The Stovebolt Site Forums The Shop Area Engine Shop I want an automatic transmission

1958 chevy 3200 - 235 3 on the tree.

I drug the ol' truck home last March after not running for 15 years.

I replaced the rear main seal, carb, fuel pump, oil bath filter with a spin on, new roller bearings & power brakes.

Now that it runs & drives reliably, stops safely & I'm not worried about getting stuck somewhere.

I want to keep the 235 & bolt in an automatic trans. Since it is a 3 on the tree there are no holes in the floor for the shifter & I don't want any.

so the question is - what does it take to do a swap of this type?

I assume I will need a new steering column with the shifter. I may convert to power steering while I have it apart - but that is a different post.

I have never worked on a clutch or transmission - removal seems straight forward - but putting it back together correctly I'm worried about.


Is there a website that goes through this.

Do you want an original automatic or a modern automatic?

The Hyrda-Matic was an option with the 235 when your truck was new. One option you have would be to replace the 3-speed and column shift with a Hydra-Matic and the factory type shifter.

If you desire to run a modern automatic you need an adapter plate such as available from Stovebolt Engine Company or Buffalo. You can find Buffalo on the inliners.org site. I'm sure Stovebolt Engine Company comes up on google easy enough.

You can easily convert your 3 on the tree shifter to work with an auto trans. You'll want to disable the 1st and reverse stuff in the shifter box. Then you can make linkage to go from the 2nd - 3rd shifter arm to go to the transmission.

If you're not happy with your axle ratio, this is the time to think about a 700R4.

I am thinking about going this same route on my 59 Apache 235/3spd. Does anyone know a good way to hook up that 700R4 TV cable to an old 1 barrel carb?

It's not that difficult as to geometry (sorry, I can't tell you the exact pieces).
1. find the length of travel the 700R4 cable makes between idle and WOT.
2. is there a part of the existing linkage that moves that far (sometimes an existing arm can simply be extended)?
2a. if yes, does it go the right way (push or pull)?
2b. if no, try to find a linkage point (hole, bushing, stud) that is easy to reach, away from the carb and manifold as much as possible. Measure the travel the same way.
3. compare the distances - this is your leverage ratio. Example: the 700 moves 4", the throttle moves 3". You need a lever in the same plane as the carb shaft that with 2 link positions (holes, studs) in that ratio: 4:3 (the arm operating the 700 must move faster than the link from the carb). Use Heim joints or ball/sockets rather than "L" shaped ends or clevises, and allow some adjustment for length in more than 1 place.
If the useful carb bits move the wrong way, the link should be a bell-crank with opposing arms to reverse the 700 motion, etc.
Sometimes you just can't get the lengths right, and the trans cable moves too far. In this case, use a small spring and some slack distance.
4. return spring operates at 90° to the link

You can keep both the factory shifter and column with simple modifications. Pop the access plug off the top of the shifter arm box at the lower end of the column, wipe away the grease, have a helper hold the shift lever in the low-reverse position and through the access hole weld the tang of the selector to the notch in the shift arm. The low-reverse position is a more natural feel for an automatic than having the lever way down near the dash in the second-high position. For power steering the column will have to be cut leaving the shaft several inches longer than the tube so the new linkage to the p/s box can be attached. A bearing/bushing is fit to the shaft and inside the tube at the bottom and a linkage rod is run from what used to be the low-reverse arm to the selector arm on the automatic. The bottom of the column also has to be anchored. I have several pictures of this on my photo site which show the floor anchor, the bottom of the column bushing held in with a set screw, and a finished picture which shows a safety switch which only allows it to start in park. Scroll down to the last three pictures in the 2nd row. http://s32.photobucket.com/albums/d41/coilover/

YOu guys are something else - Thanks for the advice - time to start reading up.

A couple of more things to consider. Your 235 mounts on the sides of the engine at the very front, and at a very strong cast iron bellhousing where it sits on a crossmember. The 3 speed trans then cantilevers off the back of the bellhousing A modern automatic mounts at the very rear, not at the bellhousing. That's a lot of weight to hang between the front mounts of the engine and the rear transmission mount. I'm sure someone's got the answer. My thoughts would be to side mount the 235 at about the middle of the engine, and use the rear trans mount with a new crossmember. Or use the front mounts of the engine and figure some way to mount off the newer automatics bellhousing using the original? crossmember. Both of these options require some fabrication. The Tom Langdon adaptor get's the engine and trans connected, I didn't see where it addressed mounting in a vehicle. I did not look at the Buffalo adaptor.

John