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700/900 Series General Forum for the Volvo 740, 760, 780, 940, 960 & S/V90 cars |
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Diff RatioViews : 647 Replies : 6Users Viewing This Thread : |
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Oct 27th, 2018, 00:08 | #1 |
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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. |
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Oct 27th, 2018, 02:34 | #2 |
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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).
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Oct 27th, 2018, 08:36 | #3 | |
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Oct 27th, 2018, 08:52 | #4 |
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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 |
Oct 27th, 2018, 14:59 | #5 | |
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Quote:
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.
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Oct 28th, 2018, 08:06 | #6 | |
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Oct 28th, 2018, 09:52 | #7 | |
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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!
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