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Old 11-07-2015, 10:19 AM   #1
e015475
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Jag IRS on Air Bags

This is my first time fabricating an air bag suspension. Could find very little on the web for Jag IRS on bags, so looking for any advise or comments, so here goes......

This is where I'm at so far. This is a Series III Jag IRS with a later model Jag XJS locking differential(basically a Dana 44). 3.54:1 ratio and will be using a 5 speed WC T5 out of a V8 Camaro (with an S10 tail shaft to get the shifter in about the right position in the cab). Everything is just tacked together at this point.

Engine is down 3 deg and the diff is up 3 deg. Still need a lower support rod or rods to keep the diff from tilting under hard acceleration.



I'm sure there is better IRS out there than the Jag to start with, but this is about nostalgia and a plush ride, not corner carving ability.



I didn't like the stamped sheet metal cradle the Jag IRS comes mounted in so I fabricated this 'ladder' that supports the diff. It is mounts to tabs welded into the frame rails. The end tube has urethane bushings and the ladder bolts in with a single 1/2" diameter bolt on each side. Inboard Jag brakes are a PITA to service, so I made it so the whole IRS would 'drop out' with these two bolts. A little shimming will also be possible to get the alignment correct with the use of some washers. (sorry about all the painter's tape)

The air bag is mounted on a trailing arm that hangs from the Jag's lower control arm outboard pivot point to a cross member about 3' in front of the rear axle. The pick-up point of the front of the trailing arm is on the same axis as the inboard pivot of the Jag's lower control arm. I mounted it this way so the force of the airbag would not create a moment or torque on the needle bearings in the lower control arm.



The Boss wheels put the tires too close to the rear fenders and were close to the bed sides too, so I narrowed the Jag IRS about 2.5" (mini tubs are next). Cut the lower control arm on a band saw, sleeved it and put it back together. Took out the Jag axles and made new half-shafts out of parts in the Spicer catalog (the Jag half shafts are a forging, and I had some real doubts that they could successfully be shortened, but I'm told the Cobra kit car guys do it) Camber is about one degree negative and will be shimmed to zero at ride height.

The air bags are Slam RE5 with the internal bump stop for compression. The shock will have to provide the extended limit. Need recommendation on shocks that will work well with airbags. Travel will be about 5.5". With the bag aired-out the running boards will be about 3-4" off the ground. I may box the frame around the rear IRS mounts and notch the frame with a half circle of pipe to let it drop a little lower.



Another shot of the rear end. The bearing carrier now hits the frame rail when the bag is aired-out, so will have to trim the outer 'bell' of the bearing carrier about 1/4" to clearance it.



This is the 49 GMC that the Jag IRS is under. (had to pull the steering wheel up out of the way - granddaughter likes to stand on the seat and pretend she's driving) Fenders waiting on the mockup of the IRS to be done so I know where to cut the bed sides for the mini tubs. I put the rear end center line at 36" from the end of the frame rail - if anyone can confirm that's a good measurement to get the wheel centered in the fender I'd really appreciate it.

Phil
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Old 11-08-2015, 08:02 PM   #2
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Re: Jag IRS on Air Bags

Looks great.

Nice looking truck!!
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Old 11-08-2015, 08:11 PM   #3
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Re: Jag IRS on Air Bags

Very cool
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Old 11-11-2015, 09:28 PM   #4
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Re: Jag IRS on Air Bags

Really cool! Ive worked on a good number of series 1 xj's and a few mark 5-8. When i was adding my step notch i was real close to swapping in a jag irs. It looked like it would fit perfectly. Keep us updated.
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Old 09-10-2016, 11:54 AM   #5
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Re: Jag IRS on Air Bags

love the set up. I might need to pick your brain when I get started on mine
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Old 09-10-2016, 04:13 PM   #6
e015475
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Re: Jag IRS on Air Bags

Might be slim pickins, but IM me anytime
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Old 09-10-2016, 10:49 PM   #7
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Re: Jag IRS on Air Bags

I think your crazy but the good kinda crazy lol.Hope to see the truck finished soon.
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Old 05-17-2018, 08:55 AM   #8
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Re: Jag IRS on Air Bags

Any updates on the build?

I just acquired an IRS out of an 84 XJS and would like to see what work others have done.
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Old 05-17-2018, 07:47 PM   #9
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Re: Jag IRS on Air Bags

The truck is painted, cut and buffed.



IRS is in and shocks installed, gas tank is in.........





Rod end bars are in to steady the diff and hold the pinion angle





Have the brake cable done and pulled a brake handle out of an XJS in the junkyard - still need to fab a bracket and decide where in the cab I'm going to mount the ebrake handle

Modified the factory pedal set to take a Wilwood clutch master cylinder. Adjusted pedal ratios to get best feel out of the brake booster



Remote mounted the Hydro Boost about 15" back on the frame rail to get it away from the headers. Sorry no pics installed - it is dark under there! Master is a from a Corvette disc/disc ('79?)



Here it is sitting out on the apron in front of the garage - no air in the bags



New instruments



Four gallon air tank installed under the cab, mounted on the outside of the frame rail



Right now I'm working on getting the factory pedals to work just right with the hydroboost and the hydraulic throw out for the trans,


Still have glass, engine wiring, relocate coils, radiator/fans, boost pump, swirl tank, Viair mounting, air plumbing, fuel plumbing and brake plumbing before I can put the bed wood in and get it to the upholstery shop.

Last edited by e015475; 05-17-2018 at 07:54 PM. Reason: images loaded wrong
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Old 05-18-2018, 02:10 PM   #10
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Re: Jag IRS on Air Bags

Exceptional work!

Looks Great!

I'm collecting parts (and trucks) for now. When time/life permits I'll tear into one.

Thank you for the pictures.
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1949 - 3600 Update suspension, engine and drive it.
http://67-72chevytrucks.com/vboard/s...d.php?t=691034
1953 - 3100 Code 504 S-10 Swap
1955.1 - 3100 Bare Metal Build - 383 & Air Ride
http://67-72chevytrucks.com/vboard/s...d.php?t=691261
1965 - Buick Special & 1965 Buick Skylark
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Old 05-26-2018, 06:18 PM   #11
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Re: Jag IRS on Air Bags

A friends dad back in the 70's had a Jag IRS in a lowered gold 69 stepside. The tailgate had a wheat scene painted on it with "Golden Harvest" underneath. Serious hot rodding days with lots of crazy stuff everywhere. Your's is the first I've heard of since - love it - those inboard discs are beautiful!
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Old 05-28-2018, 12:28 AM   #12
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Re: Jag IRS on Air Bags

That's a beautiful work of art.
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Old 05-29-2018, 09:48 AM   #13
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Re: Jag IRS on Air Bags

Thanks for the kind replies. It's appreciated.

A jag rear end is a little unusual these days and there's a lot better technology available, but seems like every plastic hot rod kit I built as a kid had a jag rear end, so that's what came to mind.

I'd just rebuilt the suspension on this car before I sold it to start the truck, so it was kinda fresh in my mind anyway (it had a 5.3L LS motor too)

.

In hindsight, a more conventional suspension would have put me on the road a lot quicker, but for me it is all about the tinkering to get it to work and I'm not too worried about when I'll get to drive it.

Thanks again
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