standard to automatic

[Geos 72]

Hello to everyone out there, I have a 72 Chevy C10 Cheyenne that was an originally a 6 cyl. with a manual three speed tranny with the shifter on the column. Before I bought it who ever had it put a 350 in it (bored out to 30 over) and put the shifter on the floor. At first I didn't mind the shifting but now I'd like to switch it over to automatic. I realize I have to get an automatic tranny, an automatic steering column w/ the linkage, transmission lines and probably a different radiator since the one that's in it doesn't have any tranny line hook ups. I thought of using a transmission cooler but two transmission shops that I called told me they would not recommend using a cooler, they said the radiator would be much better. Has anyone out there ever done this? Am I going to be sorry I even tried to do this? The truck is in pretty nice shape but it's no show piece. I sure would appreciate any advice. Thanks, George

[SeniorVerde]

I would use a radiator with the provisions for trans hookups AND a tranny cooler.
You might have to also make or find a correct crossmember to go with the new tranny.

There is also the potential that your new trans will be a different length than the old manual and you may need to have a different shaft made to match the new length/splines of the new trans.

I'm currently working through these issues on my own truck converting from a 4 speed to a TH400 auto. New Radiator, Crossmember, drive shaft with carrier bearing, trans cooler and lines, and the throttle position sensor from a donor truck so kickdown works again. Th400's use electric kickdown, TH350's use a cable, Overdrive stuff have their own tricks.

I have no strong preference to stick/auto, but I have a bunch of TH400's and it's easier to bolt 'em in and out not worrying about clutch alignment, clutch pedal throw adjustment, throwout bearings...

[hamjet]

Hi, as far as the steering column, its alot of unnessisary work if you don't mind looking at the old manual shift part on the column, (after all you've been looking at it this long), I'd get a nice automatic floor shifter for it. you already have a hole in the floor anyway. As far as the trans cooler, I personally would use a cooler in front of the rad. unless your rad. is in shabby shape. I've done it on a street strip nova I use to have and never had a problem. If they didn't work all your speed shops wouldn't be selling them...Good luck in which ever way you end up going....OH MAN< I JUST GOT BEAT OUT BY SENIOR V!!!!!

[MARKDTN]

A TH350 is the same length as the standard 3-speed and likely has the same yoke. You can fab a crossmember pretty easily, or find a used one. Non-tilt auto columns are not that uncommon, but you need the whole linkage which can be harder to find. I would buy a new radiator with cooler in it OR if it is in really super nice shape a good radiator shop can swap the tank to one with a cooler. You can find lines in later trucks or cars or just get a new set from one of the vendors. You could use an add-on trans cooler, but I would not use just that alone. There is a reason that the cooler is in the radiator from the factory. If you want another cooler in front of the radiator too, that is OK.

[Geos 72]

I'd like to thank all you guys that responded to my question. Thank you for your input and your advice but with everything I heard today I think I'll just leave it the way it is. I do have other issues with the truck which are more important. Thanks to everyone again, George

[oldschool18]

I just did this swap and its pretty easy, I used a 350 turbo I had laying around and had it rebuilt and it fit like a glove. And I added a 350 motor and a 4 core rad to keep everything cool, I don't have any of it running yet but it was easy to do.........If its something you wanna do down the road just slowly start getting stuff when you can or when you come across a good deal.

[70cst]

Originally Posted by Geos 72

I'd like to thank all you guys that responded to my question. Thank you for your input and your advice but with everything I heard today I think I'll just leave it the way it is. I do have other issues with the truck which are more important. Thanks to everyone again, George

Good decision ...

Its best to take one step at a time.

[Steve Cole]

How about the wiring harness? If he had a manual tranny, then the harness wouldn't have wiring for the neutral safety switch would it?

[MARKDTN]

Originally Posted by Steve Cole

How about the wiring harness? If he had a manual tranny, then the harness wouldn't have wiring for the neutral safety switch would it?

That would be handled with the auto column.

[Steve Cole]

The steering column doesn't have the wiring for the neutral safety switch. Don't those come off the back of the ignition switch?

[Tx Firefighter]

You'll also need to deal with the starter. 72 models with standard transmission had the starter mounted to the bellhousing with three bolts. Automatics mounted the starter to the block with 2 bolts. You can either swap the entire starter or just the nose cone. Your choice.

Original standard transmission type of starter nosecone.



Comparison of the two. Standard on the left, automatic on the right.

[71tahoe]

Originally Posted by MARKDTN

A TH350 is the same length as the standard 3-speed and likely has the same yoke. You can fab a crossmember pretty easily, or find a used one. Non-tilt auto columns are not that uncommon, but you need the whole linkage which can be harder to find. I would buy a new radiator with cooler in it OR if it is in really super nice shape a good radiator shop can swap the tank to one with a cooler. You can find lines in later trucks or cars or just get a new set from one of the vendors. You could use an add-on trans cooler, but I would not use just that alone. There is a reason that the cooler is in the radiator from the factory. If you want another cooler in front of the radiator too, that is OK.

A transmission cooler in the radiator is also a warmer in the winter. For a New York winter you should run any auxiliary cooler before it goes into the radiator so the fluid is at a working temperature.

Originally Posted by Steve Cole

The steering column doesn't have the wiring for the neutral safety switch. Don't those come off the back of the ignition switch?

Column would supply the switch but it might have to be spliced into the ignition like mentioned. I'm sure someone on the board has a schematic



Also, the existing crossmember at the bellhousing must be removed. (Might have been mentioned but I didn't recall seeing it.)