Lotus Elan

Diff Input Shaft Bearing Replacement

PostPost by: Maulden7 » Sun Aug 18, 2019 1:30 pm

I need to replace my diff input shaft bearing, can this be done with the diff in situ?

Thanks for any advice.
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PostPost by: types26/36 » Sun Aug 18, 2019 2:22 pm

Yes, you may have to heat up the diff casing after removing the dirt from the circlip groove and the circlip of course.
A sliding hammer usually pulls out the shafts.
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PostPost by: paddy » Sun Aug 18, 2019 2:33 pm

types26/36 wrote:Yes, you may have to heat up the diff casing after removing the dirt from the circlip groove and the circlip of course.
A sliding hammer usually pulls out the shafts.


Is that true for the input shaft?

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PostPost by: types26/36 » Sun Aug 18, 2019 2:43 pm

Paddy, I am refering to the shafts in the diff although I suppose they are output shafts.
The input shaft would be the diff pinion
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PostPost by: Maulden7 » Sun Aug 18, 2019 3:11 pm

Thanks guys.

To be clear, I am talking about the first bearing behind the diff input shaft connection to the propshaft. It sits in the diff nose housing.

Perhaps you can take the diff nose off after disconnecting the propshaft?

Never done this before, but obviously I would prefer not to have to pull the diff, but if I have to ... !!
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PostPost by: types26/36 » Sun Aug 18, 2019 3:22 pm

I doubt it but even if you could the diff would require setting up with the new bearing and crush sleeve which could not be done in place.
Edit. just relised I think you want to take the diff out of the alloy casing....... :roll: dont know!
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PostPost by: bitsobrits » Sun Aug 18, 2019 3:36 pm

While I can imagine it may be possible to do a bodgy change of the bearing in situ, you don't want to do that. If the input shaft bearing is in need of replacing, then it's time for a diff out clean, inspection, and proper set up of the differential.

The R&R of the Elan differential is a substantial chore, but not technically difficult. And you'll find a bunch of other things that need attention while you are there :D

If you are not equipped (tools or talent) for the diff disassembly/setup/re-assembly, taking it to a specialist shouldn't cost a ton if you present them with the lump vs the entire car.
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PostPost by: Elan45 » Sun Aug 18, 2019 4:14 pm

And you'll need a way of compressing the rubber donuts. You can make a temporary one out of hose clamps screwed together.

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PostPost by: promotor » Sun Aug 18, 2019 4:34 pm

Maulden7 wrote:Thanks guys.

To be clear, I am talking about the first bearing behind the diff input shaft connection to the propshaft. It sits in the diff nose housing.

Perhaps you can take the diff nose off after disconnecting the propshaft?

Never done this before, but obviously I would prefer not to have to pull the diff, but if I have to ... !!


Why would you only want to replace the one bearing?

You won't be able to remove the bearing shell unless you have a tool that probably hasn't even been made for this job yet! Just replacing the bearing and not the shell isn't advisable.

What are you trying to achieve / rectify?
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PostPost by: Maulden7 » Mon Aug 19, 2019 2:08 pm

Thanks for the comments all.

The car has solid drive shafts (sliding spine type) so no rubber couplings to deal with.

The diff had a full rebuild / set up & a Quaife ATB installed only around 5k miles ago (by Tony Thompson) All new bearings, uprated diff output shafts etc

The car was not used for some time whilst a full engine rebuild was completed. There was no noise before the rebuild commenced, but was apparent the first time it was driven with the rebuilt engine???

I now know that the diff has to come out.

Thanks again.
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PostPost by: types26/36 » Mon Aug 19, 2019 2:57 pm

Maulden7 wrote:The diff had a full rebuild / set up & a Quaife ATB installed only around 5k miles ago (by Tony Thompson) All new bearings, uprated diff output shafts etc
There was no noise before the rebuild commenced, but was apparent the first time it was driven with the rebuilt engine???Thanks again.

Well I would be "having a word" with the diff rebuilder ..........5K and noisy :roll:
Are you sure it is a diff bearing? could it be a vibration......diff touching chassis? exhaust touching body? engine mounting collapsed? air box touching body? ........
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PostPost by: Maulden7 » Mon Aug 19, 2019 4:05 pm

Thanks Brian - it's definitely the front diff bearing.

Twice now I've had the back end up in the air on double axle stands each side & the front wheel very securely chocked. The first time it was just me, & I ran the engine in gear at tickover, the noise definitely seemed to be coming from the front of the diff, not he diff itself.

The second time I got a very knowledgeable mate to come round for a second opinion. With me in the car & him underneath (with a stethoscope type device) I repeated the test, only this time I was able to change engine running speeds of course. The diff itself & all the output shaft bearings are quiet, the noise is coming from the diff nose, & exactly where the front bearing sits. There is also a noticeable vibration from this location (it can be felt with the hand - changes with the engine revs ... as does the noise) & everywhere else is smooth.

I never did suspect the diff itself, it's just not a "diff noise", it's more a "grating type" sound (just like a bearing where rollers have broken up)

Btw ... I did check everything when static (& confirmed that the diff was full of oil!!) before any load tests.

Diff to come out then!
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PostPost by: nmauduit » Mon Aug 19, 2019 5:16 pm

just to be sure, have you checked the prop shaft (rear yoke bearings)?
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PostPost by: promotor » Mon Aug 19, 2019 5:56 pm

Maulden7 wrote:Thanks Brian - it's definitely the front diff bearing.

Twice now I've had the back end up in the air on double axle stands each side & the front wheel very securely chocked. The first time it was just me, & I ran the engine in gear at tickover, the noise definitely seemed to be coming from the front of the diff, not he diff itself.

The second time I got a very knowledgeable mate to come round for a second opinion. With me in the car & him underneath (with a stethoscope type device) I repeated the test, only this time I was able to change engine running speeds of course. The diff itself & all the output shaft bearings are quiet, the noise is coming from the diff nose, & exactly where the front bearing sits. There is also a noticeable vibration from this location (it can be felt with the hand - changes with the engine revs ... as does the noise) & everywhere else is smooth.

I never did suspect the diff itself, it's just not a "diff noise", it's more a "grating type" sound (just like a bearing where rollers have broken up)

Btw ... I did check everything when static (& confirmed that the diff was full of oil!!) before any load tests.

Diff to come out then!


Couple of things to check - diff flange to oil seal shield - is that touching something?
Any play in the pinion bearings? If so, could be the crush washer hasn't been fully crushed. However, of the TTR diffs I have seen they have a solid tube and not a crush washer - hopefully this is the correct length otherwise if it's too long it won't allow the bearings to seat properly, if at all.
If there is no noticeable play in the bearings but the bearings are only just seated and not really pre-loaded this won't be good for the diff when it is under running conditions / load in terms of possible bearing noise and the teeth contact patch of the crownwheel and pinion not being held in the correct place.
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PostPost by: rgh0 » Mon Aug 19, 2019 8:54 pm

When you did the tests did you have the rear wheels at normal ride height?. If they were at full droop with the car supported off the body or chassis then you will get significant vibration transmitted to the diff from the output shafts

regards
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