9" Pinon Angle

[gnsteam]

I have a new pair of Ruff Stuff 9" spring perches for the purpose of moving the axle back 1" and adjusting the pinon angle to reduce the needed of shims.

Not knowing the final ride height and various other dimensions of the rear driveshaft to 9" pinon. What would be your best guess for the amount degrees of rotation I should go for when welding on the new perches? Not trying to get it perfect, but perfect would be nice. Just looking for something close. I'm OK with shimming after the fact if necessary.

This will be final set up.
Duff 2.5", 11 leaf springs
Duff Eibach Shocks
Axle moved back 1"
Explorer 5.0, 4R70W, Dana 20

 

[Broncobowsher]

Just bolt the axle in and eyeball it.
After you have all the weight on it go and do some measuring. Loosen the U-bolts and adjust as needed.
Once dialed in, burn them in.

Broncos are well known for a high degree of inconsistency from one build to another. Using someone else's numbers won't get you the angle you need. It gets you the angle someone else needed.

 

[Madgyver]

before and after pics.
I lowered the rear of my bronco and ended up with a driveline bind and bad pinion angle. after replace a clutch and tightening up the trans/tcase crossmember, it had to be fixed. i rotated the spring perch and drilled a hole an inch forward to move axle back.

 

[bigjhoov]

Bolt it all up loosely, rotate axle to desired angle, tack perches in place, disassemble and weld perches. Because of the cv at the transfer case you can almost point the pinion right at the driveshaft, but I like to set them with about 2 degrees of downward deflection. The pinion will try to rise under power.

 

[bigmuddy]

Bolt it all up loosely, rotate axle to desired angle, tack perches in place, disassemble and weld perches. Because of the cv at the transfer case you can almost point the pinion right at the driveshaft, but I like to set them with about 2 degrees of downward deflection. The pinion will try to rise under power.

Perfect! saved me time from writing the same..

 

[garberz]

With the Duff/Deaver springs, the perches will likely be in the stock location. 4R70 trans and moving the axle back, puts is back to a stock driveline geometry, which 2 1/2” springs don't really have much effect on.

Mark

 

[bsquared]

X2 on what BigJHoov said. That will be your best bet, especially since you are planning on doing the welding. Good luck, B2

 

[gnsteam]

Thanks everyone for the advice. I will follow the plan as described by bigjhov and others.