Volvo RWD 140-160 Forum

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Rear end gearing differences help. 140-160

posted by SprtWgn on Tue Sep 16 08:16 CST 2008
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last visit: Fri Apr 6 11:56 CST 2012

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I've found an M-41 w/ driveline and column switch to upgrade my '72 145 (currently M40). The seller is also offering a rear end from a 142.
I know little to nothing about gear ratios or the differences between what the various 140's were equipped with.
Right now, with the 4-speed and stock rear in my 145 it seems like I could benefit from a slightly shorter 1st gear since it seems to have a tough time starting from a stand still especially on hills. Would a different rear end gearing help this problem and is a 142 rear the right choice?
Thanks for your help!
Dave
'72 145 (due back from the paint shop in a few more weeks)

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Rear end gearing differences help. 140-160

posted by Blue Horse on Tue Sep 16 14:45 CST 2008
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last visit: Mon Apr 8 17:57 CST 2013

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Your stock rear axle is almost certainly a 4.10:1. There is a good chance the one from the 142 is as well, or it could be a 4.30 if it is out of the same car that the M41 came from. The 4.30 would give you slightly better acceleration at the cost of a proportional reduction in gas mileage and increase in engine noise. However, the difference is so small, it's hardly worth the effort to swap the axle.

What year is the transmission? Those made from 1973 to 75 have a lower ratio in first gear than the earlier ones, and should be exactly what you are looking for, and you can then keep your original axle.

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Rear end gearing differences help. 140-160

posted by Gary L on Wed Sep 17 02:20 CST 2008
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last visit: Wed Oct 22 10:26 CST 2014

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If looking at a 4.10 vs 4.30, I agree... less than 5% difference, and probably not worth the effort and expense. But there were some early 140's with the 4.56 rear (I think we're talking about the B18/M41 combo here, for the most part). So it might be worthwhile to find out exactly what the guy is selling. Many are illegible after so many years, but all diff's originally had a tag on the exterior of the housing that shows the gear ratio as assembled at the factory. Some of these tags just have the ring/pinion gear tooth count (41/10 or 43/10), while others will have the resultant ratio (4.10 or 4.30).

I also agree on the gearbox comments, as there is nearly 9% difference between the early and late (73 up) 1st gear ratios - 3.13 vs 3.41.
--

Gary L - 1971 142E ITB racer, 73 1800ES, 02 S60 T5
BlueBrick Racing

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Rear end gearing differences help. 140-160

posted by matt b on Wed Sep 17 03:47 CST 2008
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last visit: Tue Oct 14 16:33 CST 2014

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one other thing to keep in mind is the flanges... if the new driveshaft with the M41 is a big one, you'll need at least the flange from the donor car rear end. And if you do need to swap flanges.... the splines may not be the same. If that is the case (probably isn't), swapping the rear might be easiest after all...

--
-Matt I ♥ my ♂

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