Where to recalibrate my speedo *DELETED*

Post deleted by 41LINC

First off, has there been any changes to the rear-end ratio or (less-likely) tire size? Either one could throw the speedo off, and would require you to do some detective work. In particular, it's possible that someone changed the rear-end to a more "highway-friendly" ratio, resulting in fewer engine rpms at a given highway speed. Without changing the speedo gear, the result would be lower-than-actual speedo readings.

THE FIRTS PLACE TO CALL IS "BOBS SPEEDOMETER SHOP" IN SUBURB OF DETROIT...

CHK HEMMINGS..BOOK OR ONLINE..POSTIVE YOU'LL FIND AN AD..I DONT WEB SITE..BUT OLD SCHOOL...MAKE CERTAIN NO COLUMBIA SWITCHGEAR OR OVERDRIVE THAT CHANGES SPEEDO..MUST HAVE 16'' TIRES....

Post deleted by 41LINC

Sorry - I may have made a mistake.

When my speedometer says 55MPH, I am actually going about 45 MPH

To find the rear ratio clean off the differential housing around the fill plug and the drain plug. If you have a 4.44 ratio you should see a 9 - 40. If you have a 4.11 ratio a 9 - 37 will appear. Sometimes these numbers were not punched in straight or very hard and may be hard to read. Usually a car supplied with an OD will have a 4.44 ratio and a nonOD car will have the 4.11.

Bill

Actually the non overdrive cars from '42 to '48 had a 4.22 axle. There were a few 1946 cars with overdrive that came with the 4.22 ratio but all other years with or without overdrive were 4.44 to one.

Thank you Bill!

I just crawled under the car and there it was - 9 40 -

plain as day!!

Thanks for your help

Mike

Hey '41, Ok, now that you have determined that you do have a 4:44 rear end, the only other variable is the speedometer drive at the front end of the driveshaft, the ratio or number of teeth written on the top of it, should tell you what ratio it is for and it should correspond with your 4:44 ratio, if you have a 4:22 speedometer drive that would account for your variant readings, when you get your Columbia in with it's speedo changer, I don't know what you will be faced with then, hopefully it will all be the same, good luck

Post deleted by 41LINC

Not unless you cut a window in the floor board, the speedo drive is right at the front end of the drive shaft, on the top. If you are being thrifty and don't want to buy a duplicated parts book that are available, one of us will cross reference what ever drive you have and identify it for you. Makes me think of one of my favorite movies, "Same Time Next Year" where Alan Alda has a watch with a broken stem, and can't be set right, so being quick with numbers he extrapolates every time he wants to know the time, not a perfect analogy, but close, probally would take the best part of an hour to pull that floor board and carpeting, but as Alda says in the movie, "I like it that way", R

Post deleted by 41LINC

Just looked in the Ford book, which is much more explicit, but not X rated, and it says the 21 is used with the 4:44 gears and 7:00 16 6 ply tires, 7:00 16 4 ply tire use a 22 tooth gear, and the Ford # is 18 12270, which is a 1932 Ford #, but they are all the same, only the number of teeth is different I would hit all the obsolete Ford places, and advertise free on the FordBarn site, you might very well turn one, and your speedo will be right on, unless you are a real purist, and enjoy an arduous frustrating task, scrape all of the old gasket off of both sides, the floor and the pan, and put a coat of permatex form a gasket on the floor, and drive her home, if the old gasket is just torn in a few places, you can patch it with the permatex too, hope all that helps, Rolf

Post deleted by 41LINC

Huh???? I never said or implied you send your speedometer anywhere, the 21 tooth gear you now have is correct for your gearing and 6 ply 7:00 16 tires, if that is the tire you are running, then your speedometer does need to be calibrated, if you have the more normal 4 ply 7:00 16 tires, they are a lot smaller in diameter than the 6 plys, and as any one who has put on different size tires knows, they make a big difference in speedo readings, good luck, R

Dear O.C.,MAYBE should be good riddance,instead of good luck.diz

Post deleted by 41LINC

regardless of the tire size you are using you can get you speedometer calibrated at any shop that calibrates the local cop cars and highway patrol. I had it done to mine, They put it on a dyno and run it at calibrated speeds and if needed remagnatize the magnets till its within 1 mph +or-. I have had 3 cars done and ran up to 100mph each. then you will get a certificate of calibration.

My son does calibration for the air force on all thier equipment and cars so dont let anyone tell you it cant be done, just have to find the right shop.

And pay the price, what ever it is, probally plenty, and when you replace any component at all, go back and do it again, probally bringing it right back to where it was in the first place, a really typical 2000 solution, lots of luck, a # 22 speedo drive might cost these days $5-$10, but it is way too much trouble to fix it right, Diz, I think I may be leaving soon, permanently, won't that be a relief?? Rolf

It cost me $175 to have my speedometer calibrated and that included having the speedometer rebuilt. Anything worth doing is worth doing right the first time.