73-87 Chevy _ GMC Trucks > 4 Wheel Drives
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
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