97 f250 HD differential gear ratio - Diesel Forum - TheDieselStop.com
Ford Diesel Forum / Powerstroke Forum
Ford Diesel Forum / Powerstroke Forum
Go Back   Diesel Forum - TheDieselStop.com > Ford Diesels > Power Strokes 1994-1997 General

Power Strokes 1994-1997 General Technical discussion of topics related to vehicles powered by the Power Stroke engine in 1994 through 1997 models.

TheDieselstop.com is the premier Diesel Truck Forum on the internet. Registered Users do not see the above ads.
Reply
 
LinkBack Thread Tools Display Modes
Old 08-11-2005, 12:50 AM   #1 (permalink)
Member
 
Brianedwardss's Avatar
 
Join Date: Mar 2005
Location: Oregon City, OR
Posts: 78
My Photos: (2)
Feedback Score: 0 reviews
97 f250 HD differential gear ratio

Hi, I just bought a 1997 f250 4x4, ex-cab, HEAVY DUTY, 5-speed.

Ok, this is the issue. My axle code is C5. the C5 code always has been the 4.1 rear end ratio. But, my truck is turning 2500 rpm at 70 mph.

the truck has 255/85-16 tires. doing the math, (5280/8.65 x 4.56 x.76 /60 x 70 = 2472) indicates that I have a 4.56 rear end. I had a buddy drive beside me on the phone and my speedometer was accurate!

does the C5 code on a 97 HD indicate 4.56???? I'd like to know cause for just being my daily driver, 2500 at 70 is way to low, especially with diesel prices the way they are!!!
__________________
1988 F-350 srw, Crew Cab, 2WD, 7.3L, Rebuilt C6, 4.10 Rear, Manual GP Switch, No Soup Bowl. Getting a 3.08 Rear Soon.

ASE Master med/hvy Truck Technician
Brianedwardss is offline   Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
Old 08-11-2005, 01:10 AM   #2 (permalink)
Senior Member
 
Join Date: Dec 2003
Location: Tucson,Arizona
Posts: 671
My Photos: (0)
Feedback Score: 0 reviews
Re: 97 f250 HD differential gear ratio

Not sure about your code or your math (no disrespect, I make mistakes all the time), my truck has 4.10 gearing and spins just below 2500 @ 70mph every morning. On the math part, I could not follow the "/8.65". Where does that come from? I assume the overdrive is .76.

BTW, I get better mileage running 65 or under, but I can't stand to go that slow. Getting right at 18.7mpg running 70mph.

Bill
__________________
Bone stock 94 1/2 DI turbo 4x2 F250, Rancho steering stabilizer to eliminate front end shake, sensor safe clamp mod, filler neck mod

Gun Control: The ability to consistently hit what you are aiming at.
Graduate, UA, Mech. Eng.
arizonian is offline   Reply With Quote Quick reply to this message
Old 08-11-2005, 09:14 AM   #3 (permalink)
Senior Member
 
Join Date: Jan 2003
Location: Florida
Posts: 178
My Photos: (0)
Feedback Score: 0 reviews
Re: 97 f250 HD differential gear ratio

My 97 Owners Guide has C5 as a 4.10.
__________________
2002 F250 Stock PSD Crew Cab SRW
1998 HR Endeavor MH w/275 Cummins Diesel and MD3060 Allison 6 speed

PREVIOUS TRUCK 97 F250 PSD 3.55 Draw-Tite Slider, pulling 2850RK Keystone Montana DIY Exhaust brake with TC Lockup
redtopman is offline   Reply With Quote Quick reply to this message
Old 08-11-2005, 11:36 AM   #4 (permalink)
Senior Member
 
Join Date: Jun 2005
Location: New Jersey
Posts: 304
My Photos: (0)
Feedback Score: 0 reviews
Re: 97 f250 HD differential gear ratio

I have a 1984 Chevy M1008 Pick-up running 4.56's and 235 85 16 tires. I can not even hit 70! The governor kicks in at about 3600 and I hit that at about 69 MPH. Your RPM sounds about right for 4.10's. I have 3.55's in my 96 and 265 75 16 tires and I run about 1800 at 70.
Rick
__________________
1996 F250 S/C, Auto, BD convertor, transgo kit, 3.55's, 285-75-16's, Switched 10k, 220K Miles
rickf is offline   Reply With Quote Quick reply to this message
Old 08-11-2005, 12:02 PM   #5 (permalink)
Senior Member
 
Join Date: Sep 2003
Location: Washington State
Posts: 1,601
My Photos: (32)
Feedback Score: 0 reviews
Re: 97 f250 HD differential gear ratio

Hey Brian!

I have been considering tires sizes and gear options so I happen to have thrown together a little spreadsheet...

Based on 4:10 gear, the ZF-5 OD ratio of .77, and 255/85-16 turning 629 revs per mile, the theoretic rpm at 70 mph is 2,316 rpm.

Reality when compared to the figures my spreadsheet generates has shown that if I add about 3% to the claculated rpm, I come real close to what the tach shows. Your calculated 2,316 ends up at 2,385. So if you are on the low side of 2,500 on your tach, you are probably calibrated about right.

For reference, if I plug in 4.56's with your OD and add the 3% factor I come up with 2,653 rpm...?

Last thoughts, the PSOM is supposed to be adjusted when you change tire size, though you say you have confirmed your speedo's accuracy.
Finally, you could jack up the rear end and (since the "C" in C% represents a locking dif you shouldn't need to block the opposite wheel) rotate the tire one revolution and see whether the driveshaft rotates 4 time (for a 4.1) or closer to 4.5 times (for a 4.56).

Good luck!

God Bless,

TC
__________________
97 F350 XLT, 4x4, Toreador Red, CC, PSD, MLE0, ZF5, 3.55 l/s, LUK clutch,Velvet Rides, ISSPRO gauges, v/cover vented to tailpipe, DPPI downpipe - modded to 4" right below firewall seam, open element intake using Duralite filter, coolant filter mounted between washer fluid bottle and jack, gutted EBPV, 99+ I/C installed using early 99 Y-pipe and custom pipes, 4-pos chip, BigBopper Seat Mod, Bilsteins, 130cc injectors, homegrown 4" exhaust, uses 36" Magnaflow muffler (Model #12773 body is a full 30" long - nice and quiet!) Custom Fuel System using Carter electric pump, Aeromotive regulator and frame-mounted filters...
2003 Tahoe MS27TT (27' Lite travel trailer), Prodigy Brake Controller.
1991 5.0 LX, runs 12.57 @ 109 mph
My Intercooler/Fuel System Install Webpage (section on CCV Mod too): http://members.localnet.com/~boys3/
TimC63 is offline   Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
Reply

  Diesel Forum - TheDieselStop.com > Ford Diesels > Power Strokes 1994-1997 General

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Diesel Forum - TheDieselStop.com forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Display Modes

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On



Wheel & Tire Center

Powered by vBadvanced CMPS v3.2.3

All times are GMT -5. The time now is 05:13 AM.



Powered by vBulletin® Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Search Engine Friendly URLs by vBSEO 3.6.0

vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.