Speedometer revolutions per mile

ohhiken

Does anyone know what the revolutions per mile is on the speedometer/odometer in the step-downs? Mine is a 53' and I got the correct drive gears for the 700R4 that is currently in it. The drive and driven gears were according to the rear-end ratio and tire size. But it spins the speedo faster than it should. Most of the GM speedos were from between 940 to 1020 revs per mile. So apparently the speedo in the Hudson must be less revs per mile? 

I don't have any kind of revolution counter to count the revs on the speedo for a mile. I guess I could try by hand and get carpal-tunnel.

Also, does anyone know the manufacturer?

                                    Thx for any reply, Ken Hamilton, Oregon

Ol racer

FYI
I suggest going into www.tci.com then use their 'Speedometer Gear Formula' to get the Info your looking for....

RichardD

install 'Speedometer App' on your smartphone to get accurate speed.

available for both iPhone & Android

I am now wondering now why mine is accurate?? But I was told it was a 51--darker gold color-- (mine is a 3.07:1). Will have to check again.

Lee ODell

Kenneth is correct about Hudson speedometer error.

Had speedometer shop check my 52 Hornet. They could have added the adaptor that mounts between cable and transmission to correct error, but I opted to keep the read out card in the car to remind me.

Speedometer - Correct speed
30 - 28
35 - 32
40 - 36
45 - 40
50 - 45
55 - 49
60 - 53
65 - 57
70 - 62
75 - 67

I was a little nervous watching and hoping the rear tires would not jump the rollers because there was a concrete wall about 25 feet away.

You are welcome to copy the speedometer chart for your own reference. It may be close to you speedometer.

Lee O'Dell

Per

Ken,

My 1951 Pacemaker with overdrive (including the 4.56 axle ratio that came with overdrive) had the speedometer error Lee describes.  After I then changed the axle ratio to 4.10, the speedometer has agreed just about exactly with the devices along the roads in my area that tell how fast I am going.

Per

Glowplug

Easiest method of determining speed of my 53... Speedo App on my iPhone is precise. So, gave up on making my speedo seem ok!

dave11

Lee

Sounds like the speedometer is out about 10%, is there not an alternate gear for the end of the drive cable at the transmission, that has more teeth that can be installed ?

Dave

RichardD

Checked mine with the speedometer app today and it was 5 MPH fast; I am OK with that; probably a Hudson standard anyway~~~ 3.07:1 rear and 2 plus larger tires(2.35 x75x15)

Lee ODell

I forgot to mention the odometer reading was 100% accurate even though the mph was inaccurate. Also, I am running 225R X 75 X 15 with 3.07:1 gears.

It is interesting that different brands of tires marked same size can be different diameters. When I bought my 47 Hudson PU it had 2 - 16" different brand tires on the rear marked the same size but one tire was 1" taller than the other. On the front was one 15" and one 14" tire. When I first saw the truck I thought it had a bent frame. Replaced tires and wheels and truck set level.

A speedometer shop test is not expensive and they can tell you if a simple gear change will fix it or something else. The test only cost me $35 and I new what I had and what options I was given to correct it. I wasn't pressured in anyway to buy the fix. My choice was to keep the comparison readout in the car. I believe the adaptor with correct gears was about 50-75 dollars. If its just a cable gear chance should not cost much.

Think I will oil the speedometer. I've had it about 5 years and no idea the last time it was oiled.

Lee O'Dell

cpr3333

I forgot to mention the odometer reading was 100% accurate even though the mph was inaccurate. 

How does that work?  Aren't they driven from the same cable?

I've had one rather cynical co-worker tell me that the speedos were optimistic because it also racks up miles faster, making cars 'need' service sooner and lose value earlier.

cpr3333

Thanks.

I learn something new every day.