TR2/3/3A Gear oil in the gear box?

[joe kumpel]

Dumb question..........my service manual says SAE 30 in the gear box.
Can this be correct? I thought gear oil in both differential and gear box.
Thanks

 

[TR3driver]

Motor oil was the official factory recommendation until about 1960 or so. There was even a service bulletin in 56 or 57, warning against using gear oil in overdrives (but saying it was probably OK in non-OD gearboxes).

 

[CJD]

I'm running 90w-140 synthetic in my non-overdrive box, and have no complaints. John Alan posted an interesting test last year. It showed that the 30w is about the thickest you want to use in an overdrive box. With more viscous oil the overdrive pump pressures go cosmic. So, when I rebuild the TR2 overdrive, it will get straight 30w.

 

[Marvin Gruber]

straight non detergent 30 wt

 

[sail]

Welcome. No dumb questions. Here are a couple results from a quick search in Triumphs. Many opinions:

https://www.britishcarforum.com/bcf...il-goes-in-your-TR3-4-Trans&highlight=gearbox
https://www.britishcarforum.com/bcf/showthread.php?93359-TR6-gear-oil&highlight=gearbox
https://www.britishcarforum.com/bcf...raight-SAE-50-for-OD-Tranny&highlight=gearbox

 

[TR3driver]

John Alan posted an interesting test last year. It showed that the 30w is about the thickest you want to use in an overdrive box.

Which of course is very strange, since the early factory recommendation was 50 weight in temperatures over 70F. They also delivered a whole bunch of A type ODs with 90 weight. So that test "shows" that the factory was delivering cars that would blow up instantly. Kind of silly to say that, after all these years when they obviously didn't blow up ...

Most likely, IMO, that OD had been modified with shims under the accumulator spring, causing the spring to reach coil bind before the relief ports were completely open. BTDT (but none of the articles seems to mention the possibility).

Adding greatly to the confusion is the fact that motor oil and gear oil are deliberately graded on different scales. 90 weight is actually thinner than 50 weight! (at the same temperature, of course, they all change viscosity wildly as the temperature changes).

 

[CJD]

Which of course is very strange, since the early factory recommendation was 50 weight in temperatures over 70F. They also delivered a whole bunch of A type ODs with 90 weight. So that test "shows" that the factory was delivering cars that would blow up instantly. Kind of silly to say that, after all these years when they obviously didn't blow up ...

Most likely, IMO, that OD had been modified with shims under the accumulator spring, causing the spring to reach coil bind before the relief ports were completely open. BTDT (but none of the articles seems to mention the possibility).

Adding greatly to the confusion is the fact that motor oil and gear oil are deliberately graded on different scales. 90 weight is actually thinner than 50 weight! (at the same temperature, of course, they all change viscosity wildly as the temperature changes).

From what I remember about the tests, the OD's didn't "blow-up", but rather had issues dropping out of overdrive when the pressures doubled the specs.

 

[TR3driver]

From what I remember about the tests, the OD's didn't "blow-up", but rather had issues dropping out of overdrive when the pressures doubled the specs.

More likely getting stuck in overdrive. The extreme pressure forces the cone clutch harder into the cone. But in my case, the excess pressure did eventually "blow up" the OD. Among other things, it broke the snap ring that holds the clutch assembly to the carrier bearing.

 

[CJD]

You're right...the way I worded it was confusing. They would stick in overdrive if the pressure was to high. I've been flipping through the old posts, but can't seem to find the test Alan John posted. Maybe he'll chime in...

 

[TR3driver]

Check the Quantum Mechanics website. I'm pretty sure it's still up there.

 

[CJD]

I'll look, thanks!

And Marv has an interesting point...all gearboxes recommend non-detergent oil. Even boat transmissions recommend non-detergent. Why is that? Non-detergent is relatively hard to find.

 

[Marvin Gruber]

John,
I found 30 wt non/d on the shelf at Auto Advance. I did buy a couple of extra quarts. I kinda remember something about non/d didn't attack the bronze bushing in the trans.

Marv

 

[TR3driver]

And Marv has an interesting point...all gearboxes recommend non-detergent oil.

Well, not "all". Standard-Triumph never said "non-detergent", and actually recommended the same oil as for the engine (before they started recommending gear oil).

I've heard several theories as to "why". The one that makes the most sense to me is that the detergents are intended to help keep dirt (wear particles) suspended in the oil, where they can be removed by the filter. But in a gearbox without a pressure filtration system, it is better for the wear particles to settle to the bottom rather than getting splashed back onto the gear faces and bearings to increase wear.

If you do stick with motor oil, I suggest Valvoline Racing (the "Not Street Legal" stuff) in 20W50. It is a low detergent oil, but the high levels of ZDDP will help protect the weak spots in the TR2-6 gearbox, which is the counteshaft bearings and thrust washers. I used it for many years (based on advice from Ken Gillanders and Herman van den Akker) and it works well enough.

But Redline MT-90 (which is a GL4 gear oil as recommended later) will make it shift better.

 

[joe kumpel]

Thanks to everyone for all the good info and insight. Since I'm running a non-overdrive gearbox I
think gear oil will be the choice.

Again, THANK YOU ALL