Warthog 87

m hopin someone can help me. Watched a bunch of videos of people basically rattling to hear themselves talk. I don’t need history lessons or how a car works. Just wanna know what size shim I need. The driveshaft is -17 degrees on the bottom however if I place the angle finder…my phone it says -18 degrees. Lol checked all over and that’s the readings I get. So figured I’d go with the -17 since I did see all the people in the videos measuring on the bottom…bout all I could get from em. The axle or pinion measures -6 degrees. Measured from rear diff cover bolts, the little metal shelves? On the pumpkin and the u joint. The pinion nose slopes up so didn’t figure that was a good spot. Anyway that leave’s -11 or -23 if I add them. Thought I was supposed to have a positive number to subtract but that’s the numbers I got. Does this seem high? With a 6 degree shim I’m still at -5? It’s a cherokee xj 87 with rubicon express 3.5 leafs. Not sure if I will need to do any shimming on my comanche or not but the cherokee is up on the building block first. Any help would be greatlyappreciated!

4.3L XJ

Forget driveshaft angle. It is meaningless. First, year of XJ. Second, type of driveshaft, single or double cardan

Warthog 87

1987 Cherokee xj, stock driveshaft stock joints. Will change to whatever I need but it’s the stock rear shaft at the moment. Whole truck is factory except what I’ve been replacing.

Warthog 87

also no sye or tranny drop. Gonna rebuild the t case and tranny plus engine when I get to that point. Doin suspension and axles at the moment. Also wouldn’t think this matters but the fuel tank is off and interior out at the moment. Doin a complete and total rebuild. Don’t know much about shims ect but from what I’ve read the goin sizes seem to be 3 to 4. Also read 6 was too much so I’m at a stall at the moment. Any knowledge drops would be awesome. I know engines and chevys ford and some dodge but new to suspension and Jeeps. Been learning as fast as I can.

lawsoncl

What's the angle of the output of the xfer case, versus the angle of the pinion? Should be parallel, or the pinion tipped slightly down from there to account for spring wrap under load.
https://www.motortrend.com/how-to/pinion-angle-change/

Warthog 87

Not sure the t case angle I can measure it to I guess. It’s a 231 so where did you place you measuring tool? Wanna make sure I do it right.
I read that article as well but didn’t get much from it. Sounded more for car build as opposed to jeep stuff. To me anyways. I know lots of things crossover. Just don’t know what does and doesn’t.

Warthog 87

I can’t be the only person with this rig setup. I was hopin someone had the same rig or close and could say this is the shim I used. Yes not all Jeeps are the same but a renix unit with rubicon express springs ect can’t be that different can they?

Jim Malcolm

With the stock OEM slip-yoke style driveshaft, the angle of the driveshaft is meaningless. You simply need to make sure that the tcase output and the pinion gear are almost parallel, with the pinion angled slightly below parallel to account for it lifting up when you accelerate.

Don't confuse yourself. Including the driveshaft is just making it more difficult. Just slightly below parallel, that's all you need to worry about...

Warthog 87

Thank you for that clarification! I’ll measure that now see what it be!

Warthog 87

Ok so I measured from the t case output shaft housing…the end where the d shaft yoke goes in and the unjoint space on the input yoke and it’s -4 degrees. So since that tilts one downward towards the rear and the pinion tilts downward towards the front at 6 degrees that leaves me at 2 degrees? Which means leave it be?

Jim Malcolm

With the t case pointing downward at 4 degrees, you want the pinion to tilt upwards toward the front at ~2 degrees, so it sounds like you need 8 degree shims

Warthog 87

That’s a huge shim! Maybe I’m not explaining it right. Basically 4 degree on t case and 6 on the axle end. The lift is only 3.5”. An 8 would be 2 degrees per in? I’ve gotta get someone to show me I guess cause this has become incredibly dumb at this point. I see people do this all the time and I know they don’t have any shims. I’m just trying to get everything lined up as I go while I’m there. Gonna go with a 4 and hope for the best. Can’t seem to get a straight answer and getting more confused by the moment. Thanks anyway people

Jim Malcolm

Rear axle shims - Jeep Cherokee Forum

The bottom half of the image is what you have. If you rotate the image so the t case is pointing down, you can see that the pinion would be pointing up at the front. 8 degrees is certainly in the ball park. A lot depends on whether you have lift shackles or not, since they drop the rear of the spring, pointing the noise of the pinion gear up toward the front...

Edit: This certainly can get confusing. Your up can be my down, all depending on how you look at it. Hopefully that image helps...

4.3L XJ

Now measure the face of the transfer case, like at the fill plug and remove the rear of the driveshaft and measure that. Subtract the values and that is the degree shim you need

Warthog 87

Axle

T case
This is what phone app says. Each pic is labeled t case or axle. Got a level and set phone on it for a straight edge to keep for bobbin around. As accurate as I could get em. From the tail shaft opening and from the diff cover bolts. Phone facing same direction