Planning to change my differential fluid this weekend. Looks like Mobil 1 75-90 is the way to go, and the FAQ has been helpful with details. But I still have a couple of questions - how many bottles of this stuff do I need? It's pretty expensive, hoping I need only one. This leads to my next question - how can I tell when the thing is full? Do I keep filling until it runs out of the fill port, or is it over-filled at that point?

Any suggestions from rear-axle veterans would be appreciated, thanks!

-Ben

I did mine with the rear of the body resting on jack stands, allowing the rear end to hang all the way down. The bottom bolt on the differential cover is the drain. If you put the lube bottle in hot water for a few minutes it will flow a little better. I was able to squeeze it in drectly from the bottle, but you can't empty the bottle completely this way.
Scott

95 940 wagon

Hi Ben,

Great question.

Back in the high school auto mechanics class we were taught to poke one's little finger into the filler hole and bend it down as far as one can at the first joint - the level of fluid in the differential should come to the middle of the finger nail of the average size pinky finger. That was for American cars. IIRC, there was concern for overfilling.

On the other hand, of the 4 Volvos I've worked on they all had been filled to the point where the fluid was running out of the filler cap when removed.

Oh boy, I have confused myslef now. :^)

Dan
--

The most important tip for draining and filling a rear diff is to always remove the fill cap first. If you don't, you run the risk of draining the case and finding out you cannot remove (or worse you've stripped) the fill cap. Then you're really screwed.

HTH,

someguyfromMaryland

If you want to make sure it's full, fill it slowly to the top, then let it settle for a few minuits, then top it off. gear oil is rather thick and takes a minuit or so to flow into all the bearing spaces when filling cold.
--
-------Robert, '93 940t, '90 240 wagon, '84 240 diesel (she's sick) , '80 245 diesel, '82 Mercedes 300SD

Dear Ben,

Good a.m. and may this find you well. According to Volvo pocket data booklet (700,850,900 cars) 1991-96, the amount of oil needed for the diff is:

Diff Liters
Type

1030 = 1.30
1031 = 1.75
1035 = 1.40
1041 = 1.45
1045 = 1.30
1055 = 1.50
1065 = 1.35

A liter is 33.8 US ounces. Thus, you will need 1-2 quarts.

The diff type should be found on a data plate on the unit.

Hope this helps.

Yours faithfully,

spook

spook,

Where did you get the pocket data book? I've seen you reference it many times here and would love to have one.

Thanks,
Bean
--
'80 242GT 92k, '94 945T 123k

Thanks for all the advice, folks. I'm going to feel much more at ease doing this now. Spook, your speedy access to those specs is really impressive, thanks a bunch!

-b

One bottle. Fill to the point it overflows out the hole, then button it up.

Not sure how much you'll need, do you still have the owner's manual. It will probably say in there.

The fluid level is correct when it starts seeping out of the hole. The car should be on level ground when filling to ensure the correct fluid level. When I filled mine (I think I used 1.5 bottles...) I used a long, clear tube. Stuck it in the hole and routed it into the drivers side wheel well. You can jam either a funnel into the other end of the hose or just insert the tip of the bottle into the hose and squeeze.

If you've never smelled gear oil you're in for a not so nice surprise. :)

Have fun,
Bean
--
'80 242GT 92k, '94 945T 123k