Hey folks,

I just finished installing a new drivetrain in the electric jag (still need to update that thread) that has a lot more torque and I’ve discovered a new problem…

Under high torque acceleration, the subframe ‘rocks’ around the axle direction so much that the driveshaft lifts up and contacts the driveshaft tunnel! I’ve ordered new subframe and radius arm bushings, but mine aren’t that old so I’m not confident that’ll do the trick. Has anyone successfully solved this problem?

A few ‘before’ and one ‘after’ shot below. 3” driveshaft.

 

Radius rods attached to the bottom plate and the body/frame. Lickahotskillet and icsamerica have both done something like that to reduce that torque effect.

Dave

 

Back in the day, we termed it axle wrap.

1. Long radius arms. Chevrolet trucks used them. NASCAR guys took up on the idea.
2. Traction Masters A firm in LA sold them. Beefed up the front section of the leaf spring with a short arm.
3. Way back a fellow i Ontario designed a track bafor his hot XJS used on the drag strip. Posted on J-L. Durn, name just escaped. His car bought from Andrew Weinberg, Jaguar Specialties. we see him here at times..

Carl

 

I have the same problem, thought it was going to go away when I finally rebuild the rear end, guess not,, I think the xjs has an extended base plate on rear cage to bolt to body, but cannot remember exactly

 

Forgot to add pic

 

I used to read the 'modifications' he did to his car. He wanted to buy the diff from my Belgian (or Swiss?) XJ6 with the 3.05:1 gear set. I declined his monetary offer.
He did weld some serious torque rods to keep the rear 'happy'.

 

Darren, are you using a one-piece drive shaft or the original two-piece? Last year there was some discussion between the two, but not a clear-cut winner. This will be my next big thing.

Dave

 

I’m using the one piece, other than the rub I get if I act stupid on the throttle the difference is negligible, I do t recall the size now but it may be in the swap manual, you cannot go over a certain diameter driveshaft, I stayed without what I was told, and as measured when car isn’t moving I have just over half inch clearance, but there’s a small dimple the protrudes into tunnel and theta what rubs on mine.

just like all the issues I have run into, I will sort it out!

 

Dave, just a heads up, get motor mounted exactly where you want it before measuring for shaft, i thought I had, but because I didn’t have the downpipes mounted, I was off by half inch, had to shift motor back so downpipe would clear steering rack!

 

3” diameter driveshaft has a half inch clearance to that bump in the driveshaft tunnel. I’d bet yours is 3” like mine.

 

Thanks for that tip. I've already elongated the flange holes in the head pipes so that I could rotate them to gain a little more clearance on the rack and move away from the "frame" on the right side. Because the drive train was out of the car when I bought it, I had no idea the drive shaft would run so close. I'd better roll under and contemplate the best way stabilize the bottom of the cage.

The motor/trans mounts fit perfectly, I don't think I could move the engine if I wanted to.

I can see where the diameter of the drive shaft would be very important if it runs that close to the floor pan.

Dave

 

Even with my traction plate tied to the trunk floor and all new bushings and cage mounts. The single piece shaft rubs the tunnel insulation slightly. 550 ft # of torque in action.

 

You may want to look my post in this thread.
https://www.jaguarforums.com/forum/x...9/#post1865899

This is the idea... ended up running two rods from the diff plate to fabricated bushings mounted to center bearing mounting holes. So far so good. I'm running 450HP on sticky Michelin Super Sports and it has survived many track days with a manual. I'll post up a pict asap.

 

Darren, Clyde, icsamerica (don't know your name), do you think the 2-piece drive shaft would have more clearance or move vertically a less amount? I'm assuming I will need to adjust the front drive shaft if I keep the 2-piecer. That being the rubber isolated shaft, a new one will be need, rear shaft will be OK as-is.

Dave

 

Two piece shaft is 2” OD and cleared just fine for me. My problem was that it buckled under high torque at the center support bearing u-joint and the driveshaft itself banged around to the center support bearing mounting structure. Your mileage may vary!

 

Bry5on, thanks for that bit of information. The ability of the stock center support being able maintain the center U-joint in it's proper position had crossed my mind. I'm thinking my mileage may be a little different than your, but there is no doubt that I will need to show off on occasion.

Dave

 

The electric drivetrain does rolling burnouts up to about 30mph, I hear you

For what it’s worth, I’ve decided to go back to a two piece and try to solve the center support bearing issue. There’s not much to be gained from a one piece and adding a bunch of structural supports just to make that happen doesn’t seem worth it to me. On to driveshaft #3!

 

I am going to take the liberty to quote some info I have from a known purveyor of Jaguar Conversions.
QUOTE: "The recommended driveshaft tube diameter is 2 1/2" for all applications to avoid interference issues in the transmission tunnel"
When I spoke to my driveshaft builder he recommended 2 3/4" which is what I went with.
I will wait to see what would happen under hard acceleration.

 

While we are on this subject, anyone have part numbers for the bushings and mounts? Maybe in poly???

 

If we are still talking about the cage mounts, here's what I used.- SNG $100 (4) Rear Subframe Bushes CAC3067U