I'm Stuck
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Joined: Dec 2006
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From: Emmett, ID
I'm Stuck
Well i'm stuck, i have a 79 f100 stepside that i am upgrading from a c4 to a c6 it will run a 351w. I have found the proper tranny that will fit but have no idea what im doing. I have searched the threads but have found nothing relavent to the questions that i need answered. Question 1 - Is it ok to use the c4 crossmember to mount the c6...the reason why i ask is because, the c4 has 1 bolt thru the middle of the crossmember that holds the tranny mount on, where as the c6 has 2 bolts coming off the mount down thru the top of the crossmember that i will have to drill because i cannot find a c6 crossmember that is the the width of my frame like the c4 member.
Question 2 - Will i have to install the motor with tranny attached, to drill the holes properly to get the right pinion angle or does it matter.
Question 3 - Will i have to shorten, lengthen, or just keep the driveshaft the same length.
I have had zero luck with this site and answering alot of my questions, but i have not tried this particular forum for the this question, i have lost a lot of confidence in asking questions for fear nobody will reply, please help, i would appreciate any feedback or advice, thank you.
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First off, you can beef the C4 to handle the 351, you needn't put in the more power-hungry C6 in the first place.
--you can use the cross member, just drill it.
--since the c4 is either 24 5/16 or 30 19/32 vs the C6 @ 33 1/2, and the front to mount is different too, you will probably have to move the cross member. See the charts:
TCI - TECHNICAL INFORMATION: Transmission Dimensions
--install the motor w/ or w/o trans? Depends on your shop, crane, trans jack, work surface, skill level, easy of install in your vehicle. Will it go in that way? Up to you.
--Driveshaft: Looks like it has to be shortened, but not until you have everything bolted up and secure, then measure. Then measure again.
IMO you really should rethink the whole thing and shop for a trans builder who can give you a solid C4 build. In fact the above site sells C4s, look at their propaganda on their trans or call them and get their opinion on your vehicle and a C4.
Good luck. Remember, this is the internet, I've never worked on much of anything, I just read a lot.
I do mean good luck to you.
--you can use the cross member, just drill it.
--since the c4 is either 24 5/16 or 30 19/32 vs the C6 @ 33 1/2, and the front to mount is different too, you will probably have to move the cross member. See the charts:
TCI - TECHNICAL INFORMATION: Transmission Dimensions
--install the motor w/ or w/o trans? Depends on your shop, crane, trans jack, work surface, skill level, easy of install in your vehicle. Will it go in that way? Up to you.
--Driveshaft: Looks like it has to be shortened, but not until you have everything bolted up and secure, then measure. Then measure again.
IMO you really should rethink the whole thing and shop for a trans builder who can give you a solid C4 build. In fact the above site sells C4s, look at their propaganda on their trans or call them and get their opinion on your vehicle and a C4.
Good luck. Remember, this is the internet, I've never worked on much of anything, I just read a lot.
I do mean good luck to you.
