Alternate Trans/OD Oil Selection

[RAC68]

Hi All,

Recently we discussed the selection of engine oil for our Healeys and, as Healey Nut can attest to, several new informative perspectives were exposed as a result of Bob's reference of the 540 RAT forum (https://540ratblog.wordpress.com/2013/06/20/motor-oil-wear-test-ranking/). When considering oil selection for use in the transmission/OD, a search of past Forum threads brought out that, although SAE 30W non-detergent was officially specified back in the day, many have, and are, using everything from Royal Purply and Red Line transmission fluids to various single or multi-viscosity oils ranging from 60W and 20W50 down to 10W30. So, as exposed in the 540 RAT blog, it strikes me that our selection may be able to be more independent-fact based rather than solely reliant on general operational impression. Additionally, by making a selection with the advantage of knowing the lubricant’s Ware Protection Index, an improvement in transmission operational longevity can also be one of the beneficial gains achieved.

When looking at how we have selected engine oil in the past, viscosity, with respect to operating temperature, has been the primary selection criterion. Along with availability/convenience, price and oil company hype. Preliminary selections were made and further evaluated through operating experiences resulting in user recommendations that have helped others to do so. The selection of a Transmission/OD fluid alternative has been typically based upon a more definitive factory specification for SAE 30 non-detergent oil. Although I am not aware of the actual average operating temperature of our Transmission/OD, I expect it will fall closer to the higher (212F) testing temperature than that of the cooler for oil comparisons.

SAE Oil Viscosity is measured in centistokes (cSt) with a higher number representing greater resistance to flow or thicker oil. Measured at 40C (104F) and 100C (212F) operating temperatures with the number in front of the W indicating Winter or cold operation. As previously stated, based upon the factory’s Transmission specification for SAE 30 non-detergent oil and not being aware of a standard operating temperature range for our Transmission/OD operating temperatur, I would base my fluid comparisons at the high temperature reading rather than the low.

@ (104*F) / @ (212*F)
SAE 30 98.0 cSt / 11.4 cSt
5W40 87.2 cSt / 14.7 cSt
10W30 71.8 cSt / 11.5 cSt
10W40 96.5 cSt / 14.7 cSt
20W50 170.0 cSt / 20.2 cSt

Given the factory specification of SAE 30 provides an 11.4 cSt at operating temperature and this viscosity can be closely reflected with a multi-viscosity of 10W30 or even 5W30 it could be logically expected that choosing one of these alternatives would provide the Transmission/OD with greater protection and greater longevity. However, it would still take actual experience to validate the performance of the Transmission/OD and if it meets personal satisfaction.

It is much more of an open question that choosing a multi-viscosity oil that substantially jumps the operating viscosity, such as 20W50 with a cSt of 20.2 or approximately 177.2% increase over SAE 30 will benefit operating performance and will be more dependent upon operational experiences to justify the change. However, choosing a 20W50 lubricant with a Ware Protection rating greater than the replaced oil will still provide better protection even if operating performance is found to suffer.

Now, when looking at the targeted oils listed within the 540 RAT blog, Castrol Heavy Duty 30 wt. conventional oil holds the highest rating for this viscosity at 88,089 PSI while a multi-viscosity 10W30 from Mobile 1 Advanced Full Synthetic registered a PSI of 115,635 and at 20W50, Castrol GTX, API SN conventional, at 96,514 PSI, holds the record for this oil type. Given these reasonable choices, price and actual experience in operation would be the final selection triggers.

As a result of my analysis, I expect to change my present Transmission/OD fill from Red Line 90 to a 10W30 from Mobile 1 a similar viscosity profile of a conventional oil.

That’s my thoughts, what do you think?
Ray(64BJ8P1)

 

[Bob_Spidell]

I'm sticking with Redline MT-90 in my Healey gearboxes. Not only do they seem to shift smoother and go into O/D quicker, but I just went through the gearbox from my BJ8 with over 200K miles on it and the gears were pristine. I've run various conventional oils, and who knows what previous owners put in it, so probably any decent oil--as long as it doesn't have 'extreme pressure' additives--is probably OK. Gearboxes aren't subject to heat and other stresses like engines are.

 

[Keoke]

"

actual experience in operation would be the final selection triggers.

​

YEP:

Ease of shiftng & Operating pressure as a function of Temperature.

AS an aside ,if you travel long distances a lot pick an oil that is compatible with both the engine and Tranny, then U only need to carrry one type of spare.--- Just A Thought

 

[John Turney]

The gear oils, like MT 90 are not tested by 540 RAT, so it would not be appropriate to compare it to a motor oil.

 

[Michael Oritt]

I am a big fan of Redline MT90 and use it in my Healey as well as both Elva race cars. The Healey has a Toyota five-speed which is such a strong, positive transmission that it would probably work well with any appropriate oil. However the boxes in the Courier (MGB four-synch) and Mark IV sports racer (MGA three-synch) both thrive on the Redline and absolutely shift better and faster with it versus the Castrol 30 that I used before switching.

I've lately started using an Amsoil EP product in the dogbox of my Ginetta and it is very impressive, so I may try using Amsoil's equivalent of MT90 in one of the other cars in the future as it is relatively affordable and I have a distributor very close to where I live.

 

[Bob_Spidell]

"... Amsoil EP product ..." That doesn't mean Extreme Pressure, does it? Those additives usually contain sulfur compounds that are supposedly not nice to brass components.

 

[Michael Oritt]

Bob--

Yes, it is a GL5 Extreme Pressure oil not suitable for boxes with yellow metal and the G4 has an all-steel dog box. I mentioned it only because I was extremely pleased with the way the stuff works and Amsoil seems to be well-respected, so perhaps they have a GL4 gear oil that is worth my exploring in the future. I cannot always get MT90 on shelves near me and the Amsoil distributor is only a few miles from my garage.

Here is a link to the technical sheet on Amsoil's "Manual Synchromesh" synthetic oil but I cannot find a GL rating on it:

www.amsoil.com/lit/databulletins/g2080.pdf

 

[Bob_Spidell]

I get my MT-90 off my front porch

 

[pan]

I use Penrite Gearbox Oil 40 weight. Are Penrite products available in the U.S.A.?
I chose the 40 weight because I live with in sub tropical South East Queensland, Australia. The label says the viscosity is 25/60 and “not suitable for rear axles”. This oil has performed perfectly in the twelve years that I have used it. In that time I have done several long trips. To Adelaide, South Australia three times (over 1,500 miles each way), Port Stephens, NSW (500 miles each way), Melbourne, Victoria twice (1,200 miles each way. One of these trips included travelling further to Australia’s island state, Tasmania) and the overdrive has performed perfectly with no issues related to the oil.
Cheers,
Alwyn

 

[Lin]

Do we know what oil Toyota actually recommended for the Supra transmission? I use MT-90 but I am curious.
Lin

 

[RAC68]

Hi All,

It was not my intention to promote any changes for those satisfied with the oil being used but to suggest how we could use the new information gained in a more educated selection of an alternative. As a present user of Red Line MT90, although pleased with ist shifting performance, I have been forced to incorporate a Stop Leak to stop, or at least slow, its tendency to leak. This was done with the agreement of MT90 and the Stop Leak representatives who saw no issues with their combination and suggested the preportion. However, since my decision from SAE30 non-detergent to MTL and then MT90 was based on the experiences of others, a web artical by Quantum Mechanics, and Red Line promotions, I can't technical validate my decision.

My intention for this post was to suggest an approach for selecting an alternate oil to the one specified by the manufacturer that could be based upon more definitive independent information recently received from the 540RAT blog and I am still looking for your feedback on that approach.

Ray(64BJ8P1)

 

[Michael Oritt]

Hi Lin--

Browsing online sites produces an about-even split between those who use 20-50 engine oil and those who use a GL4 gear oil such as MT90. In addition to my empirical experience which gives superior shifting, etc. to the Redline product in semi-problematic synchromesh transmissions such as the MG boxes in my Elvas I am of the feeling that an oil specifically designed for gears, as opposed to engines, cannot be anything but better.

 

[Bob_Spidell]

IMO, synthetic gearbox oil > non-synthetic gearbox oil > engine oil (just avoid EP oils). Changing the gearbox oil is a bit of a pain, I usually go 15-20K miles between drain and fill.

Similar discussion going on the Mustang forums (the Getrag in the newer cars is not particularly highly thought-of, supposedly made in China). FWIW, here's a couple that get mentioned frequently:

https://www.bgprod.com/catalog/drive-line/bg-syncro-shift-ii/

https://www.amazon.com/Ravenol-J1C1002-75W-80-Manual-Transmission/dp/B00FGXB15O

What we need, obviously, is for 540RAT to apply his research skills to gearbox lubricants. So far, at least, no one's brought up the 'detergent vs. non-detergent' argument. I hope no one does.

 

[John Turney]

.... So far, at least, no one's brought up the 'detergent vs. non-detergent' argument. I hope no one does.

I think you just did.

 

[Lin]

Mike,
‘I am happy with MT-90, I am just curious about the manufacturer’s recommendation. What does Toyota say?

 

[Michael Oritt]

Lin--
'
Go here to see what looks like a scan of a Toyota manual which says "SAE 75-90 or 80-90" and "API GL-4" which jibes with what we have in MT-90:

https://htftp.offroadsz.com/marinhaker/programi/toyota/Manual Transmission/W56 & W55/26descript.pdf

 

[Lin]

Got it! Thanks.
Lin

 

[RAC68]

Hi All,

From thread responses, it appears that experience backed by personal references are what most are using to select lubricants such as transmission/OD fluids. Since there are so many seemingly appropriate trans fluid from which to select from and little authenticating independent information available, this approach is an understandably good way to narrow the selections and come to a decision. On this basis, I see no need to have, or reason to expect, any comments on the approach initially presented.

Thanks all,
Ray(64BJ8P1)​