: need help with spedo in cad powered chev truck

09-17-11, 02:19 PM
this spring i put a 425 in a 86 c10. my truck origanaly had a 350/350 with 2.73 gears. i realy dont know what the motor is out of. i was told a 79 fleetwood but idk what gears/tire size they had and i dont have a tach so im havin issues with knowing how fast im going. iv herd they (the cads) had something like 2.23 gears but i need sum more info. ik the 350 and 400 both are 1:1 final. also im not sure how tall my tire is right now butt will maesure and post. lets just say 30" for now bc thats close

09-17-11, 03:35 PM
The 425 came from a 77-79 Cadillac deville, also was in other models. The deville would have a th400 with 2.28 rear gears but some trim packages gave it a posi with higher gears. I think the tire size would be 225/75/15.