Picked up a 3.58 with Power-Lok but one of the four studs that mount to the IRS assembly behind the driveshaft attachment flange is missing. Would a UNF (almost all the diff stuff is imperial if I remember right) thread bolt could be a good substitute?

 

I used to remember the thread pitch on all the XJ40 and X300 diffs

I THINK it is M10x 1.25mm but check it to be sure.

The XJ40 used BOLTS and the X300 used studs if I remember correctly.

Either bolts or studs will work fine.

bob

 

I'm pretty sure it will be a metric thread. Nearly all the fasteners on an X300 are metric, off the top of my head I can't think of any inch sized ones.

 

Lug studs?

(I'm actually asking and want to know so I can shop for new lugnuts, but there seems to be some ambiguity)

 

With reference to Jagboi64, I have measured it and can advise that the front pulley (crankshaft) bolt is in fact not metric ( perhaps the only non metric on a X300).
It is in fact 3/4" x 16tpi SAE and requires a 1 5/16" spanner or socket. A metric 33mm is slightly tighter fit being 0.013" smaller.

John Herbert
(1996 XJR)

 

They used that bolt for a long time it goes back to E Type at least!

 

Almost 99.99% certain the UJ to stub axle connection nuts are 11/16 matched to whatever UNF thread that is. That’s why I thought the mounting studs behind the driveshaft flange would be imperial too.

 

They are. I mangled them quite badly with using metric tooling and not paying anykind of attention while changing the diff.

 

I measured the spare differential I have and those threads are M10x1.5.