vibration under power

[DThibault]

My 93 4wd still vibrates when I accelerate. When cruising at 65 or so it goes down the road pretty smoothly. Lots of rebuilt stuff in it including the Getrag, the transfer case, the rear end, the injectors, and I switched the driveshaft off my smooth running other truck. I can't figure it out but as I power up I can feel it resonate through the truck. It seems like it is timed with the engine rpm but I put the clutch in and rev the engine it sounds smooth. I don't really feel it pick up cadence as the mph's increase. Has anyone heard of a clutch or pressure plate out of balance? Just looking for ideas from other peoples experience.

 

[Leper]

uJOINT, DRIVESHAFT BALANCE, AND PINION BEARING, ALL COME TO MIND.

 

[JGrefenstette]

check your carrier barring on the drive shaft, if its a extended cab... grab the shaft and see if theres slop in the bearing. the surrounding rubber usually goes to crap. you might want to check the bolts on the transfercase mounts and the motor mounts too. thats an easy fix to just tighten them up if thats the issue.

good luck

 

[CToney]

I had transfer case bolts loose as well as the yoke on the rear of the transfer case was worn allowing the ujoint to move up and down. Is the truck lifted? Check transmission mounts etc.

 

[DThibault]

No, its a regular cab and I swapped the shaft from another truck that's smooth as silk. I've got new urethane mounts on the transfer case and all the body mounts are the same. The only thing I didn't check are the engine mounts and I will do that. fthe pinion bearing was replaced when we rebuilt the rearend. Thanks for the suggestions, if anything else comes to mind be sure to post.

 

[TWorline]

It is your urethane mounts, they are quite a bit stiffer than the stock sponge rubber mounts. I noticed more vibration in my truck after switching to them at the transfer case.

 

[JGrefenstette]

i just put those mounts in my truck too. now that you mention it, it really does vibrate a lot more, but the reason i replaced them is because the stock mounts had so much slop in them, they were to squishy. so i guess these polyurethane mounts cause some heavy vibrations down the drive train?

 

[TWorline]

I would have to think that the vibrations were there all the time, now it is not being dampened by the rubber isolators so it is transferred to the frame more efficiently by the new mounts. Just try to imagine what it would be like with solid motor mounts!

 

[JGrefenstette]

ah yes! now its all making sense!!! since i put those mounts in everything in the cab rattles and vibrates like crazy... i couldnt figure it out, becuase i did my exhaust at the same time as the mounts, but now i know its the mounts.

 

[91W350]

Mine was a worn yoke on the back of the transfer case. It took me for ever to see it, the U-joints caps were actually spinning before I caught on. Speedy one am I not? Glen

 

[DThibault]

I checked all that stuff out, I really think its in the engine. I have replaced the injectors and the thing has great power so I don't think its a valve or anything. I'll keep looking. There is a diesel mechanic that lives a town away and may have to ask him to give a look. Thanks for the suggestions. Are there any engine ones?