Leave the rear end alone, toss in an m41. You will not have any decreased performance, only good performance and good gas mileage. You won't regret it.
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Kyle - 244! - Kawasaki Ninja 250R - Oregon Volvo Tuners?

....or you could leave the rear end and just put in a t5 .

http://people.umass.edu/tcroy/articles/rearends.htm

"140/160 series bricks had the following rear end ratios:
3.31:1 ---- 164/164E Automatic
3.73:1 ---- 164/164E Stick (4-sp & 4-sp + OD)
4.10:1 ---- 140 w/ B20 (automatic and 4-sp)
4.30:1 ---- 140 w/ B20E/F (4-sp + od)
4.56:1 ---- 145 w/ B18 (4-speed! no overdrive)"

So, my memory is horrible. Big surprise. :-)

I must of had a 4.30:1 rear end, then. Looks like the 4.10:1 is the "correct" ratio for an M40. Could be interesting with an M41, in terms of highway fuel economy, but I still think that performance would suffer.

I agree with RepairManJack's advice. I had a '71 142E about 15 years ago. Came stock with an M41 and wound to only 3200 @ 75 mph with the O/D engaged. In 4th the tach needle hovered around 4200 at the same road speed! I believe that this car had a 4.10:1 rear axle, but it has been several years so my recollection may not be correct.

IIRC, the tallest ratio available in a stock 140 was 3.91:1. I am not sure what your cam will do to the performance characteristics of the engine, but IMO a stock B20E would not be very tractable with a 3.91:1 and M410. Volvo's stock setup with the M41 and 4.10:1 final drive gave you short 1st and 2nd gears for acceleration, 3rd and 4th for cruising at moderate speeds with reserve power, and a "5th" overdrive gear for long-legged highway cruising with good economy. I used to get 27-28 mpg on the highway, better than most new cars back in 1991 and still better than many new cars today!

It is going to be a relatively high-revving engine any way that you slice it (my 240 cruises at 2700rpm @ 75!), and my feeling is that a taller final will make the car harder to drive. A stock B20E makes peak power at 3200-4000, right around your normal cruising speed in O/D. A 3.91:1 will give you the same engine speed in 4th, but at a slower road speed. It will also diminish low-end acceleration and highway fuel economy. Get the extra gear! :-)

well, I'd go with the M41 if you don't want to high-rev to keep speed on the highway. M40 had to rev around 4000 to keep me at 70+ mph. About 3500 for 60-65 mph. The M41 is sooooo much nicer.

The 71 probably has a J-type OD which has a lot of torque and would probably not break under load. Small u-joints are another story...


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1967 P220 Amazon, 1972 145S, 1973 1800ES, 1977 245 DL, 1983 245 GL, 1986 745 GLE, 1990 745 GL, 1995 945....