ZF5 S5-42 and 47 different size tailhousing

Hi guys,
I learned a useful and important fact during my zf5 swap: the tailhousings on the 42 and 47 are different lengths. The length of a 47 tailhousing is about 2 inches shorter than a 42. The tailhousing cannot be swapped between a 42 and a 47 (but you can swap tailhousings between a S5-47 and an S5-47M).

Why is this important: crossmember location. If you use a 47, you can use the same crossmember as the 4x4 M5OD, but you need the gussets from a different truck that has a shorter transmission. You will need the gussets that hold the crossmember straight instead of angling back a couple of inches. Then you can use all of the existing holes in your frame and you will not need to modify the crossmember at all.

Also, and more importantly to some, since the innards of the gearbox attach directly to the tailhousing, everything except the case is interchangeable between the S5-47 and S5-47M! I took a core Z55 S5-47 from a 96 F250 that was spent and had a cracked tailhousing and just kept the case. Then I took a S5-47M that came out of a 97 F150 and kept the tailhousing and innards out of it and rebuilt it.

I don't know if they are easier to find, but the S5-47M gets you most of the way to a S5-47 FWIW.

Good info! Thanks for sharing.

Chad - I wasn't aware of the tailhousing differences, nor that there is a S5-47M.  Torque King says they came on the 1999-2001 SuperDuty trucks with gas engines, so are they stronger than the S5-47?

Anyway, good info.  Thanks for sharing it.  

Hi Gary,
I don’t have a ton of background info on the S5-47M but I’ll tell you what I know. Visually the 47M is identical to the 47 except for the bellhousing pattern. It has a setup for a 3 bolt starter and is patterned for the 5.4L Triton engine. I think the M stands for “modular” and that line of engines from Ford was called Modular. I’m talking a little out of school because I’m not at all familiar with that generation of Fords. It looks like ZF just modified the bell portion on the 47 and Ford slapped it into a new generation of trucks. If so, the only improvement in durability you’d find in the 47M would come from the case and I don’t know if they made that any thicker. I’m honestly not sure if all of the internals are “identical” but it would seem that they are at least interchangeable.

Really the key is the tailhousing interchangeability. I’ve seen a number of ZF5s with cracked or broken tailhousings. I think it is caused by a broken u-joint at the front output that sends the driveshaft banging into that brittle aluminum tailhousing. If that happens to your 47, keep this info in your back pocket and head out to the JY for a 47M.

Thanks, Chad.  

Is the 2"difference in the out put shaft and why they cant be swapped?
If so and you are rebuilding the trans then you could use the tail housing the matches the out put shaft if the housings bolt to the main case.
Dave ----

Can you swap output shafts between the 42 and the 47? I know that there are some fundamental differences in the design of the two transmissions (besides the thicker case) that channel forces inward instead of outward. Not sure what that means for differences in the output shaft beyond the change in length. Also, everything in the tranny attaches to the tailhousing and then is slid inside the case for assembly, so there may be differences in the tailhousing besides the length that makes it impossible to interchange. Anyone out there ever try to put a 47 tailhousing on a 42 or visa versa?