My 96 crew cab 4x4 has the 4:10 gears, done my mods and was wondering
if changing ratio from 4:10 to 3:55 will increase fuel mileage and top end speed?
If so what do ya'll think it will be and approx costs to change ratios. You have to do both front and rear I believe. Will it hurt the towing ability, pull a camper a few times a year,total combined weight is about 18k.
Top speed now is 80/85 mph, usually run her around 70/75 range, running over 80 sounds like its wound up at that point and fuel mileage
is 13-14 normal driving 17/18 interstate running 70ish with cruise now.

 

I wouldn't switch to 3:55. 3.73 seems to be a good compromise which is probably why Ford doesn't use the 3:55 anymore in the F250/350.

 

I have 355's in my 97, With all the low end torque there is no problem towing.No doubt your rpm's will come down on the highway,but is it worth the slight increase in mileage,I doubt it.I would leave well enough alone.

 

I love my 4.10's and with the 5-speed 1st gear is LOOOOWWW! I wouldn't trade it for anything else.

bender97f250, what part of PA are you from?

 

WilkesBarre - 5 miles from FortyFort !!

 

I guess I asked you that before. It's hard to keep track of who you come in contact with on this forum.

How warm was it there today? Almost 90 in TX.

 

86 and very humid, 78 as we speak.

 

Keep sending the warm weather north! I waited over a long winter for this, just opened the pool and cant wait to jump in and swim some laps.

 

There's another thread about this conversion here -
http://forums.ford-trucks.com/ubbthr...5&o=31&fpart=1

 

I am thinking of changing to 3.73's also. Just to bring the RPM's down @ freeway speeds if nothing else. My fuel mileage @ 75 MPH is terrible.

 

3.55's should give you about a 5 MPG increase over 4.10's
I don't know if it will tow good enough for you, because I have never towed 18K pounds
but that gear ratio does tow a '51 Jeep ****** and a Massey Ferguson 135 pretty well

 

I just pulled a 1978 (heavy) 28 ft camper with my 97 4x4 crewcab. It has the 3:55 gears in it. I only pulled it about 50 miles but it's through some windy hilly stuff here in Kentucky. I had no complaints at all. And when I filled her up 2 days later I still had avg. a little over 16 mpg. I hope everyone's having a great day. Mike