transmission slippage

Discussion in 'Mechanic and Repair' started by 1MajorTom, Feb 19, 2007.

  1. 1MajorTom

    1MajorTom Former Moderator
    Messages: 6,073

    Exmark Metro HP Belt Drive:

    Transmission slips in 3 out of the 5 gears. What I mean by slip is as the machine is going forward, it will cut out and catch again. It doesn't always do it, it does it intermittently but it does it often.
    The picture shows the interior gears on their shafts. Gears, shafts, and internals all look great. I have narrowed it down to what I think is the shifter keys. They are shown on the left hand side of the picture. There are 4 of them, they slide on the shaft as you select the gear. This is the only thing I could think it could be. If anyone knows anything else, shed some light if you will.


  2. MowerMedic77

    MowerMedic77 LawnSite Bronze Member
    Messages: 1,164

    Yes the shift keys are more then likely your issue, but you may also have to inspect the gears were the keys engage the gears. I have seen them wear the gears also, but this is usually worst case. If you are using a sulky of any kind I would not use it any more they tend to kill peerless trans, also shifting on the fly is a no no. The only other thing that wears them is leaving them in gear when transporting and not strapping them down they rock back and forth and this adds to the wear. Hope this helps:)
  3. Restrorob

    Restrorob LawnSite Fanatic
    Messages: 11,029

    Also clean the grease off the large bevel gear and input pinion gear then check for wear (Chipped or sharp teeth) also the input shaft bearings for play. This is another area where slippage could happen.

    Good Luck
  4. topsites

    topsites LawnSite Fanatic
    Messages: 21,653

    There are several things that I know will cause this, my tranny did this for a long time and I could not figure out what it was...
    btw, the gears look fine, as do the keys.
    It is VERY unusual for these parts to wear, here is what I found:

    The reason these trannies only slip in certain gears is usually an issue due to torque, meaning only 3 out of your 5 gears put out enough PUSH (or pull whatever) to cause a worn gear or spline to slip, while the other 2 gears are easier on that so it doesn't slip. In most cases, it's a pinion or bevel, or some part along the main input OR output side that's causing this, meaning the center pieces that you have in the picture are not the cause (as these are the central part of the system, you'll want to check the output and input ends first).

    Before you get too deep, and since you already have this apart:
    I would first check the outer splined couplings, there is one on either side of the transmission where the tranny's main axle connects to the outer two shafts that lead to your belt pulleys... Sometimes these splined couplings wear off a few teeth, especially on the fine-spline (I think 30 or 36 spline) couplings, and will likely require replacing both outer and the main center shafts. IF this is your problem, I would go ahead and make the switch to the coarse spline (aka 9-spline) system as this will last considerably longer.

    You should also check, there is a c or e-clip or some kind of clip on some of the older style couplings, one on either side of the coupling itself, to help secure it onto the axle(s). If any clips are missing or broken, they will need to be replaced. If absolutely no clips are present, it is possible you have a newer, clip-less system (I prefer these myself).

    Other notes:
    On the fine spline system, it is unusual for the splines to wear completely.
    Instead, as the coupling has some play from side to side, usually the inside or the very outside of the splines will wear, and then when you're moving about in the yard, the coupling slides a bit and just enough play develops where the splined shaft hits that smooth spot, blam!

    If all that is ok...
    Get up under the Wb, and:
    Check the tensioner pulley, make sure it's bearing is not worn.
    (you will have to completely loosen the transmission belt for this)
    If it is wobbly, play in the tensioner can cause intermittent belt slippage.
    Check the main belt pulley underneath the transmission, make sure it is securely held in place and does not wobble (you will have to completely loosen the transmission belt for this), sometimes the key shears or the pulley or the axle wears out.
    If it wobbles, it could be the pulley, the key, or the Input shaft or parts along it.
    So along that same line, check the Input shaft (that's what the axle is called that holds the bottom pulley and goes UP inside the transmission). There sits on top of this shaft, an Input Bevel Pinion (some people call it a planetary gear) which is basically a pyramid or cone shaped gear, and make sure this is not worn.
    While you're dealing with the Input Shaft, you might remove the top clip that holds the Input Bevel Pinion in place, and remove the pinion and check the top of the shaft AND the inside of the pinion for wear (yes, this stuff is splined together, the shaft and the gear).
    Last but not least, check the Input Shaft's tightness in the bottom of the transmission, there exist needle bearings where the shaft goes through the case, make sure these are not worn and the shaft doesn't wobble.
    ANY play or wear on these parts can cause the Input shaft's top gear OR bottom pulley to move a little, and this causes slip.

    Hope that helps.
  5. topsites

    topsites LawnSite Fanatic
    Messages: 21,653

    btw, here are the lessons I learned throughout my experiences with that fine Tecumseh system:
    ohhh yeah, replace the belt just in case oil got on it or some other bs.
    That's while you're checking the tensioner and main belt pulley, replace this so you know that's not it.

    Because after I went through the headache you're going through...
    IF it's not the belt tensioner, the belt itself or the main belt pulley AND the outer splined couplings are fine...

    IF the problem is evidently in the transmission itself...

    I ordered a brand new transmission (yes, the whole thing).
    And, when it arrived, I simply replaced old with new and had my mower working.
    This took care of that, first things first, I said to myself.

    Now much like yourself I'm a DIY'er and it burns to splurge $200 to fix a problem with a system that's not much worse than a 12-speed bicycle tranny, so I kept the old tranny and when I get a chance, I pull it apart, find out what's wrong with it, order the parts, fix it, and set it aside for the next time this problem comes up, I got a working spare and once again it is a simple matter of swapping trannies and the Wb works. :)

    Peace out man, good luck with that thing.
  6. Jason Pallas

    Jason Pallas LawnSite Bronze Member
    Messages: 1,335

    Topsites - this is excellent advice. I think you've covered it all. I've taken these trannies apart numerous times and I think you've done a great job of almost all the failures I've tended to see.
    Like you said, these trannies are cheap - only about $200. It's almost not worth the time to try to fix them. I just fix them when I get time and use them as spares / back-ups. (BTW Bunton used to make these damm trannies that were $700 to replace!!! They were similar in theory... that's how I learned to fix trannies. At $700 a pop it was worth it! They were hard to find/in short supply - so, we had to learn to fix them by neccessity. We found out that John Deere made a repair kit for $105 that had all the parts to repair most of the parts that would go).

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