Diff oil grade

[andyf]

What is the correct grade of gear oil for a marina diff? Is the 80-90 grade ok?

[h_m_cumming]

Re: Diff oil grade

EP90 so EP80/90 should be OK

[stevejgreen]

Re: Diff oil grade

EP90 so EP80/90 should be OK

There is some discussion over the grades of Hypoy, GL5 is allegedly not compatible with bronze bearings so GL4 should be the choice for BL/TR vehicles.

Personally I think this is a bit academic on a low mileage car that could have remnants of 30+ year of oil in it.
If you were changing the diff centre I would suggest removing the axle from the car, giving it a good flush, and fitting a drain plug.
On an old axle try siphoning out as much old oil as possible, then refill with whatever new Hypoy is at hand. It can't do any harm, only good.

[stevejgreen]

Re: Diff oil grade

I did add a section towards the end of my Differential article

"LUBRICATION
Both the Triumph and Manna rear axles specify EP90 GL4. The current supply of oil seems to be EP90 GL5. This apparently is an improved lubricant. There is a difference of opinion as to the suitability of GL5 in older transmissions as it has higher levels of additives that may attack the bronze parts of gearboxes and differentials,especially at higher temperatures. The evidence is sketchy and I will leave you to draw your own conclusions but the problem seems to be evident at temperatures not usually experienced in a Marina.
Many of our differentials have probably never been thoroughly cleaned internally since the cars were built and some will contain remnants of the original oil. If the opportunity arises I recommend that the internal parts are thoroughly cleaned, a drain boss welded to the lowest part of the axle case and the axle filled with whatever new oil you decide to use. Any new high pressure oil will be a good thing rather than to worry about which one to put in."

here or there

Differences between GL4 and GL5

[lil_red_roadster]

Re: Diff oil grade

Comma still market an EP80-90 GL4 spec oil...I'm sure your local factor could obtain if not readily to hand.

http://www.commaoil.com/productsguide/view/6/183

[b_caswell]

Re: Diff oil grade

< www.widman.biz/uploads/Transaxle_oil.pdf > Some light reading for a rainy day.

[stevejgreen]

Re: Diff oil grade

I suspect that Ben wanted to say that GL4 is the preferred grade for Triumph gearboxes and differentials.

[b_caswell]

Re: Diff oil grade

There seems to be no definitive answer on Triumph forums or technical papers as to which oil to use and it gets even more complicated with overdrives with some people using 20/50 oil.(apparently recomended by Laycock but not Triumph).... I think the premature failure of the bronze thrust washers and synchro rings as well as other parts is more down to inferior replacement parts than the EP protection of the extra sulphur in GL5.
Added a day later some homework to read.< http://www.machinerylubrication.com/...ur-ep-gear-oil >