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Rear diff bearing replacement - what else to do at the same time?


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Following on from my project thread, it looks like I may have the unenviable job of dropping the diff in my garage. It looks like when a driveshaft UJ seized last year, it caused damage to one of the diff's output bearings. This has given me some movement in the inner driveshaft and brake drum, giving me an MOT fail.

Once I confirm this, I'll set to work on pulling the diff and replacing the bearing. Aside from the bearing, what other things will I need to replace or are handy to do at the same time? I'm already thinking about doing the UJs on the propshaft, and someone has mentioned the brake cylinders, but what else is there?

Also, will I need to grab new seals with the new bearing? I've put a pic below for reference :)

imageproxy.php?img=http%3A%2F%2Fi673.pho

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The seal is an o ring which can be had in a pack for a 40mm bottle trap (don't ask how I know!). Remember to use thread lock whne bolting the prop shaft back on. This was a recall I understand so may not appear in the manual. I would change the brake shoes tooo!:P

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2 hours ago, mikeeech said:

The seal is an o ring which can be had in a pack for a 40mm bottle trap (don't ask how I know!). Remember to use thread lock whne bolting the prop shaft back on. This was a recall I understand so may not appear in the manual. I would change the brake shoes tooo!:P

Good call on that o-ring! Although SJS seem to sell them for 47p each so I'll probably go for those! Will probably take a look at the brake shoes, although they looked good 6 months ago when I had the drums off to replace the driveshafts.

So right now I'm thinking I'll need the following for a diff repair/service:

  • 2 x DIFF OUTPUT SHAFT 'O' RING (part 30 in diagram)
  • 2 x DIFF OUTPUT SHAFT BEARING (part 25 in diagram)
  • 2 x OUTPUT SHAFT OIL SEAL (part 29 in diagram)
  • 1 x DIFF PINION OIL SEAL (number 4 in diagram)
  • 1 x DIFF END COVER GASKET (not in diagram)

Those are the parts from SJ that I can see available. I'm wondering about the following part numbers from the diagram though and whether they'd need replacing:

  • 6 (Bearing, outer)
  • 8 (Bearing, inner)
  • 12 (Bearing, differential)

What do you guys think?

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26 minutes ago, mikeeech said:

Get more o rings than that or you'll end up in B&Q... and end up with a bottle trap without all the bits.

Humour me - why do you say that? And how many would you recommend me picking up?

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Dave,

Ignoring the cost factor, which is of course critical, I would err on the side of caution and replace all serviceable parts.

Ultimately for the sake of a few quid and your sanity it has to be worth it?

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Is the price for that bit in Yen or £?

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4 minutes ago, oilmagnet477 said:

Dave,

Ignoring the cost factor, which is of course critical, I would err on the side of caution and replace all serviceable parts.

Ultimately for the sake of a few quid and your sanity it has to be worth it?

Oh, I completely agree. I was just wanting to confirm whether my list of things regarding the diff there was comprehensive, in terms of the serviceable parts.

Think I'll get new wheel cylinder kits providing the 3/4 inch bore ones will work (will check with SJ). May as well get it done now and get it done right.

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52 minutes ago, oilmagnet477 said:

Dave,

Ignoring the cost factor, which is of course critical, I would err on the side of caution and replace all serviceable parts.

Ultimately for the sake of a few quid and your sanity it has to be worth it?

I brought x2 from sj sports cars and fitted my inner drive shafts on a Sunday and pinched them as I tightened up the bolts (the tension in the bolt loosened suddenly) and removing the shaft revealed that I had broken the o ring. I ordered x3 (one to be safe) but got the second try wrong as well hence the bottle trap. You would think you could just buy an o ring... Since they are cheap I would get more than you need since it will take a week to get replacements off eBay if you do nick them or you could find yourself buying something with a suitable o ring in it....

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Hi Dave, from memory, to replace the output bearings, you have to split the retaining collars that hold them in place to remove them. You therefore need new ones of these. If I remember correctly the replacement collars need heating before fitting.

hope this helps

dan

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3 minutes ago, eclat22 said:

Hi Dave, from memory, to replace the output bearings, you have to split the retaining collars that hold them in place to remove them. You therefore need new ones of these. If I remember correctly the replacement collars need heating before fitting.

hope this helps

dan

It does, thank you. I just checked the manual and read this:

Quote

Remove the inboard driveshaft retaining collar by first splitting it with a chisel. DO NOT attempt to remove the collar without FIRST splitting it.

2 x RETAINING COLLAR for OUTPUT SHAFT BEARING; and 2 more O-rings added to the shopping list.

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12 minutes ago, eclat22 said:

Hi Dave, from memory, to replace the output bearings, you have to split the retaining collars that hold them in place to remove them. You therefore need new ones of these. If I remember correctly the replacement collars need heating before fitting.

hope this helps

dan

Good shout that... I completely forgot about those... I got my bearing pressed on since heating the collar was a bit hit and miss

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A did use a cold chisel to take off the collars ( just a smart blow with a medium weight hammer ) and upon reassemble, I not only had to heat them but sand for some more clearance on the inside of the collar.

Be very careful when reassembling the collar next to the rubber/neoprene seal as it is very easy to tear or rip it. Don't ask me how I know. grrrrrrrrrr 

 

atb

Richard

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Dave. Just for your info. She had new brake cylinders, shoes and adjusters the year before you bought her The slides were done and s/steel H pieces fitted to the brake shoes, that's the little bit's that go on where the adjuster slots into the shoes.

 

John.

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1 hour ago, johnpwalsh said:

Dave. Just for your info. She had new brake cylinders, shoes and adjusters the year before you bought her The slides were done and s/steel H pieces fitted to the brake shoes, that's the little bit's that go on where the adjuster slots into the shoes.

 

John.

Thanks for the info John. Was going to ping you a message a little later but that's nice to know as in that case I might pull them from my shopping list :)

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  • Gold FFM

When the diff was out I also had a new plate made for the handbrake cable hanger, the bit that hangs on the rubber mounting. I also had a couple of plates made up and fixed to the floor pan where a PO had cut the floor, these were simply fixed with silicone so that they could be removed for servicing the rear handbrake in the future and the silicone would stop any ingress of water into the rear of the car. It was a simple fix with a bit of galvanised sheet metal. If my memory is correct, I think I also replaced the flexi brake hoses at the same time.

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15 minutes ago, black eclat said:

After you have replaced all those bearings, you will undoubtedly need some shim material to make sure you have minimal end-float on the hub carrier.

Assume I'm dumb and not 100% sure what you mean (a very fair assumption in this case). Where would I be shimming and why?

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Ok, The inner drive shaft, item 24, is held in place by the retaining plate, item 28, holding the bearing in against the diff casing, the bearing itself, held securely on the inner drive shaft by the retaining collar, item 26.

When assembled, you want to ensure that the bearing is held securely in place so you get no end float of the inner drive shaft. In my dictionary, I describe end float as the axial movement of the inner drive that results when you push or pull on the inner drive shaft.

Having the bearing secured is achieved by "nipping" the bearing, i.e, squeezing it tightly into position. The figure given in the manual is .003 to .008 of an inch. What this refers to is the gap that exists between the back plate and the inner drive shaft retaining ring when you assemble, without the retaining bolts, the inner drive shaft into the diff without the back plate O ring. 

Using feeler gauges. measure the space between the back plate and the retaining ring, call it measurement "A".

Subtract the nip or end float figure, .005 inch, from the space figure "A".

What your left with is the required thickness of your shim. This shim is item 27 in the first image.

This will ensure that when you fully assemble the diff, your inner drive shafts will be secure in the diff casing.

I do hope this makes sense!!!

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19 hours ago, black eclat said:

Ok, The inner drive shaft, item 24, is held in place by the retaining plate, item 28, holding the bearing in against the diff casing, the bearing itself, held securely on the inner drive shaft by the retaining collar, item 26.

When assembled, you want to ensure that the bearing is held securely in place so you get no end float of the inner drive shaft. In my dictionary, I describe end float as the axial movement of the inner drive that results when you push or pull on the inner drive shaft.

Having the bearing secured is achieved by "nipping" the bearing, i.e, squeezing it tightly into position. The figure given in the manual is .003 to .008 of an inch. What this refers to is the gap that exists between the back plate and the inner drive shaft retaining ring when you assemble, without the retaining bolts, the inner drive shaft into the diff without the back plate O ring. 

Using feeler gauges. measure the space between the back plate and the retaining ring, call it measurement "A".

Subtract the nip or end float figure, .005 inch, from the space figure "A".

What your left with is the required thickness of your shim. This shim is item 27 in the first image.

This will ensure that when you fully assemble the diff, your inner drive shafts will be secure in the diff casing.

I do hope this makes sense!!!

Hugely useful, thank you.

My buddy "loves" working on diffs so once it's dropped I'll take this advice and the manual over to him and we'll get it sorted.

Sent a message to SJ about parts 6, 8 and 12 but they haven't responded as to whether they're available :(

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Be warned that replacing the bearings, 6,8 & 12, require some fair setup skills with dial gauge measurements to determine tooth contact and diff backlash. The service manual has 3 or 4 pages of quite involved procedures on how to set the diff after replacing these bearings. Do you have or need a copy of this manual?

When I overhauled my diff, I just did the inner drive shaft bearings. B-)

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Hi Dave,

Just as a note, as I also agree with Michael and don't think the fail in the shaft bearing in itself should cause further faults deeper into the diff - and if the brake cylinders are ok - and also the sealing towards the propshaft is not leaking... Many ifs here - but then you actually don't have to drop the diff to replace the shaft bearing.:)

You just remove the outer shaft, the brake drum and brake shoes. Then you unscrew the four screws/bolts to the plate (28 in picture above) and the backplate to the brake drum. Then you need to use a slidehammer to remove the inner shaft (and naturally the same if you have to drop the whole diff). I drillad a small piece of a flat iron as the picture below and fitted it with the regular brake drum screws. Then just slide away...? The hole in the backplate to the drum is big enough to let the bearing pass through. Then its "just" to remove and replace the bearing and the sealing - but that's another story where your buddy can come in handy. Good luck on any route you need to continue! 

Atb

Per

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Sorry - wasn't able to post picture but it is anyway just a simple pice with two holes for the screws and one more in the middle for the hook to the slide hammer...

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6 hours ago, permelite said:

Hi Dave,

Just as a note, as I also agree with Michael and don't think the fail in the shaft bearing in itself should cause further faults deeper into the diff - and if the brake cylinders are ok - and also the sealing towards the propshaft is not leaking... Many ifs here - but then you actually don't have to drop the diff to replace the shaft bearing.:)

You just remove the outer shaft, the brake drum and brake shoes. Then you unscrew the four screws/bolts to the plate (28 in picture above) and the backplate to the brake drum. Then you need to use a slidehammer to remove the inner shaft (and naturally the same if you have to drop the whole diff). I drillad a small piece of a flat iron as the picture below and fitted it with the regular brake drum screws. Then just slide away...? The hole in the backplate to the drum is big enough to let the bearing pass through. Then its "just" to remove and replace the bearing and the sealing - but that's another story where your buddy can come in handy. Good luck on any route you need to continue! 

Atb

Per

 

Interesting. Thanks for that idea Per. Doing it this way,would I still have room for using feeler gauges to measure the space between the back plate and the retaining ring, as per what Michael was talking about?

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Sorry Dave, can't say. Don't even know if you can get access to all screws in the backplate with the diff still in the car (mine is currently out as I had leaking brake cylinder and front sealing and all bushings totaly dry and hard like stone - so I can't check on my car now). Have you noticed noice from the diff making you worried that something is not good? I only have experience from my own car but would guess known problems with the diff in these cars primarily is related to the shaft bearings. But I am not sure about that and there is surely better knowledge on that from someone else here. I thougt I only mention the possibility to replace these bearings without dropping the diff as I have just gone through the pita of getting the damn thing out. But it might be a swift thing on your car as it seems your diff has been out quite recently. Mine have probably been sitting there since the car was new. I'm at least sure its not been out during the 30 yrs it has been mine. 

Atb

Per

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Sorry, read your question again after posting and noticed i had misunderstood. Thougt you where deeper into the diff. There should be room for the feeler gauges - can't remember but think I would even if its probably 29 years since I made the replacement. Only remember cutting one or two o-rings before success. It seems I mede fairly ok as I managed to drive to Spain and and back to Sweden without problems with the diff. There were other problems though... ?

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