Gps is very handy for checking speedometer error or accuracy for that matter.

Y's guys rule!
Looking for McCullouch VS57 brackets and parts. Also looking for 28 Chrysler series 72 parts. And early Hemi parts.

MoonShadow, 292 w/McCulloch, 28 Chrysler Roadster, 354 Hemi)
Manchester, New Hampshire

I have a dana 44 , 4.09 ratio from a 56 Ford wagon in my 56 crown vic with 3 speed od,great on low end and cruise at 70 mph easily getting usually around 17 mpg.I have put over 30 thousand on the car with no issues with the rear end  Carl

I never drive that fast.  I did when I had a 55 Montclair convertible in high school.  Hopefully I learned  after wrecking a few cars.  Larry

Larry

That's a close guesstimate, Charlie. My speedo is off by about 10 mph (give or take).If drive at indicated 70 I'm a rolling speed bump; if I drive at 80 by the speedo I'm keeping up with most traffic. Also, the automated speed warnings around here prove me out. I pass one one in a 35 mph zone regularly. If my speedo says 45 the sign says I'm doing 35.

Dobie, with those tires, and ratios, your engine should be around 2500rpm for 70mph.


Lawrenceville, GA

The automatic axles will be way too tall unless you live in the flatlands and never leave. The 4.09 is what Ford specified for the 3 speed w/OD and I can't 2nd guess the engineers. I live in middle TN and I find I can use OD on any hill I've encountered. The cars with a straight 3 speed (no OD) had a 3.73 axle, if you want something a little taller you might try to find one of those. That would give you an effective final ratio of 2.61:1 in OD. Still too tall IMO although you'd get phenomenal gas mileage.

P215 75R 15 Diamondback (Toyo) wide whites.

Sorry for my disjointed comments.  I have 3-axles all marked 45A.  The one in the car is 41/13. One in the back is 45/11 the other is 41/13.    I generally use it for short trips as we live in a valley where a long drive is 30 miles round trip.  I very seldom take the car on the highway.  It looks like I have two axles for an automatic and one for a standard.  So I guess the decision is made.  I appreciate the help.  Larry

Larry

Tires are 215/75/15.  The rear axle is 41/13.  Both axles in the back are marked 45 A by the filler plug.

Larry

Carl and Dobie:  Does the 409 rear axle work well with your 3-speed transmissions?  My  has the -speed with overdrive and a rear axle designed for the merc-o-matic which is to high.  It seems to me it the rear end should have a ratio of about 370.  I also have another rear axle from a 55 or 56 merc that is 307.  I will have to check the ratio on the axle in the car.  Thanks Larry

Larry