Got one of these with a duramax. It developed a vibration over 45 MPH. Felts like drivetrain so I checked the u joints, they were good but the driveshaft was rusted/rotted up pretty badly, had a new one made and it definitely helped a bunch but it still has a vibration. Between the driveshaft rear yoke and the rear end there a vibration dampener on the pinion, just like on the crank of an engine. It's about 6" in diameter or so. Wondering if this could be bad too. This is also rusted up pretty badly.

It's 4 wheel drive and the front DS u joints are tight.

FYI, it's not tires.

Anyone ever run into something like this?

Thanks

check motormounts?

Same thing happened to mine... I had a u-joint vibration so I changed the joints & hangar bearing, but then had a different vibration. I loosened the hanger bearing and moved it slightly (the mounting holes are slotted) and the vibration went away. It's like you need to have a little "pre-load" on the bearing if that makes sense?

quote:

Originally posted by BD104X:
Same thing happened to mine... I had a u-joint vibration so I changed the joints & hangar bearing, but then had a different vibration. I loosened the hanger bearing and moved it slightly (the mounting holes are slotted) and the vibration went away. It's like you need to have a little "pre-load" on the bearing if that makes sense?

My DS is one piece deal, short bed, ext-cab. No center support.

quote:

Originally posted by 67TSCHEVY2:
check motormounts?

I have not along with the tranny mount but will give them a look.

The vibration starts around 45 to 50 MPH, coasting is worse vs under load also.

quote:

Originally posted by TOP38:

quote:

Originally posted by 67TSCHEVY2:
check motormounts?

I have not along with the tranny mount but will give them a look.

The vibration starts around 45 to 50 MPH, coasting is worse vs under load also.

Top,
I agree with this. We see this in my transmission shop all the time. You would be suprised at how beat up the trans mount gets. Also, Power-brake the truck in forward and reverse and see if you feel a bump. If you do, replace the engine mounts.

quote:

The vibration starts around 45 to 50 MPH, coasting is worse vs under load also.

This leads me to examine the pinion bearing real close. It's hard to hand "rattle check" HD units.

We used to have to grab a handful of worm gear clamps and balance the driveline on the road, I think it was Phord vans that were the worst.

Add weight, move it around to gauge effect, keep at it until it was smooth. Last resort, but it worked.

Update: Motor mounts are good but it did need a tranny mount. The new mount definitely helped a bunch. Most of it is gone but there is still a slight vibration present. The pinion feels good, we did dump the rear gear oil and it looked very good, nothing on the magnetic drain plug so I don't believe it's bad. So I am still thinking it could be the vibration damper that's on the rear yoke. Any other thoughts?

since you are in the rust belt check the emergency brake shoes and that they both are releasing fully.

quote:

Originally posted by 67TSCHEVY2:
since you are in the rust belt check the emergency brake shoes and that they both are releasing fully.

Rear brakes done about a year ago, I never use the E brake also. Also the truck rolls freely.

The backing plates often rot out and leave everything hanging.

If it were me, for less than $120, I would change the yoke, and the pinon seal. While I had it off, I would pull the front pinon bearing and take a look at it also.

https://www.rockauto.com/en/mo...05&pt=13594&jsn=2638

My Duramax had a crazy vibration that took a while to show its ugly self and it was the parking brake on the passenger side.

Deteriorated to where parts were getting hit by the flutes of the rotor.

I am doing a complete frame repair and rust removal and needle scaled everything including that weight on the pinion.

I replaced the rear u-joint years ago and did it again recently looking for a slight noise.

Mine has a 1 piece 5” diameter aluminum shaft 8’ bed

I doubt it’s that weight on the pinion causing your vibration.

If you haven’t already done the mid shaft support and bearing , check it by sliding under and push it up , if you have excessive clearance it will shake at speed. Had to do mine at 166k but was smoother than stick when done. New universals , bearing and mount assy, balanced.
By chance did you lower it???

quote:

Originally posted by sr4440:
If it were me, for less than $120, I would change the yoke, and the pinon seal. While I had it off, I would pull the front pinon bearing and take a look at it also.

https://www.rockauto.com/en/mo...05&pt=13594&jsn=2638

If I need that, it's not that one, need the one that has 1.375" U Joint caps, 4X the money!

quote:

Originally posted by SCDIV1:
My Duramax had a crazy vibration that took a while to show its ugly self and it was the parking brake on the passenger side.

Deteriorated to where parts were getting hit by the flutes of the rotor.

I am doing a complete frame repair and rust removal and needle scaled everything including that weight on the pinion.

I replaced the rear u-joint years ago and did it again recently looking for a slight noise.

Mine has a 1 piece 5” diameter aluminum shaft 8’ bed

I doubt it’s that weight on the pinion causing your vibration.

OK, that's 2 votes for the parking brakes. No idea why any truck needs disc's in the rear to stat with!!!! I will give that a good look and get back to all. I have owned the truck for a while now, got it with 68K on it and it know has 155K so the backing plates could have issues. Obviously I had more than one issue too.

quote:

Originally posted by BP758:
If you haven’t already done the mid shaft support and bearing , check it by sliding under and push it up , if you have excessive clearance it will shake at speed. Had to do mine at 166k but was smoother than stick when done. New universals , bearing and mount assy, balanced.
By chance did you lower it???

My truck, extended cab w/a 6.5' bed has a one piece driveshaft. And no, it's at the stock ride height.

My GMC is a 2500HD and was a pita to do the parking brakes

I replaced everything including the backing plates. Had to pull the axles and the hubs

My truck got so bad parts were falling out in my driveway and the truck jerked to a stop !

It’s a terrible design and reminds me of early Corvettes where I first saw that style. They corrode and rust bad in there and not using them doesn’t help.

Top 38, did you find it?

quote:

Originally posted by BP758:
Top 38, did you find it?

Not yet, between weather and time I haven't had a chance to look further.