Rear diff light won't come on

Diffs, axles, lockers, transmissions, portals, that kind of thing.
kdiqq
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Rear diff light won't come on

Post by kdiqq »

So when I first got my 710M from Scott, he said he tested the locks and all was fine. The day I got the thing I went on a dirt road so that I could test them as well. Center diff came on, rear diff came on, and front diff came on. But the rear diff light was very dim.

The next time I tried the rear diff light would not come on at all. I ended up replacing all the lights and sockets. Now though, the rear diff light still won't come on. I chased the wiring back to the switch and ground out the wire and light came on nice and bright. When the lever is actuated I can feel the piston move (when I had the slave removed) and I can head the spring moving back and forth. I tried testing the rear locker on pavement but I can't hear the tires scrubbing. I'm worried the rear diff lock is not working. Any one have any experience with the switch failing? I have my suspicions since the like was originally dim, but until I can get it in the air, I'm not convinced it's engaging.. Any insight is greatly appreciated!

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pcolette
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Re: Rear diff light won't come on

Post by pcolette »

The swtches (09-60-18) do fail occassionally. Unfortunately they're expensive for such a little switch. You could try removing it and cleaning it up to see if that helps.
Paul C.
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'73 Swiss 710M
'89 Puch 230GE
kdiqq
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Re: Rear diff light won't come on

Post by kdiqq »

Does the switch sit below the fluid fill level? As in, if I I pull it, do I need to have fluid on hand? I was surprised to see its actually not leaking too bad in there. Small pool at the bottom.

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undysworld
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Re: Rear diff light won't come on

Post by undysworld »

Not quite sure what you're referring to. The reservoir is behind the levers in the dash, so it's obviously above the locker slave (unless you're parked nose-down into a ditch). The levers control the "master cylinder" of each circuit. There are rubber connectors between the reservoir and the levers which sometimes leak, and can cause the slaves to not operate.

When you pull a lever, it pressurizes the slave. The slave compresses a spring. When the splines align with a collar, the collar engages. Only then will the light illuminate. It indicates that the locker has locked (or unlocked), regardless of where the lever is.

A leaky differential can leak fluid into the locker area. Is this where the pool is? What is it? Brake fluid or gear lube? You should not be leaking brake fluid there.

You can verify whether that locker is locked by raising the truck and seeing if the rear differential gets locked up (or not).
kdiqq
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Re: Rear diff light won't come on

Post by kdiqq »

I'm referring to the switch that makes the locker light illuminate. This is the switch in the witches hat. Everything up front is fine. I can hear the spring moving in the witches hat and I can feel the piston moving when I remove the slave.

The small pool of fluid is gear oil in the housing. I could identify that smell from several miles away lol

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undysworld
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Re: Rear diff light won't come on

Post by undysworld »

Does the switch sit below the fluid fill level?
The switch is lower than the levers and reservoir (where you fill it), so yes the switch is below the fluid fill level.
As in, if I I pull it, do I need to have fluid on hand?
Not sure what you're asking. The levers operate on fluid provided by the reservoir above them.

Sorry, but I feel like I'm missing your question.
kdiqq
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Re: Rear diff light won't come on

Post by kdiqq »

Sorry, I know I'm not as clear as I need to be when I sent messages on my phone.

I was trying to figure out if I would have any fluid spill out of the witches hat if I pulled the switch out of it to test it.

I don't have any fluid for the rear diff, but if the fill line was above this switch then I could pick up some fluid on my way out of work today and make sure it gets refilled when I pull this thing out. :)
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pcolette
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Re: Rear diff light won't come on

Post by pcolette »

There are 3 plugs on the rear diff: the drain plug on the underside, the fill plug above and in front of the switch cover and the level check plug which is somewhat hidden in front of the axle. The procedure is to fill gear lube thru the fill plug until it begins to flow out of the level check plug. When it does the lube is at the correct level.
IMG_3828.jpg
IMG_3828.jpg (270.01 KiB) Viewed 6451 times
IMG_3831.jpg
IMG_3831.jpg (311.34 KiB) Viewed 6451 times
The level check plug and the diff indicator switch are at the same level on the differential so you may have some gear lube come out when you remove the switch if the diff was overfilled. But you shouldn't have to add any gear lube unless the level is below the hole the switch was in.

Here's what a new switch looks like:
IMG_3832.jpg
IMG_3832.jpg (150.38 KiB) Viewed 6451 times
Over time I've found that the plastic insert portion of the switch becomes loose and allows gear lube to leak out which is probably why you found lube under the switch cover.

Good luck!
Paul C.
_________
'73 Swiss 710M
'89 Puch 230GE
kdiqq
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Re: Rear diff light won't come on

Post by kdiqq »

Wow really incredible pictures. Thank you that! Exactly what I was looking for.

For a 710 with 22000km, what's the likelyhood that a rear diff lock took a dump vs the switch? I get to speculate for the next couple of hours till I go home haha
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undysworld
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Re: Rear diff light won't come on

Post by undysworld »

First off, is the locker locking? Raise the rear of the truck and flip the 3rd switch. Then see what happens when your rotate one tire. Does the other one move at the same speed in the same direction? Even if the lever is actuating the locker mechanism, the switch only closes after the locker actually engages.

I'd peg the switch as more likely to fail than the locker, BUT, I'd first test out the switch. Pull it, supply the 24v to one terminal and ground the other terminal. If you can push in the switch and the light illuminates, then your switch is good.
kdiqq
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Re: Rear diff light won't come on

Post by kdiqq »

undysworld wrote:First off, is the locker locking? Raise the rear of the truck and flip the 3rd switch. Then see what happens when your rotate one tire. Does the other one move at the same speed in the same direction? Even if the lever is actuating the locker mechanism, the switch only closes after the locker actually engages.

I'd peg the switch as more likely to fail than the locker, BUT, I'd first test out the switch. Pull it, supply the 24v to one terminal and ground the other terminal. If you can push in the switch and the light illuminates, then your switch is good.
That's what I don't know yet. I haven't gotten the chance to raise the rear of the truck yet and actually turn the wheels. I will this evening though.

My plan for testing the switch is to just remove it, press the switch and measure resistance. It should go closed once engaged. I tested the wiring by pulling the one lead to ground and the light illuminated.
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kdiqq
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Re: Rear diff light won't come on

Post by kdiqq »

So the rear locker is not engaging.

I got it off the ground and I can't do anything to make it engage. I pulled the sensor and it works fine. I pulled the SC and I can move everything by hand. I pushed on the piece that moves the selector fork and nothing happened. Here's whats odd though. I pulled the sensor and could visually see the piece that is pushing the sensor. When I engage the rear locker, the piece moves forward. But not enough to touch the sensor and set it off... Any ideas on what could be going on before I have to pull the witches hat? :(
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pcolette
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Re: Rear diff light won't come on

Post by pcolette »

I would give the rear locker hydraulic line a good flushing and then bleeding. In fact it's not a bad idea to do all three. Those lines often develop a nasty, waxy buildup in them and/or in the fluid reservoir and a thorough flushing & bleeding can make a huge difference.
Paul C.
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'73 Swiss 710M
'89 Puch 230GE
kdiqq
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Re: Rear diff light won't come on

Post by kdiqq »

So I have new intel...

I went offroad in to some light mud. All lockers off it spun one rear wheel. Rear locker engaged, BAD grinding noise when attempting to roll.

Here is the funny part... Center locker engaged and rear engaged and BOTH WHEELS LOCKED and no grinding noise!!!!

Anyone have any clue what's going on?!

The light still didn't come on. I hate that I just got this and fighting driveline issues :(
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Jimm391730
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Re: Rear diff light won't come on

Post by Jimm391730 »

Make sure you have enough fluid in the reservoir to fully engage the dogs; sounds like it only got "half engaged" part of the time.
Jim M.
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