I am looking for a chart that lists the speedo gears, and how many teeth each gear has for which rear end. I think they are the same for all the trans in a Mav, but not certain. If anyone has this info, I would appreciate it. Thanks,
If they're for a C-4, I would think they'd all be the same. The only factor that I can think of that would be variable to affect accuracy would be differences in tire height for different model cars. Anyone else have opinions about this?...
Well I'd like to know more!Because i just switched over from 2.79 gears to 3.80 ,this was done just a few hours ago so i have yet to check the speedo,only drove it around the block ,will do a break in later today,but i would think the speedo would be off because of the gear change,matter of fact i thought i read some where that they were color coded for differant rear gear raito. Hmmmm!
Get a CJ Poney Parts catalog. They have gears listed in there by rear ratio. Although I believe anything over a 3:55 had a reducer on the speedo cable. You can probably call them too. www.cjponyparts.com
Here is the formula from the ford catalog, Drive gear teeth X Axle ratio X Tire rev per mile divided by 1000 = 7 x 3.73 x 815 = 21.3 Brothers performance sell up to 23 tooth for autos and manuals
Not sure about C4's but Standard transmissions generally had different drive gears on the output shaft depending on the original rear end ratio .... so you need to know the number of teeth on the drive gear to determine the proper driven gear ... I know C4 teeth are actually cast into the output shaft where standard trannys have a replaceable nylon gear ..
Thanks guys. I will do some more research, and get this up on the board. Might be a good thing to know, since we nearly all end up changing gears in our cars. Later,
Same thing for C4's... my new tranny has a different number of teeth on the drive gear. Unfortunately I don't know how many, so I can't determine exactly how many teeth I need on the driven gear based on the formula. Unfortunately I think I need 22 teeth, so I'll have to settle for 21 or take a chance on the 23 tooth gear from Steeda. For now I'm leaving it alone and subtracting 10 from my speedometer at highway speeds.
Subtracting ten won't work since it's a percentage rather that a set number that your speedometer is off by. Here's a way to tell what you need. Hop on the freeway and drive for ten mile markers. What your odometer reads will be off by the same percentage as your speedometer (if it reads 8 or 12 miles, it's off by 20% etc...) adding one tooth on your driven gear will slow the reading by approximately 5%, subtracting one tooth will increase the reading. Ford dealerships carry several different gears in stock. I used to have a list of part numbers, colors and tooth counts that I put together when I worked at the Ford dealer here, but I have since lost it.
I know it's not 10 at all speeds, that's how far it is off at 70 mph. I didn't mean to imply it was always off by 10. On the city streets I just try to keep fairly close since it's not off as far. I should just drive 70 everywhere so it's easier to tell.
Here's some other helpfull formula's MPH = RPM, MPH X TRANS GEAR X AXLE GEAR divided by TIRE DIA X 336 = RPM sample 70 X .65 (T-5 5th) X 3.73 Divided by 26 X 336 = 2193 RPM RPM = MPH RPM divided by TRANS GEAR divided by AXLE GEAR X TIRE DIA divided by 336 = MPH, sample 2193 divided by .65 divided by 3.73 X 26 divided by 336 = 69.99 MPH If you have a tach you can check to see how far off your speedo is off. You can also check max speed in each gear. Tammy's car is geared for 174.6 MPH in 5 gear @ 5500
Thomas; do you have a chart that tells which cable gear goes with what rear end...for a stock Mav with C-4?
Seems no one has the answer,best i could come up with for the 3.80 gears i put in was that i need a 21 tooth driven gear.anyone else find anything out?
