Another reverse solenoid question for Spicer 4-speed.

[lou432]

Okay, I loaded up and was ready for my trip to Syracuse New York today . going through my pre travel check and lo and behold she wouldn't go into reverse. I said no big deal who needs reverse! And then thought about it and said let me find out why.
  Check the switch and the wires replace the switch because it was cheap. Continuity in the wires and 24 volts coming in to the switch. So check the relay picture below. It's been replaced 2 years ago. Along with the solenoid. Picture below.
  So how do you tell if the relay is bad? I can't even see the cylinoid on top of the transmission without Burying my head in grease covered hoses from the pull out compartment in the rear of the coach on the floor. So another question is, exactly what do I do to manually put her in reverse?? The search features here do not come up with the same threads every time. I'm really confused as to what mechanics take place when it's operating correctly at the transmission. In other words descriptions on what I and a helper if required need to do to manually put it in reverse. Thanks gentlemen any help is certainly appreciated.

[lou432]

#2

[lou432]

#3

[Lin]

Testing the solenoid relay is pretty easy.  You should have 24v supply to your switch. When you throw the switch, it should have 24v at the other wire.  if it does not, the switch is bad.  It sends current to the solenoid relay, so you should find 24v at the input terminal.  If it does not, there is a short between the relay and the switch.That magnetically connects a full time 24v source to the wire going to the transmission solenoid. You generally can hear it snapping. If that does not happen, the solenoid relay is bad.  If the transmission is getting 24v, then it could be the transmission solenoid or there could be stuck or some other mechanical failure.

From my limited experience with the Spicer, although I dislike them I considered them pretty hardy, so would expect the problem to be before the transmission.

[Tony LEE]

I ran for a few days with Betty getting out, opening the back door and pulling on a rope to mimic the operation of the solenoid.

Inside the solenoid is a contact which provides full current during the pull-in and then reduces the current once it is in hold-in to prevent the windings from burning out. If the contact is bad, the windings won't be energised.

[chessie4905]

You need to remove the cap off the end of the solenoid where the wire is attached. Remove power wire and nut securing the stud to the cap. Remove two small screws holding cap to solenoid. You will see a pair of contacts. These disconnect the pull in coil in the solenoid and leave holding coil powered as long as the switch up front is energized. You need to power the solenoid and observe that the points open when solenoid makes it's stroke. The gap specs aren't listed in the GM book, just that the points open. Adjust for point gap when energized by adjusting linkage that connects plunger to trans shift rod. The linkage may appear to be sloppy loose when done, but as long as the points open, say .035 to.060. If the points look burned, you can dress them with a point file or Emory paper. I had a problem with our 4104 several years ago. It wouldn't go into reverse when warmed up. Problem appeared to be solenoid weakness. I got a new one from Luke and same problem. I finally dug out the manual and adjusted per the instructions. Linkage was too tight. Adjusted and never had any more problems.
  I actually created the problem, when a few months before, I replaced the wire end on solenoid because it looked crappy. While I was back there I tightened the "excess slop" in the solenoid linkage. The result was that the solenoid couldn't initially move enough to move the reverse lever and open the points. Once adjusted, it worked fine and linkage was sloppy just like before I fooled with it.Lesson and the cost of a so!enoid learned.

[luvrbus]

I get tired of trying to repair or find a replacement for those solenoids.I am just changing those over to air.I use a Bendix TW control valve a Norgren or a cylinder from a old road ranger transmission make a bracket which is simple and easy.Run a 1/4 supply line to the TW valve on the dash a 1/4 inch line to the cylinder on the transmission and you are done.No more electrical problems after that 

[zubzub]

I like Clifford's idea, although  really the solenoid is pretty simple, can be quickly cleaned and adjusted, the relay controlling it is auto electrics 101 and should not challenge anyone either.  The problem is the solenoid is a little wimpy so anything amiss causes problems, air would be nice and very easy to do with a cylinder, I might use a lectric valve to control it, but I'm not scared of simple circuits (just black boxes).

[chessie4905]

I can see why Clifford likes air setup, but on GM, they are right there easy to check or maintain.

[lou432]

Thanks gentlemen, to clarify I have replace the switch. The relay indicated in the very last picture the real shining one new 2 years ago and sealed with no access to the interior. The other two pictures are attempts at viewing the new two-year-old solenoid which I can barley see from hatch inside the coach much less get to it from under it. Without jacking it up or having a bay under it. And then I'm not sure how they got to it putting the new one in. To clarify my question earlier. The other two pictures show the new shiny solenoid attached to a swivel lever that looks like a open-end wrench attached to a shaft. When operating correctly does the solenoid push the lever into reverse or pull the lever into reverse? I'd like to attempt to put it into reverse manually as indicated in one of the other threads with one person operating the switch up front and one pushing or pulling reverse. Just looking some Direction so I know I can get it in reverse when needed. Until I resolve electrical. Thanks again gentlemen have a great Memorial Day and if you served in any capacity thank you and God bless!

[DoubleEagle]

In the case of my 05 Eagle, I would pull towards the outside of the body to engage. Your arrangement might be different, but you have a 50% chance of being correct if you pull it. Have a way to push it back or you won't be going forward.

[Tony LEE]

Going back isn't an issue as there should be a strong spring returning the lever to the "off" position.  Pull the rope, driver slips it into second position (reverse) and then the rope is let go.  Go to neutral and the box resets to normal forward mode

[gumpy]

Lou, in the last photo, it looks like that solenoid might be hitting on a hose. Is it possible the hose is interfering with the free movement of the shift solenoid?

Regardless, if your helper just pulls the lever in the direction that the solenoid would push it when enngaged, while you operate the switch, it should shift and allow you to get it into reverse.

[bevans6]

What happens is this:  Dash switch on, shift lever in neutral.  Solenoid's pull in coil is energized, about 30 amps, and the slug inside the solenoid is pulled in, thus pulling in on the end of the lever.  As soon as the slug is pulled all the way in it operates a points mechanism that shuts off the pull-in coil and the hold-in coil (6 amps I recall) stays active as long as the switch is left on.  The lever will pull the shaft in the transmission top housing out.  When the shaft is pulled out it disengages the 1/2 shift rod from the shifter from the 1/2 shift fork, and engages the reverse shift fork.  This also locks the 1/2 shift fork in neutral so it can't move (the 1/2 shift hub on the main shaft of the tranny is also reverse gear).  Now, when you shift into the second gear position on the shift lever you are actually operating the reverse shift fork inside the transmission, which moves the reverse idler gear into engagement with reverse on the layshaft and reverse on the main shaft.  As soon as you are in reverse you release the switch, which turns the solenoid off.  Nothing happens at that point because the gearbox is locked into reverse.  As soon as you are finished with reverse, you shift into neutral.  That releases the shaft in the transmission top housing, and a spring forces the shaft back into the 1/2 position and puts the slug in the solenoid back into it's normal ready position.

So if you want to shift into reverse without the solenoid you need to move that shaft out from the housing into the reverse position, then shift into reverse, which locks the shaft out while you stay in reverse gear.  You can do it from the top with a screw driver or obviously you can hook a rope onto it and pull it from the passenger side engine bay.  You only need to pull it out while actually doing the shifting, your helper doesn't need to hold it out once you are in reverse gear.

Sometimes the internal switch (just exactly like a set of ignition points to look at) fails and the pull-in coil doesn't get switched off as soon as the solenoid has fully operated.  That burns out the solenoid if current is left on too long.  For this reason it is always good practice to hold the dash switch on for the minimum period of time to allow you to shift into reverse gear - just in case it is stuck in high-current pull-in mode.

Hope this explains how shifting into reverse works.

Edit:  in the picture, the large straight cut gear in the foreground is the 1/2 sliding hub and mainshaft reverse gear.  The little straight cut gear to the left is the reverse idler gear.  It is slid into engagement with the big gear when you shift into reverse.  The grinding you hear when you shift into reverse is the teeth on those gears getting eaten up.  For interest's sake, that gearbox is sitting with first gear engaged, the hub has slid down and is engaged with first gear, which is the bottom helical cut gear.  Second gear is the one directly above the sliding hub, and you can see the coarse splines on the main shaft that it slides on.  The gears are engaged to the main shaft when the sliding hub slides up those splines (which are about 1/4" square splines, and slides over the tiny little matching teeth on second gear.  Those tiny little 1/4" square teeth are what grind when you shift into second (or any other) gear.  This is why you try really hard not to grind gears - those tiny little teeth get eaten up.

Brian

[DoubleEagle]

All of these details makes me glad I have a Allison now. When I had trouble with my Spicer there was no spring return action at all and I had to push and pull.