Th350 to 700r4 swap

[baddawgcustoms]

I have a short shaft th350c trans I am using to mock up the trans mounts, but still have the idea of using a 700 in the end. My question is if the th350 and the 700 would mount the same. I just don't want to spend the money right now on the 700 but I want to finish up my frame/trans mounts and decide between the 2 later, and I'm sure somebody has done the swap to know. Thanks ahead of time!

 

[PotvinGuy]

Just curious, why the 700? 350 or 400 or Power Glide are easy and cheap trannys for our little cars. And the 700 has the touchy TV cable complication.

 

[rbsWELDER]

Does the 700R4 come in a short output end like the 350?

 

[Screaming Metal]

TH-700R4 Basic Information
http://www.hotrodders.com/articles/TH-700R4_basics.html

 

[Indycars]

I have a short shaft th350c trans I am using to mock up the trans mounts, but still have the idea of using a 700 in the end. My question is if the th350 and the 700 would mount the same. I just don't want to spend the money right now on the 700 but I want to finish up my frame/trans mounts and decide between the 2 later, and I'm sure somebody has done the swap to know. Thanks ahead of time!

With any other trans than the TH350, the mount with have to change by some amount. See dimension "C". If you use the 200-4R, at least the driveshaft does not change, the length and spline are the same as the TH350. See dimension "A".



The 200-4R has better ratios, but with more than about 300 HP, you will need to look at some stronger parts. All depends on the tires and how much traction you get. Suspect it would be the same for the 700-R4.

 

[2old2fast]

It seems that since we've entered the "world of overdrive" everyone thinks they need one .... I personally like the sound of humming down the road at 2500-3000 r.p.m. ....... but then again , I'm old
dave

 

[PotvinGuy]

It seems that since we've entered the "world of overdrive" everyone thinks they need one .... I personally like the sound of humming down the road at 2500-3000 r.p.m. ....... but then again , I'm old
dave

But our brains can stay young. Behind my bulletproof old 400, I changed my rear end from 3.90 to 2.60, hardly noticing the change around town, but cruise at 2000 rpm on the Interstate. And get better mileage.

 

[choppedtop]

I run 2000 rpm at 70 mph with the 700r. The rear end is a 3.53 with 29.5 rear tire diameter.
Lee

 

[Hotrod46]

You certainly don't need overdrive, but they're common enough in the salvage yards now that they are an option. My local yards are getting thin on 350's and 400's, but they're still around. The last 700 I had rebuilt cost about twice as much as a 350. The throttle valve issue isn't that bad if you understand it.

In my opinion, the only reason to run OD is so you can run performance gearing and still cruise at a decent RPM. If you don't care about that, then you don't need it. I drive my car long distances, sometimes as much as 500 miles a day, and I don't like the constant high RPM drone. The wind noise is bad enough. My mileage is about 20-21 on the highway. I don't think it would be terrible even without OD, but every little bit helps. I have 3.42 gears and if I didn't have OD, I would have to run something like 2.50's to get the same cruise revs.

 

[baddawgcustoms]

Thanks for those charts indycars, that's one definitely going in the ol notebook. Cruising rpm is my biggest reason for considering the overdrive, and my intentions are running lake pipes so the high rpm sound at 70+ is a consideration as well with the exhaust coming out pretty much in front of you. And thanks for everyone else's input as well. I already have a good 350 and the local trans shop I've known for years says complete rebuild for about $400 and it will be new and tough, and around $800 for a 70o i would still have to buy. As I said just wanting to keep my options open so it looks like all I need to do is make the trans mount adjustable a couple of inches. That's what I needed to know and you bucket heads always come through. Thanks!

 

[Indycars]

Thanks for those charts indycars, that's one definitely going in the ol notebook.

Glad all the work I went to for myself could also help someone else!