IRS into a '68 El Camino = Jag XJ6.

[RichardSIA]

Been doing research and even bought a second frame.
Since I want my '68 to handle much better at speed but am not drag racing I want to add IRS and rear disc.

Of course I have been pushed to use 'Vette parts.
The batwing and mono-leaf create some real issues, the track may also be a bit wide.

Turns out that the Jag rear is only off by 3/8" per side, not enough to notice.
With the original four coil over shock set-up and the EC's lighter weight I should be able to use one coil over and one air shock per side.
So I still get to keep load leveling capability I would lose with the 'Vette.
Coil overs can be had in different weight ratings, the 'Vette mono-leaf is NOT easily changed.

I will have to remove the original rear spring pockets to make room for the Jag mount.
Other than that this looks to be pretty strait-forward.
Complete Jag rears, with posi and decent gears are readily available for $500.00, sometimes less.

I intend to document the fab and build.
The same set-up will also fit 68- 72 Chevelle's.
Mostly posting at the IRS forum but can also update this thread if there is interest?
If this goes well I may make up extra conversion parts.

[lees02ws6]

What year XJ6 is the IRS from? I really hate inboard brakes, they have to heat up the side gear seals like crazy, and they are a pain to get to.

In the 90's Jaguar finally put the brakes on the knuckles instead.

[RichardSIA]

About a 76, yes inboard disc brakes.
Same as the XKE I used to have and it was the front brakes I used to overheat in the mountains.

Not a big deal to run some ducting to the rear disc and calipers.
Electric fans, water vapor cooling, lots of possibilities if I see an issue.
Since it's my conversion I will probably "Uncage" the diff which will also improve access to the calipers.

I know some folk have done a hybrid version using the later outboard brakes.
I want minimum unsprung weight.

[lees02ws6]

The vette leaf from the c4 can be had in multiple ratings from 148 in/lbs up (I was able to get a different rate spring from a junk yard for $75). It's not hard to change out at all. On the ground i can compress the spring at the knuckles with bottle jacks, remove the bolts, and then undo the center mount bolts (with the chassis supported of course).

I think the jag rear is ok though. Post up pics, should be an interesting build.

[RichardSIA]

One issue with the C4 is that they must have sold very few manual trans cars as all the rears I find are Dana-36.

The Jag rear is basically a Dana-44, and since I'm not drag racing should be fine with my current 350 or the 327 and M21 I am building.

I will document the heck out of this as I think I may be the first to do it.

[lees02ws6]

You can find Dana44's, but you pay a premium for them (usually no less than $1500).

http://www.ebay.com/sch/i.html?_trksid=p2050601.m570.l1313.TR0.TRC0.Xc4+da na+44&_nkw=c4+dana+44&_sacat=0&_from=R40

[RichardSIA]

At those prices I would be better off to buy a whole car during the winter and part out what I don't need.
Just saw an ENTIRE C6 suspension still on the frame for only $1900!

I should have only about $1,000 into my Jag conversion when it's finished, including custom springs and a pair of air shocks.
This is not check-book build,*I'm doing it myself and have to pay for it myself.

[srh3trinity]

I like irs as much as the next guy, but how good is the geometry in the Jaguar setup? It is an old design and likely more designed for comfort instead of performance, right? There is a guy on here using a 350z setup. That would be intriguing to me as they were built to handle.

[RichardSIA]

Except for the track width it is the same as used in Jag XKE's.

Not exactly sedate sedans made for comfort instead of performance.
XKE held the crown for super-cars far longer than any of the more modern stuff, did 150 MPH way back in 1960 for far less coin than Ferrari!
Lots of SCCA national championships among other major wins.

http://www.supercars.net/cars/5383.html

"As did the Jaguar XK 120 of the late 1940s, the Jaguar XKE validated its performance claims by winning the very first race it ever contested. And it did so in a thoroughly convincing way.

On the sunny spring afternoon of April 15, 1961, after 25 quick laps of the tricky little Oulton Park road course in Cheshire, future world champion Graham Hill took a race-prepared Jaguar XKE roadster to victory over a field that included an Aston Martin DB4GT, another new Jaguar XKE, and a pair of Ferrari 250GT short-wheelbase berlinettas.

On such a resounding note began a long and impressive competition career for Jaguar's new sports car. Impressive, especially, in that nothing about the showroom XKE was ever meant for racing. It was primarily a road car that made good use of design principles proven in racing -- such good use that it could go to the track and, often, beat far more exotic and expensive cars".

[RichardSIA]

Today I picked up a Jag XJ6 rear end in trade for the tired SBC 400 I pulled out of the El Camino.
I only wanted $150 for it, a very good Jag rear would have been around $500 and probably still in need of some rebuilding.
I got a rear with all the important pieces and TWO center sections.
One is an open diff and 3.31 gears, the other is a posi with 3.54 gears.
It will need new LCA bearings and brakes, probably new rear seals too.

By the time it is "Right" I will be spending a bit more but it will be virtually new.
And still significantly less expensive than a 'Vette D-44!
Now have what I need to begin figuring out the frame mounts.

With even better rear cornering traction I think my main issue will become curing the front end under-steer.
This car really plows, I want much more neutral handling.
Found a thread on jeep faster steering box conversions, interesting but will not cure the lack of front grip.
How do I fix that without getting crazy expensive?
Yes I am cheap, never saw the point of just throwing money at a hobby until it becomes too expensive to enjoy.

Pics.

82500
8.5" x 15" rims clear just fine!

82501

82502

[andrewb70]

So what happens when the axle breaks?

Andrew

[Bryce]

So what happens when the axle breaks?

Andrew

safety chain to keep the wheel sort of conected to the car.

[RichardSIA]

So what happens when the axle breaks?

Andrew

Same as Corvette!
But I've never even heard of an axle breaking.
U-joint failures yes, same as Corvette.

Making real progress on this now, have it all mocked up and very close to welding.
Did cut away most of the spring pockets, so I'm truly committed to it now.
Upper mount is a "K" shape with the forward legs going into the old upper trailing arms pockets.
I will also run a lower mount into the old lower trailing arms pockets.
Just need to set the differential height and angle.
My Jag IRS mounting should be stronger than the original stamped Elko frame, it may even stiffen the chassis.
Also making it a drop-out mount for ease of service down the road.
Only having to weld in two brackets.

[andrewb70]

safety chain to keep the wheel sort of conected to the car.

Sounds special, especially when going around a high speed turn at 100mph...LOL

Andrew

[RichardSIA]

Looks like I will be using the 3.31 rear diff.
The 3.54 is just too low for long trips.

And one more hurdle jumped!
Needed a cross member and engine mounts to mock-up my engine and trans before welding up the IRS rear end mounts.
Have to check drive-line and pinion angle.

No original cross-members to be had locally and Summit wants silly money for them.
So I'm getting one that will do the job from Joe Vega in AZ.
Engine frame mounts, cheap motor mounts and a high end trans mount will come from Summit Racing.
Motor mount set is just for checking fit but the trans mount will be used in the actual build.
Once I get this all mocked up late next week it may be worthy of a picture.

Next major quest becomes finding a hydraulic throw out and adjustable dual MC system.
I want to be rid of the power brake booster while running four wheel disc brakes.
I think I'm at about the end of the cheap progress.
From here out I expect to start spending more money.

327 and the Brownfield heads I have for it do not have so many mounting holes as a 350.
Anyone ever figure out a GOOD non-power assisted rack and pinion conversion for these cars that I could put in myself while the body is off?
Do not want to create bump-steer or a spectacularly large expense.
Car is intended to lean toward "Pro-Touring" much more than drag race even though it will retain 15" wheels and the mediocre TA's that seem to all that is available.