Just watched a video of a Mazda gearbox stripdown. There was no signs of an actual oil pump. However I have concluded the following:
The input and output shafts live in the “upstairs” in the box whilst the layshaft sits nearer the bottom, typically submerged in plenty of oil. So with engine running, and with a constant mesh gearbox of course, all of the gearwheels on the layshaft and output shaft turn together and consequently get a good splashing of oil. (It’s only the actual output shaft that stays still until a selector ring slides across to engage a gear of choice, with the splines on the shaft)
However, if the vehicle is towed, rotational input to the gear box is now reversed...the output shaft is whizzing round by virtue of the prop shaft BUT as it is in neutral, its gears are not actually engaged with the shaft, merely sitting still whilst the shaft is spinning merrily away. So as we are towing along, all the actual gear wheels in the box are stationary, the only movement being the output shaft itself...NO splashing about of oil..output shaft gets starved of lubrication, overheats, etc.
Hope this makes some sense.
Totally agree with Colin above: a short tow is not going to cause a problem.
Yes, my head was in R380 mode where the internal oil pump is driven off the rear of the lay gear cluster. As mentioned in a CM Gearbox the input shaft drives the lay gear cluster but the output shaft doesn’t as the 4th gear sits on a bearing and ‘freewheels’ until engaged. I used to run the transmission training course at Volvo light years ago and on some of their transmissions the pump feeds the 5th gear housing.
All a long way from the days I stood up front teaching Maxi 5 speed training 🤣
BR
Colin
