Rear Differential

[smithw44]

I have a 1997 ford f350 i do not have a metal tag on my rear end and im trying to find out if i have a locker of not in it to determine what oil i need to run and how much oil. Ford says 75-140 synthetic...others say 80-90 gear oil but i dunno if i need the additive anyone have any ideas i think i have 355's in it.

[blageurt]

As soon as you remove the cover you will see what it is ... the VIN and the door sticker will tell you the Axle code ... 39 is the Open 3:55 ....I use 80W90 and change it every 50,000 kms ( half of recommended service interval) Alot of guys use synthetic but since I change it myself and am Old School I use Dino....

[94_turbo]

Originally Posted by smithw44

I have a 1997 ford f350 i do not have a metal tag on my rear end and im trying to find out if i have a locker of not in it to determine what oil i need to run and how much oil. Ford says 75-140 synthetic...others say 80-90 gear oil but i dunno if i need the additive anyone have any ideas i think i have 355's in it.

jack the rear axle off of the ground..truck in neutral...turn either wheel..if the other turns the same way..posi..if not open..open,,75w140,,,posi whatever Ford says for that year..

[madpogue]

What does it say under "Axle" on the door jamb label?

[smithw44]

Never thought about about looking on the door jamb I will do that today and post on here. Thanks for everyones replies

[smithw44]

the axle code on the door say C9

[smithw44]

axle code on the door says C9 i called ford with the vin number and they said there computer doesnt go back usually more then 10 years couldnt help me told me to find metal tag on axle...to look it up what numbers in the vin would tell me what kind axle is in this?

[dieselsmokerdoug]

with the info i have c9 is a limited slip with 355 gears

[smithw44]

yeh thank you!i looked it up on google and found a chart from ford listing all there rear ends and the axle code. appreciate your help!