Jag IRS angles

[Ben Bateman]

I'm getting a bad feeling about my set-up. I first mounted my Jag IRS with the wishbones horizontal as viewed from the side so that tire travel would be vertical. Doing this points the pinion upward. My 33" tall rear tires already place the pinion higher than my trans output shaft so pointing the pinion up makes for an unhappy driveshaft. I next relocated the rear end with the pinion horizontal (0 degrees) which matches the trans output (0 degrees). The problem is that the pivot shaft that the wishbones mount to points down 8 degrees when I do this. Any suggestions?

[Milt Atkinson]

The half shafts (drive shafts to each wheel) should be level with the ground at ride height and weight ... that is how I set mine up and have had no issues with it in about 2000 miles. My pinion angle is zero ...

[Ben Bateman]

My half shafts are horizontal, but to get my pinion angle to zero, I had to tilt the whole unit forward. Now my hubs are tilted 8 degrees. I understand that there are different side brackets with different caster angles, but this unit is fully rebuilt and painted so it's not and easy task to change them. Nothing binds when I bounce the chassis up and down, but I don't know how that relates to going down the road.

[Milt Atkinson]

I don't understand ... the "hubs" are tilted 8 degrees? ... Lee, where are you ... you need to chrime in on this one!

[Ben Bateman]

After a little more reading, I found that there are "0 degree", "3 degree" and "6 degree" side brackets. The top of the cage on a stock Jaguar has a 6 degree tilt to it to match the slope of the top of the differential. With my side brackets, the only way to get the wishbone and hubs parallel/90 degrees to the ground is to tilt the pinion up 6 degrees. Since my pinion is already 2 inches higher than the trans output shaft I have big problems. Anyone want a freshly rebuilt Jag? I'm about ready to toss it for a Ford 9 inch.

[Milt Atkinson]

On my setup, the pinion angle was determined by the bracket fabriacted to mount the third member to the frame. The only difference I am aware of is the XKE and the XJ were different pinion angles. I have the XJ rearend and the hubs are paralell to the ground and the difference between the output of the trans and the input of the differental is at zero degrees ... the actual pinion angle might be something other than zero, but I raised or lowered the tailshaft of the trans to get zero difference ... maybe that is what you mean.

[Milt Atkinson]

Ben, I have to confess I “cheated” when I converted from my Ford 9” rear-end to the Jaguar rear-end. I was really sweating the conversion until I found out that California Custom Roadsters (CCR) offers the complete bracket conversion kit. The only difference is if you have a XKE or XJ Jaguar rear-end. The main bracket that mounts the center housing sets the whole geometry of the rear-end. Get that bracket welded centered and straight and everything else falls right into to place. The kit from CCR includes the center bracket, shock mounts, stabilizer brackets, stabilizer bars and two dog bones. I opted for one more bracket to convert from manual brakes to power.

I got everything from CCR and two hours of welding it was ready … four hours later I had the Jaguar rear-end mounted and wheels on the ground. I did have to raise the back of the trans about one inch to match the third member. New drive shaft, bled the brakes and out for a test drive.

With the install brackets from CCR, the complete conversion was a “simple” weekend project.

Hang in there ... the JAG rear-end is well worth it!

[frank_a]

I built my chassis from CCR plans and just hoped everything would work out. It did, other than my camber adjustment was way off. Fixed that and now need new meats!

Good luck Ben, don't give up!

Frank

[Ben Bateman]

I just dug up a scan from a magazine about identifying jag rear ends. 60-74 XKE (mine) has 6 degree side brackets. 65-69 3.8S had 3 degrees while 70-87 XJ6 and 76-95 XJS had 0 degrees. Further, the article says that CWI would use a 6 degree angled x-member mount and 0 degree side brackets for street rods with low engines because a large pinion angle isn't necessary. I did have my mount welded "flat" at first. The control arms and hub were happy, moving vertically, but I disovered the pinion problem when I started to measure for my driveshaft. So I cut out my x-member and relocated it 6 degrees down, which made the pinion zero degrees, but now my control arm is down 6 degrees. I guess I did read about the different side brackets long ago, but since I was fabricating my own mount I figured that everything would just fall into place. It didn't.

[frank_a]

I am nowhere near the wizard with this stuff that you are Ben, but my IRS was out of a 72 or 73 XJ6. I thought the CCR plans worked for both XKE's and XJ6's. All I know is I drove mine a long time, and other than not realizing there was a camber adjustment (duh), never had any drive line problems, wheel hop, weird noises (other than vroom, vroom). Wish I could help more!

Good luck!

Frank