Welcome to our resource for MG Car Information.



TR parts and Triumph parts, TR bits, Triumph Car Spares and accessories are available for TR2, TR3, TR3A, TR4, TR4A, TR5, TR6, TR7, TR8, Spitfire and Stag and other TR models are available from British car spares and parts company LBCarCo.

Triumph TR6 - Red Line MTL in O/D Gearbox

I searched the archives and didn't find a discussion on using Red Line Manual Transmission Lubricant (MTL; 75W/80W gear lube) in O/D gearboxes. I've been using non-detergent 30W for years (as recommended by John Esposito) in my 'A' O/D with no problems. I noticed that MTL is rated GL-3/4 and its viscosities are equivalent to 5W/10W/30 motor oils. My main interest in MTL is the realization that dino motor oil suffers rather severe viscosity loss (about 5 viscosity units) after only 5,000 miles. MTL offers other benefits too.

Anyone running MTL in their O/D?


Rick O.
Rick Orthen

I've just drained my unit of transmission oil and am pulling the clutch and tranny out for clutch replacement. I don't know what oil was in the od transmission, but on draining it, it did not look had two different colours (yes I spelled "colours" the right way). I would be interested to know what is recommended. The lub specification in the manual states SAE 90 Hypoid. Since I don't know zip about these lubs, can you help.
Erin, Ont.
Pete Russell

Hey Pete. There was a good thread or two in last year's archives on gearbox lube. For a non-O/D gearbox, you need a gear oil with API service classification GL-3 or GL-4. No 'modern' GL-5 as it contains higher concentrations of sulfur that will erode the brassy parts inthe gearbox. It may take decades to erode, but it is a factor nonetheless (and its fun to debate).

Guess nobody here uses MTL in an O/D . . .

Rick O.
Rick Orthen

Rick I never used the Red Line fluid but I have been using the pennzoil synchromesh fluid for a few years in a J type OD. It is suppose to be safe for yellow metals. Car shifts very smooth and the OD engages fine. It is very light so cold mornings are not a problem. I used it into late winter last year and it worked great.
Joe Perruzzi


In another thread (another life?) dealing with a slow shift problem, Roger H from down under advised to " save your expensive MTL for another gearbox - it is not really suitable for wet clutch overdrives - (refer to the previous thread in the archives under "synthetic oil")..........
Refill with Redline MT-90 (has 50% higher viscosity than MTL at 100C).

Although the 'slow shift' into O/D is the same, it does seem to shift smoother in all gears, up and down. As was expected, the synthetic is finding ways to escape the confines of the gaskets and seals, and I swear it's even seeping thru the trans case. (prolly not, it's just me..........) I think the MT-90 was a good change!


Rod Nichols

Just chipping in for an update

I have had the MT-90 in the OD/box for nearly a year now and it still feels as good as ever. A few months ago the were a couple of times the O/D jumped out of gear (when cruising, thankfully) but that was quickly traced to a loose connector at the solenoid.

We had a track day a couple of weeks ago and it got a real hammering. Engaging O/D in third at over 5000 with pedal to the metal and not a hiccup. I was also assured (by Redline) that there are no compatability issues with non-ferrous maetals as I have phosphor-bronze in the gearbox in place of the needle roller bearings.

Roger H

Thanks R & R. I assume you two have 'J' units. I do not have slow engagement with my 'A' unit running with 30W ND motor oil. Just seems like such an ancient fluid to be using; guess I'll leave it alone as I'm a bit hesitant to put MT-90 in there. MTL maybe if it doesn't affect the annulus clutches.


Rick O.
Rick Orthen

Hi Rick,

I am running the MTL in my tranny right now and like it, but it is drippy.

I replaced most of the seals on my tranny when I had it out this summer, but not the little o rings on the shifter/top housing (which Don Kelly advised me to do, but I was too excited to get the tranny back in), which are now seeping a little fluid. I have considered going back to the Statlube, but since this is my only leak (knock on wood), I will probably just live with it.

Ignatius Rigor

Ignatius--Do you have O/D?

Rick O.
Rick Orthen

Hey Rick,

Whoops, missed that part of the discussion (Coffee hasn't kicked in yet.) No, I don't have OD.

Ignatius Rigor

Hi Rick - advice given to me by Redline is NOT to use MTL for that specific reason (the shear capacity of the oil in the wet clutch assy is not high enough). If you can check out the Redline website, it gives info which is not specific to the mechanism type, but you can see the difference in the technical data (shear characteristics).

The overdrive itself is the part of the car that I know the least about, never having had one apart. I had mine professionally re-built and I'm happy to leave it that way!! What I am told, is that the functioning of the A and J types is basically the same. The main difference is the way that each unit is engaged. The A via a solenoid/lever system, and the J by a soleniod acting more directly on the oil galleries. The parts are not interchangeable, but the operation is very similar.

I would caution use of the MTL in an A or J type, but have no hesitation in recommending MT-90 based on advice to me and personal experience.

BTW, I have not seen any leaking from gaskets or seals since the re-build with the syn.

Roger H

Danke Roger & others. The A O/D operates at a higher hydraulic pressure (450 psi or so) than the J. I assume the 90W gear oil has the same equivalent viscosity of 30W motor oil when you consider they're measured at different temps. So from that perspective the swap to MT-90 should be OK (as your experience shows). Guess MTL is definately out, so that answers my original question.

I brought this up since I knew Esposito's recommendation for ND 30W oil was founded in the same recommendation from Laycock going back to the 50's. But many better lubricants have arrived on the scene since then and I wanted to be sure I was taking advantage of lube improvements.

Rick O.
Rick Orthen

This thread was discussed between 19/10/2004 and 21/10/2004

Triumph TR6 index