[TR] Suggestions

[Alan Myers]

 Hi Fred,

This question has come up quite a few times over the years. 

Specifically for the gearbox WITH overdrive, Triumph originally called for 90wt gear oil, the same as in the non-OD gearbox and diff. However...

A lot of people have come to think that's  way too heavy for many OD, so a "racing" motor oil (non-detergent) of lighter viscosity is now generally recommended. But I strongly suspect the weight you choose depends on the wear and tear in your particular OD. A higher mileage unit might be able to run 50W (which is roughly equivalent to 90wt gear oil viscosity).? But, that is probably too heavy for a recent rebuild without very much wear.

Go to www.quantumechanics.com and see if you can find the tests that John Esposito has done with O/D units. He rebuilds them, so probably knows better than any of us. That also has given him ample opportunity to stress test some units with various oils, something that most of us will never have a chance to do. (I looked quickly at the site and don't see the article about oils... might need to email John.)

His recommendation for his freshly rebuilt units is 30W non-detergent (racing). I think 40W might be okay in a car with some wear. Or mix half and half 30W and 40W. 

John specifically recommended avoiding multi-viscosity oils and any with detergent. Multi-viscosity such as 10W40 were shown to cause lockups. And, detergent oils foam up which isn't good for either gearbox lubrication or for the hydraulics of the OD unit.

Personally I'd avoid most synthetic motor oils because many are extended-life formulas with lots of extra detergents. Synthetic or non-synthetic gear oils (non-GL5) might be usable, but - again - for ODs it's probably best not to use the heavier ones like 90wt, unless your's is a really high mileage OD. I'm also a little bit leery of using synthetics with oil-bathed clutches, like those used in the OD unit (and also most motorcycles). However, if formulated for this sort use, like some of Redlines, it will probably be fine so long as it's not too heavy viscosity.

The ideal thing would be to pressure test your specific overdrive unit with different weights of oil. The A-type runs somewhere between 450 and 500 psi, if memory serves. So that's what you are shooting for. Too heavy viscosity can cause over-pressurization, and might lock the unit into overdrive. Too light viscosity might under-pressurize and may make the unit sluggish to shift into OD. 

Gearbox WITHOUT overdrive is another thing entirely. In that case Redline synthetics like MT90 or their 75W90 are good. Non-synthetics in this weight should be fine, too. Whatever you use, just avoid any GL5 formulas. Those have sulfates in them that can attack and eventually damage the brass or bronze parts in the gearbox. 

The diff uses the same oil as the non-OD gearbox (unless you have a limited slip installed). 

Off to the Concours at TriumphFest!


 


Alan Myers
San Jose, California
amfoto1 at aol.com
'62 TR4 CT17602L (a work in progress)
http://www.triumphowners.com/640


 

-----Original Message----- 


From: FRED E THOMAS <frede.thomas2 at verizon.net>
To: triumphs <triumphs at autox.team.net>
Cc: Shop-Talk Mailing List <shop-talk at autox.team.net>
Sent: Thu, Oct 1, 2009 2:13 pm
Subject: [TR] Suggestions/

I would like the lists opinion on types/weight etc. of oil used in the gearbox
W/OD and rear differential, many thanks for your help   FT