'case: the exhaust y-pipe is the main culptrit on my truck re ground clearance. I'll get the ground clearance under the 'case back once I get the new t'case setup; as long as the 208 is in there it doesn't seem anything else is warranted.