Changing rear Diff Ratio Ford 10.25
Thread Starter
|
Senior User
Joined: Nov 2002
Posts: 294
Likes: 2
From: Central Coast, California
Changing rear Diff Ratio Ford 10.25
Well truck is a 91 F-250 7.5 reg cab long bed. I was curious as to what the benefit would be if I went from the stock 3.55 gears to say maybe 4.30's. Right know with the E40D and 3.55's stock 235/85 R16 tires the motor is turning about 1500 at 65MPH and just seems to lug the hell out of the motor when the peak torque is at 2100 RPM and HP is 240 somewhere around 3600 RPM. So I went ahead and installed a switch inline with the grounding circuit which controls the Torque Converter Lockup Solenoid in the valve body which seemed to help but still it seems the gears are not quite matched right. If I run in 3rd down the highway i turn about 2300 RPM at 65 and notice I do not have to give the motor as much throttle then i usually do if i am running in 4th. So If I am thinking correctly would it not be better if I went with a 4.30 rear end ratio?
Lead Driver
Joined: Aug 2006
Posts: 5,670
Likes: 13
From: Sand Lake, MI
My 95 is exactly the same thing, 460/E4OD/3.55 and runs at 1500rpms at 65mph.
Has plenty of power to push itself along at that RPM, even up and over a hill in OD without dropping out with just a little more push on the pedal to make up for the fact its going up hill.
Creates plenty of power at that RPM, I'd look for a problem elsewhere other then gearing. The motor doesn't need to run at "peak power" just to push itself down the road.
Tune up perhaps? and make sure the EGR functions as it should?
Has plenty of power to push itself along at that RPM, even up and over a hill in OD without dropping out with just a little more push on the pedal to make up for the fact its going up hill.
Creates plenty of power at that RPM, I'd look for a problem elsewhere other then gearing. The motor doesn't need to run at "peak power" just to push itself down the road.
Tune up perhaps? and make sure the EGR functions as it should?
FTE Legend
Joined: Jun 2006
Posts: 31,930
Likes: 1,499
From: Ottawa, Ontario
Do you just drive this truck or do you haul with it? IMO.. 3.55 gears is a nice compromise for fuel economy when unloaded, but is less than optimal for hauling. If you rarely or never travel at more than 70mph 3.73 or 4.10 gears will improve pulling power and may even improve milage cruising in OD. More gearing will further improve power but will start to impact milage, remember the big motor gets thirstier the more you rev it.
Thread
Thread Starter
Forum
Replies
Last Post
IcutMetl
Big Block V8 - 385 Series (6.1/370, 7.0/429, 7.5/460)
16
Aug 9, 2010 01:54 AM
IcutMetl
1987 - 1996 F150 & Larger F-Series Trucks
5
Jul 16, 2010 05:15 PM
mregister
1999 - 2016 Super Duty
7
Sep 12, 2009 10:20 AM
