Differential thrust washers

[Mark Wilson]

I've replaced both sets of thrust washers in my 3.9:1 diff, which I bought second hand and seemed a bit sloppy. The fibre washers had worn to virtually nothing, as I understand is normal, and the copper spherical washers measured 35 thou compared to 58 thou for the new ones (cheap digital caliper). The copper washers took a lot of persuading into place, and once in the diff gears would not move at all. Took them out again and put the originals back - loose again but better than before, presumably due to the new fibre washers. So it would seem I need intermediate thickness copper washers, but haven't found anyone offering different thicknesses, and being spherical I can't just reduce the new ones. Any ideas?

Mark

[philthehill]

Mark
Can you please enlarge as to the fibre washers?
The link below is to the MG Midget diff which I presume yours is.
http://www.moss-europe.co.uk/shop-by-mo ... 500cc.html
Unless I am missing something I cannot see a reference to fibre washers
There are two thicknesses of spherical washer listed.
Pt No: 2A7062............0.035"
Pt No: 2A7062Z..........0.054"

[Declan_Burns]

Phil,
This could be what Mark is referring to.
Regards
Declan

[philthehill]

Declan
I suspect that you are right but Mark makes specific reference to both spherical washers and the fibre washers.

I think I have found the answer to the above - Mark's reference to fibre washers I believe should be correctly termed/referred to as Tufnal washers. That material is and can be used for the sun gear thrust washers.

The planet gears spherical washers. Pt Nos above come in the two thicknesses but item 19 (sun gear thrust washers) in the parts link above comes in varying thicknesses ranging from 0,035" >>>>>0.48".
Varying the thickness of one washer often has a knock on effect on the other thrust washers.
A selection of thrust washers in this case would be beneficial to re-assembly and obtaining the correct clearance.
Whilst there does not appear to be details in the Minor wksp manual as to the backlash dimensions between sun and planet gears (I am happy to be corrected) the Morris Marina wksp manual Pt No AKM 4580 section 51/5 on the other hand gives a comprehensive description of setting the backlash between the sun and planet gears.
It states that there should be zero backlash when assembled which can be obtained by use of the various thickness thrust washers.
It will be stiff to turn when assembled dry but when lubricated the movement will be easier and acceptable.

Phil

As an aside the Morris Marina workshop manual is a good supplement to the Minor wksp manual as many of the specifications/details/torque settings that are lacking in the Minor wksp manual can be found in the Marina wksp manual.
Many of the items/parts used in or on the Minor can be found fitted to the Marina that is 1098cc/1275cc & 1800cc.

[Mark Wilson]

Phil, Declan,

Many thanks. It is an MG diff, and Declan's pics are correct. I don't think I've seen the sun gear washers referred to as Tufnol before, but we are definitely talking about the same thing and it sounds more technical than fibre! As I've tried both thicknesses of spherical washer I will order some alternative thicknesses for the sun gear washer. I can see that the interaction means that either set of washers could alter the backlash. I'll let you know how I get on.

[philthehill]

Mark
Many thanks for the reply.
All of the Midget rear axle parts lists that I have scoured just refer to 'Thrust Washers' and do not specify the material they are made from.
Personally I would refit the 0.035" planet spherical thrust washers and adjust the thickness of the sun gears thrust washers to suit.
Unless the diff carrier is worn - the same thickness thrust washer should be fitted between each sun gear and the diff carrier.
You know that the there is backlash when the 0.035" planet thrusts and the new Tufnal thrusts are fitted so I would try the next size/thicker Tufnal sun gear thrust washer.
The aim is for zero backlash but still have the ability to turn albeit stiffly.
Phil

[Mark Wilson]

Update. I've done exactly as Phil advised, and no surprise, it worked! I ordered two sets of sun gear washers from Moss, .040 and .046, and also bought new .035 spherical washers (same size as original but they looked a bit past their best). The .046 allowed assembly without the brute force needed previously, but still too stiff to turn by hand, or even with a half shaft. The .040s were perfect, no perceptible backlash, just moderately stiff t o turn.

The only issue I have is that while the .046 and the .054 are made from Tufnol or a phenolic resin of some sort, the .040s are made of what appears to be brass. Doesn't EP90 dissolve brass fairly quickly? Is there any alternative oil for diffs?

(Edit - I've now done what I should have done and searched for answers on the EP90 question. Sounds far too theoretical a problem for me to lose any sleep over it!)

Thanks for all the help

Mark

[greendefender123]

Think its only gl5 that dissolves brass.

[amgrave]

Yes, your right, avoid GL5. Use only GL4 spec.

[smithskids]

I have been doing the same with one of my spare diffs and ordered spherical washers from ESM and they do 2 sizes. When measured they are 0.058" or 0.036" . the others were Paxolin and were 0.33". I kept some old ones from spare diffs and they vary enough to juggle the numbers to get a just turnable diff.