454/400/NP203 to 454/700/NP208 Swap

[Misled]

OK, I have searched for this answer, but can't find anything for sure....

My buddy has a 1979 Chevy K20 he bought brand new (yeah, I'd like to have it!!) The only drivetrain change is the swap from a 400 small block to a 454 big block. It has the 400 auto trans and 203 full time transfer case.

We found a nice 700 auto trans with a 208 transfer case from a mid 80's Blazer. This truck is more of an occasional driver with the even less often need for 4 wheel drive.

My question is........what issues will we encounter swapping them out? These are the areas I thought about;
* u-joints (are they all the same)
* crossmember (will the 79 one work)
* driveshafts (will ones from a mid 80's K20 work without modification)
* column shift linkage (will the 79 stuff work without modification)
* cooler lines (really not a biggie in the grand scheme of things)
* speedo cable (will it hook up OK)

I may have tons more questions.......AND I told him I would post the question here and that you guys were the absolute truck experts!!!!!!

Thanks a bunch!!!

Misled

[b454rat]

I'll see if I can answer some...

* u-joints (are they all the same)

The older truck should have 1350 joints in it, the newer will have 1310.

* crossmember (will the 79 one work)

The crossmember should work, just might need to be moved back or forth. Not sure of the length on these combo's.

* driveshafts (will ones from a mid 80's K20 work without modification)

The driveshaft on the older one will have a bolt on yoke. The newer will have a slip yoke. You could find a shaft off an 80's 3/4 4wd, but will need to change the u-joint off the t-case with a conversion joint. The front shaft should bolt up, use the one off the 208.

* column shift linkage (will the 79 stuff work without modification)

The stock column shifter will work, but won't be able to down to first manually.

* cooler lines (really not a biggie in the grand scheme of things)

Should swap over with next to zero issues. Might have to rebend just a wee.

* speedo cable (will it hook up OK)

Will hook up.

[Dooley]

Since the truck is an occasional driver, I wouldn't change a thing. If he is trying to increase mileage on this occasional driver then I would buy a top shelf part time kit for the 203 and a set of free wheeling hubs. Does it have 3.73 or the 4.10 gears?

[Misled]

Dooley,
There are issues with the 203 internally that will require it to be removed regardless. If we gotta pull it, we might as well use the 208 since we have it and it and the trans were rebuilt recently.

I believe it is a 4.10.....

Thanks,

Misled

[Dooley]

Originally Posted by Misled

Dooley,
There are issues with the 203 internally that will require it to be removed regardless. If we gotta pull it, we might as well use the 208 since we have it and it and the trans were rebuilt recently.

I believe it is a 4.10.....

Thanks,

Misled

I was unaware of the transfer case problems. Right, why you have it out it would be a good time for an upgrade!
While you will have to do a few small mods, it will not be the changeover from below!