gear ratio

MII

MII

Junior Member
I am kind of new at this, but here goes
my 49 Fi really revs up at 55 mph, and the ratio is 4: 27
what is the best solution to drive at 65 and reduce rpms
 
Others with more experience than I have will chime in on possible solutions. A few choices come to mind: you can change the ring and pinion in the rear end, buy an overdrive unit or even something simple as larger diameter tires. Here's a website that you can play with to see what rpm you are turning at 55 once you measure your tire diameter. BTW, 55 is pretty fast for the design of the truck back then. I'd guess 45 was 'top' speed back then.
http://www.advanced-ev.com/Calculators/TireSize/
 
rpm is 2770 at 55 wonder if a complete rear assembly can be adapted that will give a ratio that do 22 2300 at 55
 
Overdrive transmission is the best way to go. Most 49-51 Merc cars with 4:27 came with OD. Mercs with automatic came with a 3:31 rear but may be harder to find. Standard transmission Mercs also came with 3:91, 4:27 and 4:55. Or, consider installing a more modern rear.
 
thanks Fordy, that will keep me out of mischief for a while
Walt built the engine and it is very good--just started driving it
 
I will keep it off the interstate til I find an overdrive transmission
is there one that is a floor shift I really don't know how they shift
 
MII: Measure the wheel mounting surface to wheel mounting surface of your present rear to find what other rear matches. For instance, the stock WMS to WMS of 49-51 Mercs is 64 1/4 in. 1970-73 Mustang 9 in. is also the same distance. Keep in mind that the wider your tires are, this distance may have to be altered. Rim width and offset also changes what may be needed for adequate fender tire clearance.
 
You must log in or register to reply here.
Back
Top