Hey guys. No news yet on the '90 convert revival. Stuff has come up and progress is slow but I haven't given up.

This pertains to my '88 xjs that has diff noise and I'm hoping a fluid change will stop it or at least quiet it down a little. I've searched the forum and there's a few threads about xk8's and xkr's but I couldn't find any on xj models so I thought I'd start one for posterity.

What's the proper diff oil type? and whats the diff's oil capacity? Anybody have a brand preference?

 

Pretty simple in my opinion, but then I am a masochist.

Raise the rear, SAFELY, I use ramps, slide under the beast, there is a "male" drain plug visible through a hole in the tie plate, remove it, the plug that is. I use a 1/2" socket extention bar, reversed with an open wrench on the male end square, you will see it clearly when under there.

Filler plug, HAHAHAHA, this will test your wierdest sense of humour to the max.

Remove that tie plate, FEAR NOT, it is only a tie plate, and nothing will jump out at you, except maybe some old road kill, sandy oily gunk, and maybe a park brake pad or 2.

The fill plug is "male" 1/2" and is up on the top of the rear cover of the diff casing. It is "feelable" and if you are VERY good, you might see it, but I doubt it.

I use Nulon SAE90 Full Synthetic LSD spec GL4-GL5 oil in all the V12's and some of the others. Spec is 1.5ltrs, but read on, you may need a tad more.

Filling the thing:

I use a plastic tube, about 10mm diam, one end in the diff hole, carefully (not really) threaded out to the RH side of the car, where I tape it to something like a step ladder, floor jack handle, at about 1.5mtrs off the ground, Insert a funnel in the this end of the hose, fill the funnel with oil, sit on the chair you have handy and consume beer/JD/whatever, and keep that funnel full. When it dribbles out the filler plug hole, ITS FULL, remove the tube (get drowned in oil) and refit that plug. Drink more Necta, clean up the mess, refit the tie plate (after you cleaned it of course) and lower the car, and drink some more.

The clothes you wear will go direct to the rubbish bin, and you to a HOT soapy shower. That oil STINKS, and it will not come out of clothing, and will eventually wear off your skin. Thats why i drink.

As i said, SIMPLE task.

If the diff is noisy, I doubt this will help, but you got to do what you got to do.

 

Alternatively, you can go to your local auto parts store and buy a clear tube with a fitting that fits over the top of your fluid bottle. This tube has a twisting open/close action. Stick the end of the tube in the hole and point the bottle down. The bottle ends up over near the wheel well. Rotate open. Squeeze and fill until it overflows. Make sure you use a diff fluid for limited slip axles or use a limited slip additive. From what I recall, 2 bottles got the job done with some left over. Scott

 

ecbjag,

Great description from Grant BUT DON'T drain the diff.....UNTIL you know that you can undo that Fill Plug. The garages of the world are filled with XJSs where owners drained their diffs and then found out that they couldn't undo the Fill plug! Result...an immobile XJS! Well, a slight exaggeration maybe, but you get the point!

Paul

 

this^^^

anyhoo, the correct (approved) fluids, as per the service manual, is:
A.P.I. GL5 spec

BP gear oil 90 EP
Castrol Hypoy B EP90
Duckhams Hypoid 90
Esso Gear Oil GX90
Mobilube HD90
Shell Spirax HD90
Texaco Multigear ep90

So you can probably just go to an auto place and get some mobil hypoid 90 or similar brand

 

I agree with Ecbjag. Don't fill it until you get filler plug off.
As for filling. If you go to marine shop they have a bottle top pump you can use to fill diff. You will have to use longer hose. Its used to fill outboard leg oil but will screw on to most oil bottles. Its cleaner than using hose on bottle or funnel method.
The best method I have found available other than air pressured system I use now.

 

Damn, I forgot MY Golden Rule.

FILL PLUG OUT FIRST.

Thanks for reminding us all.

I just luv this old age memory thing.

 

Hold it now - I thought I was reading somewhere that, due to the materials in the diff, synthetic lubricants were not recommended, and in fact even synthetic limited slip additives were a poor idea?

I'm nuts about synthetics, but I just kind of resigned myself to dino bones when I read that. Is it bogus?

(I mean, if Grant's doing it then it can't be bad but still...)

 

What about the synthetic would be damaging to the diff? If you can't answer it yourself then why would you convince yourself of the same? Investigate it further.

I can't see any reason why it would be a problem.

 

Found it. From "The Book":

"According to a salesman at Quality Jaguar, the XJ-S final drive unit uses both natural leather and natural rubber seals. Therefore, synthetic lubricants are not recommended. It is recommended that synthetics be avoided in the special additive as well."

See it here.

 

You are implying that because the materials are natural, synthetic is the opposite of natural so it is bad. I need a better explanation lol.

I believe the term "natural" is referring to rubber from the rubber tree. Idk about europe, but the UK at least used this for much longer than the US. Synthetic rubber was quickly adopted after WWII in the US and became the mainstay for most items. The rubber in the engine is all synthetic, which is why it does okay with the oil around. I have heard this is why modern brake fluid tend to break down the inside of the XJS braking system, but haven't looked into it.

Honestly oil attacks natural rubber period, so I would be quicker to think synthetic rubber could be better, although I don't know the chemistry behind it.

 

I'm not implying anything, I'm simply trying to compare notes.

 

Sorry, meant to say "he" is implying

 

Thanks guys! Following the instructions from this thread and from https://www.jaguarforums.com/forum/x...-change-83383/ I was able to change my differential fluid over the weekend.

My car is a 1995 XJS 6-cylinder coupe. I've had it since summer of 2013 and it's always made grinding noises from the rear when making tight turns. Changing the differential fluid eliminated the noise completely!

Based on this thread, the other forum thread and some advice from Amazon reviews, I bought these:
Three bottles of synthetic blend differential oil One pump for quart bottles And square sockets

1. I put the XJS up on ramps in the rear, chocked the front wheels and applied the hand brake.
2. Getting under the car, I used PB Blaster on the 14 bolts on the differential plate and on the differential drain plug and fill plug
3. Removing the differential plate opened up a lot of room to get to the fill plug, so I'd recommend it highly.
4. All 14 bolts were 13mm, and six of them had acorn nuts on top. I put an open-ended wrench on the top and socket on the bottom to get them off. The differential plate was filthy.
5. I crammed a light up above the differential. Without the light, it would have been very hard to see to take out the fill plug, clean anything, or refill the differential oil
6. I cleaned up the area around the fill and drain plugs with shop towels
7. The fill plug was 1/2" male square. One of the sockets from the set above worked well. I removed that first, to make sure I'd be able to refill after draining
8. The drain plug was 1/2" female square. Another socket from the set above worked well, but you could probably also use a 1/2" socket adapter
9. The differential oil did, in fact, smell terrible and got just about everywhere
10. After draining the differential oil, I refit the drain plug and refilled the diff with the differential oil above, using the pump above. The pump worked perfectly and I would recommend it highly. Any other method seems far more difficult and time consuming
11. I ended up needing three (3) quart bottles to fill the differential until the oil started spilling out of the fill plug hole. This was mostly because the catch tube in the pump above only reached maybe 2/3 into the quart bottle, so I'd have to pump as much as I could, then switch to another bottle, pump as much as I could, squeeze the remainder from the first bottle into the second bottle, pump as much as I could, then switch to the third bottle
12. I refit the fill plug and reinstalled the differential plate

The grinding noise is gone!

 

I discovered, by accident, a really good way to fill fluids under cars.
Happened to have an old outboard engine fuel line laying around and needed to put fluid in a transmission. Initially I just wanted the length of hose to use, but thought maybe the primer bulb would work, and it did!
I use an outboard fuel line with primer bulb for all under car fluids now, in fact, I filled the XJS differential just yesterday using this method, and enough room to snake the hose into the cover from behind the cage as well.
One note though, ensure gear oil is heated a bit before pumping with the bulb, it's really thick when cold. Leaving the bottle in the sun works well.
The other advantage to this method is that you can use regular 4 litre bottles of fluid, not those 1 litre hose bottles that cost 50% of a four litre bottle.

 

As for synthetic vs. conventional gear lube ...

one well known manufacturer of modified differentials and axle assemblies
did a test with a instrumented axle assembly.

they found that while the synthetic ran cooler, the parts ran hotter.

makes sense since the only way synthetic can run cooler when the
differential is making the same amount of heat is to absorb less of
the heat being generated. see newton, et al.

so would you rather cook the lubricant or cook the parts?