Jaguar differential reinforcing plate

[Buzz]

Does anyone have a template handy for the bottom reinforcing plate that ties the fulcrum brackets together on the Jag IRS? I recall one being posted a few years ago either here or on the Unique owners' forum. No reply over there, so I'm hoping it may have been here. Worse comes to worse, I can flip my differential over and attempt to make an accurate one myself, but if there is a template readily available, I'd really appreciate it.

I plan to get one cut out of stainless steel - any recommendations on plate thickness?

[joyridin']

Mine is aluminum and wraps around so the fulcrum shafts go through it. It is 1/4" aluminum. I would probably use at least 1/4" material no matter what you use. Anything less and it will probably flex too much unless you weld in supports.

[Buzz]

Thanks joyridin'. I just cleaned up the original fulcrum brackets that were on the car in preparation for painting. Based on the other thread, I wonder if the bottom holes all line up the same between the different brackets. When I take the newer ones off, I'll compare them side by side.

[Mongoose930]

In case you decide you want to buy one:

Billet Jaguar IRS tie plates

[Buzz]

Thanks Mongoose! They've got them here as well FYI: http://www.magoos.co.nz/shop/index.php?cPath=46_211

Far better for me to have one made up - shipping and customs duty nearly triples the price by the time I get it in my hands no matter where I order them from. No biggie - I'm sure once I get the proper fulcrum brackets mounted, I'll be able to make my own template.

[legenmetals]

This is a plate that I bought from C.W.I. years ago. I am going to drill a Hole for the drain plug today and sketched some measurements for you.

It appears that the mounting holes are drilled larger for ease of installation and because of the issue with bracket locations and spacing. This one fit snug when mocked up on my car.

[Buzz]

Wow - thanks! Much appreciated! I'll get one made up on Tuesday. It's Easter weekend here and Monday is a holiday.

[Ram427]

I would get the rear geometry sorted first, toe in etc before finalising the hole positions.

[Buzz]

Good point - thanks. I wonder if anyone out there has had an issue with fitment using pre-made plates from aftermarket suppliers. Also, are the holes in the Jaguar factory bottom plates oversized to allow for alignment adjustments?
I sent a drawing to my machinist for a quote using 1/4" mild steel, 1/4" stainless and 1/2" aluminum. My intention is to use it as a floor jack location, so should these thicknesses provide a reasonable safety margin?

[strictlypersonl]

Originally Posted by Ram427

I would get the rear geometry sorted first, toe in etc before finalising the hole positions.

I suspect that the holes in the plate are there to define where the brackets go (laterally). Use shims between the brackets and the differential to fill any gaps (as the original Jag configuration did).
* That means that the holes in the plate must be located perfectly. No sloppiness allowed.

[legenmetals]

Many Cobras and T buckets have been built using only the diff mount and front
fulcrum rod attach points with a tie bar in the rear. The shocks give some rigidity but the overall suspension is sketchy in my opinion.

When I disassembled my car I noticed that the side brackets had loosened up a bit. These were not Loctited or safety wired when previously installed.

When C.W.I made the plates they had to fit multiple set ups so some flexibility was needed. This is still better than not utilizing a plate. The 1/8 stainless plate
is more than strong enough to jack against. Buzz, 1/4 stainless is overkill and heavy.

I installed a crossmember slightly above and just to the rear of the diff that I will hang another plate vertically in "tension". The fulcrum rods will pass through this plate. This will eliminate the tie bar, also, "bolting" will allow some set up changes. This plate will bolt to the lower plate that I jack against. I will have the LCA pivoting off the fulcrums that are securely mounted on both ends.

I'm toying with the design of these plates. I'm thinking I may want to incorporate a brake ducting system utilizing this plating. All of this is adding more weight, but this is not a race car.

[Buzz]

Originally Posted by strictlypersonl

I suspect that the holes in the plate are there to define where the brackets go (laterally). Use shims between the brackets and the differential to fill any gaps (as the original Jag configuration did).
* That means that the holes in the plate must be located perfectly. No sloppiness allowed.

So the factory alignment is set and maintained by the bottom plate with no provision for adjustability short of relocating the holes? I suppose the lateral (right-left) alignment could still be changed by rotating the entire cage, but toe in/out would have to remain fixed?
All very interesting - I'm learning a lot about the Jaguar rear suspension. When I disassembled mine, 3 of the 4 fulcrum bracket mounting bolts were alarmingly loose and they were not safety wired. The same bolts on the newer differential case were wired and all were tight. I suppose if nothing else, the plate (with a tiny bit of room in the holes for adjusting toe) may be added insurance agaist slacked off or broken bolts. Or, as suggested, I could drill the holes after everything is set up and then receive full benefit.

Thanks legenmetals - a rough calculation shows that a plate made of 1/4" stainless would weigh almost 9 lbs. Happy to cut that in half using 1/8". I also want to add a mounting tab on the plate for the remote bleeder screws.

[Buzz]

One other thought - would duplicating the factory mounting hole locations on a stock Jag bottom plate for that series of differential give dependably correct toe settings?

EDIT - On second thought, the shortened control arms and axles would nix that idea.

[Tom Wells]

Buzz,

Maybe I'm visualizing this incorrectly, but I think toe would not be affected by axle and wishbone length.

If the toe is correct to begin with, shortening the axle & wishbone would bring the wheels closer to the differential, but the distance between the front and rear of the tire shoulders should maintain the same distance, i.e., the toe-in.

Think of it this way, if I set the tires on the ground at proper toe-in and then move them toward each other along the axle centerline (without turning them about a vertical axis), toe-in should remain the same.

Am I missing something? (probably...)

Tom

[Buzz]

Hi Tom, my initial thought was that if the tires are set at a particular toe angle other than 0 the effect of moving them further from or closer to the differential (along the angled axes of the axles) would not change the physical angle, but it would affect the impact of that toe angle on the vehicle and therefore need to be adjusted accordingly.
I was guessing that the correct toe angle for the same suspension with shorter axles should be different from the correct setting for Jaguar's stock track width.
Suspension gurus -yes/no?
Should we set our toe angles according to the stock Jaguar specs?

[Buzz]

Looks like rear toe specs for the XJS and Cobras are pretty much identical, so I'm just going to set it accordingly and drill the plate to fit.