MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB Technical - Redline MTL vs MT-90 for Non-Overdrive Box

I have just now put Redline's MTL lubricant in the gearbox on my non-overdrive 71 B gearbox. I am hoping to quiet down a slight whirr I have when the box is in neutral.

I reading over the Redline website, I see they offer a

MTL lubricant
70w80 GL-4 gear oil with a SAE engine oil viscosity rating of 5w30/10w30

and a

MT-90 Lubricant
75/90 GL-4 gear oil which is a little heavier

I was wondering if those who already use Redline use the MTL or the MT-90.

Any feedback would be appreciated.

Thanks so much,

Jeff
J Delk

I ran the redline mtl fluid in a Taurus SHO for a while. It seemed to me that the trans began to make more noise after several thousand miles. It may have less friction, but it seems to also have less viscosity. I went back to a gl4 gear lube.

I've run my MGB o'drive trans for many miles with a mix of one pint gl 80 (the no sulfer gear oil) and the balance auto trans fluid. The trans and overdrive all worked very smoothly and reliably.

Engine oil as reccomended 50 years ago by the manufacturer is subject to shearing and is not designed for a gear lubrication application.

The most important issue is to run an oil that does not have sulfer - such as a gl5 lube - as that will damage the brass synchro parts.

Barry
Barry Parkinson

Jeff,

although i do not have any experience with this oil used by you, i run my 4 OD box in the roadster with ep 80 since many years. When changing the ep 80, there was not that much of contamination i noticed with the 20 W 50 all the time before, although i only changed the Gearbox oil 6 or 7 times within the last 31 years.

It still works and there has been no problem with the OD within more than 10 years of driving on ep 80.

Hope this helps

Ralph
Ralph

Jeff
The factory recommended a heavy grade oil for the V8 - I would follow up on Ralph's advice.

Roger
RMW

I run the MT90 in my late O/D unit as recommended by Redline. I haven't had any problems/noises in the last 2-1/2 years....
CD Dewey

Does mt90 redline oil have sulfur? If so it could be attacking your brass synchro rings. The 80 oil does not have sulfer and would modernly be the reccomendation. For instance the contemperanous datsun trans spec was 80 gear lube.

Usually 90 is only used in differentials where there is major lube shearing issues and no brass parts.

Barry
Barry Parkinson

Here is a link to the Redline site with tech info as PDF download documents for MTL and MT90

http://www.redlineoil.com/products_gearlubricants.asp?productID=46&subCategoryID=17&categoryID=7


Jeff

J Delk

The spec sheets show that redline oils are corrosion resistant and safe for brass synchronizers up to 300F and the mtl lubricants over 375f. It would be unlikely that gear lube in an mgb would be over 300f. The web site states that conventional gear oils can become corrosive at 200f.

It would be interesting to see other mfg's claims.
Barry
Barry Parkinson

Has anyone used Redline MTL or MT-90 in their gearbox for a sufficient mileage to say anything about the anti-wear properties? On paper, these oils look superb.

Tore
Tore

I've only driven about 6K miles but at some time you have to believe the engineers at Redline. Even if I had 50K miles, a sample of one wouldn't be a good test...
CD Dewey

I have only had it in a week - the MTL - but I am finding that the unit runs much quieter. This is not my imagination - it really makes a difference. The shift quality seems about the same - possble slight improvement - but the noise reduction makes it worthwhile for me. Seems to run cooler also.

Jeff
J Delk

The reason it runs cooler may be because there is less internal friction in the oil itself, but running quieter surely indicates there is less metal-to-metal contact, and less wear? Especially when you know that this oil is actually thinner than traditional 20w50.

I think I will try MTF or MT-90 in my non-OD three-synch.

Tore
Tore

I ran the Redline MTL 90 in my midget gearbox for years and swear it made it quieter. I also have run the usual Castrol 20w-50 in my MGB and Magnette gearbox for many years too without any wear indicated. However I do add a small amount of (probably 6 to 8 oz.) of Lucas oil Products gear additive to both the latter gear boxes and I'm sure that it makes them easier to shift quickly without "graunches", especially when cold. I can't see why a climbing oil like the Lucas additive which lubes the whole gear set would be bad for the tranny.
Only got 165,000 miles on the B though, maybe long term, (more than 18 or 20 yrs.) would show it's bad for the gearbox.
Wayne Hardy

I use 40 weight in the MG gearboxes and never any problem.

I use Redline in the Lambo box and it seems to shift a little easier.

If you use anything heavier than 40 in an early MG box it will not shift properly inot OD until the oil heats up a bit.
Bill Spohn

I have been using MT-90 for 2 years/1,000 miles in a non-OD MGB transmission with 67,000 total miles. It “fixed” (masks) a weak first gear syncro, and at the moment the box is working just like it should. So of course I am very pleased with it.

I did have a problem with it in my Golf (daily driver) in sub 20 degree F. weather when it seemed to turn into concrete, but I doubt that Georgia gets that cold <g>.

David Wagner

This thread was discussed between 28/05/2007 and 04/06/2007

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.