Front driveshaft angles - ‘12 2500 Suburban

[FishinGuns]

I need some help gurus. It’s getting cold and snowy and I go to use my 4WD modes on my 2012 2500 Suburban and I’m vibrating a noticeable bit in 4 Auto (and 4 High) at highway speeds. More than I ever noticed in my 2011 Silverado 1500, I had previously.

I go to the local drivetrain shop thinking I probably need a double cardan joint front driveshaft. Most 4” lifts have that option, and I’m on a Skyjacker 3” lift with new knuckles and lower control arm drop brackets, diff drop, etc.

The shop (reputable) measures the angles of my front driveshaft and my front diff pinion angle is +3.3 degrees and my t-case front output is +4.4 degrees. I’m no drive line expert, but that’s my problem right there. Can’t disagree with their diagnosis.

Has anyone shimmed the front diff on an IFS? Can I custom cut axle shims on my trans crossmember?

Shop thought I’d be fine to drive it as-is, but if it can be done, I’d rather get’er in line.

Starting to figure out why nobody does this Skyjacker 3” lift…

 

[swathdiver]

I need some help gurus. It’s getting cold and snowy and I go to use my 4WD modes on my 2012 2500 Suburban and I’m vibrating a noticeable bit in 4 Auto (and 4 High) at highway speeds. More than I ever noticed in my 2011 Silverado 1500, I had previously.

I go to the local drivetrain shop thinking I probably need a double cardan joint front driveshaft. Most 4” lifts have that option, and I’m on a Skyjacker 3” lift with new knuckles and lower control arm drop brackets, diff drop, etc.

The shop (reputable) measures the angles of my front driveshaft and my front diff pinion angle is +3.3 degrees and my t-case front output is +4.4 degrees. I’m no drive line expert, but that’s my problem right there. Can’t disagree with their diagnosis.

Has anyone shimmed the front diff on an IFS? Can I custom cut axle shims on my trans crossmember?

Shop thought I’d be fine to drive it as-is, but if it can be done, I’d rather get’er in line.

Starting to figure out why nobody does this Skyjacker 3” lift…

I'm not sure I understand all that you've written. Let me ask this, is the front differential in the original location? If so, I would say that you need to drop it and yes, ours came with drop brackets for the Zone 6.5" lift. (GMC Sierra) If memory serves, the brackets are about 3-4 inches high.

 

[FishinGuns]

My front diff is dropped, I should have measured, but I estimate 1.5” or so.

 

[Bill 1960]

I didn’t measure the before and after angles, but the differential drop brackets that came in my lift did rotate the case; it was not a straight downward drop. The drop brackets are slightly wedge shaped.

 

[FishinGuns]

I wonder if the passenger side on mine got flipped around. I had the instructions with pictures handy. I’ll look again.

Do you have any vibe issues?

 

[Bill 1960]

No vibes on mine. I’m running a custom shaft slightly longer than stock because the original would pull the boot loose from the transfer case end. Same ends as stock, single universal joints.

 

[FishinGuns]

Learning what I did today, I was wondering if this was where I need to aim to get to, keeping the same ends and fixing the angles to the best they can get to, and lengthen.

I have ideas in my head of cutting leaf spring shims in half long ways. Should work on my trans cross member in my mind. I need to get my Suburban on a 4 point lift soon and mentally map out the diff. Also look and see if flipping anything might help.

Which lift do you have, again?