Possible Drivetrain Issue?

[Ddmax]

I have a 4 speed AMC 258 i6 / 4.2l 1985 CJ7 that started vibrating off and on at speeds of about 35 mph and up. It started a couple weeks ago when it would sometimes (sometimes it was fine) do it at highway speeds in fourth gear, but today it has done it at lower speeds in 3rd gear. Only occurs when I'm into the gas, not in neutral. No scary noises associated with it, just the vibration. Vibration is not just in the steering wheel.

Any ideas on what might be causing this? I assume drivetrain related....any help would be appreciated.

 

[Lumpy Grits]

Ck your U-joints for wear.
When was the last time you lub'd them.
LG

 

[Torxhead]

A good way to ruin driveshaft u-joints is to have an out of alignment drivetrain. Like tired motor mounts or improper alignment caused from high lift springs. Axle u-joints can go bad from poor lubrication also. The Dana Spicer brand would be the best replacement. On the trail, having spare axle and driveshaft u-joints and the tools to replace them is a good bet.

 

[NorthwestCJer]

clutch!

 

[Hedgehog]

Clutch, maybe, does he feel it in the pedal? If not I'd be looking at U-joints. Don't get all panicky if they have gone bad. U-joints have a Limited life all by themselves. Get panicky if they are fairly new, but if they are old, clean the joint up, replace them and be happy it isn't anything serious.

 

[hagar]

U-joints have a Limited life all by themselves

I've never seen any wear out from too much grease.

 

[Hedgehog]

I guess I'm a little confused, nobody or I certainly didn't say the joints were over greased. How good are you at always greasing your U-joints. Lets consider this, it's commonly thought that grease fittings weaken U-joints so most U-joints have no grease fitting. You may be the type that will remove a perfectly good joint to refresh the grease, but I'd be willing to bet there are very few people that do. Even if the joint has a fitting they are notoriously difficult to actually use. So, I will stick with the thought that U-joints wear out all by themselves. I also stick with the idea that you should worry about drive train problems if your joints are wearing overly quickly.

I'm sticking with the suggestion to check the U-joints for wear. If they are good, they are good and you can eliminate them as being part of your vibration.

 

[Lumpy Grits]

OP-Have you had the drive-shafts out lately?
What recent mods have you done to the suspension etc?
How often do you grease the u-joints and slip splines?
Have you ck'd ALL the driveline fluid levels??

LG