Hi, all. I just drained and refilled the '86 Volvo 240's tranny. I know that Volvo recomends ATF type F or G fluid for this car/tranny combo. The owner's manual also recomends Volvo Thermo-oil- (which I could not find locally)for high mileage/ heavy use . However the ipdusa catalog that I recieved with the parts I ordered from them suggests using synthetic 10W30 motor oil in older, worn, high milage vehicles for better shifting performance. My car has well over 300K miles on it; so I figured it might just help out my worn 1st and 2nd gear synchros. I was a little concerned what kind of condition my fluid was in; the drain bolt looked like it had never been removed. I was gratified to note that the fill/level plug had obviously been removed a number of times.
Anyway, I noticed immediatly after the change that the tranny shifted better. The 1st and 2nd gear syncros were not like new, but at least 50% better than before the changeover.
Has anyone else tried this? Any opinions on long-term use/wear on the overdrive unit? or tranny?

 

Synthetics have come a long way, by now. Any reason to believe that type F is out of date, and another product (possibly synthetic) would perform better on this same transmission type on this volvo 240. M4x series manual transmission.

 

The reason the 10w-30 works better is because it's a "thicker" oil. Synchro rings work on friction, thicker oil provides more friction between the moving parts.
Synthetics are great in transmissions and differentials, they take a lot longer to break down and their viscosity is more stable over wider temperatures. So a car that may have a balky gearshift when cold, may be fine with a synthetic fluid.

 

I add a quart of motor oil to all my manual trannies when servicing for the reasons Andrew has put forth; M46, M40 and WC T5 all get a quart of 10W-30...but I use dino oil for reasons I don't care to go into. Many decades ago, most manual transmissions were filled w/ gear oil. Drag racers were the first folks to admit they were running ATF for faster shifts. A few decades later, auto manufacturers followed suit. The thinner fluid allows faster shifts, especially in cold weather. The flip side, as already pointed out, is a bit of gnashing on worn transmissions and particularly in hot weather. It's a tradeoff...that's why I mix the two.

 

Thanks for the explanation. I understand now. I will update from Type F to synthetic of the appropriate viscosity, and vary that with additions to suit my personal conditions.

 

thanks all, I was just wondering about this as well.

 

Should add, I've also been adding molybdenum to gear oil last few times I've changed it, makes a nice difference to shifts and gearbox noise.

 

Typhoon,

Can you clarify what how you add molybdenum, where do you get it, and why someone would use it?

Thanks.