I installed the under dash control for the 2 speed Rear on the 48 2 ton. Then the little rear box on the back of the speedo and the linkage. Everything went together fine. Tonight I was going through the factory assembly manual and noticed that the drawing showing that assembly had the gear box inverted and the linkage arm on the drivers side. I installed it with the linkage on the passenger side because that seems to be the only way the linkage connected.
Can anyone confirm how it is installed in a working truck?
just getting ready to install mine today. Like you I though the shifting arm would go toward the right side of the vehicle. If memories correct, that's how I removed it.
Wait, so are you guys saying that there's actually a gearbox that changes gears for the speedometer? I don't remember seeing anything like that on my truck. I'd been wondering how they handled speedometer accuracy with the 2-speed rears. I'd be curious to see pics as well, if anyone comes up with them.
Jim, I am assuming yours is not shifted by vacuum but by a cable or piece lf linkage? this is what the one on my 56 and 58 2-tons look like. Paul, it is on the back of the speedometer. http://www.ebay.com/itm/Speedometer-Adapter-GM-Truck-Chevy-Gmc-Stewart-Warner-/262228800301?hash=item3d0e0df32d:g:R4MAAOSwwPhWjobL&vxp=mtr
Thanks for the link. I'll have to look for that and see if my system is complete or not. I noticed that the speedo cable is not connected to my tranny, and was just dangling. That's as far as I've gone, presently.
I'm assuming that the dash mounted control like Jim's would indicate a mechanically controlled speedo adapter, and that mine will be vacuum controlled since I have a shifter-mounted rear end control. If so, then sorry Jim, I'll be of no use to you.
For what it's worth, I found a video of the vacuum version operating on a bench after repair. It seems like it should be easy to swap one of these into a previously mechanical truck if you can't get your mechanical linkages figured out. You still have the vacuum switch for the rear end, right? You could probably just tap into the appropriate line (low?) and screw this onto the back of your speedometer.
That's lame! Probably my fault though; I had the audacity to leave a comment asking a couple questions about his diaphragm repair. I guess he didn't want to put up with the hassle.
I did run across a thread from '08 where someone had mentioned using a vacuum advance actuator. Of course, all photo links were dead. It couldn't be too hard to rig something up though.
I ventured out and looked under my dash, no such mechanism to be found. My guess is that they were too lazy to do the cab swap properly. I guess I'll be using a GPS for speed.
