Salisbury rear axle lubricants

[Steven collins]

This may be a daft question but one I do not want to make a mistake on, workshop manual states Hypoid EP90 for rear axle (Salisbury type).
I would like to top up/change the rear axle lubricant can I use classic Castrol EP90 or is there a specific rear axle oil I should use?
Many thanks.
Steve.

[Ian F]

Any hypoid EP90 would do, these oils have a distinctive smell so are unmistakable.
Having said that I would use a premium brand rather than the cheapest you can find, since it is in there for a long time.

In the good old days folk would use an EP (extreme pressure) oil of a much higher viscosity in back axles to quieten them down a bit!

Ian F

[Steven collins]

Many thanks for the reply Ian, much appreciated.
I am trying to track down a slight clonking when first reversing - doesn’t do it all the time though. Measured the play on the prop shaft/rear axle which is 4.5/5mm so axle shims seems ok but there is distinct play on the half shaft, not sure how much there should be though (if any) as I cannot find any reference figures.

[Ian F]

The half shafts slide into the sun and planet gears in the diff cage. There are 4 thrust washers, one on each of the 4 gears.
The cup shaped washers are available in oversized to take up play, but all you might need are new standard sized ones.
Half shafts have to be pulled out a little and a roll pin tapped out of the shaft between the gears, otherwise straightforward.

I have done this twice on my BGT to reduce a "clonk", so it may be something for you to consider.

Ian F

[Ian F]

This may help:

https://www.v8register.net/FilesV8WN/18 ... acN-R4.pdf

Ian F

[Steven collins]

That was really useful, many thanks Ian, I do think though the job will be too much for me with only a single small garage and very arthritic hands

[Michael Barclay]

Hello Steven
Just a word of caution about the comment “Any hypoid EP90 would do”. This is not correct. You can buy Hypoid 90 oil GL4 or GL5 specification. DO not use GL5 as contains additives that will damage the brass cup washer shims. The EP90 Castrol oil shown in your post is perfect for MGB Diffs.
MGB back axle clunk is very common but easy and cheap to fix. The parts are around a fiver but as Ian says you do have to pull out one of the half shafts. I also found removing the fuel tank gave better access to the diff.
Mike Barclay

[Ian F]

Thanks Michael.

I had understood that this was no longer a problem with GL5 due to reformulation, but of course I could be mistaken!

Ian F

[Michael Barclay]

Hi Ian
I can only speak from experience.I bought my oil on recommendation from a well know oil supplier. Not knowing the difference, I put EP90 GL5 in my axle.It took out the cup washer shims in about 500 miles. I had not had a probelm up to this point but when removed the shims, them they were stepped and paper thin.
Mike Barclay

[Steven collins]

Thanks Michael, I have filled the diff so that is all sorted however, sorting out the shims will be another matter as stated I only have a single small garage so this job may be beyond me due to space constraints. might have to give the job to a garage sadly.