Driveline Vibration Help

[EricG]

Need some suggestions guys...

I've picked up a bad driveline Vibration on the 80. Starts around 25-30 mph, and only when I'm on the gas. If I'm coasting - nothing. Light throttle - some vibration. Heavy throttle - heavy vibration.

It doesn't change significantly with engine rpm when the transmission shifts.

I've gone under the truck and yanked on both ends of the drive shafts - couldn't feel any play.

Checked the front wheel & trunnion bearings - a little play in the left front wheel bearing, which I fixed ... No change.

I've looked the tires over and don't see anything, but I'm going to take it in and have them rotated and balanced. Though I'd expect that kind of problem to show up when coasting as well.

Ideas?

 

[mrniell]

check that your rear differential yoke is tight, if the nut is coming loose it can cause that kind of vibration.

 

[NateMob]

Is this something that has gotten progressively worse?

 

[CO_Hunter]

Ujoints well lubed?

 

[EricG]

Is this something that has gotten progressively worse?

Seemed to happen quickly - like I drove it somewhere in town and didn't notice it, then on the way back I did. It seems to be getting worse though ... like at first you could possibly miss it if you weren't paying attention. But not subtle at all now.

 

[EricG]

Ujoints well lubed?

Yea, I give them a squirt almost every time I change the oil. Know I did this past fall.

Are you going to be at the mtg tonight? I want to get that brake bleeder back to you!

 

[EricG]

check that your rear differential yoke is tight, if the nut is coming loose it can cause that kind of vibration.

Not sure what you're referring to ... is this internal to the diff?

 

[mrniell]

it is the nut that holds the yoke to the diff, you have to remove the driveshaft to see it.

 

[black95]

Make sure you’re checking the driveshafts with the transmission in nuetral, and the Ebrake set, so that there is no bind on the drivetrain. Check your driveshaft slip yokes too.
Sounds a bit more like a transmission mount, or motor mounts to me though. That would explain the no vibes when coasting.

 

[EricG]

Make sure you’re checking the driveshafts with the transmission in nuetral, and the Ebrake set, so that there is no bind on the drivetrain. Check your driveshaft slip yokes too.

Ok, I was doing that wrong - will try again.

Sounds a bit more like a transmission mount, or motor mounts to me though. That would explain the no vibes when coasting.

Ok, I'll see what I can see.

 

[CO_Hunter]

Are you going to be at the mtg tonight? I want to get that brake bleeder back to you!

That would be a no....

Been too busy

 

[EricG]

That would be a no....

Been too busy

Whatcha working on?!

 

[CO_Hunter]

I’ll be posting a detailed thread soon

Some will like it, some won’t but it’s not what you're thinking.

 

[EricG]

So went out and checked the driveshafts again with the truck in neutral. There is definitely some play on the diff end of the rear shaft, and to a lesser extent on the transfer case end of the front shaft. Not alot, but should be none, right?

So how many is the job to replace those u-joints ... without a press. Or recommendations for a shop?

Took a look at the motor & trans mounts - didn't see anything obvious, but will have someone rev the engine while I'm down there and see if anything moves that shouldn't.

Poked around the 80 section FAQ: how to replace the u-joints in your 80

Doesn't look to bad. But might be good to get them balanced while they're out.

 

[EricG]

I’ll be posting a detailed thread soon

Some will like it, some won’t but it’s not what your thinking.

Not what I'm thinking ... so no Isuzu?
Now I'm thinking Cummins ...

 

[black95]

I would highly recommend Driveline Service at 907 S. Sierra Madre. They’re a stand up shop.
Most of the time I buy Ujoints there, they pop them in for free. They’re unbelievably fast, I almost want to go back there with them to see how they change them so fast. Balancing is pretty affordable too.