markythesparky Posted November 23, 2018 Share Posted November 23, 2018 what is the best oil for a spitfire 1500 gearbox with overdrive oil reading a few articles all seem to have different ideas re GL-4 or GL-5. Quote Link to comment Share on other sites More sharing options...
Clive Posted November 23, 2018 Share Posted November 23, 2018 Never seen anybody suggest GL5 in a proper article. GL5, unless specifically yellow-metal safe will be bad for the synchro rings etc in the gearbox. Stick to a GL4, the factory spec. Now, EP80, EP90, EP80/90 or possibly EP75/90, all available as GL4. Quote Link to comment Share on other sites More sharing options...
sparky_spit Posted November 23, 2018 Share Posted November 23, 2018 Generally, if you use a GL4 spec oil in your overdrive/gearbox you can then use it as well in your differential and saves buying two different types. GL4 spec gives you protection against unwanted oil attack on yellow metals, which you will definitely have in your diff, and may possibly have in your gearbox. Also, you need an EP type oil (Extreme Pressure) for use with hypoid type gears. So, look for an oil that is the right viscosity (80 to 90 weight) and is EP rated and is GL4 compliant. 80w/90w EP GL4 gear oil is available from Halfords, Comma, Castrol and others. Or you can go upmarket and get top quality competition oils such Millers Synthetic CRS Nanodrive in various grades from 75w - 90w up 75w - 140w, but these are more specific to gearbox or diff (standard and limited slip) and not all can be used in both. 70 Quote Link to comment Share on other sites More sharing options...
thescrapman Posted November 24, 2018 Share Posted November 24, 2018 Some people use 20/50 engine oil in the Triumph gearboxes. Despite not seeing them have any issues I have not been brave enough to try yet. Other manufacturers did spec 20/50 such as MG for the B box. Quote Link to comment Share on other sites More sharing options...
RobPearce Posted November 24, 2018 Share Posted November 24, 2018 Technically, a gearbox doesn't have the sliding contact of a diff pinion that forces the use of EP spec oil, so using ordinary 20/50 is probably OK. On TR7s with the SD1 box, the factory even specified ATF for a while! The point is, the EP additives do reduce the wear on the (slightly sliding) slant-cut gears, so the same gearbox can be rated for higher torque if EP oil is used. I would certainly want to stick with EP90 on a GT6 but the 20/50 is probably fine for a 2000 saloon. Quote Link to comment Share on other sites More sharing options...
WIMPUS Posted November 24, 2018 Share Posted November 24, 2018 I've always been using Millers 80w90 GL4 on my Spitfire with J-type OD. Been happy about it. Quote Link to comment Share on other sites More sharing options...
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