Driveline vibe after caster correction (1 Viewer)

[terryjmatthew]

So I finally got around to installing caster plates on my 4" lifted truck and everything was great for a week or so. Noticed yesterday that I am getting a driveline rumble/vibration last night. Locked the diff and unlocked my front hubs and nothing changed.
I know Slee sells a CV driveshaft with some of their lifts, but I have never had this problem before and I have had this lift installed on two different 80's.

Planning on pulling the front driveshaft and replacing the u-joints as they appear OEM with 231,000 miles, but was just curious if anybody else had experienced this problem.

 

[inkpot]

Howdy! By doing the caster correction, you may of changed the ujoint angle enough that it is complaining. The joints on a regular DS need to be within a couple of degrees of the same angle. With a DC setup, you need the singe joint to be nearly straight, and let the DC take care of all the angle work. John

 

[KimoSabe]

How long did you run the 4" lift before installing caster plates? Is this a 91/92 80? U sure it's the front DS?

 

[terryjmatthew]

How long did you run the 4" lift before installing caster plates? Is this a 91/92 80? U sure it's the front DS?

Two months on this truck. I'm not positive it's the front, but the caster plates are the only thing I have changed in the last couple weeks.
It's a 94 btw.

 

[semlin]

you have changed the angle on well worn parts and this sometimes happens. new u-joints should fix it.

 

[landtank]

When installing a 4" lift with caster plates I strongly suggest getting a DC shaft for the front, that, and wishing them the best of luck if they don't.

 

[semlin]

When installing a 4" lift with caster plates I strongly suggest getting a DC shaft for the front, that, and wishing them the best of luck if they don't.

fair enough, but hasn't he isolated the problem to the rear driveshaft by locking the cdl and unlocking his front hubs?

 

[semlin]

ah, i see he is planning on replacing the front driveshaft u joints. perhaps i am missing something. i thought that if you locked the cdl and unlocked the front hubs the front driveshaft would stop turning.

 

[fj4068]

If the driveshaft is installed, it will continue to turn until it is removed from the vehicle because of the full-time transfer case.

 

[Ebag333]

ah, i see he is planning on replacing the front driveshaft u joints. perhaps i am missing something. i thought that if you locked the cdl and unlocked the front hubs the front driveshaft would stop turning.

Nope, front DS still turns. No power goes from the axle to the wheel, but there is still force applied on the DS and front diff.

 

[semlin]

Nope, front DS still turns. No power goes from the axle to the wheel, but there is still force applied on the DS and front diff.

i may need a remedial course in tech. ok, it's turning at the same rpm as the rear diff but it is not under any meaningful load. therefore it may still show drivetrain whine symptoms.

in that case the original poster has not isolated the problem to either driveshaft. the logical thing to do next is to drop the front driveshaft and take a test drive to make sure the problem is not in the rear before spending any money on a dc shaft.

 

[landtank]

Not sure what plates he is using but the end result is supposed to be a situation where the drive angle at the front u-joint is zero.

On a stock drive shaft the shaft actually speeds up and slows down as the u-joints work through the drive angle as the shaft rotates.

That is why you want the drive angles at either end equal so that process is the same at both ends of the shaft.

With the front u-joint at zero and the rear at something more, they typically cause some vibrations especially on deceleration.

 

[Ebag333]

i may need a remedial course in tech. ok, it's turning at the same rpm as the rear diff but it is not under any meaningful load. therefore it may still show drivetrain whine symptoms.

Yup. It's a good test because it does eliminate most of the load on it. If the vibes change but don't go away entirely, it's likely the front DS. But....

in that case the original poster has not isolated the problem to either driveshaft. the logical thing to do next is to drop the front driveshaft and take a test drive to make sure the problem is not in the rear before spending any money on a dc shaft.

I've seen instances where both DS's were pulled (one at a time) and vibes either went away or didn't. IIRC in those cases was either both DS's needing attention, or something else (t-case output shaft I think).

 

[terryjmatthew]

The truck has a FOR lift and Slee caster plates. Had the same lift on another 80 with Land Tanks plates and stock front shaft with no problems.

Planning on pulling the front shaft and driving again this afternoon.

 

[landtank]

Because of how my plates work the end result is different.

My plates yield a slightly less operating angle at the t-case end of the drive shaft, which may or may not make a difference.

 

[Ebag333]

Do you have an angle finder? If not, pick one up (uber cheap) and post the angles.

 

[semlin]

anecdotally, i am at 65,000 miles on j springs with no caster correction. u joints replaced at around the same time. no driveshaft noise. not a 4" lift though.

 

[Ebag333]

anecdotally, i am at 65,000 miles on j springs with no caster correction. u joints replaced at around the same time. no driveshaft noise. not a 4" lift though.

Generally speaking, if you do not correct caster, you do not need a DC shaft, and won't get DS vibes.

 

[nicholas]

anecdotally, i am at 65,000 miles on j springs with no caster correction. u joints replaced at around the same time. no driveshaft noise. not a 4" lift though.

Man I tried this but it felt down right dangerous on the freeway. I couldn't wait to install the landtank plates.