The Stovebolt Site Forums The Parking Lot Big Bolts Electric shifter for 2 speed differential

I was lucky enough to score an electric shift unit to replace my vacuum unit but I need a wiring diagram. Anybody have one? Also, I have converted to an automatic transmission. Will that cause issues?

Please don't double post.

3 wires go to your selector. A hot one and then the other 2 go to the shift motor. If you have a push pull switch, up is high axle. If you have a shift knob, to the left is low axle. I don't remember if the terminals are marked. If not you will just have to do it by trial and error. If you have a speedo adapter, splice it into the low axle circuit. Originally the hot wire came from the ignition switch, I would recommend going through a relay because you probably have all you can handle through the ignition switch. There is nothing to interfere with your automatic, but I don't think you will be able to split shift. I think you will have to start in low axle, let the automatic shift into high and then shift the axle into high.

I hope this switch to electric works for you. I have Eaton unit in an 85 chevy which always wanted to blow some component in the circuit board leaving me stuck in the range I was in at the time.
I pulled the unit out of the diff. and checked it and lubed it and it still happened 3 times in three years.
I concluded that it was a design problem.

Dan

The older electric shift units had points in them and no electronics. I'm not sure what year they changed from the points to electronics, but the old design was very reliable. If the points failed to make contact, they could be filed on the side of the road. I think the old style can be identified by having a 3 bolt motor and the electronic a 2 bolt motor. I think the early electronic units were not very reliable.

Hi,
I saw your post and thought you maybe able to help me. I have a '53 6400 2 ton with the 2 speed rear. Like you, I have blown the diaphram out of the vacuum differential shifter. Did your installation of your electric shifter work?
If so how did the installation go? Do you have a source for the shifter?

Thanks

Phil Stewart

I have a 53 GMC with a vacuum 2 speed. It is totally different than the electric shift box. I think the only way would be is to swap the whole rear end which would be quite simple. I haven't tried to shift mine. I had a vacuum leak so I just plugged the line at the intake manifold and put the axle in high range. I don't need a two speed because I have a GMC 270 and all I do with it is haul trash. It has a dump bed similar to yours. One of these days I have intentions of chasing down the vacuum leak. I assumed the post made by 59Shorty indicated that he had found a complete electric rear end and was wondering about the wiring.

It's been many a year since I worked on those but I don't think the drives will interchange. The electric were a lot smoother shifting.