Attn ....Joe Lucia

[bruce11495]

Joe a quick question. The 72 parts manual shows the same number for the speedo driven gear for 3:55/3:70 as 3987922. Is there an adapter to be used that takes up the .15%? I see the same part number for the 3:36/4:56, but with an adapter? Is this a typo?
TIA Bruce

[Joe L.]

Re: Attn ....Joe Lucia

bruce-----

I can't find any record or indication that it was any other way in PRODUCTION than is indicated in SERVICE. In other words, the 3.55:1 and 3.70:1 used the same speedometer drive and driven gears. It may be that the two ratios fell on "either side" of this speedometer gear combination. If so, with one gear set the speedometer reading may have been a bit low, but within acceptable factory accuracy for PRODUCTION. With the other gear set, it may have been a bit high, but within acceptable factory accuracy. That's just a guess, though.

4.11 and 4.56 ratios did use an adapter. Therefore, the speedometer drive and driven gears were the same as for much lower numerical ratios; the adapter changed the overall output speed to provide acceptable accuracy.

[Duke W.]

Re: Attn ....Joe Lucia

The difference between 3.55 and 3.70 is only about 4 percent. You take the ratio of the two numbers, not the arithmetic difference, to determine the percent difference.

So like Joe said, one drive gear probably provided accuracy within acceptable production tolerance. Four percent is not much especially when you consider that tires worn to the wear bars will increase the speedometer reading by about two percent relative to when the tires were new.

Duke

[KEN BUTCHER]

speedo drive gear C-3

Hi Bruce, you didn't say if four speed or auto. I've got some upgrade (75) part #'s

3:36 (M20) part #361002-yellow,teeth #7 with part #3987918-brown,teeth #18 sleeve assembly #338975, % error -0.68

3:36 (M40) part #8624735-brown,teeth #15 with part #1359272-blue,teeth #38 sleeve assembly #1362294, % error 1.21

3:55 (M20)-(M21) part #361002-yellow,teeth #7 with part #3987919-natural,teeth #19 sleeve assembly #338975, % error -0.54

3:55 (M40) part #8624735-brown,teeth #15 with part #1362048-black,teeth #40 sleeve assembly #1362293, % error 1.63

3:70 (M21) part #361002-yellow,teeth #7 with part #3987920-blue,teeth #20 sleeve assembly #338975, % error -1.67