Guest apd6545 Posted July 9, 2013 Report Posted July 9, 2013 I have a 48 Ply Business Coupe and at some time it was changed from 16 inch to 15 inch wheels. The speedometer is obviously off. Would taking a speedo transmission drive gear from a 49 or newer Ply, work to correct the problem. I believe that after 48 the Ply came with 15 inch wheels. If it would work does anyone have a suggestions on were I could get the gear. Thanks Quote
desoto1939 Posted July 9, 2013 Report Posted July 9, 2013 Instead of changing the gear put your GPS in the Plymouth You can run it on the battery in the GPS. You do not need to know where you are going but just need the GPS to calculate your MPH. The corralate the speed on the dash unit to the GPS. You might find out that the difference is not that far off and then just note what 50 is based onthe GPS against the speedometer. Do this for several speeds such as 25, 35, 45, 50, 55 and 60 to get the adjustment numbers. If you do not have a GPS then have your wife follow you in a modern car. get on the highway and do 35 and get her reading via you cell phone conversation. you will get close enought and then do the other speeds. These are just suggestions. Rich HArtung Desoto1939@aol.com Quote
Young Ed Posted July 9, 2013 Report Posted July 9, 2013 A 48 plymouth would have come with 15s. What size tires do you have? So unless someone changed the rear end ratio you should be good on that. Quote
P15-D24 Posted July 9, 2013 Report Posted July 9, 2013 I have a 48 Ply Business Coupe and at some time it was changed from 16 inch to 15 inch wheels. The speedometer is obviously off. Would taking a speedo transmission drive gear from a 49 or newer Ply, work to correct the problem. I believe that after 48 the Ply came with 15 inch wheels. If it would work does anyone have a suggestions on were I could get the gear. Thanks Are the new wheel and tires actually a different height? If not you don't need to change anything. Quote
Niel Hoback Posted July 10, 2013 Report Posted July 10, 2013 I think the 6.00x16's on the 46-47s are almost the same diameter as the 6.70X15's on the 48's. Speedometer difference should be negligible. Quote
Don Coatney Posted July 10, 2013 Report Posted July 10, 2013 OK Niel, what is that avatar picture? Have a bigger copy of the picture you can post? Quote
Merle Coggins Posted July 10, 2013 Report Posted July 10, 2013 Looks like a self propelled side car. Pretty cool. Quote
Plymouthy Adams Posted July 10, 2013 Report Posted July 10, 2013 http://www.microcarmuseum.com/tour/mopetta.html Quote
Guest apd6545 Posted July 11, 2013 Report Posted July 11, 2013 According to the spec sheet the 48's came with 16 inch wheels and the 49 started using 15 inch wheels. That explains why my speedo is running fast. The question is will a 49 or new gear work in a 48 and does anyone know a source for the gear. Quote
plyroadking Posted July 11, 2013 Report Posted July 11, 2013 I've had a similar issue with my car, changed tire size and gear ratios, from what ive ran across Plymouth used either a 16, 17, or 18 tooth spedo gears. I have tried all three in my car and it seems that each gear reads about 10 mph slower than the next. So if your off by about 10 mph you might get by with just switching gears out. Currently i have the 16 tooth in my car and with 235/75/15 tires and a 3.73 rear end ratio it reads 10 mph slower than im actually going, i have not found a 15 tooth gear yet. 1 Quote
Young Ed Posted July 11, 2013 Report Posted July 11, 2013 According to the spec sheet the 48's came with 16 inch wheels and the 49 started using 15 inch wheels. That explains why my speedo is running fast. The question is will a 49 or new gear work in a 48 and does anyone know a source for the gear. What spec sheet is this? My 48 was a 76K mile junkyard car and it had 4 matching 15s on it. Quote
_shel_ny Posted July 12, 2013 Report Posted July 12, 2013 (edited) For what its worth. Edit: Apparently D-A, so chart removed. Edited July 12, 2013 by shel_bizzy_48 Quote
BobT-47P15 Posted July 12, 2013 Report Posted July 12, 2013 If you look in the Parts Maunal on P 269 (in my copy), it specifies that certain size wheels were used, either 16 or 15 based on serial number of the car, but does not list the specific year timing. It was my understanding that tire size changed sometime during the 1947 model year from 16 to 15. My 47 came with what seem to be stock 16 inch wheels, so it must have been an earlier model. I haven't researched it as I run 1955 Chrysler wire wheels which are 15s and don't care which size was original. However, I have saved those original rims--just in case. My speedo is approximately 15 mph fast.......If it says i"m going 50 -- I'm really only going 35. Have used the GPS to check speed on occasion....and also the cell phone with "now how fast am I going, Honey??" So, I have just learned to live with the thing. , Quote
Don Coatney Posted July 12, 2013 Report Posted July 12, 2013 Just read your response below and elected to delete my response. Find another web site if this one sucks. Quote
Guest apd6545 Posted July 12, 2013 Report Posted July 12, 2013 I Have tried to respond, a number of times and I hit some key and everything disappears never to be seen again. Your web sit sucks. For most of the responses I received for my query, I have to say D-A applies. This used to be a good forum, does not seem so any more. I am sending this before I hit another key that wipes out the screens. To all the D A's that gave me advise on speed test, learn something about math. I know it is hard to follow a thread, But if you concentrate just a little you can make it through to the period Quote
Dave72dt Posted July 12, 2013 Report Posted July 12, 2013 a 49 gear will probably work in a 48. If it has the same number of teeth as the 48, it won't change how far your speedo is off. You will need to know how many teeth are on the current gear and how far off the speedo is and which way to determine if you need a smaller or higher count gear. I can't pinpoint a manufacturer or direct source for a gear but someone here probably has one. Different rear gear ratios, different size tires will take different gears for the speedo and who knows if the rear gear or trans in your car are both original. Replacement of either or both at one time in the car's life could easily lead to inaccurate speedo readings. Quote
Plymouthy Adams Posted July 12, 2013 Report Posted July 12, 2013 and you may also note that you were asked a very specific question that you failed to answer but yet there is the expectation of a clear and precise answer...do your part..the forum will run smoother... Quote
larryconnors Posted July 12, 2013 Report Posted July 12, 2013 apd, go to the tech tab on this site and look uunder reference for p15 and you'll see that all P 15's switched to 15" tires by Dec 1947. Your car has the correct wheels. Quote
Young Ed Posted July 12, 2013 Report Posted July 12, 2013 apd, go to the tech tab on this site and look uunder reference for p15 and you'll see that all P 15's switched to 15" tires by Dec 1947. Your car has the correct wheels. Yes I tried to tell him that too. He doesn't seem to believe us. I suspect all he really has is a 65 year old speedometer showing its age. Quote
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