Rear Gear info

Mineral Grey

Well-known member
I have found some info for changing rear gears. thought i would post for anyone else that might find this useful:

i have 3:31 gears and at 120 km RPM's are at 2000. i was looking to change the gears for more out of the hole gump..
so moving from ( 3:31 to 3:73 ) = 1.1269 multiply by 2000 rpm = 2254 your new rpm for the higher gears or
( 3:31 to 4:10) = 1.24 would be 2480 RPM at 120 km.
i'm sticking with the 3:73 not that i'm worried about fuel mileage, but rather don't want to be too hard on the engine with the long trips i plan on doing .
i know there are charts out there, but they don't take into count the rim and tire sizes on your cars, so this math will be correct for your ride.
 

Mineral Grey

Well-known member
dealer will be doing the install. might be a bit more pricey but will be worth it, will hold them to any issues and warranty .
 

Ohtobbad

Administrator
Staff member
I went to 373's in my 08 and loved them. great compromise for playing but
also long trips.
 

67 AGAIN

Enthusiast
There are gearing differences between the SN95/New Edge cars and the S-197. I believe it's from the transmission gearing.
A 4.10 in an S-197 automatic has more affect on final drive than a 4.10 in the previous generation. That's why the 4.10 is a popular gear for previous gen auto shifters versus S-197. For S-197 auto, I would suggest 3.73 is plenty of gear. Your rpm will be quite high if you go higher.
I'm no expert on SN95 and New Edge but I know S-197 V-8 autos are born with 3.31 while manuals are born with 3.55 OEM.
So even advice from what manual guys like may not translate well for auto guys and then again from generation to generation. This is then compounded if it's generation to generation and auto versus manual.
For the S-197, a two gear jump is considerable and noticeable. Unless you spend a lot of time at the strip, it's plenty.
Automatics, 3.31 to 3.73 is lots.
Manuals, 3.55 to 4.10 is also lots.
Mineral, I think you made the right decision.
 

Canuck121

Administrator
Staff member
Good info right there.

Cant go wrong with this mod. Makes the car much more fun no matter what you go with 😀
 

Ohtobbad

Administrator
Staff member
True, likely biggest factor is how you plan on using the car.
If you like trips and long drives, stay away from low gears.
If you going for short cruises around town then go nuts.
 

helimech

Well-known member
I have 4.10s and at the moment they are perfect. More power or stickier tires would require an upgrade to 3.73s and brake cooling.
 

67 AGAIN

Enthusiast
It slipped my mind yesterday.
I tend to forget about them because Ford Racing no longer sells this size, but there is a 3.90 gear available for our differentials.
It slots neatly between 3.73 and 4.10.
It's still available from other gear manufacturers.
I checked on it this summer and found some.
I have 3.73 in my car up from 3.55 in a manual. This was an excellent setup prior to ported heads.
I'm now leaning toward something to get me higher up the rev range quicker after I did the heads.
I did not and still don't want to go to 4.10's to avoid the very high rpm's during highway and distance travel.
I'm not a strip guy and really don't care for the quarter mile so 4.10's are not for me.
I'm into twisty back roads and road courses so the 3.90 is a better fit for me.
It's still a two gear upgrade from 3.55's.
I'm not adverse to doing high mileage days.
I'll do Moncton/Amherst and back or Quebec city and back in the same day for a car show. Easily 800 to 1000 km.
Like Trevor says, it's important to give consideration to what you plan on using the car for.
 

Mineral Grey

Well-known member
tks for the input everyone, since i do a fair amount oh hwy travel into and around Maine, New Hampshire, and PEI. most are 3 hour bursts at a time, i am sticking with the 3.73, cuz i tend to be around 120-140 when traveling. cant wait till i get them in and get some more miles on.
only about 17 weeks before i take it home again..
 

Ohtobbad

Administrator
Staff member
even with 3.73 set up, you will notice big improvement out of the hole.
Was huge on my 08, loved it and still good for long trips.
 
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