Eaton 2 Speed Rear End Out Of Sync. Help Please!

[mcshane85]

Hello, first post here. Thanks in advance for your knowledge and apologies if I am asking a question that has already been answered in the archives! (If you know where it is and send me a link I will gladly reference it!)

I recently bought my first dump truck! It's a 1985 Chevy C70 with a Detroit 8, air brakes, and the 2 speed rear end. I paid $3,000 for it, and it works pretty good, besides the fact it has ben stuck in low gears. I just replaced the 2 speed shift motor and the circuit board/wires that seem to be notorious for corroding.

Good news: now when I depress the clutch and pull up the red shift lever I can hear a clunk in the rear end signifying a shift to the high gears.

Bad news: upon shifting to the high gears the truck began lurching like a 15 year old learning to drive a standard transmission in the Walmart parking lot! There was also a dull sound similar to what happens when a stick gets stuck rubbing the spokes of a bicycle. I tested it out on my back road at low speed, so I am hopeful I did not break anything (worse).

Possible clue: Before I put the new motor in I tried using a jumper wire to jump it into high gear. (Picked up that little tidbit on this forum!) I wonder if when I did that I got it stuck in between gears somehow. If that were the case I would think the truck would show similar symptoms in both low and high gears, but I don't know.

Has anyone run into this problem? Thanks again for any help you have!

 

[Pops52]

1st thing I would do is drop the gear oil into a CLEAN pan and take a close look. Then regroup.

 

[MG84]

The way those 2spd axles work is the motor shifts a fork which holds spring pressure against the mechanism that actually shifts it. If it hasn't been shifted in a long time all of that could be gummed up and its not fully engaging. It's also possible the spring that holds it could be weak or broken. You also need to make sure the motor is moving the little worm gear fully from one end of travel to the other. I haven't dealt with the "newer" ones much that use the circuit board, but on the older ones there needs to be voltage on either the hi or lo wire (depending on the switch position) all the time. Lastly, someone could have just torn it up and it would only hold on the low side. They are pretty tough but not indestructible. Be sure to get it working properly and get someone with experience to give you a good lesson on how to drive it.

 

[crane operator]

Unfortunately, there’s probably a reason it was locked in the low side. I like pops idea of looking for carnage in the oil.

You might also try just jacking up the rear. Have someone pop the red button while you are rotating the rear by hand and see what it feels/ sounds like. Be better than driving it around testing it.


I haven’t been into a two speed rear for over thirty years,
But likely the two speed has high gear issues.

 

[cuttin edge]

If you were between gears you would have no movement.. Keep in mind that a 2 speed rear axle is more like a splitter than a high low. I have seen people try to do 1 through 5, pull the button and then try to go back to first like a ten speed. It don't work that way.

 

[Delmer]

As far as I can remember, they could be changed by hand with the motor removed. I'd try that and see if you can get it to stay in high by manually moving the shifter with the cover off. I like the idea of jacking up one wheel before driving it.

 

[Truck Shop]

Eaton 2spd electrical diagram

Hoping someone has a schematic for electric shift Eaton 2spd axle in an ‘82 Ford LN7000. I’ve only owned it for about 7 yrs. Currently, it’s in low range. Using a tester, I’m finding the lead to the speedo hot no matter switch position and both leads to the shift motor are hot. Before I pull the...

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already a thread on this from a ways back.