gears

[David Pollock]

 4.1 to 1 was probably the most popular, followed by 3.9 to 1.  A 3.7 to 1 ratio was often found in Desotos 46-48 and that is a bolt for bolt swap.   If you are running a 3.9 gearset and use overdrive for a 30% reduction, your final drive ratio is effectively about 2.7 to 1 which is very likely going to overtax the 201 engine, but it works great with the 218 and 230  and 251 engines.  I have used 3.7 to 1 ratios in pickup trucks with good results and have overdrives in several other cars. I am going to try one in my 40 which has the 201 engine but I suspect it will only be comfortable in overdrive running downhill with a tailwind. My recommendation is the 3.7 to 1 gearset. Less troublesome too as the overdrive can be a headache if the electrical components are worn.

[Don Coatney]

quote]

If anyone is in need of an overdrive gearbox George Asche in Pennsylvania rebuilds and sells them. His contact information is below.
Don Coatney

[Carla]

Brian, as a practical matter, fitting an overdrive gearbox, if you can find one, is really the only way to go if you want a reasonably comfortable way to cruise at 'freeway speeds' without losing the bearings in your engine.

I've fitted overdrive boxes to a few cars, and its an easy job. The drive shaft must be shortened a bit, which is best done by a specialist driveline shop.....unless you have/can borrow a suitable long bed lathe, and can do a good sound weld. (the driveline must be straightened to .002 min runout after welding, and really should go to a specialist firm for balancing)

When fitting an overdrive box, I always brought the wiring for the solenoid out to a simple switch, which I mounted on the gear lever. The idea is that you use the overdrive exactly the same way as you'd use an electric-shift  two-speed axle on the usual sort of 1-1/2 or 2 ton truck, except that you must remember to have the overdrive switch 'off' or 'in low axle', so to speak, before using reverse.

Without an overdrive box, the grades on the roads where you live will control your choice of back axle ratio......if you live in the 'flat country' of the plains states, pulling power on steep hills may not be an issue for you.......you could fit a 3.54 ratio, trading off brisk acceleration for a faster cruising speed at a safe engine rpm.

Conversely, if you normally run roads with moderately steep hills, then a 4.1 or 4.3 axle is your friend on the hills, at the cost of top speed, of course. 'There's no free lunch' This is why the mega-million dollar public investment for good roads in the '50's and '60's was followed by the development of the higher hp V8 engines. With twice or three times the hp of the earlier sixes, you could run medium steep grades easily at the 60-70mph 'cruising speed' now common.

Remember, when these cars were new, there were very few roads which were themselves built to allow what we now consider 'normal' cruising speeds. The generality of roads, aside from a few main highways, and the 'downtown' streets in larger cities, were merely graded and gravelled, and became 'washboards' after a winter or two.

cheers

Carla

[Jim Yergin]

Here is some rear axle ratio info from the Plymouth factory parts book:

P11,    P12 economy   3.73

P11    Coupes      3.9

P11    Sedans, Sed Del,   4.1
Utility Sed, Suburban,
P11 Coupes (special),
P12 2Cpe & Aux Cpe

P12    Conv Cpe & Sedans   4.3

P12    (special)       4.56
(also cars w/18? wheels)

A 3.54 rear axle became available with P14 and P15.

[captbrian41]

Jim, George Asche had told me of the location of the stamping and I found a stamping (39) which I think means I have a 3.90 rear end ratio. What I woul like to know is what ratios were available in '41 that would let me get a little more speed on the highway while at the same time dropping the RPM's a little. If there were a dcouple of different ratios I think that woud be the way to go instead of overdrive which was nt an optin in that year.
thanks
captbrian41

[Jim Benjaminson]

If you check the differential housing, it will tell you the ratio.  There is a flat spot near the top of the pumpkin with the ratio on it.  If you check some of the older postings on this board, you will find a photo showing you the exact location.

[Jim Yergin]

My '41 wagon has a 4:11 rear axle.
Jim Yergin

[captbrian41]

Does anyone know what rearend gear ratios were available from the factory in 1941. I think I have a 3.90 in my '41 coupe and before I make the jump to overdrive I would like to know if I can get a little more top end with a different rearend. George Asche mentioned changing out the rearend but I would like to know what ratios were available. Keeping the car original seems to be the priority and if overdrive was not available till '51 or so then a rearend change might be the way to proceed.

thanks,
captbrian41