36" Scag Mower

Discussion in 'Mechanic and Repair' started by riovanna, Aug 6, 2007.

  1. riovanna

    riovanna LawnSite Member
    Messages: 11

    I have had a 36" belt driven Scag mower for about four years now and I am just now starting to have problems. When I went to sharpen my blades I noticed the belt has a crack in it, so I bought a new belt, I have not put it on yet. The mower is bucking in first and second gear but runs great in third gear, will the new belt resolve the bucking problem??

    Thanks for any help with this issue!!
  2. MowerMedic77

    MowerMedic77 LawnSite Bronze Member
    Messages: 1,164

    I am assuming the cracked belt is your deck belt, which runs from your lower engine pulley to the deck. This belt will not effect drive, but you can check the trans belt that runs from the upper pulley on your engine to the trans pulley and is tensioned with an idler. Make sure your idler is not locking up and that your belt is not cracked or has chunks missing, but your issue would more then likely happen in all gears not just 2nd and 3rd.

    Do you run a sulky or a seat?
  3. riovanna

    riovanna LawnSite Member
    Messages: 11

    I do not run a sulky or seat, and it bucks or skips in 1st & 2nd gear and runs fine in 3rd gear so far. You are correct in that the belt that I saw cracked was the deck belt. Is it a big deal to get to the trans pulley?? I have the manual showing that belt and the idler that you mentioned, is it very involved getting to that belt and fixing it or the idler?? If the belt is cracked or missing chunks would it be safe to say that is the problem??

    Thanks for the help once again!!
  4. WhitakerServices

    WhitakerServices LawnSite Member
    Messages: 159

    I had a similar problem with my 36 scag. The problem was wear on the transmission keys. I was confused at first because my problem only occurred in 2 nd gear but after replacing the transmission keys. the problem was solved. Most of the time wear on the keys is from either pulling a sulky or parking in gear with no tie downs. Hope that helps.
  5. MowerMedic77

    MowerMedic77 LawnSite Bronze Member
    Messages: 1,164

    No it is not a hard belt to replace, since you will be replacing the deck belt it will be a good time to replace this belt also since the deck belt will have to be moved to remove the trans belt. The idler pulley is usually held on with a castle bolt that has a 9/16 lock nut holding it in place you can loosen this nut and slide the idler over and remove the trans belt, then reroute on the new belt. I usually slide the idler back against the belt as tight as I can buy hand and tighten that 9/16 lock nut just snug. Then with a large screw driver or pry bar you will have to put extra tension on the belt(idler) so as not to slip when mower is on inclines(an extra set of hands are good for this part) then tighten the nut.

    To answer your question on if the belt could be your problem I say it could but I would think your issue would happen in all the gears. I tend to lean more towards the shift keys and 2nd and 3rd gears having wear. If you always run in these gears and shift on the fly or leave it in these gears in the trailer and don't lock the mower down then the constant rocking and use on them will lead to your issue.
    YankeeC|ipper likes this.
  6. Restrorob

    Restrorob LawnSite Fanatic
    Messages: 11,029

    I would also say if the keys are worn the mating surface inside the gears are most likely worn too.
  7. riovanna

    riovanna LawnSite Member
    Messages: 11

    I think we have it narrowed down to the transmission keys or shift keys - I usually run in 2nd or 3rd gear and I do shift on the fly quiet often between these two gears - I tie down the mower on the trailer but never use the hand brakes (should I do that??) - and I have noticed that even after tieing it down if there is any slack in the rope it will release on its own and slip an inch or two backwards on the trailer several times until I retie it tight again!!

    So if it is the keys is that something I should try to fix on my own?? and also the mating gears??

    Thanks for the help!!
  8. MowerMedic77

    MowerMedic77 LawnSite Bronze Member
    Messages: 1,164

    I discourage tearing down the trans unless you are mechanically inclined. May be cheaper, faster and easier for you just to order and replace with new.
    Try this link http://www.j-thomas.com/ there is an identification plate on the trans usually will start with 700 *** this is the best way to get the correct trans for your application.
  9. riovanna

    riovanna LawnSite Member
    Messages: 11

    Hello MowerMedic77 & WhitakerServices:

    I am going to buy a new Peerless Transmission for the 36" Scag Advantage & change the belts at the same time - is the transmission a big job taking it out and putting the new one in?? Any hints or suggestions
    would very much be appreciated!!

  10. MowerMedic77

    MowerMedic77 LawnSite Bronze Member
    Messages: 1,164

    Removing and replacing is not overly a hard job, just take your time and keep track of were items came off and how they will need to go back on.

    1. Jack the rear of the mower up to a good level to work comfortably at(use stands).
    2. Remove the rear belt guards and tension springs from the side drives followed by the belts.
    3. Remove the trans belt and at this time I usually remove the set screws and sometimes the snap ring holding the trans pulley onto the trans thous exposing the bolts that hold the trans to the frame(do not take out yet).
    4. The side drive pulleys come out as assembly don't try and take off the pulleys unless you are replacing. You will see that they are held on the frame with two 1/4 bolts and lock nuts, remove these and pull the shaft and bearing and pulley as a unit.
    5. Remove the splined couplers from the trans and also undo the shift lever at the top of the trans and your electrical connection for the neutral safety switch.
    6. Now go back under the rear frame and undo the four bolts that hold on your trans (may need to remove the woodruff key from the trans input shaft)
    and your done :cool2:
    7. Well as far as removal :laugh:
    8. Then I just reverse this process starting with re bolting back the trans.

    Good luck I hope this helps :)
    P.S. If you have a digital cam take some pics of each of the steps that way you will have a quick reference to how the parts go back on.
    And then post them so I will not have to type this again:laugh:
    YankeeC|ipper likes this.

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