Gearbox oil temperature?

[TTM]

Hello,

Since I have had a not-really-cheap gearbox built a few months ago I have become more sensitive to gearbox care and was wondering if some of you on here monitored your gearbox oil temperatures, especially on race cars.

I was a little bit shocked by the colour of the oil that came out of my previous standard turbo gearbox, as even with it using the oil cooler it looked like a mixture of bubble-less coke and fanta, while the oil was gold-ish when new. Now that my new gearbox has no more oil cooler (968) and thay my engine develops quite a bit more than a standard turbo engine, I am pretty certain that it will cook the oil at a quicker rate and that the factory-recommended oil change interval is not really suited anymore.

Any real-world feedback on this?

Thanks.

 

[Paul 290T]

Hi,

My only experience is that when i first changed the factory fill gearbox oil on my 220T at the recommended 50k miles the gear change improved thereafter. I concluded that 50k miles is too long.

 

[GPF]

Not a race car, and not even a 944, but I run a front mounted oil cooler on my modified Noble. The gearboxes can't take the torque from the big power cars without quite a bit of modification, and heat in the box can be a problem. The FMOC is fed from a temp controlled pump and seems to be a good fix as the gearbox oil doesn't need any special care now.

I did need to have the gearbox casing machined for take off and return pipes though.

 

[TTM]

Graham, what oil pump do you use? I guess the pump is after the cooler?

 

[GPF]

It's a Mocal - I think it's the TCP1.

Not sure if it pulls the oil through the cooler or pushes it - I thought it the latter but could be wrong.

 

[TTM]

Thanks.

I will wire an oil temp sensor over the weekend. Not sure I will get a relevant reading since I plan to use the oil filler port that may not be bathing all the time, but it will be better than nothing.

And now the £0.02 question : under full load, should gearsets or the R&P warm the oil up the fastest?

I'm not a gearbox expert but these transaxle gearboxes seem a bit odd to me in the sense that there seems to be very little oil circulation between the differential housing and the rear casings, at least when there is no built-in cooling system forcing the oil through.

PS : any chance to read a bit more on your Noble? It sounds like you did some cracking upgrades...

 

[Lowtimer]

I would want an oil cooler, especially if tracking it, because in that case you will be giving it prolonged and repeated use of the extra power. For ordinary road use I find I never get full power on for more than ten seconds at a time, usually more like 2-3 seconds then back to light throttle for a period which will allow natural cooling, so if it is a daily driver and not tracked I doubt it would make a huge difference. I'd probably change the oil fairly regularly though, and use only the best, as the ability to maintain oil film integrity under higher than usual loads is what seems like the important point to me.