So I built a Super Truck 2005 F650 Pickup and would really like a gear change right now 2300 rpm = 60 mph. I estimate the ratio to be 6:17.
In order to research a new gear set I need Diff info, Tag is long gone so all I have is the VIN which for some reason all the Ford Dealers cannot decode and the Axle code in the jamb (6B) which means nothing. I find it hard to believe the diff and ratio cant be identified by the VIN.
Someone please direct me or help
Thanks so much

 

Welcome to FTE.

The ratio is not in the VIN. You should have a 17 digit VIN and there are some decoders on line. Ford should be able to decode it as well, if they are a heavy truck dealer.

You did not provide a VIN in your post.

Axle code 6B-- can't find that one.

Can you post a picture of the tag on jamb?

 

VIN 3FRNF65C45V201895

Ill get a door tag pic tonight

 

Click on your VIN now. It will take you to a decode. Still no axle ratio, but other info.

 

I know those trucks come with one and two-speed rears (depending on weight rating). Eaton, Spicer make manual transmissions and rears for the F-650 and I'd check with them -- there may or may not be some stampings on the axle to help. Once you pull it you'll also see internal markings / part numbers to help decode.

That's a pretty stout ratio you've got there, it sounds like a Eaton 21060S - 41 spline or even a Eaton 17060S - 39 spline; but without the tag, you'll probably have to pull it (along with parking brake if equipped that way) to confirm.

 

Just jack up the back and check it. Then no guessing. Spin the tire one revolution if a limited slip count the driveshaft turns. Doesn't get any easier than that