Pinion angle, 14 bolt swap, 4" lift spring

[stangtjk]

I'm working on the rear suspension of my 72 to fix what the previous a$$clown put together.

So someone prior to me swapped in a 14 bolt and did a terrible job with it. Not sure what the 14 bolt came from but the spring perches were about 1" too far outboard and whoever installed it just forced the springs out to match. This was on top of a 4" lift block that had two slivers of flat bar stock welded on the rear of the block to presumably to adjust the pinon angle. I use the term welded loosely as there was only a few tacks which didn't stick to the cast blocks as they fell off when I unbolted everything.

The shock mounts they had installed were some goofy aftermarket ones that had 4 holes for positioning the shocks but the same quality of welding was involved. Two of them I knocked off with no grinding in about 6 hammer strikes. To top it off they weren't located in the right spot either. They were also about 1" too far outboard so they used a longer bolt through the 2 tabs and instead of the shock being between them is was cantilevered off to the inside. Both mounts were all bent up as a result.

So yesterday I cut off the factory spring perches, crappy shock mounts and tossed the lift blocks they pulled the hack job on.

Now I've got everything mocked up with new spring perches and 4" lift springs and need to figure out where to set the pinion angle. The lift springs came with wedges attached but I think I want to toss them and just set the angle with the perches. I know the angle at the diff should match the angle at the t-case but right now all I've got are axles under a bare frame. Anyone know what angle I should be shooting for?

[hemi43]

The angle of your engine/transmission in relation to the ground determines your pinion angle. In other words, the angle of your front U-joint MUST be the same as the rear U-joint. Try to aim for between 1 and 3 degrees. This is difficult to do in a lifted vehicle because the engine was placed at a certain angle from the factory for a stock ride height. Obviously you can't change that angle without major modifications, so you may have to live with a larger angle than recommended.

[stangtjk]

Thanks for the reply, I'm familiar with that diagram but as mentioned all I'm working with is the bare frame and axles. Engine/trans and t-case are not installed so I have nothing to compare angles to at the moment. I figured this had been done enough times that someone might know where it should set without having to install the rest of the drive train. I guess I could tack it in place just to hold it together for now and cut it loose to set the angle when I get it back together.

[hemi43]

Originally Posted by stangtjk

Thanks for the reply, I'm familiar with that diagram but as mentioned all I'm working with is the bare frame and axles. Engine/trans and t-case are not installed so I have nothing to compare angles to at the moment. I figured this had been done enough times that someone might know where it should set without having to install the rest of the drive train. I guess I could tack it in place just to hold it together for now and cut it loose to set the angle when I get it back together.

Ah, sorry I should have realized you had no engine in. Yeah, I guess tacking it in is your only option if you don't want shims later. Thankfully the springs are on top of the axle so you won't need to support the weight of the truck on tack welds while you work on it.
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[67Steven]

Just bolt the new perches on with the u-bolts until you get the truck together. You're not driving it, so there is little reason to weld it up now. I finished the rear axle as one of the last items before I tore it apart for paint.

You can also run a CV up by the transfer case. This is what I did and I have 0 vibration issues.

[cleszkie]

It should be noted that the diagram that was posted was for a driveshaft with regular U-joint ends. However, with a 4 inch lift, you might consider installing a CV joint on the driveshaft end near the transfer case. If a CV joint is used, then there is no angle at the axle pinion. The pinion and driveshaft are aligned to point straight at the transfer case output. All of the driveshaft angle occurs in the CV joint.