Pinion Angle Help

[Backwoodsballer]

Hi all, I am new to the forum.  It’s rare for me to feel the need to make any posts about questions since everything has been discussed at length usually, especially pinion angles.  My issue seems to be odd which is why I’m looking for some help.

My truck (1978 k10 long bed) has what I believe is a 4” suspension lift (no blocks, full leaf lift) and 3” body lift.  The issue I’m having is that I believe my truck has a pinion angle that is pointed too high leading to vibration issues.  From what I gather, most people don’t need angle blocks with a lift on long beds and if they do need them they are installed to point the pinion higher toward the transfer case.  In order for my transfer case and my pinion to be closer matching in angles I would need to install angle blocks backwards to point in down some.

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


Am I correct in thinking I need to install angle blocks backwards to try and get my pinion angle closer matching to the transfer case?  Or would this be a candidate to drop the tcase to lessen the difference between the tcase and driveshaft?  Either way, I think something is wrong here and is likely causing my highway vibration issue

Thanks everyone

[VileZambonie]

There are several factors to consider but if your feeling is that the rear pinion is up too high with a 4" lift, I would question why? Some pics would help. A body lift is going to affect linkage and cause other potential issues if dropping the transfer case. Flipping the spacers on the transfer case can help get a better driveshaft angle if necessary but I wouldn't with the body lift. Spring length, arch, hangers and shackles also change things so you need to figure out what's going on. Did the vibration just start? Are the u-joints good?

[Backwoodsballer]

I wish I knew more about the actual specs on the lift, the truck is newish to me.  The vibration I get is only at highway speed and feels like a shake more than anything.  In an attempt to try narrowing down my issue without throwing money at i, I figured I would start with taking measurements on the driveline angles.

I already put quality u joints on the rear shaft within the past month.  With the measurements I took it looks to me like my rear pinion angle is pointed very high in comparison with the transfer case. 

The reason I’m trying to get clear answers on this is because I’ve heard people with block lifts don’t need to add shims since it’s not really changing the geometry, but my spring lift must have changed it in a way that caused the pinion to point up

[Backwoodsballer]

Here are a couple pictures of how it sits now.  Without a double Carson I don’t think the pinion should be so inline with the driveshaft.  With the pinion measuring 9.9 degrees and the trans at 2.2 I was figuring I need to drop the nose of the pinion down to match or get close to the same angle the trans has, from what I understand that is what u joints like in order to cancel out vibration.

[Chevygold]

If yours is a longbed does it not have a 2 piece prop? At least that would help with the prop shaft angle out of the tranny?

Graham

[Backwoodsballer]

Yeah it’s a long bed with a “1pc shaft”.  Technically it’s 2pc but I know what you mean, I don’t have a carrier bearing on mine

[VileZambonie]

Can't really see anything from your pix. Does the vibration change if you decel or shift into neutral?

[Backwoodsballer]

No, the vibration remains the same on the highway during decel and remains if I shift the truck into neutral until it coasts to about 55mph where it smooths out

[Mike81K10]

Is there any unusual noise with the vibration?

[Backwoodsballer]

Nothing unusual, the vibration feels like it’s in and out if that makes sense.  Sometimes it feels like the truck is going back and forth between the rear going up and down and side to side.

[JohnnyPopper]

How is the condition of the slip/yoke? does it lessen after lubing it up?

I had a worn out one on my '78.

Is there anywhere that can spin the driveshaft to check balance?

[Backwoodsballer]

From what I could tell it felt normal but I’m no expert.  I could take it to a shop that specializes in drive shafts to have them inspect it, there is a shop not too far from my work.

I had my buddy with a square body lifted with blocks and his driveline angles are way different than mine.  Primarily the trans to driveshaft working angle is about 5 degrees for him where mine is around 11 degrees

[berserk]

No, the vibration remains the same on the highway during decel and remains if I shift the truck into neutral until it coasts to about 55mph where it smooths out

This is exactly the issue I am having! I recently did a 1 ton axles swap, every single thing in the axle is new/upgraded, new u joints and 2.5" soft ride springs. I haven't even checked the pinion angle yet, But did put my truck in neutral and shook the drive shaft. I found that I have play on the rear output of the transfer case. I would guess a 1/16th each direction. This seems to be a very obvious issue that would affect my drive line. I just got my other transfer case out of storage and will be addressing that shortly. But in the meantime I have a video that might be helpful to you.

Mods if this isn't allowed I'm sorry, I won't directly link it. But if you search YouTube for  "Tom Woods Custom drive shaft channel" video entitled " diagnosing drive shaft vibrations" it was very helpful.

Please when you find the solution please let us know for future members searching, I will do the same!

[JohnnyPopper]

FWIW

Gear Vendors (in my neck of the woods) states that 6 degrees is the right mark.

[Backwoodsballer]

I might try to install my wedges and see if that makes any difference.  I have 6 degree wedges at home now, ill install them backwards so the pinion will roll down making it alot closer to the angle the transmission has.

I was hoping someone else on here ran into this before but it doesnt seem to be all that common