How can I find out what the gear ratio is in my differential? The sticker on the axle housing says it's a 373. But the sticker had been painted over. This is a new rear end and it doesn't act like the old one that I know was a 373. The engine bogs down at low rpm with no torque. I have heard that if I jack up either rear wheel, mark the positions of the wheel and the flange on the rear drive shaft where it attaches to the differential, that 1 turn of the wheel should equal 3.73 turns of the driveshaft. Or is it the other way around? Didn't Volvo make a 3.49 ration differential? I'm thinking mine was rebuilt(paint over the sticker) and it's not a 373 anymore
Thanks
Jim

Here's a way to get the answer without getting your hands dirty.

http://www.competitiondiesel.com/Phil/bg/

Go to the bottom of the page, use the formula.

You didn't mention the year, engine, trans, but for the automatic, third gear, no OD is a 1:1 ratio. For the manual, 4th gear, no OD is also 1:1. There is also a calculator to compute tire diameter.

Here is a link to an owner's manual for 1989 which includes all of the gear ratios. To get the manaul for your year, simply change all of the '89' in the URL to the year of your car.

http://apps.volvocars.us/ownersdocs/1989/1989_240/89240_04.htm

1 turn of the wheel should equal 3.73 turns of the driveshaft

That is correct.

Didn't Volvo make a 3.49 ration [sic] differential?

Volvo didn't make differentials at all. I'm not sure if there is a practical ring/pinion combination that results in a ratio of 3.49:1. Anyway, that's not one you'll find in a 240 rear axle.

The most common are 3.91:1, 3.73:1, 3.54:1 & 3.31:1. I believe they also used 4.10:1 and a 4:30:1 early on.
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'80 DL 2 door, '89 DL Wagon

I was told that if you divide the number of teeth in the ring gear by the number of teeth in the pinion, you get the rear end ratio. I have 41 teeth in the ring gear and 11 in the pinion. Thoughts please?

That would, obviously, be 3.73:1.
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'80 DL 2 door, '89 DL Wagon