Just speculating at this point.....but, if i changed out the axle with one with a lower gear ratio...i think the stock one is 3.73:1....with another dana 30...i've seen some with 3.31 or 3.51:1....what would this do???...i guess i'm looking for better highway milage...but would it effect non highway driving too much....could i counter that by driving with the OD dis-engaged when not on the highway..????any ideas....anyone done this???....thanx..........j.

Thanks for the input......i guess if i feel like i really have too much time on my hands, i'll think about putting in an aw-71L....maybe the lock up feature might help the mpg a little and it's not too difficult to do.....j.

I think Volvo got the ratios right on these as delivered. These cars are already rather slow off the line and a ratio change is going to make it much worse.

If you really want better fuel economy then I agree that a manual transmission and rear end changeover are in order.

The other thing which seems like it would help would be to get an AW transmission with a lock up torque converter. Didn't the 940s have this type?

John

John,

I would agree with Jorell. I swapped a 3.31 into my son's 83 244Ti w/ AW71 in an attempt to get better MPG and make the engine less busy at highway speed.
It calmed it down on the highway but I've seen only about 1-2 MPG increase with the 3.3 rear end. Off the line performance really has suffered. I just pulled the 3.3 and installed it in my 86 244DL w/M46. The 86 original 3.31 rear end was damaged and this is a direct replacement for the old diff. I'll going to try a 3.73 as a compromise between the original 3.9 and the now removed 3.3 on the 244Ti. I think the 3.73 is about the best choice behind the AW, at least for N/A 240s. A good tune up, clean air filter, properly inflated tires, real synthetic oil(engine & rear end)and ATF will probably get you more MPG and certainly demand a lot less effort than a rear end swap.

I have an 88 745. It was originally AW70 automatic and 4.10 rear axle. It is now M46 overdrive and 3.31 axle. So much nicer to drive, and it gets 29-32 MPG. I highly recommend the conversion, though it is an awful lot of work. I don't know if it would be worthwhile or not to swap just the axle, and keep the automatic transmission. The ratios might not work well together. If you have ABS, you will need to find an axle from a late car with the appropriate tone ring in it.

It will make your car slower and you won't get any better mileage. If your car has 3.73 you have an automatic. You can pick up a 3.31 from axle from a 5 speed but I wouldn't if I were you. If you want better mileage swap in the 5 speed and 3.31 axle. You will get better mileage.

I'm running a 92 245 with an AW70 and 3.31 rear end from an M47 5 speed car. It is very doggy off the line and doesn't make much power until about 3000 RPM. If it were a freeway only car, this setup would be fine and might save gas, however, in the city you will find that the gas pedal is to the floor any time you accelerate. .. so you don't get run over by Buicks.

When I have the time, I plan on changing the rear end out with a standard auto trans ratio unit. Even with significant power mods to the engine, it's all being lost in the torque converter due to the rear end ratio.

jorrell
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89 244 171K miles, 92 245 241K miles, 06 XC70, 00 Eclipse custom Turbo setup