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Triumph TR6 - Trans & Gear Oil & Gl-5

I've read some stuff recently about not using GL-5 gear oils in your transmission as the additives in the oil will
wreck the brass bits in the trans. Is this true?

Can GL-5 be used in the rear end?

If GL-5 is a "no go" where can I find GL-4 oils? My gear oils at home (CTC & NAPA) both say " meets GL-5 standards" - so I assume these oils are out?


Aivars Berzins
Aivars Berzins

The early GL-5's had some sulfur based additive that would attack copper alloys when hot. I confirmed that at the time, gosh, 7-8 years ago, by calling an engineer with Mobil. The Mobil 1 gear oil likely caused my transmission failure after about a year of operation, but performed fine in the differential for 7-8 years. I don't think there are any brass parts in the differential (please let me know if there are!), and it's not as hot as the transmission, either.

I recently read that the sulfur additives have been replaced in most GL-5, so the bronze/brass corrosion is no longer an issue. I recommend you research the oil you are considering and see if it's acceptable, since MOST is not ALL.
Brent B

From the reaearch I did including talking to the Mobil & Red Line folks, the EP additives in some GL5 oils will attack yellow metals at high temperatures and brass syncro's seem especially affected. They recommend only GL4 in transmissions.

Red Line's MTL & MTL90 are GL4 synthetic transmission oils and seem to work well in the 6. My local NAPA carries Sta Lube 80w-90 conventional GL4 gear oil in quart containers and they also sell a great pump for a few $$.

I use the MTL90 in the gearbox and Valvoline synthetic 75w-90 in the diff w/ no problems.

74 TR6


check the archives last year as there is a sizeable debate about this

Yes, there was a sizable debate to be sure. Bottom line...GL-5 is a No NO for the tranny. I contacted several suppliers of GL-5 and they said not suitable for yellow metals. The thread is March 2002 "Differential GL-5 OK?" Be sure to read the ENTIRE thread as u will see my tail eventually goes between my legs:) IT appears that GL-5 is OK for the diff. But even this is still open to debate.
Rick C
Rick Crawford

Do yourself a stress reduction favor and pick-up a 5 gallon pail of StaLube GL-4; it'll last the life of your TR and beyond. I still don't understand how the modern GL-5 gear lubes proclaim on the bottle compatibility with GL-3 and GL-4 applications.

Rick O.
Rick Orthen

Thanks for your help! I guess I should make a practise of searching the archives prior to posting.

BTW Referring to my 82 Mercedes 240d 4 speed std trans. a lot of the guys with the same vehicle were using either motor oil or ATF in the manual trans. I used 10w-30 motor oil synthetic with no problems. Shifted great - even on those cold -20 c mornings.

Aivars Berzins

Aivars Berzins

Not trying to open a can of worms, but this is a response
I received from Shell Canada:


Good morning!

As per your query regarding the applicability of Shell Spirax HD 80W90,GL-4/GL-5 oil, for your standard transmission with yellow metals, it can be used as long as the system temperature does not rise above 90C. The
additive formulation of the Spirax HD 80W90 is 'passive' so should not react with metals; however, Shell does not guarantee the oil's performance in this application since additives may react under certain conditions.

I would recommend that you contact your vehicle dealer to confirm the
use of the Shell Spirax HD 80W90 oil.

Hope this information proves helpful and please do not hesitate to
contact me should you need further assistance,

Carolina Baker
Shell Technical Help Desk

SOOOOO................. how hot does the oil in a TR6 transmission get????

Aivars Berzins

My response from shell back in March 2002:

"Dear Mr. Crawford,

Thank you for taking the time to visit the Shell Canada web site.

In response to your inquiry, the Spirax product is not recommended for
applications where high temperature is a factor in equipment with yellow
metals. This product is not a problem with yellow metals only when the
temperature of the equipment does not exceed 90 deg celcius.


Lilianne Walker - Technical Department

Shell Canada Products "

Aivars, my question was on the same product. OK..who knows the temp of our trannys?
Rick C
Oh Ya... Aivars did you contact your vehicle dealer yet:)
Rick Crawford

Hm? I probably should not post anything after my 1st beer, but what is magical about 90C? Is there a chemist in the group? If I remember anything from chemistry, then the reaction rates simply increases to a point that is considered beyond some arbitrary threshold. If this is right, then at lower temperatures the reactions still happen?! I have enough challenges with mechanics and try to avoid adding chemistry to my hobbies.

2 cents - I use Redline 'MT' (Manual Trans) in the trans, Redline 90 in the Diff. Guaranteed 'safe' and the shifts are quick and slick. Peter
Peter Gooch

I was trying to find some Redline locally here in the wilds of PEI - but good luck!!! I've searched up and down for a GL-4 oil to no avail, I think it will some 15w-40 eng oil in the trans.


PS Rick C.- I tried to contact the dealer - but for some reason with no sucess??? DOH!
Aivars Berzins

For the last 12 summers (over 70,000 miles) I've used Valvoline 20W50 engine oil in my gearbox which also has an overdrive. I change the oil every 3,000 miles and have never had a problem. Ken Gillanders of Temple City, California told me to use this or the Valvoline "R" (the racing version), if I could get it.

Don Elliott, 1958 TR3A
Don Elliott

In general the rate of most chemical reactions doubles for each 10C temperature increase. Used to be called the Arrhenius Rule. The 90C "limit" is based on some arbitrary rate of corrosion that was observed - and probably somewhat severe within a short period of time. So even at 70C, corrosion will STILL occur, but at roughly 1/4 the 90C rate. Tranny's get hot, so why risk it? If you want a good synthetic - use the Redline 70W-90 NS.
Brent B

I agree fully. When I got my respose from Shell back then, I immediately drained the dif of the Spirax...I had only put on, I think, 300 miles. The bottom line is Shell does not say 100% safe with yellow metals...the reason not to use it. Thanks for the technical side Brent.
Anyone else feeling a little De Ja Vu here?
Rick C
Rick Crawford

I ordered the Redline NS from Moss and had it in my tranny till a couple months ago, but the stuff is really drippy, so I switched to Stalube GL-4, which I luckilly found at a local auto supplier. The drip has slowed considerably.

I guess tranny seals should be on my list for things to replace when I pull my tranny out to fix the clutch. I am not sure what I will put back in. The car seemed to shift smoother with the Redline, but not so much so that it was worth the drip.


I would stay away from the GL5 for the transmission it is OK in the diff, there is no yellow metal there. If you can find the StaLube GL4 buy it, but I have only found it in 5 gallon cans. You can also buy online at This is a great place and delivery is very fast. They sell a 2.5 gallon bottle of Mobile 424 Multipurpose transmission/hydraulic flud which is an 80 weight GL4. I have been using this for a long time in an overdrive trans with great success. It is part number 60002722 and sells for $28.22 US. Steve
Steve Yott

Steve-A petty detail, but the thrust washers on the sun gears in the diff are yellow metal, at least in the early cars. They were later changed to fiber (phenolic resin). The thrust washers on the planet gears might be yellow metal too.

As a counterpoint - the differential doesn't run nearly as hot as the transmission.
Brent B

This thread was discussed between 06/04/2003 and 17/04/2003

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