Pinion Angle Help

[ehjorten]

I'd say from your third picture it doesn't look like you have any angle on that rear u-joint. U-joints need to have a little angle on them to keep the needle bearings spinning; at least 1° If not, the U-joint life will be severely reduced. From you numbers I would say you want an 8° shim to angle your rear-end down to like 1.9°. Typically with leaf-springs you will go a little past equal angle between the transfer-case and the rear-end. If your powertrain is angled at 2.2° then you would want your rear-end angled at almost 0°. This is because when you put torque to the rear-end the pinion wants to climb the ring-gear and the leaf springs will flex in an S-shape, called spring wrap, letting the yoke rotate up.
The problem with U-joints and lifts is that a U-joint has a practical limit for a working angle. Typically this is going to be around 15°. They can go steeper angles, but even by 15° the U-joint life is drastically reduced. For you your working angle at the transfer-case is 11° and your working angle at the Rear-end is 3.3°, assuming your measurements are accurate. If you put in an 8° shim then your working angle at the rear-end will be about 11.9° and your working angle at the transfer-case will be about 11.6°. Your driveshaft will lengthen slightly, so you want to be sure that you have proper engagement of the slip-yoke. Depending on your engagement now at the slip-yoke, it might have to be lengthened. I think you want to be sure you have at least 2 inches of engagement. That could be another source of vibration.

[ehjorten]

BTW...on my 8" lift in my crew-cab I have a two piece driveshaft. The carrier bearing is spaced down slightly to improve angles. I had a very bad vibration in it when I bought it. The problem was, 1) not enough engagement in the slip-yoke because of the lift, and 2) the 2-piece of the shaft was bent, only 0.150". I had it lengthened...i.e. re-tubed and the slip-yoke replaced (it was worn-out from not enough engagement), and the vibration totally went away.

[Backwoodsballer]

I'd say from your third picture it doesn't look like you have any angle on that rear u-joint. U-joints need to have a little angle on them to keep the needle bearings spinning; at least 1° If not, the U-joint life will be severely reduced. From you numbers I would say you want an 8° shim to angle your rear-end down to like 1.9°. Typically with leaf-springs you will go a little past equal angle between the transfer-case and the rear-end. If your powertrain is angled at 2.2° then you would want your rear-end angled at almost 0°. This is because when you put torque to the rear-end the pinion wants to climb the ring-gear and the leaf springs will flex in an S-shape, called spring wrap, letting the yoke rotate up.
The problem with U-joints and lifts is that a U-joint has a practical limit for a working angle. Typically this is going to be around 15°. They can go steeper angles, but even by 15° the U-joint life is drastically reduced. For you your working angle at the transfer-case is 11° and your working angle at the Rear-end is 3.3°, assuming your measurements are accurate. If you put in an 8° shim then your working angle at the rear-end will be about 11.9° and your working angle at the transfer-case will be about 11.6°. Your driveshaft will lengthen slightly, so you want to be sure that you have proper engagement of the slip-yoke. Depending on your engagement now at the slip-yoke, it might have to be lengthened. I think you want to be sure you have at least 2 inches of engagement. That could be another source of vibration.

Thank you so much for this, this was exactly what i was looking to clarify here.  I had the same understanding that i need to get the pinion to point down more to be more-so on the same plane as the trans.  Ill work on shimming my rear axle this week and report back.

[ehjorten]

There are aluminum shims and steel shims. Some have a clearance hole for the spring center pin, some bolt to the spring pack. I suggest getting the steel shim that bolts to the spring pack. You may need a new, longer center pin for your spring pack. The most important thing is that the Center Pin engages the hole in the axle pad so that your axle does not shift on the leaf spring.

Something like this: https://www.wfoconcepts.com/i-30504779-8-degree-steel-axle-shim-2-5-wide.html

[Captkaos]

My measurements below were pulled using the Tremec driveline angle finder.
Transfer case: 2.2 degrees
Driveshaft: 13.2 degrees
Rear pinion: 9.9 degrees

can you confirm that you measured off the flat surface and got 2.2 Degrees DOWN on the T-case output and 9.9 degrees UP on the Ujoint face of the axle?
Ideally you want them both to be in the same plane if the T-case is pointed down 3 degrees the axle should be 3 degrees up.  If what you are posting is what I stated above you are 7.7 degrees off.

check this link out..
https://www.4crawler.com/4x4/CheapTricks/Driveline-101.shtml#Single-Cardan-Measurements

[Backwoodsballer]

Yes I can confirm all measurements were made on flat spots on the transmission and rear axle.

Thank you for helping clarify, I think this thread will help a lot of people in the future just to understand what we are looking for

[Backwoodsballer]

Just wanted to update, I put in the 6 degree wedges I had here on the truck tonight and it brought the pinion angle down to a reasonable 3.3 degrees.  I’ll try to take it for a ride tomorrow, hopefully this helps my issue.

Also I noticed that the hole in the axle where the leaf spring retainer bolt goes in was totally wallowed out, it honestly looked like the axle might have been shifting back and forth in the hole so much that it almost made a slot.  I made a spacer to put in the hole and welded it up, it was literally the size of another bolt head.

[JohnnyPopper]

Increasing the angle of your pinion to it is more out of line with your driveshafts seems to be going in the opposite direction, i.e. adding more work/movement to your rear U joint.

I think the problem is either 11 degrees is too much, or your slip joint yoke is worn.

If you can move it sideways or up and down, I suspect it's worn and wobbling. When I would grease mine up it smoothed out till the grease worked out.

[Backwoodsballer]

I did check the slip joint on the driveshaft and i seemed to be tight, i did grease it within the past 2 weeks as well.  There is not really any movement at all in the drive shaft when i get under there and twist / shake it, then again im sure it doesnt take much movement to cause a vibration so i might be missing something.

Matching the pinion to the trans in theory should allow the rear u-joint to cancel out the vibration from the front u-joint however this working angle will definitly cause my u joints to wear down more.  Im hoping the test drive proves this to be correct.

I think the only real fix for me with this amount lift / driveshaft angle is to get myself a double cardon driveshaft or a CV end on the transmission side then setup my pinion angle to point at the transmission.  There is no slip yolk for my transmission now, my driveshaft bolts directly to the output shaft by the u joint.

[Backwoodsballer]

Well I took it for a ride yesterday and today.  To me I think the vibration is worse.  It’s not vibrating around 40mph and anytime I’m on the throttle, which it was not doing that before.  I really thought getting the pinion angle and transmission on the same plane was going to fix it but oddly enough it made it worse.  On top of that it looks like I would need a longer driveshaft to keep it this way anyways.

I think I’ll be taking out the wedges and putting it back to the factory setup.  I’ll have to chase my wheels next for this vibration issue I was getting at highway speeds

[JohnnyPopper]

Makes sense, I would still have the balance checked to rule out the drive shaft.

I think there is a CV or double U-joint coming off the Xfer case going to the front axle on my K10. It a pretty sharp angle being so close to the front.

Just thinking out loud: from a geometry POV, angling the pinion downward increased the angle at the transmission U-joint.

Keep us posted on what you find, happy hunting!

[Mike81K10]

Can you take it to a shop where you can run it in place at speed while observing under the vehicle for problems?

[Backwoodsballer]

Yeah i certainly could try that out to see what might be vibrating.  Even seeing if the driveshaft is running true would be worth that exercise i think.   One thing i did notice last night when i went back out there was that the slip joint in the driveshaft seemed to have some slop (like JohnnyPopper mentioned earlier).  There is not slop that i could feel by hand when twisting it, but there is slop when i push up and pull down on the shaft.  Maybe this is exaggerated since my driveshaft is stretched to the max right now but it doesnt seem normal to me.

I was also looking into just picking up a double cardon shaft from Tom Woods for the rear and pointing the pinion up to the Tcase, but thats a hefty chunk of change for a potential fix.


I had my buddy check his angles on his 80's K10 long bed with a 4" block lift in the rear and they are much closer to my original measurements, his truck drives smooth as silk:

His Truck:
-Trans 5 degrees
-DriveShaft 8 degrees
-Pinion 10 degrees

My Truck (Original Measurements):
-Trans 2.2 degrees
-DriveShaft 13.2 degrees
-Pinion 9.9 degrees

My Truck (New Measurements):
-Trans 2.2 degrees
-DriveShaft 14.0 degrees
-Pinion 3.7 degrees

[ehjorten]

One question...are your U-Joints still properly phased, front to back? They should be lined-up so that the yokes on both ends of the driveshafts are aligned. See the pictures and explanations located here: https://managedmobile.com/driveshaft-phasing-importance/

If you took apart your slip joint and didn't keep them properly aligned, this could be a source of vibration.

[Backwoodsballer]

Thanks  ehjorten, My U joints are in phase properly.  I actually look the driveshaft out and laid it on my garage floor on sockets to make sure it was perfect before putting it back in.