Pinion Angle Moron Question

Flivver250

TJ Addict
Supporting Member
Joined
Jun 3, 2018
Messages
2,416
Location
Dubai/Florida
I have tried what I think are every conceivable combination of pinion angles. I can change the vibration, but not eliminate. Attached is a picture of the protractor on my transfer case output. The shaft is pointing down towards the floor at an 8° angle. What angle should I have the differential pinion point? I assume if the TC is pointing down, the pinion should be point up. Is that correct? I have a Tom Woods driveshaft with three u-joints.
IMG_2699.JPG
 
According to the book with a CV shaft your pinion should be in a straight line with the shaft so if it’s at 8 so should the pinion. That’s the starting point anyway, everyone seems to come to a different final angle on the pinion based on trial & error, I think my driveshaft is a degree or so steeper than the pinion, that was the sweet spot on my TJ. If you’ve tried a bunch of different angles are you sure your vibration is even coming from the rear shaft?

Also consider the impact of varying weight as it can change your pinion angle, for example when my TJ is in the garage it’s usually empty, the spare is off & the tank is close to empty but when I pack it up for a day in the mountains I add a toolbox at around 80lbs, a spare that’s around 100lbs plus a full tank of gas which adds close to another 100lbs, toss a cooler in & altogether that’s probably 300 extra pounds compressing the rear springs which is enough to drop the angle a degree or two. Oh, & my fat 140lb ass too.
 
So if the TC is pointing downward at 8°, my differential should be pointing up at 8°? The only weight change would be me and an occasional one passenger.
 
From the OP,
"I have a Tom Woods driveshaft with three u-joints. "
This means to me that he has a CV Joint drive shaft.

@Flivver250
If that is the case, the Red line on the picture below shows what it's need to be accomplished.
1547730515619.png


I do spot this Double-Cardan Measurements once. I bet You will understand better how to correctly measure this angles after read the section Double-Cardan Measurements. I do always adjust the axle 1.5 degree (aprox) below, this seem to be enough to compensate any mechanical movement torque may force on the suspension.
You will have to play with it three or four times, it took me more to me to get the LJ sweet point that is very different than the Sport 99 sweet point.

Good Luck!

Note:
The linked article author I do think has a Yota 4 Runner but the procedure for CV joints should be similar to our TJ's
 
  • Like
Reactions: Daryl
Worthy of note: I did have the rear 4.56 pinion gear replaced as it was howling. It is quiet now and properly broken in. I actually change the gear lube twice after break in. I did not forget the additives.
 
Worthy of note: I did have the rear 4.56 pinion gear replaced as it was howling. It is quiet now and properly broken in. I actually change the gear lube twice after break in. I did not forget the additives.
You have a Tracloc LSD in the rear axle? Not to mention that most appropriate axle gear lubes already contain the friction modifier additive that is required by the Tracloc. No other additives are required.
 
Last edited:
I do have the Tracloc.
Next time you buy GL-5 gear lube for your axles, look on the back label for a statement similar to 'Compatible with limited slip differentials'. Most include that statement that means the friction modifier additive required by the Tracloc has already been added to it.