vibration when in 4wd on cj7

[bksmith]

ok, i'm stumped. I have a "shimmy" or a "vibration" when in 4wd on my '7. It only happens when i shift the transfer case into 4wd

(not when i lock the hubs and have the tcase in 2wd [thus, it is not front driveshaft vibration])

so i'm thinking maybe the transmision mount is soft or torque is affecting the transfercase to transmission connection somehow

4.2 I6
sr-4 transmision
d300 t-case

stock driveshafts, and usualy happens in 2nd gear when accelerating

thanks.

	Transfer Case Mounted behind and driven by the vehicle transmission, the transfer case transmits power to the front and rear driveshafts in 4WD Jeep vehicles and offers high and low range.

[hi_c]

Not sure about those old CJs, but I'll list the obvious checks that we sometimes overlook when frustrated by vibes... also you're not using 4wd on pavement, right?

Motor Mount
Tranny Mount
Worn Universal joint(s)
Tires - balanced/aligned/pressure check
Worn Bearings
low fluid in T-case

Again, these are the obvious. Good luck. I hate vibes.

[MOngo1970]

It seems to me that it would be a component that was static when in 2WD and dynamic in 4WD...the only thing I can think of that fits the discription would be the drive shaft. A thorough inspection of the front drive shaft looking ftom the T-case to the Diff for anything bent or missing that would throw it's ballance off.

[Deerhunter30]

I like MOngo's line of thinking....I was also thinking front driveshaft. Sometimes they can get bent and cause from a little to a lot of vibration in the front end.

[BakedAlaskan]

With the t-case in gear you are adding pressure to the front driveshaft and 1 if not both axle u-joints. This will defintely add vibes. I replaced both my axle joints. One was obviously toast, the other appeared tight. Turns out too tight, you couldn't move it by hand. Replacing this made mine go away. But I did mine since I was in there doing bearings hubs rotors, etc.......

I would bet replacing the front driveline joints will solve it since they are more apt to cause the vibe your descibing. I would look at it first. Beside it is easy compared to the front axle joints.

[bksmith]

I have just replaced my front axle u-joints like a month ago but this is the first time i have truly had it in 4wd. (it just snowed here in KC, GO CHEIFS!) the ujoints in the driveshaft are all "spinning" free and lubed up. I don't know about the front axle though, i know they could do with some fresh grease.

on the driveshaft...
i drove for 3 days with the front hubs locked so that my front driveshaft would spin but while still being in 2wd that i felt no vibration. the vibration i feel in 4wd is mostly felt through the stickshift and the transfercase lever. it feals like the the torque of the engine is twisting the trany and t-case... this is what led me to believe some of the old rubber mounts are bad.

thoughts?

[phatyaspen]

ya man i would check you tranny and tcase mounts, that would cause a vibration in the shifter

[hi_c]

Please refer to my original list of checks:

Motor Mount
Tranny Mount
Worn Universal joint(s)
Tires - balanced/aligned/pressure check