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I need to get the 90 degree adapter for the transmission to hook the cable to; my parts manual tells me to use a 6T drive gear and 13T driven gear which I assume would be behind the yoke and I don't want to take that apart. I hate to buy a 1:1 adapter and find out it's wrong, I'm sure they cost a few dollars. Anybody got an idea how to figure out if I need a different ratio adapter?

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2 hours ago, Freightrain said:

I bought a ratio adapter off ebay years ago.  Not expensive.

Using the numbers 6/13= .46

Try to find that ratio adapter?  Or close to it.

I got the 6/13 off a chart that specs which to use for which transmission and diff ratio. Do you suppose that was so you could just use a 1:1 adapter?

 

14 hours ago, mowerman said:

Speedometer shop they usually have everything you need although these days I don’t know where are you would find one good luck

On the Mack Museum website, the old truck parts supplier list shows Bob's Speedometer Svc. in Howell MI. There's also Deluxe Speedometer and Cable Svc. in Denver.

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I used Deluxe speedometer in Denver for a new cable for my hot rods tach drive distributor.  Quick service and great part.

 

I have no clue about ratios.  My B was direct drive speedo when I bought it.  Now its electronic.

IMG-20180116-202556-655.jpg

Larry

1959 B61 Liv'n Large......................

Charter member of the "MACK PACK"

 

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17 hours ago, h67st said:

I got the 6/13 off a chart that specs which to use for which transmission and diff ratio. Do you suppose that was so you could just use a 1:1 adapter?

You can use a 1:1 adapter for the start. If you have it handy or able to purchase cheap. Than test driving the truck you relate speedo reading with GPS or another true source. If any difference is found (I'm pretty sure it would) you divide the actual speed by the speedo figure and the result is the adapter ratio you need for correction.

Никогда не бывает слишком много грузовиков! leversole 11.2012

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  • 1 month later...

You can guess, or you can pay someone to figure it out, but there is a great source of information regarding speedometer ratio adapters not far away: 

Tom has done a great job of explaining the math for those who want to tackle it.  I have just figured out what adapter I need to make the speedometer right after a rear axle change, thanks to Tom.

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