It looks like a Jag ifs subrame is in the plan for my 48 F-1. Thanks for all the info on the swap, thanks to Bill-49 williard for all his info. Since I'll buy a complete donor car, I'll also have the irs. Original plan was explorer rear, but the jag and ford bolt patterns differ. Before I consider using a gm rear, or redrilling the explorer axles, what about the jag irs? I know it was common years ago, but you don't see them much anymore. It doesn't look that difficult to fab if you use the stock "cage", but what about reliablity? Since the diff doesn't move, what about u-joint angles? Any info?

 

Or, you could put a truck bed on the back of an XKE.

 

Couldn't resist it, sorry. Not sure what the question is here. The jag rear and front could be problematic for the CG of the entire vehicle. These trucks tend to be top heavy and the loading could be a real problem. Unless you are after a show truck perhaps....

 

Rusty,

Check out gallery and posts by 55f-100paul, scrape and halfdone for some pictures and info on jag IRS.

 

rhopper-
You might want to check out Concours West Industries (www.cwiinc.com) for some ideas on the Jag IRS. They might even have a crossmember you could use to hang yours.

 

Rusty, Take a look at this website:

www.uk-hotrods.co.uk/garage_scene_stuff/me/page%20l.htm.

There are good pics of jag IFS and IRS in a 55.

 

The Jag rear end is very reliable from what I can tell. Nobody seems to have been junking the cars because the rear end went bad. It isn't done very often because it requires a bit of work to fab a cage. The stock JAG cage is butt ugly and hides what is a pretty neat looking piece of equipment, the rear end housing. I suppose you can use the stock cage but everyone that I've seen being done built their own tubular cage (square or round tubing).

I have my donor car and will be disassembling int he next month or so. For now, I can't speak to the u-joint angles but I don't suspect it will be a real big problem.

 

The SJ Jag rear is plenty strong for < 500 hp IMHO, and with the front IS will give you a truck that rides and handles like a jag. I'd definitely do it!
As to driveshaft angles, the tranny and rear end should be parallel to each other from the side, but not at the same height. You do NOT want a perfectly straight line through the driveshaft or it will vibrate like crazy and tear up the U-joints very quickly

 

I have had a lot of experience with Jags and they are most reliable. Mount them as close to stock as you can geometry wise and keep in mind that the trailing arms that locate the lower control arms have to pivot in the same plane as the INNER pivots for those lower arms. (Hope that's clear) The center gear set has a couple of degrees built into the housing and I have found that fabbing the rear x-member on the same level as the top of the frame rails is a very good way to go, you can adjust your engine and trans mounts to get the same pinion angle on both ends of the drive shaft. Spicer makes a u-joint adapter that bolts to the flange on the Jag center section and mates to a Ford passenger car u-joint. Norm Francis (I think he's in SanDiego now) makes an extra capacity rear cover for the Jag that looks like a quick change and is far and away the best on the market. These things are the catzass when it comes to looks and ride. Good luck and go for it!

 

rhopper,

I just finished cleaning up and reinstalling my Jag rear end. I modified the stock cage because I didn't want to mess with the suspension geometry. It doesn't look as good as some of the after market stuff but it didn't cost me a fortune either. Also If you want a limited slip look for an XJS donor car because they came stock with one.

Paul

 

Hi rhopper,

I am in the middle of fitting an XJS IRS with limited slip diff. I have just added a number of pics to my gallery of the way I am going about it. There are a few different options. I chose not to use the original cage but to fabricate a frame and weld this in place.

Its not too dificult, but does require you to be able to fabricate the frame, weld it in place and box the rails. I have nearly finished my rear end. I should have all the fab and welding complete by the weekend.

Cheers
Lee

 

Lee

I like your Jag rear install. The double crossmember and plate is VERY neat.

I have done similar with two tubes and a plate before.

The notching you did on the chassis is interesting. Looks like it will turn out well.

The way I fixed the same problem was to mount the coilovers to the outside of the rail. They are still angled slightly, but not much. You need to play with spring rates, but you have to do that anyway in any swap.

 

Rhopper

The drive shaft needs to have a minimum of a couple of degrees angularity at the uni's to "exercise" the joints, otherwise they WILL lock up and tear themselves apart.

Set the gearbox and diff mainshafts in the same plane (matching angle to horrizontal), but offset to each other either vertically or crosswise.

Sometimes the best setup is too offset the motor for steering clearance which offsets the tailshaft aswell......usually enough to exercise the uni's

 

Thanks Halfdone,
I got the idea straight out of Truck builder magazine, they did the same thing in an F100 a few years back. Although they didnt bother with the notching and it all looked very close. I am actually looking to put air on the rear as well as the front, but I havent quite worked out how to yet.

I saw your work from your gallery, looks very nice. I did think about relocating the springs/shocks on the outside as you have done but thought that the inner side at an angle allowed for more space in case the air springs need it.

I gather that you have done a couple of these now, how do you find the ride?

Thanks
Lee

 

The triangular boxing is a great solution! Triangles are much stronger than rectangles, so it should be plenty strong. I'm considering a Jag swap next winter, but I didn't want to alter the original geometry and spoil the original superb design. IMHO I wouldn't bag it if you are planning it to be a driver.