code for rear axle?

[mexicanjoe]

Hey guys I noticed the code for the rear axle on my '89 F-250 with a 5 speed was ::: 39. is this for a 4.10 axle or am I mistaken? I checked the tag on the rear axle and it read: V9C and some other numbers I couldnt make out.... What say ye brethren of the compression combustion...?

 

[Randy Bush]

Looks to be 3.55 from what I can find.

 

[DaveBen]

According to this site: https://www.blueovaltrucks.com/tech...y-your-ford-truck-axle-from-the-door-sticker/. it is a Ford 10.25 axel with a 3:55 ratio.

 

[mexicanjoe]

This explains why at 60 mph my engine is turning 2100 rpm !!

 

[DaveBen]

Not really. At 60 mph you should be turning about 1750 rpms with 3:55 gears. What you are seeing is more like 4:10 gears. All of these numbers depend on tire size.

 

[mexicanjoe]

im using stock tire size at the present time. I tried to lift the rear diff and spin the driveshaft and count the revolutions of the tires. Well that didn't work...... the drive shaft turned 2.1 times and the tires would turn once??? This weekend I plan to pull the rear cover and check the assembly and check the gears.... I believe at some point the PO may have swapped differential.... This because the axle tag has a 4.10 number on it........ so we will have a gear reveal this weekend!