I have a "67" F600. Last fall it started slipping out of gear (the two speed) when the rear end had no torque applied. Under load or decelerating it never slipped out. I think it was the low side that was slipping out. The high side has never slipped out. I'm sure it is the two speed because I put a lower geared rearend in it but used the same two speed unit. It is an eaton (electric) not sure of the model.

 

Welcome to FTE.

So it will slip out into a false neutral? How do you get it to engage--shift it to high?

You will probably have to take it apart again:

http://www.google.com/url?sa=t&rct=j...66330100,d.b2U

 

You may want to check the control box first, its whats mounted to your trans shifter, and it could be the two speed shifter in the rear, there are 2 sets of points in it, they can go bad.

 

That is what I was planning to do today. I'll let you know what I find. To reengage the rearend, all I would do is match up the rpm s and it would lock in.

 

How are you shifting the two speed? You can't just shift them like a transmission.

Post 5 here has video from Eaton on how to do it.

https://www.ford-trucks.com/forums/1...-problems.html

 

I understand how two shift a two speed rearend. Not entirely sure how they work but I'm starting to understand. I took the two speed unit off of the rearend tonight and I think that the motor is smoked. And, yes the points were corroded. Where do I get one of these old things? I have a few number off of the 2 speed but I can't be for sure that they are the model numbers. Any help is appreciated. I'm still not sure why the rearend was slipping out of gear. Somebody mention a false neutral above and that is a good way to describe it. As soon as the torque on the rearend was removed it would act like it was in neutral. All I would have to do is match up rpms and it would go back into gear. Not sure if the two problems are related as I don't understand completely how the thing works. All I know is it is nice when they do work.

 

IIRC without looking at the diagram, I think they are a planetary gearset in place of a regular ring gear. Thus, you have a regular ring and pinion set up, but inside the ring gear is this planetary set that runs at the lower (or is it the higher?) ratio when engaged. Thus, if the speeds are not matched, it won't shift.

From what I've read, low range is the default if things won't work, and low range is the more difficult to match to at any road speed as low range means higher engine speed.

Millions were served, and parts are available. Maybe a bigger Napa store that actually knows what a medium truck is. All the Eaton stuff is on line. I gave you an Eaton link earlier, you can find others with a simple search. They show the tear down and repair info.

 

Thanks everyone. Got the truck back together and it all works great. I met an old boy earlier today. He is a mechanic and said he used to work on a lot of d straight trucks and two speeds. He said that sometimes a weak motor and touchy points are likely the cause of my rearend coming out of gear. My motor and points are toast and I put new in and all is good. I went about 5 miles down the road and got my big round baler out of the shed and pulled it home without incident. Thanks again!