Differential advice

[mgcjag]

Lots of great info there from Bill.....Al have a look at your diff where iv put the arrow....stampings can sometimes identify the year of the diff....possibly you whole diff is a replacement....Steve

[angelw]

Steve Wrote:

possibly you whole diff is a replacement

Hello Steve,
I read through Al's post again, and I had missed that the diff ratio is 2.88 to 1, and that
Al Wrote:

One other point is that my diff preload looks as though it's done by shims between diff case and the inside face of the diff bearing. Totally different to the workshop manual I have. Is this right for a type 2 or is it a type 3!

I wrongly comprehended that when I made my previous post, thinking that the pre-load was via shims between the face of the output shaft bearing housing, and the diff housing.

His diff is actually the next generation on from the Type 3 and is NOT a Type 2 diff. His differential is most likely out of an early XJS, and is definitely a replacement for his original diff, which would have been a 3.07 ratio.

This would explain the 2.88 ratio, the one piece output shafts, and the collapsible spacers for pre-loading the output shaft bearings.

Regards,

Bill

[tim wood]

I thought that the car in question was an automatic which from my memory means a 2.88 diff.
Happy to be corrected

Tim

[angelw]

Hello Tim,
Actually, you're correct. A 2.88 ratio was used with the 2+2, which is what Al has. However, the fact that pre-load of the diff centre bearings is made via shims under the bearings, and taper roller bearing used for the output shafts, makes it a later model than a Type 3.

Regards,
Bill

[alunwill]

Many thanks for the input so far.

Having bought a partial restoration, I'm not sure if this diff has ever been fitted to this car. That's what you get for picking a job up part way.

I cleaned everything up this morning because I'm still chasing the source of the debris,

Bill, the spring I mentioned is the one around the top of the inner output bearing, photo attached.


This diff has had a hard life. Traces of overheating and a gear which is showing signs of having crunched something up.










Steve, The number you refer to is 90E 83496, is that 1983?

Al

[mgcjag]

Hi Al...90E I think is 1990 so S3 xj6..the spring is probably fron an oil seal....are you aware that diff mount brackets are specific to E types..so if this diff was just in a box of parts the mounts may also be xj6....how about the irs cage, driveshafrs, wishbones etc...do you have larger xj6 parts or E type parts....Steve

[angelw]

Al Wrote:

the spring I mentioned is the one around the top of the inner output bearing, photo attached.

Hello Al,
That spring is not a part of a Taper Roller Bearing and is most likely as suggested by Steve.

When you get to the point of setting the pre-load of the diff centre bearings and gear backlash, you will end up assembling and removing the bearing cones from the diff centre a number of times. These bearings are easily damaged due to typical difficulty removing the bearings. To avoid this, I use a set of bearing cones that I've honed the bore of the inner race to be a close running fit on the diff centre bearing journals.

Because the bearings are made within a tolerance range, I use the bearing cups that are going to be used in the repair, and measure the height difference between my trial set of cones and the new bearing cones that will ultimately used. To do this, I:
1. place the bearing cup on a flat surface and place the Trial Cone in the cup
2.sweep the top surface of the bearing inner race with a dial indicator and set it to zero.
3. repeat step 2 using the bearing cone that will be ultimately used in the assembly.
3. note the difference between step 2 and 3 above, and use this amount when calculating the required shims to use to obtain correct bearing pre-load.

As Steve has pointed out, the IRS Cross Member mounting brackets that attach to the differential are unique to the E Type, therefore, you need to determine in your's are correct before you go much further. They are quite hard to find, but if your's are not correct, I can help you with these parts.

Regards,

Bill

[alunwill]

Looking at the spring you're correct, although how that popped so neatly around that bearing is another thing!

Steve, I have a new irs cage from one of the usuals. It came with the car and it is for etypes.

The mounting brackets as you say are something else. Is there a specific measurement regarding the differences I can check. If not I'll get the cage out tomorrow and physically check it.

Any views on the gear wear and the overheating - just running with low oil?

Would you trust it or change it.

You've got me thinking about the rest of the rear axle bits although I do recall checking them against my spare cobra bits which are xj6 and noticing these were shorter.

Al

[mgcjag]

Plenty of info on the mounts/dog bones if you search... here is one viewtopic.php?f=3&t=10004&hilit=Dog+bones as re diff condition the gears dont look great to me plus whatever else needs doing....I would be looking around.....are you keeping the car auto or converting to manual?.....Steve ps you could just look at fitting one of the new LSD units keeping your crown wheel and pinion and o/p shafts

[alunwill]

Bill,

Thanks for the offer of the feet but I've just checked mine against the irs cage and everything aligns.

[angelw]

Hello Al,
For the amount of work required in refurbishing your current diff, plus the work involved getting at the diff for a second time after you get to the point of the car able to be driven, I would be replacing the gear set.

If you get another complete diff, and it happens to be a Type 3 with the Double Row, Angular Contact Output Shaft Bearings, retain your current Output Shaft assemblies, for the opposing Taper Roller Bearings system is far better than using the alternative angular contact bearing and spacers being supplied by regular Jaguar parts suppliers. Your output shaft assemblies will fit a Type 3 diff housing without any modification whatsoever.

Regards,

Bill

[alunwill]

Finally got around to reassembling my failed diff. Replaced all the gears and a new set of clutch plates. It's torqued down ok. Quite balanced as it settled so my thoughts were, internal alignment must be ok!

Advice please from those with more experience than me before I start to rebuild the carrier.

Should there be any movement between output shafts on the bench.



Alun

[mgcjag]

They are set with preload so no endfloat...Steve

[alunwill]

Hi Steve,

I'm talking specifically about the internal lsd case. With the o/p shafts slipped into the ends should there be any noticeable rotational movement of gears within the diff case. I'd assume it should be locked.

Alun

[mgcjag]

Jag lsd....Crown wheel side the o/p shaft should have no rotation to the c/w.......gear side you may feel very slight becaus of the gears.....what lsd did you use....you never did come back to be about the gears I had......Steve

[alunwill]

Hi Steve,

Thanks for that.

I decided against the Quaife. Nice unit but dimensions weren't quite right against the 4hu. At least on my measurements! OK if you had a lathe.

I used another salisbury 4hu. I was lucky. An old friend had a partially stripped unit F.O.C.

It had a good inner lsd. Just needed to replace the clutch plates.

Apologies about getting back, but I've been in and out of hospital for last month so little contact with the world. Back to the build now.


Al

[alunwill]

Having been laid up for the best part of 6 weeks, I'm finally getting around to finishing my diff rebuild.

Output shafts set up, no real issues
Clutch plates replaced and replacement set of gears installed
End float shims defined for diff side bearings and preload
Run out is zero
Because it's a 2.88 ratio diff, the standard pinion height of 2.265 doesn't apply so I've used the original shim under the pinion inner race of 0.030.

Backlash set to 0.008

Crown gear mesh pattern is attached. What's the view from the more experienced - OK or does the pinion height need to change

[mgcjag]

Can't really see you marks its all too greasy.....what should the pinion depth be on a 2.88 better to know and calculate shim....this from the service manual....Steve

[angelw]

Hello Al,
It appears that you've used Bearing Blue, which is not a good choice in this application, Because it's rather sticky, it doesn't easily display a good mark. If you were able to coat the teeth of the pinion gear teeth, and have none on the crown wheel, then it would give a better result, for blue from the pinion would be being transferred to the bare crown wheel. Of course, this is not easily possible, and having the blue applied to the crown wheel results in the blue being pushed around on the crown wheel teeth, and a not so easy to see contact area. The fact that you have way too much marking media on the crown wheel makes it even harder to clearly see the tooth contact in that picture.

What I find is a good marking media, and it leaves a very even amount of material on the contact surfaces, is the soot from a pure acetylene flame. Accordingly, if you have an Oxy Acetylene welding set, I suggest you use that. It's easy to apply a very even, thin deposit, and because its adhesion is quite fragile, it displays the contact without much effort being applied. If you don't have an Oxy set, Marking Out Blue is a better choice than Bearing Blue. It's a rapidly drying, very low viscosity Blue liquid used more in the days before CNC machines, where features that were to be machined were marked out on the work piece. It drys quickly on the surface its applied to, and because of its very low viscosity, a very thin, even coating results, which is worn away by the contact of the teeth of the two gears. Not as good as Acetylene soot, but way better than bearing blue.

Regards,
Bill

[abowie]

Apparently you can mix white lithium grease with powdered turmeric to make a yellow paste.

I managed to buy some yellow paste locally. It's much better than your blue.

From what I can see on your picture the tooth contact is too high and a tiny bit too much towards the toe.

This is how the 3.54 diff in my Mk2 ended up. The pinion height was exactly 2.265 so I left it alone, and I ended up with 6 thou of backlash. It sounds fine when driving.