Diff Ratio
 

Hi all

I was just wondering if it would be possible to tell my diff ratio from the speed/rpm?

I can jack the car up and check by spinning the wheel and counting propshaft turns etc but if I don't have to then so be it.

1997 940 b230fk with AW71 with lock up.

70mph is bang on 2500rpm and 90mph is 3000rpm.

When I convert to m90 is this likely to stay the same as I'm loving the low revs to do 70.

Sort of. If you plug the gearbox ratios and tyre size into a gear ratio calculator, then entering the rear axle ratios that Volvo used.

According to the 1997 owner's manual, autos used 3.73 and manuals used 3.31 (for saloons) or 3.54 (for estates).

Thanks Baggy, I will find out what the rear ratios ate and have a play later.

You will find a sticker with ratio at the rear side of the axle. Wide, maybe 1.5 x 4 inch
Search at the www about position of the sticker
Should be 3.71:1 with automatic
Good luck, Kay

If you look at Pg54 on of this pdf, you'll see that 5th in the M90 is 0.81:1 and overdrive on your AW71 is 0.69:1

http://www.myvolvolibrary.info/Tech_...DataPocket.pdf

At present you're getting ~30mph/1000rpm in overdrive, the new mph/1000rpm in 5th will be 0.69/0.81 x30mph which will be about 26mph/1000rpm so at 3000rpm, you'll be doing 78mph, 70mph will be about 2700rpm.

Blimey that's quite the difference then! Still at least acceleration will be good haha.

You've been spoiled! :lol:

On my AW71 (no lock-up) at 3000rpm in overdrive, it shows about 81/82mph but is in fact only 75mph (my speedo reads about 7-8% fast) and a genuine 60mph is 2400rpm so it seems my diff ratio is lower than yours, checking the book it appears to be 3.91:1 in mine.

Considering mine is the 2.8 V6 (no cat, full-fat 170bhp from the factory) i really expected a bit more, having previously had 740GLEs that had similar gearing to yours but a 131bhp B230E K-Jetronic 4 cylinder.

More of Volvo complicating things! :err: