700r4+np208 swap

[BarkinBarnacle]

Hi guys & gals,

I've got a '75 3/4 ton that I want to upgrade a bit and breathe some new life into the ol girl.

Sadly she lost her 400sb in the 90's for a 350 4bolt, Just your usual bolt ons.
She has a turbo 400/203 combo right now but I am looking to upgrade as I have a built 700r4 from an 86 with the 6.2 laying around as well as a np208 .
Any noteworthy differences minus the torque converter for the diesel application?

Im aware that I would have to change driveline/crossmember and a few other things.
Has anyone done this? Kits?
What about the floor shift?

Any info or links are greatly appreciated!

Cheers!!
Edit. Sorry tk those who read 205. I have a 208 kicking around. Not 205 :/

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[Frankenchevy]

Any noteworthy differences minus the torque converter for the diesel application?

Governor springs and weights. A trans set up for a diesel will WOT shift way early unless you swap the governor parts.

 

[BarkinBarnacle]

Governor springs and weights. A trans set up for a diesel will WOT shift way early unless you swap the governor parts.

That makes total sense. Made a note and I'll contact the local shop to order the proper set up for a gas job [emoji106]

Thanks!

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[PrairieDrifter]

That makes total sense. Made a note and I'll contact the local shop to order the proper set up for a gas job [emoji106]

Thanks!

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Personally I would keep the 400 and add a 205 behind it. Ditch the 700, depends on what you use the truck for too.

 

[BarkinBarnacle]

Personally I would keep the 400 and add a 205 behind it. Ditch the 700, depends on what you use the truck for too.

Not counting that out as a possibility if too many issues are encountered,
Intentions for the truck are daily driver/toy/wood hauler. She may have a flat deck in her future also dependent on how this idea goes haha

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[PrairieDrifter]

Not counting that out as a possibility if too many issues are encountered,
Intentions for the truck are daily driver/toy/wood hauler. She may have a flat deck in her future also dependent on how this idea goes haha

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I think cost wise and reliability/strength wise, the 700 is the least desirable here. You'll have to do a tv cable and bracket which can be tricky depending on carb then you'll need the wiring harness. Plus throw in moving crossmembers, different input and out put shafts, transfer case adapter can be a challenge. Just a whole list of things, all for a less reliable trans. The overdrive is nice, but I worry about my 700 everyday I drive it lol.

400 to a 205 is a much easier less complicated swap as you are already setup for a 400, you will need driveshafts modded most likely, then the adapter for that combo is easier to find as well. You can find conversion couplers from sites like ORD.

Then of course you'll have to swap out to manual hubs on the front axle if you don't have a part time 4wd kit already.

 

[Turbo4whl]

What is wrong with the 203 transfer case?

Cheers!!
Edit. Sorry to those who read 205. I have a 208 kicking around. Not 205 ...

I could see going to the 205 as an upgrade. The 208 is another chain drive. The 205 is gear drive.

 

[Big Chip]

Someone else already said this on another thread but....

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[Frankenchevy]

Lol...I don’t swear by my 208, but I guess it was good enough for a military grocery getter. So, does that make me bi-curious or something?

 

[Big Chip]

Lol...I don’t swear by my 208, but I guess it was good enough for a military grocery getter. So, does that make me bi-curious or something?

Ha, probably! Just to be clear, that was someone else’s meme but it was too hard for me to pass up.

 

[BarkinBarnacle]

I think cost wise and reliability/strength wise, the 700 is the least desirable here. You'll have to do a tv cable and bracket which can be tricky depending on carb then you'll need the wiring harness. Plus throw in moving crossmembers, different input and out put shafts, transfer case adapter can be a challenge. Just a whole list of things, all for a less reliable trans. The overdrive is nice, but I worry about my 700 everyday I drive it lol.

400 to a 205 is a much easier less complicated swap as you are already setup for a 400, you will need driveshafts modded most likely, then the adapter for that combo is easier to find as well. You can find conversion couplers from sites like ORD.

Then of course you'll have to swap out to manual hubs on the front axle if you don't have a part time 4wd kit already.

Basically sounds like I've given myself a make work project and in the end not really gaining anything haha.

This is exactly why I came here for opinions and input [emoji106] Totally forgot about the wiring harness aspect.

I was/am still kinda stuck on the 700 idea solely for the fact that years ago I spent ( [emoji848]hmm... around 1g I vaguely remember) for a new to me / beefed up trans to handle the abuse I put my old 86 diesel thru

That being said I will definitely be looking into the part time 4x4 kits and exploring that option.

Cheers!

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[Larry Olson]

I have a rebuilt 700R4 transmission complete with torque converter cable and new cross member that I purchased from Jeggs that is brand new and never used. I would like to sell it for a reduced price.

 

[EvilGenius]

Don't let the wiring of the 700R4 scare you. It is only 3 wires. One goes to the brake pedal, one to the vacuum switch on the firewall, and the third goes to an EGR vacuum device (you can omit this part). All the wiring does is control when TCC lockup occurs in 4th gear.

You can grab a sub-harness out of a truck in a junkyard easily. One plug at the trans, one at the brake pedal, and one at the vacuum switch on the firewall (plus one on the passenger side head if it has the egr connection). There is a guy on here that makes harnesses that could probably make you one as well. I can't remember his name though.

 

[AuroraGirl]

@gmachinz