Problem Shifting MC5B into Reverse

[MCIGenes]

I am about finished with my bedroom remodel and before I put the bed back in I need to trouble shoot and repair a shifting problem on my manual transmission. I can see the reverse solenoid pulling on the lever on the top of the tranny, but it only moves about a quarter inch. At the time the engine and transmission was not turning over so I realize there is some meshing issues. But even with the engine running and the tranny turning it will not shift into reverse. While trouble shooting this problem I discovered the parking brake is not releasing, and that is another post. Can anyone tell me how much travel I should see on the rod that comes out of the top of the transmission when the reverse switch is activated?
Any help would be appreciated.

Gene MC5B Southern California.

[zubzub]

YOu can try applying 12V directly to the "+" stud of the solenoid to see if you get more travel...
If you do get more travel, look into the rear relay and other associated electrics that send current to the solenoid. 
if you don't get more travel , take the solenoid apart , and clean it up ( they get rust and grime in between the windings and the shunting bit)  there are also 2 windings if I remember correctly, a moving and a holding each has it's own contact points needing dressing.

[bevans6]

The solenoid moves the one/two/reverse shift lever over so that it engages the reverse shift fork inside the shifter housing.  You then move the shift lever into the second gear position to actually engage reverse gear.  The solenoid moves the shift lever about 1/2".  As you look down on top of the box, you can see that the shift rod from the front of the bus is attached to the shift lever with a rod end, that lever will move over to the left until it is flush against the side of the housing.  At that point, the box is ready to engage reverse.  Just check that the lever is moving over until flush.  Makes more sense when you are looking at a gearbox I guess, I happen to have two sitting on the floor of my shop right now so I went out and looked. 

There is no issue of engagement being blocked by "meshing issues" unless you are trying to have the solenoid move the lever when the box is in gear.  You have to switch the solenoid on when the box is in neutral.  If you engage the solenoid when the box is in first or second gear, the solenoid will only move the lever over about 1/8".  If you try to engage the solenoid while the box is in third or fourth gear, the lever will move it's full travel but the interlocks will not allow you to engage reverse gear.  (I seem to think that on some GM buses with Spicer 8844 boxes you turn the solenoid on with the box in first gear.  That doesn't work well on MCI boxes, since the shift lever can't move over when the box is in first gear, only when it's in neutral.

There are two sets of coils inside the solenoid - the pull in and the hold.  The pull in coils draw more power and are switched out of the circuit when the solenoid is in the reverse position.  It's possible you have one set of coils bad, or the internal switch is bad.  It is not very hard to move the lever over into reverse position manually - you can just grab the first/second shift rod and pull it over with your hand, or use a screwdriver as a lever.

Brian

[Fredward]

The MCI 5B is probably 24 volt so you'd need to apply 24 volts (my 5A is). From your description, it sounds like the big "pull in" coil has failed and the "hold in" coil is working. The relay that controls it is in the rear electrical panel on the drivers side in the engine comparment. Check that first. The Hold in coil will not pull the rod out of the transmission enough to let you pull into reverse. Its a $260.00 solenoid and it must be adjusted correctly upon installation or the "pull in" coil will fail prematurely again. 

If you want to discuss in more detail I can describe my experiences for you. 612-eight zero one-4826

Fred

[Ncbob]

I seem that have seasonal problems with my reverse solenoid but I think it comes mostly from inactivity. For about 3 years I've simply put the beam of a strong flashlight on the solenoid and while the wife was engaging and releasing the switch up front I  give the solenoid a more than generous bath with WD-40

So far it's got me through about three stubborn periods. Now when I start the bus prior to a move I always operate the reverse solenoid and when I hear that reassuring click (or thump if you wish) I know I'm good to go.

Bob

[zubzub]

I don't know what the MCI 24V reverse sole is constructed but the 12V one in my GM comes apart, has contact points etc inside, everything can be cleaned, dressed and lubed as necessary and then it is as good as new.  Like I mentioned before, bad relays etc  will confuse the issue.  Relays also need to have their contact points dressed etc to work well.