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MG MGA - Sierra Gearbox and transmission oils

My mga is up in the air on my hoist and I am about to commence a major service as per every 6000mile recommendation....changing all fluids etc , checking settings etc etc do mods to radiator , cooling fan, heater. Two queries..
..what is the current recommendation for oil in the 5 speed Sierra box ( I used redline t90 75w90 gl4 last time..expensive !)
what oil for the rear axle ?
Neil Ferguson


That's the grade I use (75W90) in the Type 9. Presume you have a drain plug fitted?

Rear axle is a hypoid 90, as is the steering box.

Steve Gyles

Grades are ok but Peter Gamble (HiGear) strongly recommended GL4 (not 5) in my Sierra gearbox due to yellow metals i believe. I understand same is relevant for rear axle. Anyone know more?
Bruce Mayo

I just went to the local Ford workshop and asked what the right stuff was. I'll have a look and report back when I go down to the garage tomorrow (it's four floors down so I'm pleading lazy tonight). I can buy the same grade in the local supermarket so it's easy to get hold of. It's also pretty thin stuff.
dominic clancy

I did have Peter Gamble drill a drain point in my sierra box..thank ye gods. . I have re read my old files and note Peter recommended Redline MT 75w90 GL4 so just ordered some for delivery very soon. Using a shell EP 90 in the diff. and starring rack.
other issues ..I was greasing the various points and when I came to the hardy spicer I found two grease points but the front one ( just aft of gearbox and slider) seems to have has lost its grease nipple and has a small ( 3 to 4 mm ) spring sticking out about 3cm ...not sure what the spring is for. Can I just remove it and install new nipple ... I tried pulling just with my fingers but seems fairly fixed in.
Also the thin rubber boots over the greased front suspension and steering rotating joints have or are disintegrating . They look pretty useless any way..Is it a concern?
All advice gratefully received .
Neil Ferguson

Neil, I would guess that the nipple has been broken off leaving the threaded bit and the spring intact. (The spring presses against the tiny ball bearing in the nipple to exclude dirt, water etc.)

Look closely as you may have to first remove the broken piece of the nipple before replacing. If so, use an Easi-out.

Rubber boots on the steering/suspension joints are vital to exclude dirt etc. and so should be replaced.

I'm also facing the prospect of replacing these and dreading getting these old bones under the wings. Maybe we should work together!

Good luck, Barry.
Barry Gannon

Barry is a pic of this spring worm growing out of my front universal. I have now pulled the tape worm out and you are right. It is the spring from inside an extended grease nipple . The severance has left some of the nipple in the universal hole and it is going to be awkward to remove .
Two things come to mind now......what nipple to insert as a replacement ( ie thread size ....are they the standard 5/16 unf ? )
And what length should the nipple be given that the previous one was decapitated ?
Any advice from anywhere welcome ..also where to buy?

Barry..on the subject of rubber boots.. It looks a major job to replace all the boots . And I am not sure I have the timeright now to dismantle all the joints .
Is there much downside to leaving it for a few months ..also is there any interim measure ( ie external wrapping ) that can help minimise the problem . A frequently reapplied coating of very thick grease would maybe help?

I am up in southern now (Narooma) but my new house in Flinders is nearing completion at long last ....usual delay problems with the local planning bureaucrats .....and we will be moving to live in vic. from March/April. I want to join the vic club and hope tp catch up some time in the not too distant.

Neil Ferguson


I have recently had to replace this seals as well, took about an hour each side.

If you can't do it before your move, i would just focus on greasing the trunnions regularly to prevent the dust getting in. When you do the seals you can take out the distance tubes and clean everything up before reassembly.

The seals I fitted this time were noticeably thicker then the ones I removed. I found I had two sets on stock as spares - one set was the same as the ones on the car that had turned to goo, so they went straight in the trash. Unfortunately I can't say where the thicker ones came from, or even how long they have been in the drawer. But I am slightly reassured that they are still intact even though they were greased up before putting away to make sure that the quality was OK before fitting another rubbish set.
dominic clancy

Dominic......Given your advice I will tackle now whilst the car is on the hoist...will order up new boots right away.

Any advice on the correct grease nipple for the front universal ?
Neil Ferguson

This thread was discussed between 27/01/2016 and 29/01/2016

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