Ford 4.20 Rear Gear Ratio?
 

I just got a ford rear center section that has a stock 4.20 gear in it. It has 42-10 and a ford emblem stamped on the ring gear. I also counted the ring and pinion gears and they both were 42 and 10. I have never seen this ratio used or heard of this ratio also. Is their anyone that can help me with what and when this was used. Thank you for the help.

Re: Ford 4.20 Rear Gear Ratio?
 

Could have been a NASCAR gear set the had a ton of oddball ratios. Ford made them at the Serling mi axle plant. There was a 4.29 ratio that was a standard gear set.

Re: Ford 4.20 Rear Gear Ratio?
 

Wow, thank you for that information on the gear. I thought it was a odd ball gear size. I have looked all over the net and everyone that I talk to says it is a Nascar gear set. :D

Re: Ford 4.20 Rear Gear Ratio?
 

Really doubt those gears were for CUP racing. They would be spinning about 11,000 RPM @ 200MPH

Re: Ford 4.20 Rear Gear Ratio?
 

Just so you understand NASCAR some of the short tracks Bristol, Martinsville, Richmond use as much as a 6.20/6.50. A 4.20 could be used Darlington Rockingham Phoenix

Re: Ford 4.20 Rear Gear Ratio?
 

I would recount that ring gear, nascar runs a 422&a 430 never heared of a 420.
Rich

Re: Ford 4.20 Rear Gear Ratio?
 

I counted it 10 times and it always came out to 42-10. I always divided the pinion into the ring gear and it came out to 4.20. I talked to a guy at Richmond Gear and he said their were some Nascar teams using this 4.20 ratio. I think I know how to count, a least I thought I did. :rolleyes:

Re: Ford 4.20 Rear Gear Ratio?
 

Google it "early bronco with a six cylinder. Don't know anything else, but I figured I'd let you know"