Jag IRS Differential cases and stub axle seals

[Buzz]

Hi again -

I finally got the drive axles and lower arms from the "new" 3.31 IRS assembly shortened to spec. The machinist did a really nice job beefing up and balancing the shafts and I'm just waiting on the new U-joints to arrive so I can start reassembling.


I went back and forth on which differential I was going to use and had settled on the 3.31 because it just looked that much better and in better condition once I got it degreased and power washed. Both are Powerlock units and I figured that the 3.31 ratio would work a bit better in 4th gear since I rarely shift into 5th in normal driving on our hilly, twisty roads.

Once I opened up the case though, the old fluid was very milky and there were bits of thin, rusted slivers of metal in the bottom which I figured could be from the clutch pack. The assembly turns smoothly with no play or noise, but it looks like it has been waterlogged and I decided to set it aside for a future full rebuild project.

So now I've disassembled the old 3.54 unit and cleaned a bit of the gunk off of it. The fluid is clear and clean and it turns smoothly and silently with only a very tiny bit of play at the pinion. The only glaring issue is a leaky stub axle seal on one side.

The cases are both markedly different - there's a lot of conflicting information out there on positively identifying the series and vintage, but due to the botttom drain plugs on both, I know that they are both Salisbury units. The brake calipers appear interchangeable and both bolt in from the diff case outward, but the stub axle flanges and the cases themselves are different. I've attached some pics in the hope that some of the gurus here can ID the 3.54 unit so I can order the correct axle seals.

Below are the flanges side by side. 3.54 case on the left is gold below all the other stuff and the 3.31 on the right is originally red.


Here are the two cases. First the gold 3.54 with the reinforcing fins.


Next is the 3.31 case with solid bars instead of fins.



I've done a lot of checking around the various sites and forums for info, videos and photos, but I'm still not 100% sure what exactly I'm dealing with. I'd really appreciate any help in establishing what seals I need for the 3.54 case.

[joyridin']

The issue isn’t really when they were built as much as everybody calls them something different. The yellow case is a series 1. It should have tapered bearings for the stub axles. It uses series 1 brakes due to having the bolt-on bracket for the caliper. I would have to check, but the other one is a series 1.5 or 2 due to the stub axle having the bolt holes integral in the housing...or at least it looks that way from what I can see. The differential housing changes slightly also.

Regardless of which one you use, you really want to use the case that has tapered roller bearings for the stub axles. The ball bearing style used in 1968-72 are not acailable anymore.

[legenmetals]

https://jheengineering.com/jagirsgenerations.html

Some good info.

[Buzz]

Thanks guys. Here's a screenshot from the JH Engineering page that says the series one has the ball bearings and the series 2 has the tapered rollers. Also by their account both of my axle flanges, though different, have the tabs for the calipers which indicate series 2, but the 3.54 case is finned, which indicates series 1.



The brake rotors and calipers are interchangeable between the two.

[Buzz]

I suppose I'll have to pull the stub axles to see what type of bearings are in there. Since it rotates so smoothly and quietly, I was hoping to avoid a complete teardown and rebuild with crush sleeves and the whole 9 yards. Can the seals be replaced without a rebuild?

[Tom Wells]

I've just renewed the posting of the Jag IRS ID article assembled from the knowledge of Mike Bontoft here (hope it helps): Jag rear axle ID - FirstCoastCobraClub

[Buzz]

Thanks Tom - that was a huge help and it looks like the 3.31:1 diff is a '68 - '87 Series 2 unit and may or may not have ball bearings. It looks like I will have to go with a teardown and rebuild of this one as all of the new brake parts I have are matched up for this series. Joyridin' was spot on about the calipers. Although the new calipers line up with the discs when mocked onto the series 1 diff, the longer bolts needed to mount them will not clear the case. I guess I'm going to need a dial indicator now...
The good news is that the tapered roller bearings will swap onto my stub axles so if in fact I do have the ball bearings, I can replace them.

Thanks again for all of the help!

[Grubby]

Buzz,

Stub axle seals are super easy. Just unbolt the 5 bolts or so and pull it out. Keep the shims. No special tools needed.

You will see the O ring once it is out.

Replace and reinstall with the same shim.

Do both sides while you are at it. You will thank me later or maybe curse later if you have to do the other side in the car.

The O rings get hard over time and leak.

I think there are only two part numbers for the O rings. Order both if you aren't sure. They are really cheap.

John

[joyridin']

Originally Posted by Buzz

Thanks guys. Here's a screenshot from the JH Engineering page that says the series one has the ball bearings and the series 2 has the tapered rollers. Also by their account both of my axle flanges, though different, have the tabs for the calipers which indicate series 2, but the 3.54 case is finned, which indicates series 1.



The brake rotors and calipers are interchangeable between the two.

This dudes info is generally a bit off. I contacted him a few times and not to knock anybody, but he was sending me information on Corvette rear-ends from the 60's and stating they are the same design as the Jag. Use the info Tom has posted. It is correct.

[legenmetals]

This is a shot of the series 1 diff housing that I am swapping out for the XJS unit. Notice the nut on the output shaft.

[legenmetals]

I'm working on the rear diff. tonight and I thought I would share a picture before I disassemble one of the out-put shafts.

The O-ring is close to the inside radius of the bearing housing. The stiff and broken O-ring from the other shaft is laying on the table beside the out-put shaft assy..

[Buzz]

Thanks again for all of the help and info. I'll pull the stub axles out tomorrow morning and see what bearings I have. With the signs of water and rust inside in the case when I pulled the cover off, I'm really worried about the internals.
Can the internal parts from the Series 1 3:54 case swap into the Series ll 3:31 case? With the cover off and everything flushed out and sprayed with WD40, I can now hear a bit of noise coming from the outputs on both sides when I turn the pinion.

[legenmetals]

Just a note: The stub axles are the weak link with high torque cars with good traction.

[joyridin']

The bearings are cheap for the stub axles if they are tapered. The shims in between the bearings will probably match the new bearings without a problem. If it were me, I would order the stub axle seal, pull the stub axles apart, replace the seals and the bearings.

You do need a bearing press of some type. I have one from Harbor Freight I use. The tolerance is 0 - .003" end play.

[Buzz]

Originally Posted by joyridin'

The bearings are cheap for the stub axles if they are tapered. The shims in between the bearings will probably match the new bearings without a problem. If it were me, I would order the stub axle seal, pull the stub axles apart, replace the seals and the bearings.

You do need a bearing press of some type. I have one from Harbor Freight I use. The tolerance is 0 - .003" end play.

I definitely will order all new bearings and seals, etc. What I'm also concerned about because of the water and rust is the condition of the other components like the powerlock discs, etc. The 3:54 internals were working flawlessly in the car before so I was wondering if I could just swap everything into the 3:31 case and add new bearings and seals.

[joyridin']

Yes, they are all the same from that aspect. If you are going through all this work, I would buy new clutch disks. Yukon makes them for $80 and you can get them off Amazon. Do not buy the heavy duty version though. Just get the standard or your car will be jumping around corners. Do not ask how I know! LOL

BTW...all the bearings are available at any industrial bearing distributor as well as auto parts stores. I got all Timken from a local place that sells to industrial customers for about 30% less than the auto parts stores...and they were all Timken brand.

[Buzz]

That's good news. I just pulled the stub axles out of the old 3:54 case and lo and behold - tapered roller bearings! Everything looks in beautiful condition - even the o-rings look good, but it was definitely leaking.

By contrast, the internals of the newer 3:31 diff were dirty with a muddy, gritty sludge in the bottom. I definitely feel safer with the older diff so either I swap the internals into the newer case and button it up with all of the new brakes, etc. that I had ordered; or I just order a new set of seals, calipers and brake discs for the series 1. That's the easier option, but the relative weight of the brake components almost triples the price by the time I pay all of the duties and taxes. Return shipping cost is ridiculous, so exchange is not an option. Not a back breaking expense, but the wastage really bugs me.

[Tom Wells]

Buzz,

Mike Bontoft is still the guru for the Jag IRS. He moved to England some years ago and can be found here: Contact /

He may still be willing to answer a tech question or two. Might be worth a try.

Tom

[SSSammy]

Buzz, I've read the above and I'm not sure you understand about the shaft seals that are pressed into the cover. Joyridin' #14 post above refers. These seals ride on the stub axle rotating shaft and can harden with age and leak. They are particularly vulnerable to heat from the inboard brakes under heavy track use. See:

www.englishparts.com/products/gb/Jaguar/XJ6/OUTPUT-SHAFT-SEAL--Stub-Axle/19431/RTC1216.html

I recall having to buy a couple versions to get the correct ones for my ERA diff. To replace them on a one piece axle/output flange unit, you must disassemble the stub axle (yes, major PITA). To re-assemble that cartridge unit you have to torque the inner nut to pre-load the bearing correctly. I carried them to my mechanic ...

Sam

[Buzz]

Thanks Sam - I looked at the exploded drawings of the stub assembly and noted the seals, etc. It looks like a full rebuild of the stubs is unavoidable regardless of which route I go.