Replacing TH350 with 700R4

[73camperspecial]

I bought my son a 73 C20 camper special for his first truck. It is an everyday driver to school and back. We have replaced the engine with a GM crate engine and before we started, it was recommended since I planned to have the transmission re-built, that we should upgrade to a 700R4 for the added gas mileage. So I did. Engine is in trany bolted up. Now the rear mounting bracket for the transmission is lower than the cross brace and if I jack it up to try and get the brace under it hits the underside of the cab. To me it seems that the engine is tilted back farther than the original. To my question , Did I do something wrong when mounting the engine or is the upgrade not going to work in this truck or will I need to get or have made a new cross brace.

 

[HotRodPC]

If I'm understanding correctly, it would seem to me you just have the wrong trans mount. The transmisisons are basically the same dimensions but about a 1/8 difference in length since you're original Th350 should have been the 9 inch intermediate aka long shaft right? Actually should even use the same trans mount, crossmember and all.

 

[HotRodPC]

VERY IMPORTAT SO YOU DON"T FRY THE TRANS. Be sure to hook the TV (Throttle Valve) cable up for the 700r4 to the carb linkage. If you don't you'll burn up the trans. So be sure to hook it up right, and adjust it right.

Maybe a pic of the underneath of the truck will help with some suggestions. Don't go for the real close up, back off of it a little bit to take the pic so we can see the whole picture of what's going on there.

 

[89Suburban]

Boy that's a luck kid, got any pics?

 

[73camperspecial]

If I'm understanding correctly, it would seem to me you just have the wrong trans mount. The transmisisons are basically the same dimensions but about a 1/8 difference in length since you're original Th350 should have been the 9 inch intermediate aka long shaft right? Actually should even use the same trans mount, crossmember and all.

Ok thank you I will make sure the mount is the correct one and yes I have the TV cable to hook up and get some pics posted next time we are working on it.

 

[73camperspecial]

Boy that's a luck kid, got any pics?

We bought it localy from the original owner. I think the bed has been changed out . It has doors for the gas caps not sure what year that started.

 

[89Suburban]

Dayuumm that is nice!!!

 

[foamypirate]

My 84' TH350 cross member was different than the 87' 700R4 cross member I have. I tried to use the TH350 x-member with my 700R4 in the 84', but ended up needing to use the 700R4 x-member. You probably need to track down the 700R4 x-member.

 

[Stroked]

That's a great lookin truck!


Sent from my iPhone 4s using Tapatalk

 

[bucket]

That's a purdy truck!

My 84' TH350 cross member was different than the 87' 700R4 cross member I have. I tried to use the TH350 x-member with my 700R4 in the 84', but ended up needing to use the 700R4 x-member. You probably need to track down the 700R4 x-member.

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

 

[83K5guy]

Dang nice truck for your son. Glad to see some people still getting there kids a real vehicle and not the bs brand new cars now days.

 

[Driver4r]

83K5guy, I bought Myself a 76k10 and did all the work myself for a DD to school.

Nice Truck, and i will also be going to a 700r4.

 

[83K5guy]

83K5guy, I bought Myself a 76k10 and did all the work myself for a DD to school.

Nice Truck, and i will also be going to a 700r4.

The world needs more people like you and the OP. Kids now days want everything given to them and the want the new and best of the best.

 

[Driver4r]

The world needs more people like you and the OP. Kids now days want everything given to them and the want the new and best of the best.

I have to admit tho, the newer stuff gets better gas milage(compared to my 6).
But i also have more power.

 

[Mr Clean]

I went from a TH350 to a 700r4 and I had to drill new holes in the frame. I thought I had some pics, but I don't. All I had to do is, I used the rear hole on the frame, and the front holes on the cross member, and just drilled new holes in the frame for the rear holes of the cross member. I did have to trim the front lip of the cross member, so I could get access to the bolts in the rear of the pan.

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