h67st Posted December 13, 2021 Share Posted December 13, 2021 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? Quote Link to comment https://www.bigmacktrucks.com/topic/68920-speedometer-drive/ Share on other sites More sharing options...
mowerman Posted December 13, 2021 Share Posted December 13, 2021 Speedometer shop they usually have everything you need although these days I don’t know where are you would find one good luck Quote Link to comment https://www.bigmacktrucks.com/topic/68920-speedometer-drive/#findComment-484875 Share on other sites More sharing options...
Freightrain Posted December 13, 2021 Share Posted December 13, 2021 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. Quote Larry 1959 B61 Liv'n Large...................... Charter member of the "MACK PACK" Link to comment https://www.bigmacktrucks.com/topic/68920-speedometer-drive/#findComment-484920 Share on other sites More sharing options...
h67st Posted December 13, 2021 Author Share Posted December 13, 2021 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. Quote Link to comment https://www.bigmacktrucks.com/topic/68920-speedometer-drive/#findComment-484932 Share on other sites More sharing options...
doubleclutchinweasel Posted December 13, 2021 Share Posted December 13, 2021 There are several folks out there who might be able to help... https://www.texasindustrialelectric.com/800_Series_Speedometer_Adapter.asp https://speedometercablesusa.com/gear_box_adapters.html https://recordtechnologies.com/products/ratio-adapter https://www.bobsspeedometer.com/products/ratio-adapters/ https://www.dicksspeedotach.com/speedometer-adapters/ 1 Quote "Eagles may soar, but weasels don't get sucked into jet engines." Link to comment https://www.bigmacktrucks.com/topic/68920-speedometer-drive/#findComment-484934 Share on other sites More sharing options...
Freightrain Posted December 14, 2021 Share Posted December 14, 2021 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. Quote Larry 1959 B61 Liv'n Large...................... Charter member of the "MACK PACK" Link to comment https://www.bigmacktrucks.com/topic/68920-speedometer-drive/#findComment-485000 Share on other sites More sharing options...
Vladislav Posted December 14, 2021 Share Posted December 14, 2021 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. Quote Никогда не бывает слишком много грузовиков! leversole 11.2012 Link to comment https://www.bigmacktrucks.com/topic/68920-speedometer-drive/#findComment-485028 Share on other sites More sharing options...
doubleclutchinweasel Posted December 14, 2021 Share Posted December 14, 2021 Incidentally, I believe the "standard" you are trying to achieve is 1,000 revolutions of the cable per mile. For what that's worth! Quote "Eagles may soar, but weasels don't get sucked into jet engines." Link to comment https://www.bigmacktrucks.com/topic/68920-speedometer-drive/#findComment-485088 Share on other sites More sharing options...
theakerstwo Posted December 14, 2021 Share Posted December 14, 2021 Back when we had a speedo shop here they would tell you to connect cable direct with adapter taken out of it.Drive ten miles by mileage markers and see how many miles and tenths speedo head was off.Then take them the adapter to them and they would repair. 1 Quote glenn akers Link to comment https://www.bigmacktrucks.com/topic/68920-speedometer-drive/#findComment-485091 Share on other sites More sharing options...
steve s. Posted February 4, 2022 Share Posted February 4, 2022 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. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/68920-speedometer-drive/#findComment-488509 Share on other sites More sharing options...
Draggin Wagon Posted February 4, 2022 Share Posted February 4, 2022 Carl, I have a bunch of ratio boxes. I'll try to remember to look tomorrow to see if any 90 degree boxes. If you think of it tomorrow, shoot me a text to remind me. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/68920-speedometer-drive/#findComment-488510 Share on other sites More sharing options...
Draggin Wagon Posted February 7, 2022 Share Posted February 7, 2022 yep, clear forgot it. Will try to do better tomorrow Quote Link to comment https://www.bigmacktrucks.com/topic/68920-speedometer-drive/#findComment-488731 Share on other sites More sharing options...
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