Correcting Gear Change Errors

[Stupidav]

I have seen many different post on the High gear error and the Low gear error, particularly at startup. Then I ran into this problem with a 1994 VF3. First the Service Tech wanted $800.00 for the MAC Solenoid Valve, he tried it, didn't fix the problem. Then he wanted to replace the Transmission, $6000 or $2900 after core charge. Now this machine doesn't have any Gear Grinding problems or anything like that. Just 99% of the time on startup or during a speed change the unit won't change form low to high or from high to low.

Since everyone has given many differnt answers, I figured I would post my complete solution.

First we removed all the covers.


Then to simplfy the reassembly we pushed in on the spindle locator and rotated the head untill the spindle locked into place. We then marked the spindle.


We then removed the tool change cylinder assembly.


After removing the 6 bolts on on the bottom of the transmission and unmounting the Spindle Temperature switch and a minimal amount of cables ( 2 cables, the coolant hose, and one air line) we were able to lift the head up a distance to allow us to work on it without diconnecting everything.


Now obviously once the bolts were removed we were able to slide the head around to remove the belts before lifting. Knowing the the gear change is basically done by a Air Cylinder and considering our symptoms we went after that first.


The easiest way is to remove the bottom air line first. Then remove the Limit switch assembly.


Then you can remove the last air line. It does make it easier if the airlines are completely removed.


Then there are 4 screws that hold the cylinder body in place. Oncer removed you will see the "Piston" of the cylinder. PS....Pay attention to the orientation of the piston on to the shaft. It does not work if the piston is flipped over. The piston is held on by a C-Clip and there is an additional o-ring under the piston.


In our case all the O-Rings were wore flat as well as dried and cracked. This is besides all the junk in the cylinder. We were able to get all the O-Rings at a local hardware store (we did this on a sunday). Unlike what some people have said about the airports on the cylinder only being .010" ours were .030. We didn't make any modifications to them at all just a good cleaning with some Brake and Parts Cleaner, and some lite weight oil for lubrication on the o-rings during reassembly. Using caution everything went back together in the reverse order without any problems. We tested and everything is working great. Now we have another unit to do this to, but it only has the problem once every other day or so.

Overall the job took about 4 hours.

[HuFlungDung]

Thanks for the instructions and the pictures. That is very considerate of you to think ahead to take pictures to document what is involved.

[JoBwan]

Wow!! Your username should be Notsostupidav! Ha Ha!! Great info!! Thanks!!!!

[Pondo]

Very good writeup - thanks!
We had the same issue about 6 months ago. This would have saved us a TON of time.
The newer solenoid valve is much better for the shifter, so the tech was trying the correct fix. The old one is obsolete and aftermarket ones do not work for 5hit (don't ask how I know).

[Stupidav]

Sorry Pondo, but maybe I am not understanding what you have seen with the old solenoids and the new solenoids.

Both the Old and the New that we had and also had recieved are the same thing! The only difference is the New units have the Noise surrpressor built in where as the old valves did not. Reguardless of what many techs might tell you, the valves are available through almost and MAC distributor. In Michingan it is Neff Engineering, and I know they also cover a portion of Indiana as well (or atleast they used too).

As far as it making a difference on the shifter itself, both the old that we had and the new have the exact same scfm rating, so it is just like replacing your light switch. On older machines there is the possibility that one of the noise surpressors have gone bad, which would only (highly unlikely) cause a super quick actuation of the valve, although it could cause the solenoid part of the valve to go bad if the noise is too heavy. You would probably only notice something like this in the winter when the humidity is low and chances are if you do see this, it is because there is another issue like a broken ground wire somewhere on the machine.