TH350 to 700r4 swap

[R8rPhan]

So the truck I bought and have started restoring is a 73c10, that someone at some point put a 327 in.. It currently has a TH350 in it, but I have future plans to add TBI and a 700r4 to get the gas mileage under control..

I have a friend that has a 700r4 mated to a aluminum transfer case that came from a post 84 chevy truck...

He says it is good as he was using it in a truck of his when he pulled the truck apart to build something else...

What I need to know, is how do I convert the tail housing to fit in my 2wd C10?

Is it simply a matter of unbolting the tail housing and output shaft from my existing TH350 and bolting it on the 700r4 once I remove the txfr case, or is there more to it than that?

Will I have to modify the drive shaft, or will the final length of the 700r4 with my old tail housing be the same length as the TH350 is now?

What am I in for here, so I can start accumulating parts and knowledge in advance of the operation?

Thanks,
Mark

 

[74 Shortbed]

To change the output shaft it has to come apart, there's a snap ring that holds it in, not a big deal just a little time, driveshaft will need to be shortened but you can use the yoke it is the same spline as the 350..

 

[R8rPhan]

To change the output shaft it has to come apart, there's a snap ring that holds it in, not a big deal just a little time, driveshaft will need to be shortened but you can use the yoke it is the same spline as the 350..

What else will I need too to plan for?

 

[1987 GMC Jimmy]

You'll need to move the crossmember back three inches in addition to the aforementioned. Also, if you're running an aftermarket carb, you'll need to get a geometry correction kit to run the TV cable.

 

[74 Shortbed]

350 is 20 3/8"

700 is 22 1/2"

 

[1987 GMC Jimmy]

Sorry. I've read from from multiple outlets with corroboration by various individuals about the three inches. You're more experienced and you outrank me here so I defer to your judgment. Again, my apologies.

 

[74 Shortbed]

the mount is only 3/4 inch off according to this...

https://s-media-cache-ak0.pinimg.com/736x/bb/7d/18/bb7d1885f430ae0619bed45f631376a5.jpg

If you look carefully the measurements are case length not to center of the mount, it's about 2" difference to the center of the mount.

http://www.tciauto.com/tc/trans-dim/

 

[74 Shortbed]

the pic shows center of the mount to me that's what the lil oval thing is in bottom of the pic they are going from bellhosuing to middle of the mount.

23 on the 700 compared to 22 - 1/4 on the th350


I don't have a 700 here to look at and compare just going by that, at one point I had both to compare and check but it's been too long ago for me to remember what the difference was in mounting locations

You are right, the oval represents the mount but as I said, in your pic(I've had that forever and been confused by it before)the line is not in the center of the mount it is at the end of the case take another look, TCI's pic line "C" is in the center of the mount compare those numbers. And besides, I done a couple before and I'm doing one now in my Nova that's how I know, if I wouldn't have done it before I wouldn't have said ****, because I don't believe everything I here or see, only my experience...

 

[74 Shortbed]

Both are correct, I measured them.

 

[R8rPhan]

You'll need to move the crossmember back three inches in addition to the aforementioned. Also, if you're running an aftermarket carb, you'll need to get a geometry correction kit to run the TV cable.

I am running a carb now, and plan to replace it with a TBI (probably the FiTech unit).. but not sure which will come first the TBI or the tranny...

What do I need to get for that, to make the TV cable work right?

Also, does someone make an aftermarket cross member for the conversion, or is that so expensive, I'm better off making one myself?

I had to have a custom one made for my bracket racer way back when (62 chevy II), when I took out the straight six and put in a small block with TH400, and it was a PITA....

 

[74 Shortbed]

All you need to do is slide the crossmember back in the truck, can't do that in the Nova because it only bolts in one spot, I had to get one for mine when I put the 700 in..

 

[R8rPhan]

All you need to do is slide the crossmember back in the truck, can't do that in the Nova because it only bolts in one spot, I had to get one for mine when I put the 700 in..

Are there like bolt holes there already, or do I slide it back and drill new ones, or what?

 

[74 Shortbed]

There's a few holes already there since there was different options for trannys, didn't have to drill any in my 74, your's should be the same I would think.

 

[1987 GMC Jimmy]

I am running a carb now, and plan to replace it with a TBI (probably the FiTech unit).. but not sure which will come first the TBI or the tranny...

What do I need to get for that, to make the TV cable work right?

Also, does someone make an aftermarket cross member for the conversion, or is that so expensive, I'm better off making one myself?

I had to have a custom one made for my bracket racer way back when (62 chevy II), when I took out the straight six and put in a small block with TH400, and it was a PITA....

I can't tell in your pics if you have an Edelbrock or a Holley, but if you put the 700R4 in there, you'll need to get the respective carb manufacturer's geometry correction kit, which is only a few bucks. It just bolts onto your throttle arm and makes it so the TV cable isn't being pulled at an angle. It'll be Edelbrock 8026 or Holley 20-121 depending on which carb you have. If I was a gambling man, I'd guess Edelbrock.

 

[HotRodPC]

I know I'm late to this party but I'll put this up. If it's accurate, and I have no reason to believe it isn't it'll be a big help to whoever find this thread. It also has measurements to the center of the trans mounts from the face of the bellhousings.