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Hi all, I have my ‘50 3100 torn down to a bare boxed frame, and am thinking about front and rear end combinations. I had a friend swap an independent jag rear end into a ‘56 3100 years ago, and he says “go for the Jag rear end over a Ford 9”. I’m looking for opinions and info. A forum search came up with “400 answers”, none of which had anything to do with a Jag swap. Any help would be appreciated.

Paul - Here's two related old threads (2011) that should be some good info for your consideration. Lots of info and a pretty much full build picture stash on flicker in the second thread. Happy reading.

Jaguar suspension swap in a '50 GMC

Project XJ-12 PU V12 *

* Note: This one is involving a 1940 3/4 ton, but should have a lot of great relevant ideas for your thought process.

Thanks Dan

There's another option, one that might be newer, and less expensive than the Jag. Toyota Supra has a differential mounted to a subframe, with swing axles and independent suspension. it's basically a somewhat downsized version of the Jag, and those units can survive HP outputs in the 1000+ range from the beaned-up Supra DOHC six. I've got one stashed away in my "one of these days" project list, which will go behind a 390 CID Cadillac V8 in an Excalibur roadster.
Jerry

Flat Out Engineering has kits for front and rear Corvette suspensions. Less exotic than a Jag, but easier to find, cheaper... And there is a kit...

Think about parts availability. Especially for any old or major components that aren't available anymore. Whereas, these days, the Ford 9 inch is on par with the Chevy small block in the 70's, 80's and 90's. Or the LS today. Everybody makes plenty of parts for them. I thought about adding a Jag rear end in one of my projects. Firstly, they were difficult to find and when I did, the seller thought they had gold.

For instance- - - -here's a current listing on Ebay:

www.ebay.com/itm/266611482591?
Jerry

I saw that one Jerry. There is a complete Jag rear out of an ‘86 XJ6 that the guy is asking $400 for. The cradle looks a lot easier to deal with than the whole sub-frame assembly of the Supra.
On another note, I saw an ‘86 Supra for sale for parts for $500. Motor and transmission are already gone.

That price is pretty outrageous, but it illustrates a suspension system, brakes, and final drive that somebody else has already done the engineering on to make it work well. I've got the same basic setup that I acquired for a lot better price- - - - -free! I'll just modify the rear frame area of the Excalibur that was also gifted to me to make the rear section fit. The front will be a M-II setup that I purchased for $200.00.
Jerry

You could probably find the whole '80s Jaguar on FB Marketplace for $800 these days.. I see them from time to time. They were a bummer to keep running back when all those British electrics were new. Add 35 years of leaking seals and attendant corrosion, and you've got cheap projects aplenty that "ran when parked.."

My '49 has a Jag suspension under it.

You can see it here-

https://67-72chevytrucks.com/vboard/showthread.php?t=687778

There is a build thread with more details on the suspension too- starts at about post 17

https://67-72chevytrucks.com/vboard/showthread.php?t=725080

If you want some good information on Jag IRS, go here-

https://dazecars.com/dazed/JaguarIRS1.html

It is Mustang focused, but some good info.

Just a few tips -

-an IRS out of a XJS will have a locking differential (Powerloc), but XJ6s are usually an open diff
-An IRS out of a XJS with the straight six (93+?) will have lower gear ratios good for and OD transmission, otherwise you'll likely end up with a 2.88
-I've never paid more than $300 for a Jag IRS

Thank you all for the information/encouragement. I brought home the rear end yesterday, and will be going through all of the applicable posts after hoisting it out of the back of my truck

I haven't been on the forum in a while, so my reply is a bit late. I installed the front and rear suspension from an 85/86 XJS (I bought1 of each) and lowered the truck around 4 inches. It rides really nice, and power steering is a wonderful thing! I'm happy to share details.

Mike

Another good source of a frame mounted differential and independent rear axles is a Toyota Supra. They're capable of handling 600+ horsepower, and they're not as hard to find or as expensive as Jag parts.
Jerry

I have no doubt that a Supra rear end is a lot more modern than the Jag, but what ratios of ring and pinion do Toyota offer for it? Or, is it compatible with other Aisin third members for which there are different ratios available? At least on the Jag, it's compatible with Spicer rear gears, of which there are plenty available.

Toyota offers at least a couple of ratios- - - -depending on whether the car has a turbo or not. I believe one of them is a 4.30:1. There's also a 3.73. I'll be using a Supra rearend behind a Cadillac 390 engine and a turbo 350 or 400 trans in an Excalibur roadster I'm building. Maybe a 4L60 overdrive if I can find a stand alone control box. I have all three transmissions on hand.
Jerry