Your donations help keep this valuable resource free and growing. Thank you.
|
Borg Warner M12 Automatic speedometer drive gear |
Post Reply | Page <12 |
Author | |
scott
AMC Addicted Joined: Jul/10/2007 Location: Wildwood Pa. Status: Offline Points: 3498 |
Post Options
Thanks(0)
|
The reason it is best to calculate the error at a set speed rather than using what a chart says is correct is this: The speedometer head itself may not be 100 % accurate. Speedometers are supposed to run exactly 60 MPH at 1000 RPM. And that is what the charts are based off of. However, there is a lot of room for error in the speedo head. The spring could be weak, & make it run fast. Magnets could be weak & make it run slow. And vice versa.
If you calculate the error while running down the road at a set speed, this compensates for any error in the speedo head itself. It also allows for converter slippage at that MPH. My calculation above was just an example. To come up with a number to multiply your 23 tooth gear by, we need to know what indicated MPH it was 10 actual MPH slow. However, let's say it was at 60 MPH. If that is the case, the calculation should get you close. Probably the 19 tooth will get you close to accurate. |
|
amxdreamer
AMC Addicted Joined: Jul/30/2008 Location: Vancouver, BC Status: Offline Points: 8494 |
Post Options
Thanks(0)
|
Scott, what about the guys that say their cars run 145mph with their GPS with small tires and basic powertrain. Mathematically impossible.
|
|
Tony
Vancouver, BC 1970 AMX 1972 Badassador AMO#10333 |
|
amxdreamer
AMC Addicted Joined: Jul/30/2008 Location: Vancouver, BC Status: Offline Points: 8494 |
Post Options
Thanks(0)
|
|
|
Tony
Vancouver, BC 1970 AMX 1972 Badassador AMO#10333 |
|
71 Javelin AMX O.O.
AMC Addicted Joined: Aug/29/2008 Location: Minnesota Status: Offline Points: 655 |
Post Options
Thanks(0)
|
I got the 20 tooth speedo drive gear from CATC and will see how it fits and compares to the 23 tooth one that is running now. I was thinking of jacking up the back and hand turning the driveshaft and see if the gear has no binding issues before I take it on the road. I still have not gotten a visual or confirmation from anybody if the driven gear on the trans output shaft is a 7 tooth. I can't quite tell when I feel for mine. Steve
|
|
71 Javelin AMX O.O.
AMC Addicted Joined: Aug/29/2008 Location: Minnesota Status: Offline Points: 655 |
Post Options
Thanks(0)
|
Well I didn't like the longer end pin on the CATC 20 tooth gear, so I got the AMark one and it looked a lot better. I put some light grease on the teeth and installed it in the tranny and hand turned the rear wheels. I pulled the gear and could see that the teeth were meshing and making contact at the right place. I'll find out this spring, once we get a decent day here in Minnesota, if it's recording a more accurate MPH on the speedo.
Steve
|
|
vyscera
AMC Apprentice Joined: Jul/12/2016 Location: Fl Status: Offline Points: 48 |
Post Options
Thanks(0)
|
How did it work out? I'm missing the speedo gear and am trying to figure out where to start for my Machine.
|
|
71 Javelin AMX O.O.
AMC Addicted Joined: Aug/29/2008 Location: Minnesota Status: Offline Points: 655 |
Post Options
Thanks(0)
|
vyscera:
Great. It reads a lot more accuatly as was confirm with my I phone speed box app. I can send you some pictures of the installation. I had to replace the driven gear on the output shaft of the Borg warner M12. Just replacing the speedometer gear was not making any difference. Steve |
|
roadventure
AMC Nut Joined: May/23/2020 Location: Delaware Status: Online Points: 278 |
Post Options
Thanks(0)
|
According to the TSM (page 4-48) the BW M12 transmission has a 9 tooth speedometer DRIVER gear. This is true for the 2.87, 3.15 rear gear ratio. It is unlikely someone would have changed the speedometer DRIVER gear if the rear drive ratio is changed, so it is very likely that your car has the 9 tooth DRIVER in the M12 transmission.
|
|
Post Reply | Page <12 |
Tweet
|
Forum Jump | Forum Permissions You cannot post new topics in this forum You cannot reply to topics in this forum You cannot delete your posts in this forum You cannot edit your posts in this forum You cannot create polls in this forum You cannot vote in polls in this forum |