2 Speed Axle

Red Bank · Mar 5, 2010

I am working on a 1969 Chevy single axle dump truck with a 2 speed axle. A guy brought it to me to run new wires to the axle and replace the switch. The switch is missing and the wires looked ok. My question is I have never messed with one of these before and after looking at it I would assume that since it is an electric motor that to shift it from low to high and back to low the motor would turn one way to high and then reverse itself back to low? Which the only way to reverse the motor would be to for the positive wire to become negative and the negative wire to become positive which means it needs a special switch to accomplish this? Am I on the right track or I am overthinking this? The guy just bought the truck like this and I would like to test the 2 speed first before I rewire and install new switch to find out the motor on the axle is bad. Any and all comments welcomed!

willie59 · Mar 5, 2010

Aw geez man, it's been so many years since I've worked on one of those things...my brain has been updated with newer info and that info is stuffed way back in a file...who knows where in my head. :dizzy

All I can remember is the electric motor current is reversed to change the speed. Is the any wiring still connected to motor? I can't remember if they have 2 wires or three. If there is any wiring at all connected inside motor, you may be able to determine how it should be wired up. You should be able to remove an access cover to view limit switch mechanism inside the two speed box, and wiring connections as well. It does take a "special" switch on the gear shifter. You should be able to get on at places like Truck Pro, or a used one at a truck bone yard. I agree, it would be prudent to test unit before actually buying a switch and wiring it up. Meantime, I'll see if I can come up with some more info.

Had to edit my post. Man, there's a lot of cobwebs here in this part of my head!

I could be wrong, can't say for sure, but I'm thinking they used three wires going to 2 speed motor. One would be ground wire. The other two are positive wires from the shifter switch, each wire going to a seperate terminal inside the motor controller. You power up one wire, and it makes the motor turn via the ground until it hits limit switch. Then, when you move shifter switch, it powers up other wire to reverse motor, until it again reaches limit switch. I think that's how they worked, can't say for sure.

Willis Bushogin · Mar 5, 2010

2 speed

ATCOEQUIP said:
Aw geez man, it's been so many years since I've worked on one of those things...my brain has been updated with newer info and that info is stuffed way back in a file...who knows where in my head. :dizzy

All I can remember is the electric motor current is reversed to change the speed. Is the any wiring still connected to motor? I can't remember if they have 2 wires or three. If there is any wiring at all connected inside motor, you may be able to determine how it should be wired up. You should be able to remove an access cover to view limit switch mechanism inside the two speed box, and wiring connections as well. It does take a "special" switch on the gear shifter. You should be able to get on at places like Truck Pro, or a used one at a truck bone yard. I agree, it would be prudent to test unit before actually buying a switch and wiring it up. Meantime, I'll see if I can come up with some more info.

Had to edit my post. Man, there's a lot of cobwebs here in this part of my head!

I could be wrong, can't say for sure, but I'm thinking they used three wires going to 2 speed motor. One would be ground wire. The other two are positive wires from the shifter switch, each wire going to a seperate terminal inside the motor controller. You power up one wire, and it makes the motor turn via the ground until it hits limit switch. Then, when you move shifter switch, it powers up other wire to reverse motor, until it again reaches limit switch. I think that's how they worked, can't say for sure.

I dont know why all the info returns about the old 71 detroits, but I cant remember about these 2 speed rears. I never had but two and I remember that I replaced the motor and it still didnt shift and I called a friend of mine and he took the case apart and something was broke inside it. I guess my memory bank has been updated in regards to this subject also.
I agree this should be fairly simple, make sure you get the right switch
Red Bank if you cant get it figured out, send me a PM and I will ask my friend about it, and Ill post what he says
Good Luck

willie59 · Mar 5, 2010

Willis Bushogin said:
I dont know why all the info returns about the old 71 detroits, but I cant remember about these 2 speed rears.

LoL, I could still set the racks on a Detroit with my eyes shut...but can't remember jack about two speed axle motors.

Makes ya wonder...of all things Red Bank could pick our brains about, had to be a two speed motor. Hmmm. :tong

heavylift · Mar 6, 2010

http://www2.dana.com/pdf/AXSM-0029.pdf wiring diagrams and stuff

KW318 · Mar 6, 2010

heavylift said:
http://www2.dana.com/pdf/AXSM-0029.pdf wiring diagrams and stuff

Amazing how that simple old picture brings back memories, good find Heavylift.

grandpa · Mar 6, 2010

You guys are right on the money with the 3 wire concept. On the older the electric motor has the wires running directly into the motor housing. On the newer ones they run into a circut board

I think you have the older one.
Two bolts will remove the 2 speed mount as it would be easier to bench test the unit. The motor turns a worm shaft with a swivel that slips into your yoke. The yoke is connected to your two speed gear inside the rearend. Common problems with this system can be bad switch/wiring(which you need), bad electric motor, rusty worm drive, worn out yoke and finally a broken two speed gear(which requires removel of the gear mount.
And on the lighter side....ATCO's memory is going to continue to escape him ( As he is no spring chicken anymore...bah ha ha ha!)

heavylift · Mar 6, 2010

that switch is about 7 bucks.... it was held on by various means.... other than the factory clamp.... tape.... wire... string

There is also the speedometer thing that switches also...
it moves to a higher speed when you are in low... then changes to the correct speed when in high

Muffler Bearing · Mar 6, 2010

That's a pretty old one fer' sure. I've dealt with the newer style ones plenty though, moisture would get into the assembly and corrode the circuit board and make it freak out! A few times it made the shifter motor act like a windshield wiper motor! I'd move the switch to one position and the motor would just rapidly cycle back and forth!
Sorry RB, that's more of an anecdote than helpful advice

Komatsu 150 · Mar 6, 2010

It was common for the limit switch on the motor to go bad. On the old trucks the harness wires attach to the terminals on the limit switch itself. Two screws removes it if I remember right. Can be changed without pulling motor, just a little tough, and they used to be available at NAPA along with the shifter switch.

Tiny · Mar 6, 2010

I have rebuilt several two speed motors.biggest killer is the boot or seal that keeps the 90wt out and the 10wt in,Seems the seal gos bad and the 90wt gums up the parts.

At any rate if I could fix them any one can...If the wiring is good ,don't sweat the shift motor box, minus the clean up you can put a new motor and rebuild kit in 30 minutes

AUSSIE TD-40 · Mar 21, 2010

easy to work on, most of the posts do point you in the rite direction, and the the 2 speed switch that is missing gos on the gear stick so you can change the diff with your 2nd and 3rd fingers when you change gears.
works like this; going down dont use the clutch, push button down lift off the gas pedel and then back on, going up use the cluch; push in and buton up, wait for it to shift and drop revs and then clutch back up.
Going to bang and grind it a few times till you get good at it! have fun.

Jake

Red Bank · Mar 21, 2010

Update, the motor was fried and could not be rebuilt, I found one at NAPA, found a switch, found the limit switch and rebuilt the unit. I installed it and it would not shift to high, removed the link to the rear end and the motor worked like it should. The problem is in the rear end. I finished it up and called the guy, he said he did not want to go into the rear end. My pride is having a problem with letting this go and not work right but my mind is happy to have it leave.

td25c · Mar 21, 2010

With the two speed box off ,you should be able to reach in and shift the fork by hand from high to low range while turning the drive shaft with the other hand.Might try it

OneWelder · Mar 21, 2010

You should hear motor when you shift button- if not it is electrical
if you are saying the rear is not shifting it won't unless you are moving.
Once in great while the yoke sticks in the rear- just take motor assemble off rear housing (held on by two studs ) try not to damage rubber boot - then pry linkage back and forth

Komatsu 150 · Mar 22, 2010

Yea, designed NOT to shift unless the shifter gear is completely free of any load from engine or axle.

Red Bank · Mar 22, 2010

Let me clarify, when I wired up the motor and tried it, it would not shift. I jacked the rear of the truck up and tried it and still no shift, I can take a plate off of the 2 speed box and disconnect the linkage to the rear end and the motor will work like it should. I reassembled it and tried it again, no shift. I put a test light on the high terminal of the switch and the lit was dim, as if the motor was trying to shift it. The other problem with this arrangement is this appears to be a very early style Eaton 2 speed rear end. The 2 speed box is a three bolt, two wire arrangement. Everywhere I went last week had a two bolt three wire box. With the box removed from the rear end I am looking at the pivot at the end of a shifting rod. From the notch in the rear end housing this thing cannot move too far the notch is probably three inches long. I tried to move it but it would not move, was afraid to pry on it. To access the rest of the linkage the rear end pumpkin will need to be removed from the rear end housing. The owner of the truck wants me to leave like it is, he doesn't want to spend any more on it. I wished there was a quick fix, but without removing the pumpkin I don't know what else to do. But thanks for all of the replies!

OneWelder · Mar 23, 2010

use a small bar and pry it- - make sure u can wiggle drive shaft

Komatsu 150 · Mar 23, 2010

Jacking it up like you did would remove all load. One thing, all the ones I worked on were the old two wire style. A I remember the motor should run to the end of the stroke and wind up a spring. The spring does the actual shifting. Then the limit switch works and stops the motor from drawing any more power. This should happen regardless of weather any actual gear shifting happens. If it's still drawing power something is not quite right and I would think that's why the motor was fried. The shifter fork and gear are pretty stout. I wouldn't be afraid of prying on it while someone else rocks the tire. If it won't go something is broken and jammed and there are pieces. The only shifter "spool" I ever changed was because a ham handed driver had worn the teeth to nubbins from missed shifts. It's also possible someone deliberately has blocked the shifter. Some drivers just could not grasp the idea of how to shift these things.

Red Bank · Mar 23, 2010

Komatsu you described the operation perfectly, that is exactly how it works. When the test light is dim it is because the motor is trying to get the spring to shift the fork, the fork will not budge so the motor keeps trying. The owner was going to come and pick it up but I have not heard from yet

If I get a chance I may try to mess with it again, but based on all that I have done I really believe the pumpkin needs to be removed and the shifter fork and gear need to be inspected.

2 Speed Axle

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