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MG MGB Technical - TRANSMISSION OIL

According to the Haynes Repair Book and MGB Owner's Manual maintainance schedule, it's time to change the oil in the transmission of my 79 MGB 4-speed. The Haynes and my owner's manual state 20W-50 Castrol motor oil. My question is, should it be detergent or non-detergent, or does it matter??

Also it is time to change the diff oil as well.

Any thoughts and/ or experience on this

Cheers

Gary :>{D
79 MGB
gnhansen

People I've talked to who use the non-detergent oil use straight 30W and believe that any damaging bits sink to the bottom of the gearbox instead of remaining in suspension, and that the non-detergent oil froths less.

We have been using a 30W detergent oil in the 70 MGB with OD that I care for here in Minnesota. Went to Gatlinburg and back without a hitch.

dave
Dave Braun

Should just be engine oil, same grade as you put in the engine, which is dependant on local climate.
Paul Hunt 2

There is a whole lot of threads on this issue in the archives. The consensus is that the reccomended lube works, but that it is an out of date lube given the new and better products available, and would probably not be specified by a manufacturer today. A major issue is the suitability of the new oils which have been modified to protect catalytic convertors to be used as gear oils.
Barry
Barry Parkinson

RedLine MTL is a very good example of a modern lube that's known to work well in Laycock overdrives. Shifts wonderfully.
Sam

Use 80w90 gear oil in the diff.
...

Gary
If the box is a little elderly you might consider the non-member's advice. The factory also recommended a heavier oil for the GTV8.
Roger
RMW

The V8 gearbox uses gear oil of SAE90 hypoid, not engine oil, and whilst the numbers are higher I seem to recall that the actual viscosities are much the same, it was used for its gear properties, not for its increased weight. It is slightly lighter than that used in the rear axle of both cars.
Paul Hunt 2

A 20W-50 engine oil has much the same viscosity of a 80W-90 oil. It is also important to note that some "hypoid" oils are made so that they are not compatible with the bronze/brass that is in our transmissions and differentials.
CD Dewey

Here is a link to the Redline site with tech info as PDF download documents for MTL and MT90

http://www.redlineoil.com/products_gearlubricants.asp?productID=46&subCategoryID=17&categoryID=7


Jeff


J Delk

This thread was discussed between 27/05/2007 and 31/05/2007

MG MGB Technical index

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