Just put a new one in my 67.. went from a 2.79 to a 3.40.....now...my problem ..

Got a C4 with a 302 but it seems like the RPMs are alot higher at 50MPH then it was.....

also the speedometer is reading way off...like going 50 but showing 70,, What can I do to fix this problem or was the gear in the rear to much for a C4 tranny,

Thanks for any info.


NEW TO THE SITE<<GLAD TO BE A MEMBER

Corey

 

welcome to the site, you may have to change your speedo gear, i dunno since I'm still a newb in the technical department but check out this site and some other replies

there might be a calculator or something to help
http://www.allfordmustangs.com/AFM_T...rs/index.shtml

 

I know this won't help any, but I'd be doing some hella smokey burnouts with the lower gears. Otherwise, change the gear in your tranny that drives your speedo.

 

you will need to do some reasearch before buying the new gear, becasue unfortunatly, there is limitations to the amount of gears for the speedo. You may have to go with a 3.25 speedo gear, or possibly a 3.55, which if i remember correctly, the 3.25 is pink and 3.55 yellow.

 

the reason your speedo is reading high is because with the lower gears,it takes more turns of the driveshaft to turn the drive axles, therefore it will turn the speedo gear faster in the tranny and force your speedo to read alot faster. The gear in your transmission that turns your speedo is calibrated to work with your stock rearend gears, the 2.79's. You will have to get a gear that works with your gears and tire size. i have a 68 and 3.73 gears and 14 inch wheels and my speedo reads about 88 when im actually doin 65 mph at 3500 RPM. Dont worry, you dont have to much gear for your C4, Ive seen plenty more.