Another pinion angle question...

Hi guys and gals,
Been a while since I've been on here. Did a search and found a few answers, but a question lingers about what's an acceptable angle between differential pinion and trans output shaft for a cruiser. RR has a TK500 swap. With the driveshaft perfectly level (0 angle, weight-on-wheels), the trans output shaft is 2.9 degrees tail down. The trans is as high in the tunnel as I can get it. And the nose of the differential pinion shaft centerline is 0.9 degrees down toward the front. Therefore total angle is 3.6 degrees. The car is cruiser; will never see track or strip time. Haven't driven it yet, as other issues arose. Should I be looking for some 2 degree shims to put under the perches to bring the nose on the diff up a bit? 2 degrees would get the nose of the diff up and bring the centerlines of the trans and diff closer to, but of course not, parallel (around 1.6 degrees). What's an allowable difference to have for a street driver? Also, along the lines of shims, what manufacturers shims will work under the factory perches with MP XHD (factory, basically) springs? Summit shows Pro-Comp 99-400B, Calvert CLV-4-DEGREE, Beltech BEL-4977 , and Rubicon Re1466 shim sets. Is there one of those sets that works best with Mopar springs and perches?
Thanks for any knowledge you can impart.
-Marq

If needed there are some excellent utube vids on this. EDIT and in our tech archives. As you know you want them to be "fairly" close to parallel but in different planes. I read once that a .5 difference is real good but I dont remember if that was street DD or race

I suspect that before long you will be either cutting the tunnel of your RR or selling that transmission. This is more of a transmission angle problem than pinion angle. I suggest you add TKO swap to your Title so that the experts on this swap will be here shortly.

2.9 down on trans is normal, set the pinion 1.5 to 2 up for a street car

Your tail shaft angle of 2.9 degrees is good, no need to cut the tunnel or try to raise it. The problem is you pinion shaft angle of .9 degrees down. With this current configuration, the driveshaft has a "speed up , slow down" phase. It gets worse the more the suspension compresses. A link below will show you what I mean. What you want is to get the pinion angle to mirror the tail shaft angle, but in the opposite direction. So you will want to get the pinion to be 2.9 degrees up. There are shims you can buy to angle up your pinion, these get placed between the leaf spring mounts and the mount on the axle tubes.


https://www.youtube.com/watch?v=Idk3BVDVHq4

Pinion angle shims... https://www.summitracing.com/search...rder=Ascending&keyword=angle%20shims

That 2.9 degree up should be while accelerating right? Not at rest since the pinion will rise as you give it gas? So you'll want it slightly less then 2.9 up at rest?

The desire is for the tranny angle downward (3 degrees max) and the pinion angle upwards with both being on fairly parallel planes of each other and the driveshaft having a 1 degree minimum to 3 degree maximum defection measured at each joint UNDER ACCELERATION not in static mode on a leaf sprung vehicle, keep in mind the pinion can/will rotate upwards of up to 5 degrees UNDER ACCELERATION there are lots of variables that determine how much it will rotate upwards, that being said I think your current angles are a fine starting point, drive the car, see if any driveline vibration is present in acceleration or de-acceleration mode, then shim if necessary to fine tune your driveline angle due to possible driveline vibration.... chances are you'll be raising the pinion nose 1 or 2 degrees, but hold off until you've driven it

My 70 Charger with a TKO600 has a 2 degree down on the tranny and had a 1.5 degree nose down on the DANA 60 pinion in "stock" configuration, I added a 2 degree shim to raise the pinion nose upward, but these are the parameters on MY car due to suspension mods/ride height, each vehicle will have it's own variables based on ride height, and types of suspension/axle mods, etc, etc

FYI....when troubleshooting any driveline angle induced vibration, raise the pinion nose for UNDER ACCELERATION vibration and lower the nose for DE-ACCELRATION vibration....I would do so 1 degree at a time....as for a mfg recommendation on shims if needed, I used the Mopar Performance shims, no mods/zero issues, just keep an eye on the alignment leaf pin that you have plenty to align/engage the axle perch hole properly when adding a shim....

MikeG

Yes, that would be the ideal point. As Dayclona said, may be 1 degree different at rest vs. acceleration; so about 2 degrees up on pinion at rest.

Remember, as acceleration increases, the "G" forces and suspension loading slowly decrease close to "at rest". The initial movement of the suspension is greatest at the beginning point of acceleration/ "G" force . Just a small amount of difference at rest will get you close to where you need to be. If you can find out what the factory used for pinion up degrees and tai lshaft down degrees, I would start with that and makes adjustments if needed

I look for 2 to 5 degrees nose down differences on the pinion shaft and the driveshaft, done that since attending one of the old Mopar drag racing seminars back in 1978 or so. More angle is needed on stick shift drag cars than automatic drag cars according to them
As far as the front U joint and differences between the tranny output shaft and the driveshaft angles if you have 1.0 degrees differences or more on any plane your good , that angle will make the needle bearings rotate in the front U joint and not gall up from no rotation

Thanks for the input guys. Ordered a pair of 3 degree 2.5" wide shims from Summit. In theory, the 2.9 degrees down at the trans should pair fairly well with the (new) 2.3 degrees up at the diff. The XHD springs (6 leaves right, 7 left) and my old f--t driving style should minimize the spring wrap-up. Time will tell...

As an aside, I forgot how helpful the folks on here are, and how civilized and mature the behavior is. It's a breath of fresh air compared to much of the behavior I witness on the Supra forum.

Edit: Sorry, got that backwards and rechecked. It is 6 leaves left and 7 on the right.

Let us know how those angles work for you. Double check those springs - I don’t recall ever seeing more leafs on the driver side.

The spring with the most leafs in the front half goes on the passenger side.

Agree here, the e-bodies had 6 on both sides, a shorter 2nd leaf on the drivers side and for some weird reason the bottom leaf faced forward on the right, rearward on the left spring. Make sure the spring with the second leaf going all the way to the spring eye is on the right. The new mopar springs are this way, others may vary. Your new angle should be good.