I need to purchase a new drive shaft. There are 2 lengths available depending on the diff size. How can I tell if it is the 9 or the 10 inch diff.
The 2 drive shaft lengths available from the end of the yoke to the rear flange are 71-3/8" for the 10 inch and 73-1/4" for the 9 inch.
I don't want to remove the shaft to measure the total length (if I don't have to ) The tag on the door sticker lists a "B6" code for the diff, and "B" for the transmission code.

Thanks for your help
TT

 

You should have a 9.75” rear (FX4 only had a 5.4 engine back then, IIRC...). The 10.25”(?) comes with the seven-lug wheel HDPP package trucks back then.

 

Look at the tag on the cover. You can probably stick your phone under and get a picture.

 

Thanks for the reply.
Much appreciated
TT

 

Tony123,
On my 2007:
There are two tags on the rear differential (1) “75 W 140 SYNTH OIL ONLY” Located at the 2 O’clock position, (2) and at the 7 O’clock position “V805A (upper left) and 3L55 88 6L20” (bottom line).
The following info is from 2007 Ford Workshop Manual
The 88 indicates an 8.8" ring gear diameter. Yours will be 88 or 975 or 1025. 10 cover bolts for the 8.8", 12 cover bolts for the 9.75" and 10.25".
I have a question for you - How did you determine there are two different driveshaft lengths?
My first thought was to just get under there and measure the driveshaft length but with a slip joint that may not be straight forward.
Jimboy

 

Unfortunately the tags are missing on my diff. When I called summit racing to get a price on a new shaft, the sales rep mentioned the size differences to me. Stating that the shorter one was for the 10" . I guess the diff housing is a bit longer for the 10 inch. Also, the measurement is from the end of the slip yoke to the flange. My 2005 has 6 lug axles, so as mentioned above the 10" is suited for 7 lug axles.

PS: I originally measured the shaft from center to center across the U-joints. It was 64-1/8". But the sales rep said that didn't help with his ability to select the proper shaft.

Cheers,
TT