MG-Cars.info

Welcome to our Site for MG, Triumph and Austin-Healey Car Information.

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 - Gearbox lubrication

Sometime ago there was a thread about gearbox/overdrive oil. At the time I was in the process of re-building an engine but had also been in contact with Mossis oils in Shrewsbury about a better/more modern, lubricant for the B overdrive gearbox. Their tech dept recommended a Semi synthetic 75W 90 gear oil, Lodexol. My engine and box have been installed now for 3 weeks, with said oil. The gearbox is a delight and the O/D engages beautifully. One also has to assume that, since this is a properly formulated gear oil, and thus better suited to the pressures of torque transfer than engine oil, the box will be better protected to boot.
Allan Reeling


as it costs £50-00 to fill the box - is it worth it for a used box which needs to have a change ?
ap lestocq

Have since found out that Comma do the same spec oil for half the price.
Allan Reeling

Allan, I wish you luck with this experiment! Please keep the forum updated as to the long-term reliability.

Whilst multi-grade gear oil may not have been available in the 70's, gear oil of a lower viscosity would have been and there must be other reasons for not using it.. I'm sure the thinker oil will make the shift smoother and the overdrive engagement quicker, but at what cost to the overdrive clutch plates? Not forgetting the extra pressure placed on all the actuating seals and springs by the heavier oil.
If anyone has any long term running on this viscosity oil I would be very interested in the outcome.

MGmike
M McAndrew

Gear oil viscosity is assessed differently to that for engine oil. Gear oil EP 90 is approx the same viscosity as 30w engine oil. EP 90 was the oil of recommendation by BL for the V8 gearbox, because of the extra torque transferred by that engine! My main reason for using gear oil is my view that engine oil is for engines! Gear oil for gears!
Allan Reeling

I do think that the millions of miles covered by the hundreds of thousands of MGBs over 50 years (plus a number of other vehicles over a longer period) would have thrown up any problems with using engine oil in the gearbox by now, but each to their own.
PaulH Solihull

I have often thought that the 20w50 oils that are made for Minis and other combined engine/gearbox applications, like Millers Classic TransM 20w50, would be perfect for our gearboxes.

http://www.moss-europe.co.uk/Shop/ViewProducts.aspx?PlateIndexID=10336&SortOrder=1

Unfortunately I cannot find it here.

Tore
Tore

It's a bit like the person who lives to be 80 after smoking 50 a day and a diet of only bacon butties. You will never know if they would have survived to be a 100 and with a better quality of life!! Me, I'd sooner not smoke, eat healthily and put better oil in my car!!!
Allan Reeling

Allan. The 90 weight gear oil is similar to 40 weight motor oil, slightly heavier than the 30 weight you suggest. I tend to agree with Paul that, over 50 years of use with engine oil, provides a good indication that the product is suitable for the purpose(s) the factory specified it for. One might, also, argue that engine oil is not suitable for use in SU carbs in spite of the fact it has been used there for generations.

Les
Les Bengtson

Why did MG/Leyland recommend EP 90 then? I'm a bit of a cynic really. I think they realised that their original compromise to get a better shift was going to lead to gearbox failures. They did the same thing when the LT77 was declared "notchy" on gear oil and Leyland substituted ATF. I'll stick with "proper" gear oil thankyou and enjoy the benefits!! No guarantees that I will get a telegram, or whatever the Queen sends now, though!!
Allan Reeling

Allan, whilst some of the comments may be less than supportive of your choice, I'm genuinely interested in the outcomes. I can see that at some point in the future "old mix" oils are likely to be discontinued if only for economic reasons and we will need to look at the best of the available products. While your "leading edge" experiment may not be to the taste of all, you should be applauded for taking on the challenge. I hope you record all the benefits and issues encountered and report these on the BBS. I promise not to say "I told you so" if things do go wrong.
Have you got anymore info on the science of your choice?
MGmike
M McAndrew

Apart from the synchros, the layshaft is the weakest point in the MGB gearbox as far as I know. At least on the 3 synch box. When the layshaft is worn, the gears get out of mesh, and THEN the gear wheels start to wear seriously. So improved protection of the layshaft and its roller bearings should have even higher priority than better lubrication of the gear teeth.

Am I correct?

Tore
Tore

Shucks- this is past my short sight. I've been using Redline or Royal Purple 90-140 in the 3 OD trans for about 12 years. All is very well- OD activates immediately and stays, shifting is a smooth pleasure, and I believe with syn in the diff too, I must be decreasing friction loss somewhat. So, has anyone given STP cut with jack oil a go yet? Cheers, Vic
vem myers

"Why did MG/Leyland recommend EP 90 then?"

That is for the V8, with its higher torque as you said. The recommendation to use engine oil in 4-cylinder gearboxes continued long after the introduction (and demise) of the V8. Horses for courses.

I've read of Americans complaining of a very stiff shift in the winter when using gear oils. My V8 has been used in all weathers and was kept outside and I can't say I have noticed anything in particular when the weather was well below freezing, or a difference from cold start to hot running. It *is* generally slightly heavier than my roadster, although whether that is down to my particular box, or the V8 in general, I don't know. Gear oil isn't going to hurt the 4-cylinder gearbox, despite warnings from several quarters that it can destroy the yellow metal synchro rings, which I think applies to *differential* oil rather than gear oil. Note that Wikipedia doesn't differentiate between gear oil and differential oil. All MGBs uses the same oil in the diff, which is a heavier duty version but the same basic viscosity as the V8 gearbox oil.

You can decrease friction too much as far as the OD is concerned, which is why Laycock specifically instruct that friction reduction additives should not be used under any circumstances.

No telegram from the Queen anymore.
PaulH Solihull

A point mentioned by Mike is that a number of parts within the gearbox actually require friction to operate correctly. Both the synchro hubs and clutches within overdrive units require friction to work. Two examples of problems are modern cars that crunch 2nd gear from cold but get better as the gear oil gets warmer and thinner and the 70s fad for using the likes of Molyslip. This was so slippery it stopped the synchro working properly and a number of gearboxes were ruined. Personally I'm all for using the best quality oils but newer doesn't always mean better. My gearbox is 40 years old and if engine oil has kept it going this long I'll stick to that until someone comes along with scientific proof that something else is better (in this gearbox). Subjective tests are ok but the results can be influenced by how much a product cost.

Bob
R.A Davis

I've used Redline synthetic in my differential and gearbox. The differential uses extreme pressure (hypoid oil). The gearbox uses non EP Redline. I think the Redline reduced differential and gearbox noise some. Mine is a non-OD three synchro. Third/fourth synchros are factory original and are flawless at all temperatures. I wish the same could be said of 2nd. It is a replacement synchro and only worked well for a few months after installation. It left all sorts of gold flecks in the first oil fill. The 2nd gear shifts were better after I put in the Redline gear lube.

I've learned to delay the 1-2 upshift just right to avoid clashing. I double declutch on any 3-2 downshift above about 5 mph. A moving downshift is still an adventure.

One advantage of gear oil is if properly formulated it has friction modifiers to optimize synchro engagement. Engine oil formulators don't care about synchro performance.
Robert McCoy

"No telegram from the Queen anymore."
What?
That's been on my bucket list for years.
Ah well, may as well become a republic then! (lol)
Roger T

This thread was discussed between 01/01/2012 and 04/01/2012

MG MGB Technical index

This thread is from the archives. Join the live MG MGB Technical BBS now