Differential advice

[alunwill]

Advice please.

I've come to look at the diff and surprised at the amount of iron filing centred around the drain plug.

To those who are far more experienced in stripping these than me, what could you typically expect from a 60 year old differential.

The crown drive looks good although I've not checked wear pattern yet.

I've attached a photo of a magnet I used to pull it out. Probably 3 times this amount in total.

Advice would be most appreciated.


Many thanks


Al

[bitsobrits]

Though your photo is unfortunately out of focus, it still appears to me that the amount of metal present on the magnet is alarmingly high. To me this suggests a full disassembly to determine which components, exactly, are the source of all this material. I would think it would be fairly apparent once everything is clean.

[Gfhug]

Time to send it to Alan Slawson? Details to be found on here. Especially if it’s a US 3.54 and you want someone to change it to 3.07

Geoff

[alunwill]

Many thanks for the responce. I was aiming to do a full strip down. As you say steve, the amount of debris is so great the problem should be fairly obvious.

I've done input/output bearings on this style diff for my cobra. It will be interesting to split the actual diff this time.

Alun

[Gfhug]

Al, if you plan to do the work yourself then I’d still advise chatting to Alan Slawson. The bearings are difficult to find and having been doing this work over many years he is the best source for getting the bits. He does seem to be happy to help the self-builder.

Geoff

[angelw]

Geoff Wrote:

The bearings are difficult to find

Hello Geoff,
Alun's car is an S1, therefore, it will probably be a Type 1 diff, and therefore, using opposing, tapered roller bearing on the output shafts. All of the bearings for that model diff are readily available from any reasonable bearing supply.

Regards,
Bill

[Gfhug]

Thanks Bill. I know Alan has a good source of these which is why I forwarded my recommendation to chat with him. But if they are readily available then that’s good news. Thank you.

Geoff

[angelw]

Hello Geoff,
The Type 3 differential used a double row, angular contact ball bearing race, with split, two piece inner race. When assembled and held together by hand, there is a slight gap between the inner faces of the inner race halves. When pushed together via the securing nut, the two halves are pressed together until the inner faces are in interment contact, and at that point, the bearings are in correct pre-load.

Unfortunately, these bearings made by Hoffman, haven't been available for many years, and I would be surprised if Alan has any. The alternative offered by SNGB and others is a very poor replacement. It's a double row, angular contact bearing of the same ID/OD, with a solid, one piece inner race, and therefore, no scope for pre-load. They are 2mm narrower than the original, which requires a 2mm spacer ring for both the inner and outer bearing race. The spacer for inner race is located concentric by its bore being a close running fit on the axle, but SNGB supply a spacer for the outer race that has the same OD as the bearing, which is wrong.

There is no amount of available bore for this spacer to be located concentric with the bearing, and as the spigot bore outboard of the bore for the bearing, where the outer bearing spacer is located, is larger than the OD of the bearing and spacer, once the nose of the bearing retainer plate, come brake caliper bracket, starts to enter its spigot bore, sight and control of the spacer is lost, where it can then fall to the bottom of the spigot bore, unless the spacer is held concentric with the bearing with grease, or glued in place with bearing retainer. A more sensible solution would be to make the OD of the outer race spacer a slight running fit in the spigot bore. However, even with this spacer being located concentric with the bearing, there is still no pre-load of the bearing.

Later differentials, starting with Series 3, perhaps Series 2 XJ6 cars, and other models circa that time, the output shaft bearings system reverted back to that used with the Type 1 and 2 Salisbury differentials, that being opposing taper roller bearings. The angular contact bearing, with the built in pre-load would have been introduced for expedience sake in assembly; you simply torque the securing nut to press the halved of the inner race together with no further adjustment. The opposing taper bearings isn't an inferior system, in fact, it would be arguably better when sharing axial and radial load.

Given the poor alternative to the correct Hoffman bearing, if the output shaft bearings have to be replaced, it would be better to convert the differential to use the Taper Roller Bearings. The taper roller bearing and shaft assembly is entirely interchangeable with the angular contact bearing system without modification to the differential housing. New parts are not available, therefore, you have to find the parts from the later model differential. New parts not being available is not entirely correct, for I manufacture the bearing housing/brake caliper bracket as a new part, and supply the output shaft on an exchange basis. There is a "metal on" condition of the angular contact bearing output shaft, that allows for it to be re machined to the specifications of the taper roller output shaft.

Regards,

Bill

[Gfhug]

Bill, thank you for a very comprehensive explanation. Alan Slawson has overhauled a couple of diffs for me but I don’t recall if they were the 3rd version or if he converted to the 2nd version. Or whatever he did, just that he did a very fine job. And mentioned the difficulty of finding the 3rd version bearings, perhaps as an explanation to change to 2nd. Please don’t quote me on those points, just that he well knew of the problem and the work around.

Geoff

Alun, sorry for the topic drift, good luck with your work

[44DHR]

Al,
You haven’t mentioned why you are looking at the diff - as if you suspected a rumbling or clunking - but most responses are referring to bearing issues.
In my experience of working on these diffs - I can’t see what diff you have - but if it’s a Limited Slip Diff - my initial thoughts are wear and debris from the clutch and friction plates, not bearings or wear on the Crown Wheel and Pinion. In the later case that would be very apparent just looking at them and the backlash.
I have had many diffs with debris from very worn clutch and friction plates caused by lack of incorrect LSD lubrication. Check how well the clutch plates are locking the diff just by spinning the shafts - if it is still in the car - as if there is any slip, as this could be from worn plates.
Regards,
Dave

[alunwill]

I've started the strip down and I've attached a shot of the output drive. From previous posts, it would appear to be a type jag 1 diff, although Correct me please.

The project is a partial restoration so I have no knowledge of performance issues prior to my ownership. Hence the strip down.

It is a PL and as it's an automatic, it's 2.88 which is confirmed by the Crown wheel marking.

I've removed the shells holding the case in place but the case is fairly well stuck. Do I need a spreader to release this or is it a straight forward levering which I'm reluctant to do without advise.

One thing I have noticed is that the alignment marks for the two parts of the case are about 100 degrees misaligned. Picking up on Dave's earlier point of clutch plates possibly being a source of wear, could this be the cause.

[mgcjag]

Hi Al...in no expert but have done work on a few....yes it looks like the earlier o/p shaft.....iv levered the carrier out but care needed....its heavy and can jam easily...use tape on your levers so you dont have metal to metal contact i find this feels a bit safer....alignment marks...sounds like someone's been in there befor?....not sure of the issues if its not aligned correctly......I would strip the lsd down befor working on the o/p shafts if they feel OK....iv had the side gears wear causing lots of metal bits in the oil....its then basically scrap as side gears were not available
...good luck....Steve

[angelw]

Al Wrote:

I've started the strip down and I've attached a shot of the output drive. From previous posts, it would appear to be a type jag 1 diff, although Correct me please.

Hello Al,
It's hard to tell from the picture of your output shaft assembly, if you have a Type 1, or Type 2 differential. They both use opposing, taper roller bearings for the output shaft assembly, the difference being is that the output shaft itself is a two piece system, of shaft and flange for the Type 1, as shown in the following picture, whilst the Type 2 differential has a one piece shaft and flange.



With regards to removing the diff centre from the case, for Type 1 and 2 models, it should come out relatively easily. The reason being, is that unlike a Type 3 differential, where the pre-load of the diff centre bearings is obtained by shimming the actual taper roller bearing cone on the diff centre, the Backlash and Pre-load for Type 1 and 2 differentials is achieved by shims placed between the diff housing and the flange of the Output Shaft bearing housing.

With a Type 3 diff, you have to force the diff centre and its bearings into an opening that is smaller by the pre-load amount, than the side to side distance between the outer faces of the bearing cups. With Type 1 and 2 differentials, the pre-load is removed when the output shaft assemblies are removed. What is making it a little difficult to remove the diff centre, is that the OD of the Bearing Cups is a very close fit with the half bore they sit in when the caps are removed, and a bit of suction and firm fit is keeping it from being lifted out. Once you start to get the diff centre to move, it will lift out easily.

When the diff centre is reluctant to move, as in your case, if you're going to replace the bearings, assemble the output shafts, minus the bearing housings back into the differential, and use these as handles to try and break the seal between the diff centre bearing cups and their seats. You won't be able to apply enough force on these shafts to even come close to doing any damage, so do not be concerned. I have two brass shafts, turned to the minor diameter of the internal spline of the diff centre for this purpose, that I can use whether I'm going to dismantle the output shaft bearing housing or not.

Regards,

Bill

[mgcjag]

Hi Bill....any ideas on if the LSD alignment marks arnt lined up on assembly what issues there could be....thanks....Steve

[alunwill]

From Bill's post, it looks as though I have a type 2 diff or could it be type 3!

Having split the output coupling today it's a single unit. Interesting thing is it also uses a collapsible spacer to get it's preload on the taper bearings for the output shaft. I thought they used a sleeve and shims.

I managed to get the diff case out. Levering didn't touch it. I used the rag trick mentioned in a previous post and it just slid up.

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!

The Internal diff components look good. Not sure what's acceptable wear on clutch friction plates but the coating, if there was one has gone. Wear is about 4 to 10 thou.

Apart from the clutch plates, the only thing I've found is that one of the retaining springs on one of the output taper bearings was missing. Could this be the source. Has the spring gone through the mincer.

Al

[mgcjag]

Al....we need a few photos of your o/p shafts....is there a large nut on the outside,?... its not a type 3 from what I'm seeing as it looks like taper bearings.....type 3 has ball bearings....Steve

[alunwill]

Hi Steve,

Yes it does have a large nut, 1 7/8" with tapered bearings.

[mgcjag]

Hi Al...is there a large nut on the outside holding the shaft to the flange or is it all one piece....see Bill's post above....Steve

[alunwill]

Hi Steve, no it's one solid piece.

I was surprised to see the collapsible spacer. I thought these were a later feature.

[angelw]

Al Wrote:

it looks as though I have a type 2 diff or could it be type 3!

It's a Type 2, definitely not a Type 3

Al Wrote:

Having split the output coupling today it's a single unit. Interesting thing is it also uses a collapsible spacer to get it's preload on the taper bearings for the output shaft. I thought they used a sleeve and shims.

After the Hoffman Bearing for the Type 3 diff was no longer available, diffs for later cars, from circa XJ6 Series 3 on, the bearing system went to opposing, taper roller bearings, and used a collapsible spacer to set the pre-load. At the time of the S1 cars with Type 1 differentials, the call out was for circa 0.002" End Float for the output shaft bearings. By the time of XJ6 Series 3, XJS, and other models, the call out was for pre-load. It's called evolution. I suspect that your diff has had new output shaft bearing fitted in the past, and the repairer has gone with the collapsible spacer. They are more convenient to use, for it's a one time assembly to achieve the correct setting, whereas, you will have at least 2 (at best) assemblies to achieve the correct pre-load when using a spacer and shims. The collapsible spacers are known to change over time from spirited driving. I still prefer to use the spacer + shim concept, except, I only use a solid spacer and no shims, where I have them to hand in 0.025mm thickness increments, or I can make the required size "Just In Time", if I don't have the correct size on the shelf.

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 stated that shims were used in that manner in my previous Post. Your diff is definitely not a Type 3, and if the output shaft is one piece, it is definitely a Type 2. The pre-load for the diff centre bearings is set in exactly the same manner for Type 1 and 2 differentials. The shims for Backlash and Pre-load are calculated virtually simultaneously, with the Backlash being set correctly first, then shims strategically removed to get the correct pre-load, and maintain the correct Backlash.

Al Wrote:

The Internal diff components look good. Not sure what's acceptable wear on clutch friction plates but the coating, if there was one has gone. Wear is about 4 to 10 thou.

I would be replacing the plates, for you have done the hard work by having the IRS out and the diff stripped to its component parts. 0.010" wear is definitely on the heavy side.

Al Wrote:

Apart from the clutch plates, the only thing I've found is that one of the retaining springs on one of the output taper bearings was missing. Could this be the source. Has the spring gone through the mincer.

What springs are you referring to? With a Taper Roller Bearing, there should be an inner race, the bore of which should be an interference fit on the shaft, rollers, and a cage to retain the rollers. Can you post a picture of the spring?

Regards,
Bill