Jag IRS angles

[Ben Bateman]

Wizard? HA! No, I'm just a newbie. Thank goodness for the internet and helpful people like there are here. I just have a knack for bumping into unusual situations and then I read up on it. I just don't like what I'm reading. Next, I will contact my driveshaft guy and see what may be able to be done with CV joints for extreme angles.

[Ben Bateman]

[http://members.boardhost.com/IRS/msg/1276106025.html]

Here's a link to a page that EXACTLY shows my situation. Anyone have a spare parts unit laying around with good side brackets? I found some on ebay for around $125 with shipping. I'm afraid to even add up the amount of money I have tied up in this thing already. Plus now I need to disassemble it (and I just paid a guy to put it together!)

[John Eplen]

I may not be able to help Ben, but I can relay what I did to get my Jag installed. It's out of a 60-63 XKE & turned out to be the rare one (as referred in CWI's Street Rodder articles) due to having 7 holes on each side of the case. I didn't have any choice on the side brackets either since they were just as rare as the case. If it hadn't been for the guys at CWI I would have never gotten the install done since they sold me a pair of identical side brackets when I discovered my R. bracket was warped due to a hit on the R. side before I bought it.

My frame is Z'd quite a bit so, I had to build a new dropped cross member to mount the center section on. I found that my tranny/engine was at a 1 1/2o downward angle w/the frame level. Once I found that information I set about to center the case between the frame rails(and as viewed from the rear). With that done I set about to establish the pinion angle. I chose to use an angle finder (protractor) on the pinion flange for that. I ended up tack welding & breaking it loose 3 X's before I got it right. I use the old hotrodder rule of matching the pinion angel to the tranny algle. So, I set the pinion flange up at 1 1/2o's since the tranny angle in down 1 1/2o's. On a fixed rear end this would usually wear the U-joint out, but the Jag pinions are offset from the tranny output shaft so the U-joints get lubricated just fine. I welded in a K-member from the beginning of the Z on each side up to the tranny cross member which allowed me to attach a long V shaped lower support which attaches to the front 'dog-bone' & continues forward & attaches to the tranny mount. This helps hold the case to the upward 1 1/2o's angle. And, I hate to admit this, but my out side rods (radius rods) locate from the attachment points on the outside of each lower control arm coming forward to my old radius rod mounts. They mount on the outside of the frame & never come in far enough to create the correct pivot action that was in the Jag mount position.

I think the most important considerations are: 1) center the case; 2) match the tranny/pinion angels=tranny down/pinion up. I'm coming up on 50,000 miles on this, my first Jag mount experience. I've had no problems w/the exception of replacing a urethane bushing on each radius rod. I've never looked at the angle of the lower control arms to see if I had caster or camber. I think you will be in good shape if you'll get the above 2 set, the lower control arms will take care of them selves.

I would make one more suggestion. Anyone that knows me, knows that I'm a big fan of Mobil 1 products due to my 30+ year friendship w/Clark Kibler, a retired Mobil senior engineer. I would use Mobil 1 SHC 75W/90 or 75W/140 in the case. The 140 is pretty expensive per qt., but either one is great. I'll also be using Mobil 1 5W/30 motor oil in my new Tremec 5 speed tranny. I've been using that in my Borg-Warner T-10 ever since Kibler called me one day from the Corvette testing grounds & told me that they have been experimenting w/Mobil 1 5W/30 in the 6 speed trannys & would be sending the Vettes out with it from then on. Man, does it do a great job and cold weather doesn't affect it at all.

Hope I've helped & not hindered. I would hate to see you give up on the Jag cause you'll miss out on a real nice ride. Good luck & keep us posted on how how things are going. John

[Ben Bateman]

Thanks John. I located my differential step by step originally just as you did except that I set my lower control arms where I wanted them and then tacked everything in. I made radius rod mounts off of my transmission x-member in a straight shot through the fulcrum mounts which kept the control arm geometry correct. I wasn't as concerned with the pinion angle then as I should have been (I was using a spirit level then, but now I have a magnetic protractor). Now that the pinion angle is corrected, my radius rods are in the dirt, 6 inches below the forward mounts due to the incorrect caster angle. I will remove my existing brackets and see about modifying them myself first. I found used XJ6 brackets on ebay that should work too, but they are pricey. There's a major Jag supplier by me that says they can't even get them. I guess I've calmed down a little now that I've identified the issue and I understand what needs to be done to correct it.

Once this gets all sorted out, maybe it's worth noting in the Tech pages. From what I'm reading online, Alot of guys have interchanged or bought incorrect brackets unknowingly. I know alot more now than I did a week ago, but I wish I had known earlier.

-Ben

[Ben Bateman]

I ordered some different side brackets today. I'll post some side by side photos once I get them.

[Ben Bateman]

New brackets arrived and it appears that it will resolve my caster problem. The brackets use similar castings, but the mount holes are drilled differently which changes the control arm angle. Rear end is XKE, brackets are XJS. I will need to do something about my upper shock mounts now because they are no longer parallel with my lower control arms. Ugh!