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Walk-Behind Transmission Won't Shift

Discussion in 'Mechanic and Repair' started by MJS, Jun 21, 2008.

  1. MJS

    MJS LawnSite Bronze Member
    Messages: 1,316

    I have a 2001 MTD Pro gear driven walk-behind. I've done engine/carbuerator work before, and can do all the basics myself, but I don't have the knowhow with transmissions, it seems.

    The clutch on this mower is operated by clamping partially down on the pistol grips - I'm sure most are familiar with this - then the shifting is done by nudging the lever (I use my knee). So here's the problem:

    The transmission, or maybe more specifically, the rod that changes the gears on the transmission, usually will not go beyond 1st or 2cd gear after I have run the mower for 6-8 hours (near the end of the work day). Once it is in gear, it is usually very "sticky" ie. takes a lot of oomph to shift it back from 1st into nuetral or reverse, and it simply won't go into a higher gear at the end of the day.

    I thought at first that it was a lack of proper lubrication - I hit both of the zerks next to the lever, and sprayed the joints with wd-40. The problem still persists, but only after I have run the mower for a good 6-8 hours. So when I'm trying to get home in the evening, then it gives me problems :nono:.

    Anybody have any suggestions, other than to just dish out the cash and get a new transmission?
  2. GravelyNut

    GravelyNut LawnSite Bronze Member
    Messages: 1,594

    Most of that type of tranny, if it has the type I think, has a reverse, n, and 4 to 6 forward speeds. There should be lubricant inside the tranny also. That is what I suspect is dry and causing the problem. And yes, it might be too late for the tranny. Sorry, can't look it up till Monday to be sure as to what type you have. :(
  3. topsites

    topsites LawnSite Fanatic
    Messages: 21,653

    You'll need a tube of bentonite grease.
    The cover of the transmission comes off relatively easy, except you also have to unhook the shifter... The biggest problem is when you go to put the cover back on be dang careful when tightening the bolts, the entire case is made of aluminum so you'll want to just 'snug' them down otherwise you'll strip them!

    Once you have the cover off I would first inspect it all visually, then squeeze as much bentonite in there as will fit, then re-install.

    And while you're doing that, as you remove the shifter you might check and see if it is rubbing or binding against anything.

    Btw in the future, from what I have learned, with these transmissions it is best to select a one-size-fits all gear once and leave it forever alone. Don't shift these things, don't let yourself get in a predicament where you'd have to use Reverse and if you do pull it out manually instead of shifting, never ever shift that stupid thing.

    But, I had to learn that one myself, the usual way :p
  4. Breezmeister

    Breezmeister LawnSite Bronze Member
    Male, from South Jersey
    Messages: 1,784

    If you want to just add the grease, with out taking the trans apart, what you can do is remove the safety relay,it's the one that has the wires running to it. With the trans in neutral. take a clear plastic tube ( 3/8 fuel line) about a foot long, put it in the hole and the other end on the tube of grease. There is a hole in the shifter fork that will allow you to get the grease in, the tube will only go in about 1/2 an inch

    :laugh: Now this can get messy if you are not careful :laugh: But if you take your time it can be done cleanly

    What I like to do is use some black RTV on the cases when I put them back together, It won't stop the grease form leaking out of the jack shafts, but it will help to keep the back of the machine cleaner :)
  5. MJS

    MJS LawnSite Bronze Member
    Messages: 1,316

    Thanks guys, I tried what you said - put the grease in the gear box (is that what it's called) with a plastic tube, like Breezmister said. So I put it to a good day-long test today, here's what I see:

    The tranny now has no problem from R to N to 1st to 2cd, or any combination of those gears, but it won't go past second, no matter what. This is problematic, since I do most of the mowing in 3rd or 4th. It has 5 speeds, so not having the last two wouldn't be such an issue, but there's a pretty big speed difference between 2cd and 3rd.

    Any further suggestions?

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