[WPTA] Gearbox oils, for your Sunday reading pleasure

[Tom Stricker]

  I have just been thinking about gearbox oil as my OD TR3 shifting has not been as smooth as it was. I do check my fluid level religously as I burned up my first box early on driving to Carlisle.  A fine memory of our great club's team effort getting me back on the road. By the time I found a transmission at the swap meet, the club members had my car disassembled and ready for the transplant. I have always used non-detergent 30 weight as the book specified. Judging by the way it poured out of the bottle I worried that 75-90W would not work in my overdrive unit. I would sometimes add a little bit of Lucas gear oil with the 30W when topping up. This article has me confused. ATF and 75W are at the opposite ends of what I consider the viscosity scale. With ATF so thin, and gear oil so thick, I don't know how both could work. As Ed is the transmission Guru, I must admit to being lax in my transmission oil change. What product should I use next?All help apprediated.Tom Stricker 
    On Sunday, August 6, 2023, 10:54:45 AM EDT, JIM UNDERWOOD via Wpta <wpta at autox.team.net> wrote:  
 
   I found that in my MGB, the OD would slip on a high RPM shift with gear oil.  Switched to ATF and the issue was gone.  I don't know how many times I had the engine in and out thinking it was the clutch hanging up.  Ran into the same issue on a friends 79B with OD.  The TR8 gets GM syncromesh fluid which is a light viscosity.  ATF works as well and many use that.  Put Gear oil in a Rover 5spd and you will be grinding gears until it gets hot.     Jim  
  On 08/06/2023 8:50 AM EDT EDWARD WOODS via Wpta <wpta at autox.team.net> wrote:           For all of you still using engine oil in your Triumph or MG gearboxes:   And, by the way, when’s the last time it’s been changed? “Dirt is the enemy of all machinery”       Ed Woods           People confuse engine oil weights with gear oil weights. They have > nothing to do with each other. A 75w gear oil has about the same viscosity > {pourability} as 20w engine oil. Back in the days when your cars were new oil technology expecially gear oil was rather crude. 30w engine oil was  used because they did not have a gear oil that was thin enough. Light  weight gear oils are fairly new. The last 15 years or so. Gear oils are designed for shear stregnth. Meaning they cling to virtical surfaces. Engine oil does not. By using straight weight engine oils you are using ancient technology. It would be the same as putting on rayon/nylon tires, using poor fuel etc. We use 75w/80 gear oil in all but our racing boxes. These use a 75w synthetic oil. One of the boxes, a pre-war jag box had over 30,000 miles of rallies on it before it broke a gear tooth. There was no evidence of abnormal brass wear on the syncros. I have never had an oil engineer in 25+ years of business tell me that hypoid oil attacks brass. The light weight gear oils shift better and protect your gears better than any engine oil. 
Ralph Steinberg  
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