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Best gearbox oil... with overdrive?

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Lukens

Lukens

Jedi Warrior
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Looking for opinions on gearbox oil for OD tranny.
Randall, you once mentioned Redline Mt-90, but I don't recall if you were running OD.
 
I use straight 30W. Never had a problem (in numerous type A's). John Esposito a Quantum Mechanics also recommends it after doing a number of tests. Good luck.
 
Non detergent 30W motor oil

That is wht I went to after I read Joe's article. I was using MT-90 before that. I noticed no difference after the change.
 
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I do have overdrive, and I did notice a definite difference when switching to MT-90. Not so much with the overdrive, but the main box definitely shifts better with MT-90 in it.

In addition, Triumphs specifically switched away from even allowing non-detergent motor oil to be used, because the bearings in the main gearbox need the extra protection of GL4. If you poke around on John Esposito's web site, you'll find where he also recommends upgrading the bearings on the countershaft, because of this weakness.

John has a very good reputation, but his report on the effects of running GL4 in an overdrive makes no sense to me. Triumph delivered the cars with GL4 in them, and would have been hit with a hideous warranty bill if it had cause the OD to overpressure instantly. Obviously that did not happen. I can only guess that perhaps John was not using an A-type OD as fitted to early Triumphs. (I also run MT-90 in my J-types, where it also works very well.)

Or perhaps he made the same mistake that I did, and shimmed the accumulator spring until it reached coil bind without fully uncovering the relief ports. My test setup turns relatively slowly, so the pressure looked OK, but it went too high when turning 5000+ rpm. Taking out one of the shims solved the problem.
 
Actually, there is a lot more to know about oil than is contained in that Brad Penn advertisement. For one thing, the MT-90 (and thinner MTL) are specifically designed with friction modifiers to improve synchro performance. And, while many GL4 oils contain the same "active sulfur" additive that causes GL5 to sometimes corrode brass components; MT-90 does not use that additive at all.

Also, many synthetic GL5 oils don't use it either. I've been using Valvoline full synthetic GL5 in my Triumph differentials for over 20 years and it works great. The only reason I don't use it in gearboxes is because it is too slick for good synchro operation (the synchros rely on friction to do their job).
 
What is MT and MTL?

I am running 30wt non detergent in my A type but am thinking about going back to 90wt on the next change.
 
Resurrecting an old thread because I had a very odd experience today. I elected to use 30W non detergent oil in my ovedrive today, countess threads on it but John from Quantum and Mark Macy both recommend it so good enough for me.

Bought 2 quarts of STP brand from Autozone. Drained the old oil, cleaned everything up and started to pour the first quart in. It was coming out kinda transparent in color, like 30w oil but water color. Ok, well I’m not familiar with it I think I used Redline before so I thought, “ok odd but I guess it is what is is”. Then I opened the 2nd quart and started pouring, it was amber yellow. Same package 2 very different colors.

Thoughts? I’ve contacted STP through their website but no reply yet. Should I drain and start again or move on & don’t worry about it?



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I did the same...but the drum kept sticking. Went with the favorite, MT90 and have had no problems. MT90 is the undesputed favorite for OD tranny's!
 
CJD said:
I did the same...but the drum kept sticking. Went with the favorite, MT90 and have had no problems. MT90 is the undesputed favorite for OD tranny's!
Click to expand...
Agreed. I tried the 30 WT oil in my O/D gearbox and ditched it after a couple of drives when I found I could not shift into 1st when hot or cold. I switched back to MT90 and have had no problems since…
 
Was the container sealed? Someone may have filled it with water and then returned it for a refund.

Just a thought.

I would drain it and go with Red Line MT90

David
 
Definitely sealed I’ve still got the seal remnants from both bottles.

Dang I hate having to do 2 oil changes but I just don’t think I can risk it. I think I went back and forth on this before and decided on MT90 8-10 years ago. Oh well, car is still on the stands at least that’s a good thing. Can’t say I’m impressed with STP’s QC standards.
 
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Interesting reply from STP. Sounds like buck passing to me. I highly doubt Autozone said “color doesn’t matter, clear, yellow whatever”. Very disappointed in how they handled it.

“Thank you for contacting STP. We apologize for any inconvenience encountered while using the product. Regarding your inquiry, Kindly note that the product in question is a licensed product of AutoZone. Please contact AutoZone to get further assistance. We have provided their contact information below.”
 
Hi George, yes the backside is slightly different too. The amber stuff has a definite batch code imprinted on it down low in small letters, the clear one does not. I found one other reference to this same thing on an obscure off roaders website where someone had the exact same problem, but there was no resolution to it. No reply yet from AutoZone's on line customer service desk. My Redline MT 90 arrives tomorrow, so I've got another day to ponder what to do.
 
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