speedometer gear teeth

[Wayne W.]

Building a 64 300hp auto and trying to find how to know witch gear is correct. Mine is blue with 20 teeth, also seams to leak around plastic shaft of gear All help appreciated. Frist car

[Keith G.]

Re: speedometer gear teeth

Just went through that, at 60 mph it read 45, took a 22 out and put in a 18. Well the 18 was to small in diameter to touch the other gear, so I gave up. Two weeks later the clutch went out, so as long as I had the trans out it was time to whitch the other gear, you have to take the tailhead off to do that. One tooth makes about 3 mph difference.

[Wayne M.]

Re: speedometer gear teeth

Building a 64 300hp auto and trying to find how to know witch gear is correct. Mine is blue with 20 teeth, also seams to leak around plastic shaft of gear All help appreciated. Frist car

First off -- I know zip about Powerglides, but looking at parts catalogs and powertrain charts for your 1964, looks like the only choice with auto trans was a 3.36 ratio. If you still have your original rear end, that should take the blue 20-tooth plastic gear. The speedometer driven gear "fitting" does have an integral seal in the end nearest where the cable screws on. Maybe you just need a new fitting. Of course, if your tires are not the original size 6.70's, or your speedo is out of calibration, you can play around with different color gears [18 thru 22 teeth] to "fine-tune" the accuracy, at least in the range that is important to you.

[Joe L.]

Re: speedometer gear teeth

First off -- I know zip about Powerglides, but looking at parts catalogs and powertrain charts for your 1964, looks like the only choice with auto trans was a 3.36 ratio. If you still have your original rear end, that should take the blue 20-tooth plastic gear. The speedometer driven gear "fitting" does have an integral seal in the end nearest where the cable screws on. Maybe you just need a new fitting. Of course, if your tires are not the original size 6.70's, or your speedo is out of calibration, you can play around with different color gears [18 thru 22 teeth] to "fine-tune" the accuracy, at least in the range that is important to you.

Wayne and Keith-----

DRIVEN gears of 18 to 22 tooth count can be used but as far as the 22 tooth gear ONLY the "SILVER" gear (GM #3987922) will work. The 22 tooth GREEN gear (GM #3860345) will not work. That gear might even damage the DRIVE gear if installed.

The DRIVEN gear fitting was originally different than that used for manual transmissions. However, many years ago both became GM #345215 which remains available from GM. The seal in this fitting can also be obtained separately and replaced. It's GM #3869910.

[Bob R.]

Re: speedometer gear teeth

Wayne gave you the correct information for the powerglide setup. Powerglides all have a 3:36 rear and the blue gear is the corrct color for 3:36.

[Joe L.]

Re: speedometer gear teeth

Wayne gave you the correct information for the powerglide setup. Powerglides all have a 3:36 rear and the blue gear is the corrct color for 3:36.

Bob-----

....if and only if the tire OD size is the same or very close to the same as original.

[Edward J.]

Re: speedometer gear teeth

First off -- I know zip about Powerglides, but looking at parts catalogs and powertrain charts for your 1964, looks like the only choice with auto trans was a 3.36 ratio. If you still have your original rear end, that should take the blue 20-tooth plastic gear. The speedometer driven gear "fitting" does have an integral seal in the end nearest where the cable screws on. Maybe you just need a new fitting. Of course, if your tires are not the original size 6.70's, or your speedo is out of calibration, you can play around with different color gears [18 thru 22 teeth] to "fine-tune" the accuracy, at least in the range that is important to you.

Wayne, if you have a portiable navagation unit you can use that also to check out how accurate your speedo is.

[Wayne W.]

Re: speedometer gear teeth

Thanks greatly for all advice and help the part numbers seam to have soved my leak problem, you guys are the greatest. Love this hobby Thanks again Wayne 49470