Replacing TH350 with 700R4

[Driver4r]

Clean, why did you use flex pipe? That stuff blows out easy.

 

[foamypirate]

That's a purdy truck!



What was different about it? I will also be going from th350 to 700r4, I was hoping to use the same crossmember.

If I recall, the area where the mount bolts to the cross member is offset forward or backward from one cross member to the other. You probably could make the TH350 cross member work, but I had the factory 700R4 laying around, so I decided to use it.

 

[Mr Clean]

Clean, why did you use flex pipe? That stuff blows out easy.

I had a friend misunderstand what I said when I was putting my truck together and he cut out a big ass piece of pipe on both sides, so that was a quick fix, that's been over a year and a half ago. Had plans on all new 2.5 exhaust, just haven't had the time.

 

[HotRodPC]

That's what the kid PO did to my 85 85K1500 too when he put headers on. So I have that flex pipe too. I'm actually surprised. So far it's holding up well. Thankfully.

 

[89Suburban]

They won't let us pass inspection here with that flex pipe.

 

[73camperspecial]

Thanks everyone for the great tips. We found a transmission mount at the auto parts store that was 1/4" or so thinner than the universal mount supplied by the transmission shop it was for a manual transmission had the same dimensions for bolting it on to the transmission housing and the holes to bolt it up to the cross member. We used the same cross member, and drilled new holes in the frame since the 700r4 mounts about 2” 1/8” farther back than the TH350. Hope to get to start it up later tonight, have to go and get new torque converter bolts since the 700R4 that we used requires metric bolts.

 

[woodsrider250]

So, in a nutshell, rough steps for converting a TH350 Square over to a TH700 are:

1. Remove TH350
2. Install TH700
3. Relocate Crossmember
4. Install/adjust TV cable.
????

I take it you lose 1st gear position at the lever, and 2 becomes "D" or 3rd?

 

[MrMarty51]

Nice pickup and nice job,letting the son help.

 

[HotRodPC]

So, in a nutshell, rough steps for converting a TH350 Square over to a TH700 are:

1. Remove TH350
2. Install TH700
3. Relocate Crossmember
4. Install/adjust TV cable.
????

I take it you lose 1st gear position at the lever, and 2 becomes "D" or 3rd?

5. Install Fluid
6. Go for a drive.

NO, you do not lose and gear position. You shift indicator is going to be off though. The 700r4 has further shift lever travel is all.

Actually I think 5 is going to be get your driveshafts worked over to fit. Might even be easier to find different ones from an OE 700r4 truck.

 

[woodsrider250]

Roger, thanks. I wasn't sure if the drive shaft needed modded, but then when glazing through this post (likely too quick) I was thinking that might not be the case. I am likely going to go this route, and would likely/hopefully source the trans/shaft/crossmember all from one donor truck.

 

[Driver4r]

Find yourself one of the telescoping driveshafts like what came factory on my 76.

 

[82chevy350]

He would have to have a solid since his dirveshaft slips in the rear of the trans. the telescoping is for 4x4s with the np203.

 

[HotRodPC]

He would have to have a solid since his dirveshaft slips in the rear of the trans. the telescoping is for 4x4s with the np203.

X2 Yep

 

[Driver4r]

Damn, i was wrong....
Atleast ill admit it.

 

[HotRodPC]

You wouldn't be wrong if he had a bolt on driveshaft instead of a slip yoke. In that case, what you suggested is exactly what he'd do.