Rear End servicing?

[w-lewis]

My Unique kit was built in 1998, car completed in 2005. It has a Jag rear end, presumably rebuilt by Unique in 1998, or perhaps earlier. Car now has 5,000 miles on it and runs fine. I've never serviced the rear end nor done anything to it. Do I need to changed the rear end oil?

[patrickt]

Originally Posted by w-lewis

My Unique kit was built in 1998, car completed in 2005. It has a Jag rear end, presumably rebuilt by Unique in 1998, or perhaps earlier. Car now has 5,000 miles on it and runs fine. I've never serviced the rear end nor done anything to it. Do I need to changed the rear end oil?

Assuming you have a freshly rebuilt Powr-Lok LSD in there, 5000 miles is the perfect time to change it out. Use the GM Limited Slip Additive Part #1052358, now #88900330, (I use about seven ounces total) and a quart and a third of Moroso Climbing Gear Lube Part #34800, which is red in color. Do NOT remove the lower plug to drain the fluid. Instead, suck it out of the fill plug. I use a Plews 55001 Lubrimatic Fluid Quart Pump and surgical tubing.

[w-lewis]

I don't believe it is a limited slip.

[patrickt]

Originally Posted by w-lewis

I don't believe it is a limited slip.

Then unless you're racing the car, I wouldn't touch the rear diff fluid unless you have a puddle of it under the car.

[w-lewis]

Thanks for the responses. No puddles, no racing and it runs great! Just knowing the rear end hasn't been touched in 23 years makes me wonder if I need to do anything. Have a Merry Christmas!

[patrickt]

Originally Posted by w-lewis

Thanks for the responses. No puddles, no racing and it runs great! Just knowing the rear end hasn't been touched in 23 years makes me wonder if I need to do anything. Have a Merry Christmas!

Just to be sure, next time you're out in the car hit the throttle enough to spin the rear wheels for ten or fifteen feet. Then look at the pavement and if you have two black marks change the fluid out, if you only leave one black mark then leave the fluid alone.

[w-lewis]

So you're thinking I should change fluid only if I have a limited slip?

[patrickt]

Originally Posted by w-lewis

So you're thinking I should change fluid only if I have a limited slip?

Yes, most LSD manufacturers, including the service bulletins from Jaguar for their Powr-Lok, call for an initial change out between 5,000 and 7,500 with the next change out at the 30,000 mark. However, with a non-LSD rear they treat the fluid as "good for life" unless you are racing, towing, or the like.

[w-lewis]

Thanks for that info. I recall trying to burn a little rubber years ago and believe it only left a single black mark, but with my aging memory, I'll give it another try.

[Grubby]

You don't need to service the diff. If you want to do it, but not needed.

Production cars with similar differentials, like a late model Mustang, call for service at 100,000 miles. Clutch packs haven't changed much in 50 or more years.

John

[w-lewis]

If it ain't broke, I ain't going to fix it.

[patrickt]

Here is the pertinent part of the service bulletin.

[patrickt]

And less pertinent, but still interesting is Coventry West's discussion of Jag rear fluid changes. Here:
https://www.coventrywest.com/dealing-with-differentials

[w-lewis]

Thanks!

[NROTOXIN]

Originally Posted by patrickt

Here is the pertinent part of the service bulletin.

This bulletin is only about draining the Initial (special) oil. Are you suggesting that W-Lewis has this Initial fill oil as noted in the 1963 bulletin?

[patrickt]

Originally Posted by NROTOXIN

This bulletin is only about draining the Initial (special) oil. Are you suggesting that W-Lewis has this Initial fill oil as noted in the 1963 bulletin?

In the Jag service docs, they call for initial changes for Powr-Lok diffs, but not for non Powr-Lok diffs, around the five to seven thousand mark. For non Powr-Lok diffs, they call for a change out at the 500 mile mark. GM would also call for the same change out at the 5 to 7.5 mark for LSD rears and then never again. But if you did not have the LSD in it, then you never had to change it at all. If he has a Powr-Lok in there, now's the perfect time to change it out and then probably never change it again in his lifetime. If it's a non-Powr-Lok, then just leave it as is. Or, if he does manage to put 30k miles on it, then change it as per CW's recommendation. But if he's only put 5k in 20 years then I doubt he'll hit that mark. The easiest way for him to check whether he has a PL in there is to just nail the throttle and look at the marks. That's easier than jacking the car up and manually turning a wheel. Make sense?

[patrickt]

Here, I happened to have these handy...

[NROTOXIN]

So your service bulletin was completely out of scope of his situation.....got it. Now, if it is just a GOOD time as any (not mandatory) to change the fluid, that is much more in scope and makes sense.

Signed 2021 not 1963.

[patrickt]

Originally Posted by NROTOXIN

So your service bulletin was completely out of scope of his situation.....got it. Now, if it is just a GOOD time as any (not mandatory) to change the fluid, that is much more in scope and makes sense.

Signed 2021 not 1963.

The point of the service bulletin is to highlight that Powr-Lok LSDs have a break-in period of five to seven thousand miles. Back in 1963 that was news to the Jaguar folks. Non-LSDs don't have a break-in period. Most of the guys around here with Jag rears don't know that and don't realize that they should probably change out their rear fluid at the five to seven thousand mark if they have a Powr-Lok. Grubby's post above is a perfect example of simply not knowing that requirement for a one-time change out on LSDs like the Powr-Lok, whether you have an XKE or a Camaro. He's likely surprised to see that GM specifically called for a fluid change out on an LSD at 7,500 miles and then never again. Chances are, you are too. You just won't admit it.

[incoming]

OK, I'm puzzled? why not pull out the botttom plug?