Moss Motors, Ltd

Hello,

The service manual does not tell (or I was unable to see it) the clearance between the PLANET gears and the differential carrier housing, nor the clearance between the SUN gears and the carrier housing.

I am sure I have excessive clearances there (about 0.050" or more) on the planet gears.

Moss sells a variety of thrust washers in different thickness, but I am not sure what I should use. This thrust washer is Item 73 on the exploded view of the rear axle.

Reason I have noticed this is the oil I just drained is very grey and I have the feeling something is wearing out. Last thing I did on the axle a couple of years ago is replacing the wheels bearings and seals. I did the shimming according to the procedure, but i wonder now, if I do not have unsufficient clearance (recommended is 4 to 6 thous) and I just have 4 or maybe 3.

I make plans to take the axle out of the car, and check everything and make the corrections. These Planet gear float bothers me. But I will not start until I know where I am going.

Anybody can give me some info on the subject?

Many thanks in advance!

There are no published backlash dimensions to my knowledge.

First you need to drive out the  cross pin lock pin - it goes out away from the crown wheel and is locked back in place by a burr across the hole on the non crown wheel side of the carrier.

Check the cross pin for wear and renew as reqd. (pt no 100844)

Check the gear teeth for surface break up - renew as a set - gulp!!!  The same  diff gears are to be found in Triumph All TR3 Girling, TR4 TR4A TR250 TR5 TR6 Dolomite Sprint, Triumph 2000, 2500 2.5 PI, and Stag axles. Fit as a set tho!!! - Also the carriers are all the same except Stag.

You need to get the sun and planet wheels out to measure the existing washer thicknesses to give you an idea where to start when buying.

I start by fitting new washers behind the sun wheels (the big ones with the spline in them)  then refit the planets with the old thrust to get a 'feel'  Today you may find the replacement sun wheel washers are fibre not brass - they are in one size only.

Increase the size of the planet wheel washers to close the gap and reduce backlash as required using the dimensioned items available.

What you are after is a tight but free running movement when turned by a shaft in either side.

DO NOT FORGET THE AXLE SHAFT THRUST BUTTON WHEN YOU RE-ASSEMBLE.

Do not be afraid to reuse your original sun wheel washers (asumimng they are ok quality wise) to get the right running feel.

It is a game of trial and error.

The axle end float is critical to get the right clearance on the wheel bearings.

Not sure what the grey colour in the oil is.

Enjoy the day or so you will need to do this whole axle rebuild

Peter W

PS a hypoid case spreader is not required to extract the crown wheel carrier asy - I have always used 2 tyre levers.

Pinion bearing preload without the seal in is important - make up a spring balance to check the rotational load.

If in doubt folow the book (!)

Peter,

Thank you for your good information you supply. I went through the axle section in the service manual several times and indeed there is no backlash info for the sun/planet gears. Your suggestion is the way to go. Trial and error and look for tight but free.

I do not see teeth surface damage on any gear, so I may be lucky. But I definitely need new thrust washers for the sun and especially planet gears.

I will remove the half shafts and rearrange the shims sets to gain the missing thou I mentioned earlier, and this will allow me (while the half shafts will be out) to have a better feel of the tight but free movement of the sun/planet gears combination for the selection of the proper planet thrust washers.

Regarding the grey colour of the oil, I think I may know the reason. Recently, I went for a 600km trip in Dordogne and the preceding day; checking the oil levels, I found the axle was pretty low (so I also need to replace the nose seal). I had some 75w80 gear oil available and I used it for topping (needed about 4 oz). This oil has a green colour and yesterday I read that it is semi synthetic. I suspect that mixing it with the 90 EP mineral oil I use in the axle, resulted in this unusual grey colour. I plunged a magnet in the drained oil to see if a metal dust spectrum appears, but I cannot see any pattern formed. So this colour should not be the result of ferrous metal wear. Good.

Why did I top up the axle instead of draining and replace the complete oil charge? That day, just before my trip, the square drain plug had rounded and I could not remove it. It is now drilled out and replaced. At least, this small problem has highlighted a more serious one (gears back lash) and I will now correct all.

I am also wondering if the oil I used "eated" the brass thrust washers. But this was only a 600 km trip, and I doubt the wear would be so fast.

However, brass presence may contribute to the appearance of the oil (grey colour and dusty deposits)

I am leaving today for a 6 weeks professional trip and will only work on the TR when I return. When I make progress with it, I will let the forum know my findings.

Regards,

Jean Louis