Are the Xj12 the same size as the XJ6…I think the V12 E type is wider than the straight 6 E…Steve
When I did a T700 in a S1, I did it for power; all I could get. So I found a 4.09 from a UK 2.8 litre XJ. It would actually spin the tires.
It still did 2200 RPM at highway speed.
Good luck,
Rob
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Thanks for this. Thankfully, being a California and with the little use this car will get, fuel economy really is the last of my preoccupations 
It seems that local junkyard stock is mostly XJ6 S3, then XJS V12 (mostly convertible of course) and some XJ6 S2. E-type stock is nil for obvious reasons.
Traffic lights racing on El Camino Real on Wednesday nights?
Relaxed cruising on the Golden Gate Bridge to the wine country?
Swift overtakes on H17 up the Santa Cruz mountains?
I can now see a high ratio diff in my future
Oh but I need to get that car actually ON the road first
The XJS will have LSD diff but I don’t know the ratio.
The XJ6 S3 will have the Salisbury diff with tapered bearings and I think the ratio you would want.
Better avoid the Dana diff as there are very hard and expensive to fix if they brake.
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Hello all,
Reviving this thread as a differential has popped up for sale near me. Seller says it is a PwrLock from a 1987 XJ6. Does this check out?
Well, it looks like a Jag diff alright !
Power-Loc? Doubtful, as it’s a rare thing on an XJ6
Cheers
DD
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The guy says that he cannot see the tag with the ratio. I guess I’ll pass…
Almost certainly a 2.88
The early Series III XJ6s had 3.07 diffs. After '81 or so the 2.88 ratio became standard issue…for the USA cars, at least
Cheers
DD
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With the THM700 transmission and its 4th gear I can afford to go with a low ratio, so a 2.88 is not an ideal choice for me.
If you see it in person, turn one of the stub axles by hand, if the other one turns the same way, Powr-Loc. If it turns opposite way, open differential. As Doug says, almost certainly 2.88’s.
Dave
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I thought so ??? My car with .70 % OD and 2.88 loafs at 70 mph. but the LT1 has the guts to pull it, hills or no hills…
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Well, unless it’s from a 1994 or 1995. Those cars had the overdrive A/T’s, so came with a 3.-something diff.
Eric question was for a 1987 S3, not one from 1994 or 1995. Somewhat different animals.
Dave
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Now this just popped up not far from me. Very tempting, albeit pricy. Any issues I should be ready for with the outboard brakes?
Thanks.
" 3.54 posi diff (good used unit from late XJS) and good used outer hubs, outboard brakes (upgraded with new XK8 vented rear rotors and rebuilt XK8 calipers), KYB shocks all around (new), rebuilt rear sway bar type trailing arms (with new small/large bushings), and custom made stainless steel brake lines, all assembled in a good used late model XJS rear cage."
20 characters worth of jealousness…
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Rerouting handbrake cables and brake lines springs to mind, Eric - though there just may be issues with attaching the cage to the car…?
Frank
xj6 85 Sov Europe (UK/NZ)
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Aristides, what do you mean? Not sure I follow…
Thanks.
He is jealous.
…20 
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Hello Eric,
This article is quite helpful and covers the brake lines.
http://www.jaguarspecialties.com/XJSC-LS-2.asp
I believe you will also need a new emergency brake cable, the article doesn’t really cover this but the e brake pads are actually shoes in the rotor hat.
Best regards
Carl
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