Driveline angle and axle shims

[juggernaught]

All of my drive line geometry changed when I replaced my stock motor mounts with the M.O.R.E. mounts. Now here is what I have:

Transfer case pinion is: 6 degrees

Driveline is: 17 degrees

Pinion is: 17 degrees

I was hoping that with the driveline and pinion being identical, there would be no vibration. That does not seem to be the case. Under a load (heavy accel) I do get what feels like a driveline vibration.

I do have shims on the rear axle ( 3 degree possibly). I think maybe the spring pads on the axle may have been reworked at some time. It looks like removing the shims will get me to about 14 degrees.Still not close to the T/C angle. Has any one ever had to shim the pumkin DOWN (ie. shims behind the axle)?

[msalaba]

What type of driveshaft are you running?

A regular driveshaft with 1 u-joint at each end you want the tcase and pinion yokes to be parallel (same plane)

With a CV shaft and leaf springs, you want 2* up at the pinion yoke in relation to the driveshaft.

What did the new mounts do you your engine in ralation to the chassis? Raise or lower.

Also, what are the degrees you listed in reference to?

[juggernaught]

I am running a single cardan style u-joint.

The motor mounts seemed to raise the engine. In order to get enough clearance (ie. near center the fan) to the shroud I had to place a 5/8" shim plate under the poly tranny mount that was already 1/4" thicker than stock rubber. So my total change at the tranny mount was 7/8" (could have gone another 1/8"). This just about maxed out my shift tower height. I do have a '86 TJ clip (on the front of my '78 CJ) and a custom radiator, but they were on there before with the old m/m.

All degree readings are taken with the jeep on the ground and in reference to each other. The only thing that changed was the height of the engine/tranny/transfer and the driveline angle.
I believe the tranny angle is very close to what it was originally.
The pinion is still fixed. The driveline angle has changed by lifting the tranny.Unfortunatlly I did not check the angles before disassembly.

I am amazed that it ran as vibration free as it did before dis- assembly. I would like to know if any one has put shims on the rear portion of the axle/spring pack and how many degrees difference they have gotten away with. I feel that I coud easily run the setup I have now if I was only offroading. Right now I am running a 11* difference between u-joints. Yes, I know the BOOK says you need less than 3*.

[msalaba]

Is there a reason for not running these?

Prothane Mounts

This is what I'm running and I know they are the same dimension as the stock rubber mounts. An added bonus for 1/2 the price. As for "bomb proof" I've been rock crawling, mud bogging and trailriding for 6 years and the mounts still look new. (I'm also running the Prothane trans mount)

From the picture I have in my head, it seems that even if you get the geometry corrected, you could still be exceeding the u-joint angularity. iirc 23* total.... Damn CRS

What does the geometry on your front driveshaft look like? What would happen to the front geometry if you took the shims out of the trans mount and moved the fan shroud?

I'm thinking more that you should contact MORE and start squeeking. Kinda BS to sell a part as "farctory replacement" and they start moving things around. Not to mention this is raising your center of gravity. Not very desireable.

[juggernaught]

Finally rotated my 3* shims to the rear of my spring pack ( total of 6* in pinion change). Now I have only a 5* difference between tranny and pinion. Most all of the drive-line vibration is gone. O.K. for now. I actually need to replace the 3* shims with 9* shims for a 1* down pinion angle at rest.

Drive-line angle went from 17* to 20 1/2*. I am not to worried about exceeding the max. angle. Most are stated at 25-30* max.

I may end up eventually looking into a cv joint, but the cost of two ( one spare) is $$$.

The poly trans mount that I used was definately taller (1/4") than my old stock rubber one.

Everything is slowly coming together...........still tuning the rebuilt T/A 670 holley carb.

[msalaba]

The cheapest way to go CV is junkyard surfing.

I "found" mine on the floor of a body shop. Came out of an 03 wrangler. (front shaft) It had a dent in the tube. Had it re-tubed and put it in. Nice shaft, 1330 joints in the CV.

I can't remember what application the yoke was from. Maybe NP 231? But I do know the late 70's D20 has a 26 spline output front and rear.

I also hear a lot of people are using XJ front CV shafts. IIRC, these either had the NP 231 of B/W Q-trac.

I don't know about the new Q-tracs but the 70's era used its own unique spline, yoke and CV joint (Saginaw ike Chevy?)

Another source is 70's J-trucks and waggys with D20. These also had a 10 or 26 spline yoke depending on the year.

[juggernaught]

Since right now I have 1310 spicers on all of my driveline u-joints, I will just see what starts breaking first and get an idea what I want to do. May possibly go to a 1350 if I make a change. We will see........Right now everything is running excellent.

[msalaba]

The more permanent solution (and Expen$ive) is talk to Jess @ http://www.highangledriveline.com

Full custom, balanced and guaranteed. Also has the yokes required.

Good guy to deal with. He also is an avid off-roader.