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Looking at a ‘76 how easy to add OD?

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Fishwater2002

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I’m looking at a 1979 K5 and while I love the round eye style I’ll be driving it regularly so thinking I need to add OD (700R4) and I guess a NP208 while I’m there. I’ve read a few different threads and it sounds pretty involved with dealing with the four wheel drive selector linkage plus crossmember plus driveshafts. I’m actually pretty surprised that there isn’t a simpler option so wanted to throw it out there first for everyone’s opinion.

The funny thing is that I promised myself I wouldn’t go down this rabbit hole again and just wanted something simple to drive and enjoy but here I am :doah:
 
Fishwater2002 said:
I’m looking at a 1979 K5 and while I love the round eye style I’ll be driving it regularly so thinking I need to add OD (700R4) and I guess a NP208 while I’m there. I’ve read a few different threads and it sounds pretty involved with dealing with the four wheel drive selector linkage plus crossmember plus driveshafts. I’m actually pretty surprised that there isn’t a simpler option so wanted to throw it out there first for everyone’s opinion.

The funny thing is that I promised myself I wouldn’t go down this rabbit hole again and just wanted something simple to drive and enjoy but here I am :doah:
Click to expand...
It's actually a lot simpler if you do 700r4 with a np208.
You need the adapter plate for the throttle valve cable at the carburetor, easy enough to find and then a complete set of transmission/transfer case and shifter.
A slight adjustment of the tunnel for the shifter and you're done.
Other than driveshafts which at this age you probably need something done on the driveshafts anyway.
I put one in a 74 but I went the hard way and adapted it to the np203 which meant changing the output shaft in the transmission so I rebuilt it while I was there
 
Just buy an overdrive one.

You can build anything out of these trucks, they all bolt together like Legos. You don't have to though, just buy the right one and enjoy.
 
imiceman44 said:
It's actually a lot simpler if you do 700r4 with a np208.
You need the adapter plate for the throttle valve cable at the carburetor, easy enough to find and then a complete set of transmission/transfer case and shifter.
A slight adjustment of the tunnel for the shifter and you're done.
Other than driveshafts which at this age you probably need something done on the driveshafts anyway.
I put one in a 74 but I went the hard way and adapted it to the np203 which meant changing the output shaft in the transmission so I rebuilt it while I was there
Click to expand...
Seems like it’s pretty easy, every Chevy I ever owned was pretty easy when it came to aftermarket mods but I’ve read some pretty involved steps to get to what should be a simple end.
HankScorpio said:
Just buy an overdrive one.

You can build anything out of these trucks, they all bolt together like Legos. You don't have to though, just buy the right one and enjoy.
Click to expand...
Agreed, I’m a fan of the older round eyes but it’s so much easier to buy a newer one with TBI and OD done by the factory, they just don’t have the same look as the older ones.
 
HankScorpio said:
Just buy an overdrive one.

You can build anything out of these trucks, they all bolt together like Legos. You don't have to though, just buy the right one and enjoy.
Click to expand...

Fishwater2002 said:
Seems like it’s pretty easy, every Chevy I ever owned was pretty easy when it came to aftermarket mods but I’ve read some pretty involved steps to get to what should be a simple end.

Agreed, I’m a fan of the older round eyes but it’s so much easier to buy a newer one with TBI and OD done by the factory, they just don’t have the same look as the older ones.
Click to expand...

I think what he meant was that it is pretty easy to put a round eye front clip on a newer model
 

80's 700r4/np208 swap into 70's th350/np203 truck

Hey guys, I recently acquired a 75 full top K5 with a th350/np203 combo that I am starting to build. I also have an 87 K5 (that is being saved for a project later down the road) but will not be running for quite some time. Well, I would like to steal the 700r4/np208 driveline out of it, and put...
ck5.com ck5.com


 
fourwheelerjeff said:

80's 700r4/np208 swap into 70's th350/np203 truck

Hey guys, I recently acquired a 75 full top K5 with a th350/np203 combo that I am starting to build. I also have an 87 K5 (that is being saved for a project later down the road) but will not be running for quite some time. Well, I would like to steal the 700r4/np208 driveline out of it, and put...
ck5.com ck5.com


Click to expand...
Pardon my interruption… the link offers a pre 91 option, I have the trans and transfer case from Munepit (Jeff’s) 87 Suburban, likely a pre 91 but how do I make sure? I’m thinking I’m going to put it in my 68 K20.
 
bradshawtech said:
Pardon my interruption… the link offers a pre 91 option, I have the trans and transfer case from Munepit (Jeff’s) 87 Suburban, likely a pre 91 but how do I make sure? I’m thinking I’m going to put it in my 68 K20.
Click to expand...

from what I have seen it is 1993 and older use a TV cable and after 1993 use electronics to control shift; also the later ones have a lot more electrical connections
 
I’m pretty close to closing a deal on a ‘76 Jimmy so the OD idea will potentially be back on the table this winter. My plan is to drive it as is for the rest of this season and then do a swap in the winter but out of curiosity wondering how much mileage/drivabilityI’ll get by swapping out the original 350/203 combo. Correction it’s a T400 trans.

Currently the original numbers matching 400/T400/NP203/205(?) is in the truck which is pretty cool, this is going to be a weekend toy that never goes off road or driven as a daily commuter rig so it might not even be worth the hassle unless something is needing repairs which the owner is claiming that it does not. Does anyone have an idea on what they got as mpg before and after a swap like this? Just curious since I’m not buying this for mpg’s.
 
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In general, as has been discussed here many times, you don't recover money on upgrades/changes because of improved MPG, you do it to make the vehicle more useable and enjoyable. That being said, OD may be one of the most effective upgrades on the MPG front. Plus, the TH400 and NP203 are about the worst in that respect. Googling for '79 400 Blazer shows 10MPG. You're moving to an early/mid 80's drivetrain, which shows up as 13MPG, although that's based on a 5.7L. Let's call it a 25% improvement, which is huge.

So if you drive 3000 miles per year, at $4/gal, the fuel goes from $1200 to $960. If you spend $2000 on the transmission and trans swap, you break even in 8.3 years.

You also need to look at what gearing is in the truck. Some 3-speeds got rather tall gears. An OD trans lets you go deeper and the whole vehicle is more enjoyable, but of course it increases the investment.
 
If you're swapping a lot of drivetrain parts at once and MPG and reliability are big interests, you might at least weigh the option of an LS swap.
 
I don’t see which gear ratio, no RPO code listed except for the G80 locker, so I’m not sure but the 1976 brochure lists 3.73 or 4.11 for towing and this truck came with the towing “device” Actually it’s a pretty nicely optioned truck which is cool….

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