Reproduction Parts for 1916-1964 Chevrolet Passenger Cars & 1918-1987 Chevrolet & GMC Trucks
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It's been a while since I posted, but I hover around frequently. I'll try to keep this short because I'm sure you have other things to do. I have a 37 Master with 3.73 rear end. My speedometer has been reading about 19% low since I rebuilt the car. Had TFS rebuild the speedometer with no change. I was told that the issue is the speedometer gears. According to parts book, it should have the 14-5 gear set. The outside gear is 14, but apparently, sometime in the past 85+ years, the drive gear was changed. I tried to compensate by using a 12 tooth driven gear instead of the 14 tooth and when I pulled out of the shop, I could hear clunking. Backed into the shop and reinstalled the 14 tooth gear. Now I have nothing. So, I am sure I ground all the teeth off the drive gear, so don't play around with speedometer gears.
My question is, can I replace the drive gear without removing the transmission? There are no splines on the gear so I assume it is pressed on the shaft? Parts book indicates they may have changed that in 1941? Appreciate any expertise on this before I dig into it. Also, any ideas where I can find a 5 tooth drive gear? Thanks for reading.
When I had the speedo rebuilt on my 38, it was 10 MPH off. I sent it back and they made some internal adjustment. I had to make no adjustment to the car.
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1938 Master Business Coupe-Sold, now living in New Jersey
1953 210 Sedan
The parts book group 4.329 lists speedometer adapters. They screw on to the transmission and the cable attached to it. I just remember what the error is in different cars. "Post - its" on the gauge might serve as a reminder. They usually don't deviate more than 5 MPH at 60 MPH. You could try to get a pair of matched speedometer gears (group 4.337) that would correct the error. The drive gear is pressed on the U-joint and the driven screwed into the bottom of the transmission U-joint housing. If they don't match, the U-joint housing is filled with metal slivers. (If you have installed a 12 tooth where the 14 was without replacing the matching gear, thoroughly clean your transmission or the slivers will ruin your gears and bearings.) You will probably need to replace both gears.
Your initial problem might be a weak magnet in the speedometer gauge.
I found a company on line that says they can get the 602518 gear set (Which I believe is what you need) from California. I have never dealt with this company but they do advertise on the internet as a parts locating company. I called and spoke with Scott (Direct line 781-786-6726 ) https://www.usautospare.com/index.html . I agree with Lou above that best to replace both . The drive gear I believe will be on the yoke for the u-joint . It should be a tight fit but I believe is not pressed on but held in place when the u-joint yoke is tightened down.
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@tiny That's what I had figured. TFS advertises calibration in their rebuild service, so I sent it to them. When I git it back, it was the same. I contacted them and they spoke with their rebuilder. The response I got back is that there is no calibration or adjustment in the speedometer and that my problem was in the gears, even though I am pretty sure the gears were correct. That's how I got into this pickle. Some math (there's the problem) told me I may have a 6 tooth drive gear. If I find that the gear is in fact the correct 5 tooth gear, then I know I was fed a line.
@lou-macmillan Thanks Lou. So I can just pull the u-joint and replace the gear. Yes, the slivers and anything else need to be cleaned up.
@steve-d Thank you much. I couldn't find anything. I'll give them a call and report back.
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