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MG MGB GT V8 Factory Originals Technical - gearbox oil

Guys,I don't know if you are aware that the oil spec in the V8 workshop supplement manual MIL-L-2105 for the gearbox and the axle oil spec MIL-L-2105B are, according to an oil tech man both old military specs.The other thing is that EP80W90 hypoid GL4 can be used in the gearbox/overdrive without any harm to the yellow metal parts in the overdrive or gearbox,I understand some guys add ATF to their gearbox oil ,whilst this has a good effect for cleaning purposes due to the detergents in ATF it lowers the vescosity of the oil and also courses quicker wear on the gears,I am aware that we all have our pet likes and dislikes about oil,be intersting to know what others use,this of course relates to the factory MGB GTV8................cheers Derek
derek cotton

Well I couldnt be too sure on this one as I have never tried using an ep oil in my overdrive.

Will the overdrive continue to work properly. ie will the clutches continue to grip when using an ep oil?

Factory recommendation is to use engine oil.

Cheers
ian F
Ian Fraser

Ian

Although gearbox and overdrive both have drain plugs, the oil is shared, which is why the filter in the overdrive sometimes collects bits of metal from the gearbox as well as the overdrive (PO had part of a thrust washer find it's way through!).

IIRC factory recommendation was originally to use 20/50 engine oil (as the 4 cyl 1800 B) but an amendment was issued very soon after introduction of the V8 when it was realised that the much higher torque forces in the V8 could wear gears etc out quickly. If your V8 gearbox has survived with 20/50 grade you've either been very lucky (and proved that BL were being overcautious) or you drive your V8 gently enough to avoid high torque forces - can't believe that though, it's a car that just begs to be given some heavy right foot now and again ;o))

Previous car was a 4 cyl GT (with o/d) and one thing I have noticed with SAE90 in the o/d of the V8 is that engaging/disengaging is marginally slower, presumably as a result of slower oil pressure build-up and fall-off due to thicker oil and higher operating pressure (o/d on 4 cyl car uses 400-420psi on a V8 it is 510-530psi).

Laurie Webb
75 factory V8 2190 Teal blue

PS to Derek - we've already spoken about this question on the phone, hope someone provides definitive answer concerning ATF.
L Webb

MIL-L-2105 and MIL-L-2105B are the same (U.S.) military specification, with the B being 2 revisions later than the basic. This spec covers 75W, 80W-90, and 85W-140 gear oils.

Paragraph 3.4.8 is a requirement for minimizing copper corrosion. This is important for life of the synchronizer brass rings in the transmission and the copper washers in the differential.

The current revision of the mil-spec is MIL-PRF-2105E dated 22 August 1995, with validating Notice 1 to the E revision, dated 20 April 2004. What this means is that the detail specification (MIL-L-2105) has been converted to a performance specification somewhere in its revision history (according to DoD acquisiton policy).

Wayne
Wayne Pearson

going on from Laurie's advice which is spot on, a number of service centres converted 1800 gearboxes to the heavier V8 spec -

I have never heard of ATF being used in the MG boxes although it is recommended for the LT77S

Roger
RMW

Hi Laurie

Thanks for that. I might give it a try when I finally get my rebuild completed.

My brain was in 4 cyl mode at the time of my post, I was not aware of the revised factory recommendation for V8's.

Cheers
ian F


Ian Fraser

This thread was discussed between 03/02/2005 and 04/02/2005

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