so my XJS has been up and roaring for a a couple weeks.

well i managed to wipe out the trans and differential in one swing doing some saturday night racing.

so i need to figure out whats up with this diff. it fails the LSD test when i jack it up in the air in neutral and turn one wheel the driveshaft turns but not the opposite wheel. and in park if i turn one wheel the other turns the opposite direction without considerable resistance. if i turn the driveshaft and hold one wheel still i can feel just a fair amount of resistance.

this has led me to believe that the friction unit is probably totally worn out. after all it has about 95,000 miles on it.

so my options are to weld it, which is looking tempting
to replace it with another 30 year old 2.88
or rebuild it.
opinions appreciated. sources for parts and clutches definitely appreciated.

 

This is stretching the memory just a tad, so if I am wrong/misleading, so be it.

That sounds like a Dana diff, NO drain plug??. They were known in some circles as a Power Lock LSD (or a similar naming), and acted like an open diff (almost), and had a "cone style" locking device, as apposed to a clutch pack.

Yours being an '85 is more than likely that Dana diff, its a production thing, and were mostly swapped out down here for the alternative (Salisbury), with a drain plug.

If you want to go that way, get a complete cradle assembly, as the caliper mounts etc are different. I did that with mine long ago.

 

in what way did they behave like an open diff?

i know it worked before because i checked it in neutral when i first got the new motor running about 6 weeks ago. and i KNOW it worked because the car was a side winder missile. crack the throttle and the rear end would walk at any speed.
now the car acts like an open diff car and wont step the tail out without coming into a turn seriously hot.

 

Some good info here:

https://www.jaguarforums.com/forum/x...estion-123617/

I think Grant is referring to the low bias LSDs used in the 90s vintage cars, as explained by a tech bulletin in one of the links from the above thread

Cheers
DD

 

im not looking to change diffs. i want to keep my 2.88 ratio because the L67 will blow my 205's off below 40mph. i dont need anything taller.
that thread didnt really address limited slip

 

like you mention, just weld it.

it will step out at 10mph in a corner, all is well!

course dont drive in rain or snow/ice.

 

I must've misunderstood.

I thought wore out your LSD and you were seeking a repair or an operational limited slip unit. What was mentioned in the thread was use of an Auburn limited slip unit for a Dana 44 , which seems plausible to me....


http://www.4wheelparts.com/Drivetrai...FU1cfgod8YoAeQ


.......if you can still keep your 2.88 gears, of course. But, yeah, if you don't want to change differentials then buying a new Auburn differential/LSD unit is out of discussion!




The alternative is to repair/overhaul your existing limited slip unit with new springs, clutches etc. I'm betting any differential shop can fix you up with the parts you need. Or certainly Coventry West can, as they specialize in Jag diffs.

Or, as you said, weld up the diff and drive in 'perma locked' mode!

Buying and installing a used unit is an unattractive risk, IMHO. It might not last very long and there's a fair bit of labor involved if it doesn't

Cheers
DD

 

youre the second person to suggest coventry west. i think ill call them tomorrow.

my scare with welding it is not that it will walk the rearend on command, but that the rear wheels will boss around the front and cause it to understeer

 

I have run a welded rear on a circle track car, as long as the rears are spinning it will not give understeer, but if driving without spinning the rear it will.
I have not looked into this but with the level of modification you have, have you looked into a Torsen or locking diff? According to Jag rear end - Hot Rod Forum : Hotrodders Bulletin Board, The differential is basically a Dana 44 so locking carriers, ring and pinion gear sets and bearings are relatively common and come in a wide variety of performance applications. I say that the differential is “basically a Dana 44” because although almost identical to a Dana 44, it is actually Spicers earlier design for this type of differential and is called a Salisbury differential. Not all of the parts on the Jaguar IRS unit are common, especially the brake parts, however, any non common parts can be purchased from Jaguar specific suppliers and/or the host of aftermarket suppliers that specialize in putting Jaguar IRS units in other types of vehicles.
BTW, this would make it the same differential carrier that was in my old Sunbeam Tiger.

 

Some more info from another Jag forum
XJ-S Final Drive

 

I do not know how many splines on the Jag, but if it is 30, stuff is readily available.
Dana 44 Yukon Spartan Locker 30 Spline SL D44 30 Posi Locker Axle New | eBay

 

i used some Jeep ring and pinion supplied by a local drive line specialist.
he took one look at them and went out back came back with a 3.73 ratio, bolted right in,

for the 1978,3.07, i had some old clutch plates from a 1959 Corvette positraction, they , were thinner,and bellville plates, went together and still in it 20yrs,and counting, it makes a nice tight LSD yet still gives me some slip bias!