• Hey Guest!
    British Car Forum has been supporting enthusiasts for over 25 years by providing a great place to share our love for British cars. You can support our efforts by upgrading your membership for less than the dues of most car clubs. There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Upgraded members don't see this banner, nor will you see the Google ads that appear on the site.)
Tips
Tips

TR2/3/3A Mixing MT-90 with Hypoid Gear Oil?

Share this page

mrv8q

mrv8q

Luke Skywalker
Country flag
Offline
Should I do this? 1 quart of the Red Line didn’t quite fill the TR3 gearbox, and I have plenty of the StaLube 85W 90 in the garage. Can’t get the MT-90 locally, otherwise I’d just go get it.

Interwebs are mum on this subject, though I think I know the correct answer...
 
The rule of thumb and best practice is not to mix oil types. If your gearbox is "close" to being full, drive the car gently and limited distances until you get more of the MT-90.
 
Compatible meaning nothing really bad happens. But you also lose at least some of the advantage of the better oil.

Kind of like mixing Thunderbird in your single malt. Won't kill you, but might not taste very good either :smile:

I'm with Doug, order another bottle and drive with it a bit low until it gets there. But IMO there is no need to baby it as long as its just an ounce or two low. The "full" level includes a reasonable margin for leakage between refills.
 
Thanks, all. Thanks to our friends/ overlords at Amazon, they promise I’ll have another bottle today. I wasn’t keen on mixiy, so this worked out. Changing the gearbox oil was a “while I was in the neighborhood... “

I did a quick rebuild of the clutch master cylinder and am going to replace the hydraulic hose, all to cure an occasional balky-shifting gearbox. Fingers crossed...
 
mrv8q said:
Changing the gearbox oil was a “while I was in the neighborhood... “
Click to expand...

We no longer have our Spitfire but one of the modifications I made to it was the addition of an access hole on the side of the tunnel cover. I fit a large rubber grommet type plug into the hole. Whenever I wanted to top up the gearbox oil I'd peel up the carpet, pop out the rubber plug, then remove the fill plug and fill away.
 
I smiled at the Thunderbird reference as well. I actually used to sell it in a previous lifetime. 1.59 back in the day?

My gearbox takes 6 pumps over the original quart to fill... go figure. At least I know it’s full.
I plan to fill and bleed the new clutch master cylinder on the weekend, drop it from the jacks, and see how nicely my new refurbished clutch system works. Fingers crossed...

Definitely a good idea about an access hole, Doug. If I have to go back in, it’s on the list.
 
sp53 said:
Do they still make T-Bird Randall, maybe in Cal plus I thought the gearboxes drank 30 W non-detergent
Click to expand...
I haven't a clue about the Tbird; but if Gallo still makes it, I'll bet they sell it nationwide. Don't recall ever seeing it on a shelf here in CA; but then I don't spend a lot of time in the kind of places that usually sell it.

Triumph did originally recommend motor oil for the gearbox (although there is an early TSB suggesting that gear oil is OK too, without overdrive). But then, about the time the TR3A was (unofficially) introduced, they switched to specifying GL4. Ken Gillanders once wrote that an ex-factory engineer told him that they were having too many countershaft failures, and the GL-4 provided better protection. S-T and later BL continued to specify GL4 through the end of TR6 production, so evidently they felt it worked.

aTv6UrB.jpg


Personally, I really like the MT-90. Doesn't change OD performance much, but makes a noticeable improvement in the main gearbox IMO; in the form of easier, more positive shifts. My synchros are getting somewhat worn now, but with almost 200,000 miles since the main box was overhauled (1997 IIRC), I consider that pretty good service.
 
GL4 is a performance standard for gear oil; so it can be any of the gear oil weights. 90 is probably most common, ISTR MT-90 is actually rated 75W90 but Redline also offers MTL which is 75W80. I've also got a jug of 140 weight GL4 in the garage.
 
Just to button up this post... bled the clutch master cylinder, dropped the car off the jacks, and took it for a spin around the block. Car seemingly shifts fine, can’t tell any difference yet.

Going for a 50 mile round trip tomorrow morning, so that will be the real test. WooHoo, glad to see the car at its appropriate height in the garage.
 
Back
Top