Richardtr3a Posted May 5, 2019 Report Share Posted May 5, 2019 My gearbox tunnel is out and I am repairing the starter. This gives me easy access to the gearbox dipstick. What is the best oil for an overdrive box on a 3A. The gearbox is in very good condition and has been overhauled recently. I have just checked the oil dip stick and there is nothing showing. I have Comma EP90 GL5 in the box at present, bought from Moss who now only have Dynolite How often does the oil need to be fully changed and not just topped up. The nearest oil I can find is Comma gear oil high performance SX75w-90 GL5. What does GL5 mean and is it better that GL4 semi synthetic Thanks Richard & B Quote Link to post Share on other sites
RogerH Posted May 5, 2019 Report Share Posted May 5, 2019 (edited) Hi Richard, firstly DO NOT use GL5 oil. These traditionally have a high sulphur content and can damage any brass or bronze components. You MUST only use a GL4 oil. There is great debate about exactly the best oil for a GB with O/D. I use a gearbox oil. In particular Penrite GB40 GL4. It is designed specifically for gearboxes and does not harm the yellow metal. You will get answers recommending EP90 etc these work well but do ensure it is a GL4. DO NOT use an engine oil such as 25/50 as this may contain a detergent for cleaning the engine. This could cause frothing etc. Tin hat on and cowering behind a wall Roger Edited May 5, 2019 by RogerH Quote Link to post Share on other sites
Lebro Posted May 5, 2019 Report Share Posted May 5, 2019 No good hiding Roger, we know you are there ! I used to us a cheap 20/50 (as recommended by my box re-builders - Hardy Engineering,) but I have now seen the light, & my box now contains Penrite GB40 Bob. Quote Link to post Share on other sites
Hamish Posted May 6, 2019 Report Share Posted May 6, 2019 I’m no expert, so all I can contribute is that my 3a ( tr6 box with A type od) was purchased in 2016 after a recent previous owner gearbox rebuild and had used EP80/90. i use (and abuse) my car in club sprints etc. And on the road for leisure drives club runs. At the beginning of 2018 I had to do some remedial work on the box due to leaks that let me do the 2018 season and continued with the EP80/90. at the end of 2018 I had the box and od professionally rebuilt (not due to the EP oil I don’t think) and upgraded for competition and the builder supplied dynolite Gear 40 oil. This has been used for 6 months and 2 sprint competition and works well, no slippage etc. as Roger said I have been advised to stay away from GL5 version as it is not good for yellow metals. h Quote Link to post Share on other sites
RogerH Posted May 6, 2019 Report Share Posted May 6, 2019 Hi Hamish, unless I missed something in the shop I have noticed that the Dynolite oil does not specify any GL rating. I'm sure it is very good but a simply GL number would calm nerves. Roger Quote Link to post Share on other sites
mike ellis Posted May 6, 2019 Report Share Posted May 6, 2019 I have used both SAE40 and EP80/90 at various times and have not noticed any difference. Currently using EP80/90 GL4 from Halfords. Quote Link to post Share on other sites
Lebro Posted May 6, 2019 Report Share Posted May 6, 2019 All you ever needed to know about gear oils: https://www.widman.biz/uploads/Transaxle_oil.pdf As GL4 & GL5 are sulphur based friction modifiers, & the Dynolite oil states "Non friction modified" I would say it is a fine choice. Bob. Quote Link to post Share on other sites
Hamish Posted May 6, 2019 Report Share Posted May 6, 2019 1 hour ago, RogerH said: Hi Hamish, unless I missed something in the shop I have noticed that the Dynolite oil does not specify any GL rating. I'm sure it is very good but a simply GL number would calm nerves. Roger Roger I understand the concern ( having just paid for a rebuild and upgrade) but the builder recommended it and Moss says the following in their listing description. Sometimes you can only go on faith from reputable sources. “This multigrade oil replace the SAE40 & EP90 commonly used in gearboxes. It is compatible with straight-cut and synchromesh gears, and safe for use in overdrive units. It does not contain any EP type additive that would destroy yellow metals such as bronze, copper or brass. This oil does not contain any friction modifier additives which can cause slipping in overdrive clutches and preselector gearboxes, such as Cotal or Wilson.[P]Replaces oils originally specified as EP90, SAE40.” Quote Link to post Share on other sites
iain Posted May 6, 2019 Report Share Posted May 6, 2019 Penrite GB40 as recommended by the gearbox rebuilder 3 years ago.......who seems to vary depending upon what Moss are promoting! Clearly favouring a.n.other brand now:-) Iain Quote Link to post Share on other sites
Tom Fremont Posted May 6, 2019 Report Share Posted May 6, 2019 Here in the 'States SAE 30W non-detergent motor oil has been thoroughly proven. I must have done over 100K miles with my Webered TR250 O/D transmission using the stuff. There should be a detectable, if slight increase in fuel economy with this over the gear oils, giving less viscous drag. Similarly, I noticed several more miles between fill ups using a synthetic oil in the differential ( poured like water, almost ). Cheers, Tom Quote Link to post Share on other sites
Mike Graham Posted May 7, 2019 Report Share Posted May 7, 2019 I used SAE 30W non-detergent motor oil in my TR6 J-type OD for many years. No complaints, but found it was getting harder to find locally. No longer have the TR6 and my TR3 does not have OD. Cheers, Mike Quote Link to post Share on other sites
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