Help me choose a tranny

[sumran]

I would like to tap into the knowledge on the forum to help me select the best tranny for my project. I have read other threads, but the info I am looking for is scattered across several threads. My project thread is here:

http://67-72chevytrucks.com/vboard/s...d.php?t=446737

It currently has a TH350 and a 250 inline 6. I have secured a 305 motor for the project, which will get a modest build before install. No major horsepower or racing is intended. Just a nice street truck / cruiser. I believe the truck that is supplying the motor also has a TH350, but I have not checked. I was initially planning to have a 4-speed, but have abandoned that idea.

I am considering a swap to a 700R4 to add the overdrive, as I will be using the truck for interstate driving fairly often. I am not sure of the installation pitfalls of this conversion.

Additionally, I would like get some input on the good and bad of both trannys and pointers on what should done to them before install.

Thanks in advance for your input.

[N2TRUX]

Hands down the 700r4 is your best choice. Take a look at bowtieoverdrives.com for lots of good info. Personally if I were buying a motor to rebuild, I would do a 350 instead of a 305.

[sumran]

Originally Posted by N2TRUX

Hands down the 700r4 is your best choice. Take a look at bowtieoverdrives.com for lots of good info. Personally if I were buying a motor to rebuild, I would do a 350 instead of a 305.

I would have opted for the 350, but this 305 was too good to pass up. By the time I sell the parts I pull off of the donor truck and sell the scrap, I will make more than I spent; the engine and exhaust will be free. The engine already has headers and a hi-rise and it came with a very nice exhaust system.

Besides, I'm old and slow...

[sumran]

I live a few miles away from mud truck paradise. If my truck ever goes "muddin" it wouldn't be on purpose. I understand the thrill, just isn't my thing. Seems the mud truck guys up the road are very fond of the TH350 and don't much care for the 700R4. I'm told the jump between 1st and 2nd gear is a little severe at wide open throttle if you are hub deep in mud. And they don't get much benefit out of the overdrive gear. All of which may work out well for me.

I just talked with a guy that does lots of work for the mud truck guys. He gets a steady stream of trucks and parts which he converts into mud trucks. When he gets one in that has a 700R4 his customers frequently want to change it to a TH350. I have one TH350 that is a runner and another that is a rebuilder. It looks like we are going to be able to work out a swap that will leave me with a nicely built 700R4 and the appropriate drive shaft in exchange for my two 350's. I have to read up on how I want the 700 to be configured. He may want my straight 6 motor as well.

I need to work through what a fair swap would be for all the parts and pieces, but it should work out that I can get what I want with no cash outlay and get some good contacts for parts of the work that I don't want to mess with.

[sumran]

A couple of dumb questions:

1) The tranny I pulled out of my truck is a 700R style. It has an electrical plug that connects on one side and the the TV cable on the other. There is no indication of overdrive on the shift indicator or the shift lever. Is this a non-overdrive version of the transmission? I was told that a 700R is non-overdrive and a 700R4 includes overdrive. Did not find a definitive answer online.

2) I will be installing a 700R4. Will this require a new steering column? Do I need to change the shifter linkage? Did all vehicles with an overdrive have switch to turn it off or a shifter with a D3 selection?

OK. That was more than a couple of dumb questions, but they are in two groups.

[csb#356]

A th350 has a kickdown cable which might be what you are seeing and the plug might be for the lockup converter.

[lindstromjd]

Well, first, what does the transmission oil pan look like? If it looks like it's got a corner cut out of it, then it's a TH350. If it's a big rectangle, then it's a 700r4. Never heard of a non-overdrive 700r4, btw.

You will not need to change anything on your truck to install the 700r4 except for the transmission cross member. And that's as easy as moving it back a few inches and drilling some holes in the frame. Some trucks even have the holes already in them. The driveshaft SHOULD be the same length. But, it depends on what tail shaft you have on the TH350. If it's a short shaft, you'll need a longer DS. If it's a "standard" 6 inch shaft, it will be plug-and-play swap. If it's the long shaft 9 inch, then you'll need a shorter shaft. Most trucks came with a standard shaft TH350.

The steering column works fine; you'll just have an extra gear down below "1" that is your actual 1st gear. All the shifter linkage hooks up, and the shifter detent has the same spacing between gears. No need to worry about that.

As far as the lockout torque converter... Are there any junkyards close to you? You could scavenge all the parts you need for that from a 3rd generation Camaro or Firebird. Basically you need a switch for your brakes that supplies constant power to one of the terminals on the 700r4. When you push the brakes, it should take power away, and that controls your lockout. It's the simple way of doing it, and makes it so it only locks out in 4th gear.

The TV cable is the tricky part. Gotta make sure it's set up perfectly, or you'll blow the transmission quick fast and in a hurry. Bowtieoverdrives is a great source for all this, too.

[sumran]

Definately a square pan. No modulator. I have a TH350 from the other truck sitting right next to it. I had never heard of a 700R that wasn't an overdrive, but I am continually surprised by what I dont know. The guy that was going to do the tranny swap told me that they made a non-overdrive version.

I have spent too much time on bowtieoverdrives ( I don't know which is worse, the drool or the confusion). I have also spoken with Steve. That was before this question came up.

I was planning on ordering the TV cable from bowtieoverdrive, once I settled the carb install.

[lindstromjd]

Originally Posted by sumran

I have spent too much time on bowtieoverdrives ( I don't know which is worse, the drool or the confusion).

I feel the same way. I think I had to read the same thing about 10 times before I finally understood what it was trying to say for the swap. I still haven't done mine yet, but plan on it in the near future. I love my old truck, but a TH350 just doesn't do me any good when it comes to fuel mileage. I need an overdrive. And a turbo, come to think of it...

[sumran]

I spoke with Steve at Bowtie. He verified that I got bad infomation. All 700R trannies have overdrive. However, he thought, based on my shifter setup, that the transmission I have may not be original to my truck. My shift indicator only has "D", "2" and "1". I should have "D", "D3" or "3", "2" and "1".

I need to figure out what I need to change on the column and the linkage to give me the correct shifting options.

[sumran]

Well what do you know. I did have a overdrive shifter in my truck. In my defense, the indicator doesn't work, so I didn't look at it. But after my conversation with Steve today, I checked it when I got home.

So, I already have the right tranny, drive shaft, shifter and (since it was a six) a slightly higher stall on the torque converter. I think I will order the Level 2 rebuild kit from Bowtie and that will do it.