gearbox and diff oil
 

I have a 1998 940 estate and am doing a service. What oil do I need for the manual gearbox 5speed. and also oil for diff any advise please.

I just buy mine from my main dealer. At the amounts needed I’d rather just pay for the Volvo stuff.

The M90 gearbox has a very specific, factory specification for its oil. Volvo dealers can supply it at a price. There are a few threads where the spec is quoted and less-expensive alternatives are proffered.

The diff MIGHT use an SAE 90EP to API GL5 or GL6; I say "might" because the Fantasy Manual (Haynes) for the 940 makes no mention of spec whereas the 740 & 760 cites the above.

M90 is Volvo part number 31280771. Get from your dealer. The part number has changed over the years so adds to the confusion.

If your gearbox is working fine with nice smooth changes I wouldn't bother.

I used Millers Diff oil from Opie and I'm pretty certain it was 75-90 API GL-4 GL-5 but I'd need to dig out the bottle to find out. It's different oil if you have a locking diff

Cheers

Mark

I didn’t quote Volvo part numbers as each time I buy some I find that the part number on the bottle is different from the precious one so I rely on the dealer to supply the correct one as per my VIN.

Rear Diff oil spec is API-GL-5 (MIL-L-2105 B), as mentioned in the green book. Your axle should be the 1031, as it's after 91, then you should need 1.75 litres of oil as according to the TP-31685-1 green book. 1031 pre 91 is 1.6 litres of oil.

Gearbox oil (M90) capacity is 1.75 litres, Volvo part number 1161423-7 as taken from Volvo Green Book TP-4304031 which is all about the M90 and written in 1994. Since then the part number for the oil provided has been superseded multiple times, it's the same oil that is used in the M56 gearbox. The original gearbox oil spec is "Volvo 97308".

For my gearbox, I've swapped over to a Castrol oil with Ford spec WSSM2C200-D2, as that has a very similar spec to what is used in the M56. I previously experimented using Redline MTL oils and found them to be "crunchy" in the winter.

As it has been stated, there are other threads that go into depth about oils for the gearbox and diff, and the multiple part numbers associated with them. If you're looking to do the job yourself a bit of research looking into the oil specs will take you a long way if you don't want to go to your local Volvo dealership. Either way, you will not get hold of the original oils used from a Volvo dealership.

Thanks for the info. stay safe.