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MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG TD TF 1500 - Coastal GL-5 transmission gear oil

Redline MT-90 is hard to get - must be ordered.

Has anyone ever used this Coastal product - either in the 90W or the heavier SAE 85W-140. I probably do not mind the heavier oil in this constant Houston heat - terrible - but I refuse not to enjoy this TD.

Can anyone obtain Sulfur data to compare both to see if they meet yellow metal criteria?

WarrenOil.com provides very little info - impossible to determine if it is safe for use?




Michael Balahutrak

Doesn’t answer your inquiry, but I’m surprised to see you can’t find MT90. It’s available at my local auto parts store.
W A Chasser

Amazon has MT-90, don’t even have to get up to go get it, next day delivery here. George
George Butz III

I feel that GL5 is a bad choice. Could damage the brass and bronze components. MG recommended 90w Hypoid Gear Oil in gearbox, axle, and steering. (GL5 was not available in 1954.)

Few brands of GL4 Hypoid gear oil are available today. Too many trusted MG specialists recommend Redline MT-90 to ignore.

Here is more info …
https://www.mg-cars.org.uk/mgtf/files/Maintenance_Lubrication-TF.pdf

Lonnie
TF681
TF7211
LM Cook

Lonnie

Major apologies to all who read this error of mine - I had meant GL-4

I did find my old MT-90 bottle with some left over gearoil and indeed it was the GL-4

I am getting old and forgetful.

But now will entertain you with a funny story:

In draining the MT-90 GL-4 that I had run for the past 2 years of course I unscrewed the bottom drain plug. Interestingly enough the rare earth magnet I had epoxied into the plug made it very hard to pull it from the cast iron transmission case. When I did get it off it had about .5mm of very fine iron on it. Therefore the rare earth magnet did its job very well.

But not to leave well enough alone - I decided to spray some starting fluid (which I frequently use for cleaning and degreasing because it cleans very well and residue vaporizes rapidly) through a thin nozzle through the drain plug to flush out any iron particles that may still be clinging to the transmission case walls. Quite a bit flushed out - but during the second attempt the skinny tube broke loose from the spray head and flew into the case. Boy was I sincerely perturbed. Could not get it out so I went to bed.

The next day I took out my endoscope camera and did see this bright red tube laying in the bottom. Then watching it on my iPhone and using a thin copper wire I was able to dislodge it and fish out the plastic nozzle. Now I had to celebrate. Quickly I cleaned the magnet, sealed everything - filled the transmission with Redline MT-90 and went touring around town for the next 5 hours.

Indeed filling it to the high mark with fresh MT-90 GL-4 did make a significant - very noticeable quieter and very smooth shifting transmission.

Will do another flush and clean in 300 miles. But this time I cemented the bright red thin nozzle into the spray head to be prepared.
Michael Balahutrak

Do not use any Gl-5 oils in your trans or differentials. There are Soft metal thrust plates for the slider gears in the carrier. They will quickly be destroyed if you do not use a GL-4 spec oil. The thrust washers are NLA from the venders and I have yet to find an outside source for them.

Bill Chasser
TD-4834
TD/c-8151
W A Chasser

Again, RedLine MT 90.
Also use the whole quart!
Yes, it is overfilling the gearbox, and some will leak out of the tail shaft BUT it will shift better especially when hot!
Len
Len Fanelli

Ok were speaking of GL-4!
EBay, Summit racing, Moss all sell MT-90, plus others. Moss is pretty expensive compared to some other venders. Summits price is about $23.00 a bottle. PJ
PJ Jennings

Hello all.
Some years ago, I changed my end ratio. I didn't spot any yellow metal part.
However, I still fill it with GL-4.

Laurent.
LC Laurent31

Laurant,

There are bronze (i think) thrust washers/shims in the spider gears of the diff, you would not normally see them just changing ratio. They have not been available for years so if you wear them out or the oil eats them you are in trouble.
B W Wood

completed the second flush with MT-90 GL-4 and this 53 shifts like slicing butter with a hot knife
Michael Balahutrak

Laurant. The concave thrust washers I’m speaking of are within the CW carrier you would have to disassemble the carrier to locate them behind the spider gears. Trust me they’re there.

Bill Chasser
TD-4834
TD/c-8151
W A Chasser

This thread was discussed between 24/06/2025 and 16/09/2025

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