Hello,
I have a '77 F150 Explorer LWB 2WD standard cab. Currently the truck has a 400 with a C6. I will be swaping out with a 351W and a C4. My question is would I have to swap the driveshaft also? Thanks in advance.

Jamie

 

I am not sure, Measure the tailshaft from the mount to the end and see if they are the same length. If so, then the driveshaft should be fine.
Jimmy

 

I think the C4 is shorter than the C6, meaning longer driveshaft needed.

 

even if you need a different length driveshaft, it shouldn't cost you more than $60-$70. I recently had both my front and rear driveshafts shortened/lengthened as needed for a t-case swap. Including the balancing cost for both d-shafts the total was $140.

Just take a good measurement once the swap is done and bring the d-shaft into the local driveline shop and you'll have the correct length shaft within a day.

be sure to check that the output yoke of the new transmission is the same as the existing transmission. If not, check to see if you can swap output yokes between the two. otherwise you'll need either a new end on the driveshaft, or a new output yoke on the transmission. Easier to decided which to do if you havn't already spent money changing the length of the driveshaft and suddenly realize the end is wrong for the new application...don't ask how i know!

Good luck!

 

You'll need a different yoke for the C6. Just in case you didn't already know that. And yes, the C4 should be a little shorter.

 

If you need to lengthen your drive shaft, you can opt to use a heavier gauge steel too. Not much more $.
Just a question, and I hope I'm not showing my ignorance here. Why do you want a C4 instead of a C6? Is this an upgrade???

 

I'm using the c4 because it's a small block bolt pattern, I'm kind of undecided if I should use the c4, or go with the aod I have sitting in the garage.

Jamie

 

If money isn't too big of an issue I'd say go with the AOD. Both the C4 and AOD could be built to handle the 351's power, that is, if they aren't already built of course. The AOD will probably cost 2X than the C4 to get built. But you probably already knew that.