Hello!

My car (740, Turbo Diesel) has an automatic gearbox.
The oil form gearbox is cooled in the
separate loop inside the main radiator. This radiator cools
the engine too. Recently I got internal
oil leakage from gearbox oil loop to the engine "water" loop
and vice versa.

It is rather difficult to get a brand new original
radiator promptly.Instead I consider to add some separate
radiator for gearbox oil loop on the front of main radiator.
The leakage is internal, thus I would like to just seal
gearbox connectors in the main radiator. Person in the local
workshop seems to be capable to find the radiator large
enough to keep oil cool (let say below 70C) during the
summer (in Latvia T may reach +31C).

The problem is the winter. The temperature outside will drop down to
-30C and the oil in the gearbox system will be rather cool.Do any one
know what will happen with the automatic gearbox from 1987,is
it OK to have a quite low oil T?

Tanks a lot!

best regards

/Normunds

Some notes after the posting...

Perhaps the best term is not an "automatic gearbox oil" but
something like "automatic transmission liquid". I hope this
inaccuracy do not obscure the subject.

My friend in workshop is certified to weld high-pressure pipes (by the
way do anyone knows how high pressure in this gearbox may be?), so he
can add the shortcut valve to transmission liquid radiator.This valve one (me) may open during the winter season. However this solution from engineering point of view is a bit more complex... Why I have to go in this complexity if (may be) the transmission works pretty well in low temperatures too? I will be really grateful for help about the operational temperature interval of automatic transmission liquid!

Thanks a lot again!

/Normunds

I would just try to find a new radiator,If the fluids mixed you need to flush the trans very well and don't drive it till you fix it.Or you will burn up the trans.