[TR] OD Oil

[Reihing, Randall S.]

This is an interesting discussion regarding MT90 gear oil versus 30 wt. non-detergent oil in TR3 gearboxes. 

My humble opinion is that I fully agree with Randall that using MT90 gear oil is the best option for the TR3 gearbox. 

It's all about the oil film's resistance to pressure, or the maximum psi the oil film can withstand between rotating/sliding parts in close proximity to each other during periods of high loads. The maximum pressure the MT90 oil film can withstand before failure is somewhere around 500,000 psi. It's not likely that any metal-to-metal contact can occur in a TR3 gearbox that will generate forces sufficient to pinch off that MT90 oil film and allow metal-to-metal contact, a primary contributor to premature wear. Not so with 30 wt. oil whether it's non-detergent or not. The 30 wt. oil does not provide an oil film with equally high pressure protection from metal-to-metal contact that the MT90 oil film provides and while the 30 wt. oil may work in the short term, the gearbox will not have the life span of the same unit using the factory recommended 90 wt. gear oil. 

The only downside I can see is that winter driving may require some time for the TR3's gearbox to warm up or shifting gears may take a little extra effort before the gearbox and it's oil warm up a little. But then, here in NW, Ohio, I never  drive my TR3 in the winter. It's just not the same experience when it's 10-20F outside.

Randall Reihing
1959 TR3A


________________________________________
From: Triumphs [triumphs-bounces at autox.team.net] on behalf of Randall [TR3driver at ca.rr.com]
Sent: Tuesday, June 19, 2018 9:27 PM
To: 'TERRY SMITH'; triumphs at autox.team.net
Subject: Re: [TR] OD Oil

> Is the answer that, since John Esposito put it in, ...that
> NAPA 30 wt non-detergent is okay? ...Or should I just stay
> with Mt-90 as all recommend here and use the 3 quarts of NAPA
> 30 in the lawn mower?I Sorry to be so dense!!!!

We're talking opinions here.  Mine is that MT-90 is much better than ND 30.

The OD doesn't care so much, it should work fine on either one, but the
MT-90 will make the main gearbox both perform better and last longer.

And it meets the manufacturer's requirements.  ND 30 does not.

-- Randall
56 TR3 TS13571L once and future daily driver
71 Stag LE1473 - awaiting engine rebuild
71-2-3 Stag - awaiting gearbox rebuild