M1009 CUCV 6.2 Vibrations

[Doc Feel Good]

Gentlemen,

I have a quick questions/observation and need some pointers:

I am getting a vibration at around 40mph and under acceleration. This is not too violent as of yet. The vibration reduces when you let off the gas or you get above 55 or below 35.

I have heard that it can be a number of things from Harmoic balancer to driveline. I have reved the engine in neutral, I get a some vibrations off idel, but nothing too bad.

Thanks....

 

[stoney126]

Hey Pleasonton, nice to see more Cucv around here. As for you problem im sure as hell no expert but.. Does the harmonic balancer look old and dried out? From what I have read this a big problem with the 6.2. They usually get replaced witha fluid or billet ballancer. Again this what I have read i ask more questions then I give awswers.

Are your Ujoints in good shape? maybe its a combo of aging U-joints and balancer?

 

[Doc Feel Good]

Hey Stoney,

Yah I am a local Nor-Cal, I was actually born in Napa... and went to school there....

I am in the process of replacing my Glow Plugs (starts a bit hard in the AM) and my U-Joints look good.

I looked at the Drivelines:
The front has a scratch, doenst look bent, but with locking hubs the drive line should not have been rotating.

The rear looks good, weights are still attached.

I am now suspecting either the Harmonic Balancer or the Torque Converter.

I will be crawling under the rig tonight, will be looking at the Harmonic Balancer.

-Doc

 

[Doc Feel Good]

Ok.. an Update:

I crawled under the beast and found the following:

The balancer looks OK, but I have discovered that my PS motor mount is DOA... might be the cause.. but I dont know..

I have some more work to do...

 

[K5dreamer]

another M1009 owner, sweet

yup, my vote is with the U-joints, my truck did the same thing until accelerating away from a stop light, the whole truck jumped and made a sound like midgets hitting the bottom of the truck with hammers..... and then no go...... try putting the truck in 4x4 hi, and drive it, if the vibration lessens its most likely rear u-joints. its sometimes very hard to eyeball bad u-joints until your driveshaft is hanging down like a horney donkey.

 

[kennyw]

Lockouts or not, the front driveline is ALWAYS turning. Check the front driveline and and front axle shaft joints as well.

 

[K5dreamer]

Lockouts or not, the front driveline is ALWAYS turning. Check the front driveline and and front axle shaft joints as well.

eh?

lockouts unlocked, and TC in 2w hi, and the front axle and driveshaft turn? never drove while hanging out under the truck so i can neither confirm or deny, but i thought it didnt.

 

[kennyw]

eh?

lockouts unlocked, and TC in 2w hi, and the front axle and driveshaft turn? never drove while hanging out under the truck so i can neither confirm or deny, but i thought it didnt.

Parasitic drag is what causes it... it IS turning even in 2HI and hubs unlocked. There is nothing to stop it from rotating so the grease between the moving shafts is enough to get it going when you are moving down the road with enough speed.

 

[Doc Feel Good]

Update:

Changed the front break lines... too short...

The front driveline has a small impact mark, I will pull it and have it check for balance.. doesnt look great atm... might just by an aftermarket one, with a lifetime garronti..lol

 

[Doc Feel Good]

Well I had a new driveshaft installed.. it helped alot but still have a smaller vibration @25... but nothing like it was....

Time to replace the Harmonic Balancer and PS motor mount.... might just get rid of the rest.. or I may be a bit too picky...