Advice on diff input seal

Technical advice Q&A
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juicerider
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#1 Advice on diff input seal

Post by juicerider » Thu Mar 15, 2018 10:13 am

Well today I dropped the irs and one of the jobs I did was change the input shaft oil seal.
I’m thinking I may need to redo it because the rubber around the edge is not sitting rite and also should I have changed the seal gasket and the collapsible washer too?
Image
It’s a S2 OTS by the way.
Thanks
Steve

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mgcjag
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#2 Re: Advice on diff input seal

Post by mgcjag » Thu Mar 15, 2018 4:53 pm

Hi Steve......did you mark the nut location before undoing it so that you can do it back up to exactly the same position...if not then think you need to take to a Diff specialist to have it stripped set up again... Steve
Steve
1969 S2 2+2 & Building a C type replica

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angelw
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#3 Re: Advice on diff input seal

Post by angelw » Thu Mar 15, 2018 9:18 pm

Steve Wrote:
Hi Steve......did you mark the nut location before undoing it so that you can do it back up to exactly the same position...if not then think you need to take to a Diff specialist to have it stripped set up again... Steve
Hello Steve,
Except when the nut is not tightened to have either no end play, or bearing pre-load, removing and doing the Companion Flange Nut up to a different position has no effect whatsoever on the Crown Wheel and Pinion set-up, only the pre-load (or lack thereof) of the Pinion Shaft bearings. Pursuant to the instructions given in the Workshop Manual, if this nut is over torqued, or removed, the collapsible spacer that is positioned between the set of two taper roller bearings should be replaced with a new spacer and the nut tightened to the correct torqued.

Because this collapsible spacer is positioned between the two bearings, its effect is to keep the bearings apart. Accordingly, the logic is that this spacer must collapse just the right amount so that the bearing cones come into contact with their corresponding cups with the applied torque to the nut. Presumably, this occurs at a predetermined torque just shy of the specified torque and therefore, a pre-load of the bearing system will exist when the specified torque is reached. Once the cones are in intimate contact with their cups and the system starts to apply a pre-load, no further collapse of the spacer occurs (I've determined this by torquing the nut to varying torque beyond the 120 to 140lb/ft specified, up to 250lb/ft, recovering the spacer, measuring and comparing lengths. Accordingly, I see no validity in the Workshop Manual statement that "Should the nut be inadvertently over-tightened, the flange must be removed and a new collapsible spacer fitted. On no account must the nut be slackened off and re-torqued, as this will result in incorrect pre-loading of drive pinion bearings".

This system relies on so many ducks being inline:
1. just the right amount of preliminary crush of the supplied, new spacer
2. the exact same wall thickness of the tube used in the manufacture of the spacer as the original design.
3. the exact (within design tolerance) same length as the original design.
4. same material hardness as the original design

that, in my opinion, this system is profoundly flawed.

The system employed before the collapsible spacer was introduced, was the use of shims to set the pre-load on the bearings, with the final test being a specified torque needed to turn the pinion shaft (8lb/ft). For many years, I've mimicked the earlier system by using a non-collapsible spacer to replace the collapsible spacer.

I use a Master Spacer that is slightly longer than required. This results in measurable end float when the Companion Flange nut to tightened. Given the measured end float and the known length of the Master Spacer, the correct length spacer is easily calculated. The final test after the nut is torqued up is to check the torque required to rotate the pinion shaft.

I doubt when the collapsible spacer system was suggested that the words "here is a much better system we have developed" were used in a sentence, but more likely "we have developed this cheap and nasty, cost saving system".

Regards,

Bill

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44DHR
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#4 Re: Advice on diff input seal

Post by 44DHR » Fri Mar 16, 2018 10:34 am

Steve #1
The lip seal appears to be installed the wrong way round. Generally the lip seal should point toward the medium being contained. This would have the metal retaining spring on seal on the inside.


Image

Bill
You are correct in that the collapsable spacer is not the “perfect” engineering solution and that shims are the ideal solution. However the use of collapsable spacers are widely used in automotive differentials to achieve the correct preload between the two Pinion bearings. I have lost track of the number of people who bring a differential to me after “having a go at it” and in the case of the collapsable spacer this is non recoverable as once it is over tightened and reduced in length. This necessitates a new collapsable spacer to be fitted between the bearings and correctly torqued - which quite an involved process involving removing the bearing.
The accepted method to retain the spacer at it’s present crushed state is - as Steve #2 stated - to mark the Pinion shaft and nut before removal and carefully retighten it back to exactly the same position.
Regards,
Dave
Last edited by 44DHR on Sat Apr 28, 2018 2:32 pm, edited 1 time in total.
Dave Rose
1967 Series 1 4.2 FHC

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angelw
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#5 Re: Advice on diff input seal

Post by angelw » Fri Mar 16, 2018 11:00 am

Dave Wrote:
You are correct in that the collapsable spacer is not the “perfect” engineering solution and that shims are the ideal solution. However the use of collapsable spacers are widely used in automotive differentials to achieve the correct preload between the two Pinion bearings.
Hello Dave,
The collapsible spacer is positioned between the bearings, effectively keeping them apart. Pre-load of the taper roller bearings will only start to occur when the opposing cones make contact with their respective cups. If the specified torque is achieved before the spacer has collapsed to the extent that the opposing bearings cones have made intimate contact with their cups, there will be end play in the system; a condition I've seen frequently using the myriad of After Market spacers being produced for these differentials.

And yes, Steve has the seal installed the wrong way. The following pictures show the correct Inside/Outside surfaces.

Image

Image

Regards,

Bill

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juicerider
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#6 Re: Advice on diff input seal

Post by juicerider » Sun Mar 18, 2018 10:39 pm

Thanks for all your advice here.
Yeah I realised I had the seal the wrong way round when I had another look at it over the weekend. I’ve put a new seal in now the correct way round and torqued the pinion nut up to 120ft/lbs. It seems to spin ok without feeling tight.
Interestingly being a manual us import I was expecting the ratio to be 3.54 but it’s got a 3.307 ratio in it.

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valley7
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#7 Re: Advice on diff input seal

Post by valley7 » Fri Mar 30, 2018 6:27 pm

Wish I had ready this 2 days ago, I just did the same as you; I took my pinion nut off without thinking to mark it. I'm planning to take my diff into a shop to have them redo it because I don't want to take a chance.

Does anyone have any recommendations on who to buy the spacer from?
Stephen
64 XKE S1 3.8L LHD roadster
Parked since 1973 with 20k miles

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valley7
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#8 Re: Advice on diff input seal

Post by valley7 » Tue Apr 03, 2018 5:41 pm

I'm really puzzling over this. I have an S1 and I'm starting to think maybe mine is a fixed spacer instead of a crush washer. Is my setup different than the S2?

Sorry to hijack the thread!!
Stephen
64 XKE S1 3.8L LHD roadster
Parked since 1973 with 20k miles

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mgcjag
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#9 Re: Advice on diff input seal

Post by mgcjag » Tue Apr 03, 2018 6:08 pm

Hi It would really help if you put your name and model information in the signature area..are you a 3.8 .....4.2...2+2.....thanks... Steve
Steve
1969 S2 2+2 & Building a C type replica

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valley7
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#10 Re: Advice on diff input seal

Post by valley7 » Tue Apr 03, 2018 6:14 pm

Good idea. This better?
Stephen
64 XKE S1 3.8L LHD roadster
Parked since 1973 with 20k miles

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Geoff Green
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#11 Re: Advice on diff input seal

Post by Geoff Green » Tue Apr 03, 2018 7:30 pm

Stephen,

3.8 diff pinion has two shim adjustments on the pinion with a set distance spacer, not a crush sleeve. One shim adjustment sets the dept of the mesh of the gear faces. The second adjustment sets the tapered bearing free play on the two pinion bearings.

There are other differential shim adjustments for the ring gear and the output shafts.

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valley7
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#12 Re: Advice on diff input seal

Post by valley7 » Fri Apr 06, 2018 1:17 am

That is most helpful. Thank you!
Stephen
64 XKE S1 3.8L LHD roadster
Parked since 1973 with 20k miles

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