i've always heard it referred to as a 2 speed rear

that sounds exactly like one of those

 

lol, I keep thinking selective something or other but nothing comes to go with it.

 

I've heard them referred to as Auburn's (dual ratio), as I think Auburn was one of the original inventors. But that's a name associated with a lot more now.

 

Sorry Rivers. I can only remember the 3 spd column shift, 4 and 5 spd manuals in the Trashers. There were OD units avail with the 3 spd column units, and the automatics were Chrysler 727 auto's they used behind the engines. There were some 904's behind the 6 cylinders and the half cast 152s (4 cyls in the Scouts)

I do not remember a 2 speed swap in the light duties, but 500 series up had them as options in some instances.

 

That said, there were after transmission add on OD units available and used in some trucks in the last 50's early 60's/ They bolted between the transmission and the driveshaft to the rear diff. I'm wondering if that is what you were describing Rivers.

Wait, I forgot about a Planetary reduction drive. They were out back then too. Hard as hell to find anymore, but I would bet 10 to 1 that MSI in Fairbanks (where I was helping) has one or two back in the old buses. I never saw so much old mechanical couplers and gear units. Lots of old Cat parts too Lots of stuff that will NEVER see the light of day again. lol

 

Underdrive and overdrive ?

https://www.gearvendors.com/index.html

 

AK, Underdrive would be what I'm trying to find out about for IH. I assume under and overdrives would work the same way except for the switch in ratios. Check that, I expect overdrive would work automatically somehow where the underdrive on the IH Travelall I had required the transmission to be stopped and in neutral to be activated. That could very well have been more as a safety feature than a necessity. I suspect activating it while rolling would be the same as slamming on the brakes.

I'm not looking for one of these units. I'm trying to remember - figure out - find what IH called there optional system. I just thought someone here and you mainly from your comprehensive parts experience might know what IH called the system. As I said earlier, today it's been like that song you can't get out of your head. I appreciate your response. A week from now when I'm not thinking about this at all, it will probably pop in to my head for some reason. Oldtimers again? But jeeez, I'm only 65. lol Brew might know but he's ignoring me over Skylar Jr.

 

My friend has one of their OD's to add on to his C6 in his Lincoln Continental.


Whoooa.....

 

Rivers........

Four-Speed Internal-Underdrive Transmission

 

he needs another good brake video