So, I want to work out the ratio of the diff.
I'd read on several sites there were tags under the bolts?
Well, no tags.
On the top of the diff I've got the '4hu 004-25' and underneath that, 'LEYS L' and another number. -_-'

Underneath the diff cover, I've got some more random numbers, if these help:
D77 R 984

8C

L1
S112 (small, in a circle, irrelevant, more than likely?)

D7
011

LEYS C2HA
X9

I'm assuming it's 2.88; I'd just like to know for sure, as it's a donor for a hotrod. =O

Cheers.

 

I don't know what thecasting numbers mean but 3.07 and 3.31 were common on the early XJS V12s. The 2.88s were standard issue when the "HE" V12 was introduced in 1981/82

Cheers
DD

 

Hmh, right.
So what's the best way to identify?

 

like doug says, 3.07 to 1 was standard on 70s xjs.

mine 78 xjs on a rebild had 3.07,powerlok, i put in 3.73 and added overdrive, giving me 2.59 for final ratio.
great acceleration, and great cruisin,+mpg

 

A 1977 XJS has a 3.31 rear end ratio in 1978 when they installed the GM 400 transmission the ratio was changed to 3.07 which was fitted until 1982 when they went to 2.88

 

Pull the cover and count the teeth on the ring and pinion gears, and divide.

Cheers
DD

 

Ahhh, very intersting. I never knew about the trans/diff ratio change relationship.

But....the change to the TH400 came in April '77 so some confusion might still exist, especially if the car isn't there to verify what trans it has.

Cheers
DD

 

Okedoke; I just want to be sure as it's a donor part; and I'm having a gearbox (tremec 6 speed) adjusted to the ratio.

3.31 or 3.07?

 

with 6 speed gearbox, id look for a 4.11.
6speed has double overdrive, and top gear is way hi ratio.

should be a great driver, anywho get as low a final rear as you can get.
i had a 75 Jag V12, 3.31 , manual 4 speed and it really impressed me over my 78 auto box.

i would spend the extra money for custom rear gear, like 4.11 or 3.92, with that 6speed would make a great setup. OH, YEAH!!, and single piece driveshaft, Aluminum.

 

Interesting information; I fail at the internets, but have been reading up as much as I can about ratios and that.

So, I'm not really after having them adjust the gearbox to the ratio of the Jaguar diff? Or just have 5 and 6 gear high?
It's going for a Dodge Fargo, pickup truck. With a Chrysler 360 engine.
Should be a jolly little cruiser.
This is manual, naturally. =)

 

thats cool!! should be fine Mopar 360 v8, great engine.

 

It should be a great cruiser; I think I've got (and getting) all the right gear, this is my first project, apart from a Suzuki Re5...

I know it's not very Jaguar, but Ozrodders forum wouldn't let me register with my email. -_-'

Thanks for the help and input, guys!

 

the 6 speed is a double overdrive. To save your clutch and get great acceleration go to the 3:31-1 ratio or even 3:54 if you can.

 

 

Since this thread was started 10 years ago, I suspect either the OP has found his answer or it doesn't matter anymore. He last logged on in 2010!

 

Jagboi,, i agree, some very odd things happen on these JF forums, seems not connected to any thing relevent?
like mumbo jumbo?