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I have an MTD 31A-3BAD729 snowblower given to me. The instructions say 05/2005 on them, so I'm assuming the snowblower's from about that time. The auger works fine. However, the wheels hardly turn when I left the unit up off the ground. They'll spin around somewhat. I can freely turn them as well when the unit is off. However, when I set it back down on the ground, there's either not enough power to move the blower, or it'll jerk forward a few times, moving just a few feet. I checked the drive cable, and there's definitely enough tension on the transmission. That works like it should. The drive belt looks almost new as well. The spring from the drive cable to the transmission and the outer gears are fine. I suspect the transmission is bad, but wanted to get other thoughts before dropping $130 on a 618-04296 / 918-04296B transmission. Thanks.
 

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if you didnt already, take the belly pan off. you should have one large gear on the axle shaft and one smaller "pinion gear" on the transmission output shaft. both shafts are through the side of the chassis and ride on bushings. either the bushings for both are worn causing the gears to skip or the gears are stripped already and only grab when it gets to some good teeth. when standing at the back (operator position) on the left side there should be 2 visible shafts riding on those bushing. one shaft extends out and the wheel is on it and the other ends just outside the frame. put the blower on the ground and put it in forward. if the wheels are not spinning but the shaft closer to the front of the blower is, then the trans should be fine.

see the diagram in the link or go to sears parts direct and put in your model number to see

http://c.searspartsdirect.com/lis_png/PLDM/1108128P-00002.png
 

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Just a thought here but make sure that there isnt any grease or oil on the belt any where, or on the pullys themselves. Even the most minor traces of an oily substance will cause the belt to slip. If so or your not sure just spray the belt and pullys with some brake cleaner and wipe it down really good. Like I said it was just a thought and I may be reaching but its the best I got next to what has already been mentioned.

Let us know what you find
Cody
 

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No oil on the belt. The shaft coming out of the transmission isn't really spinning either. The gears on the pinion are fine. I'm still thinking it's gotta be the transmission.
 

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starting to sound that way, one last thing i can think of before it would be internal.

check the attachment of the belt pulley to the tranny input shaft.


and i can't tell but it looks like there is a spring connected to the back of the trans. i am assuming its for forward and reverse control or just to engage the unit after selecting forward or reverse, make sure what it is attached to turns or pushes and pulls into the trans without the spring. it would show plenty of tension if the trans part was stuck. when it frees up the snowblower jumps forward but the pressure or shock pushes the part back to where it is stuck.

just a couple more thoughts
 

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if it's like a sears craftsman there will be a wheel inside that moves across a spinning disc. when in centre of disc it will not move, as you shift thru gears it will move toward the outside of this disc, when on the very outside it will be fastest, in centre no go at all and everything in between is relative, when moving the other direction it will be reverse. sometimes grease gets on the disc and it will need to be cleaned or the rubber on the tire gets shiny or breaks off, the part is 20 bucks at sears, either way, just tip it forward onto the intake mouth of the auger and drop the bottom pan and look in there, hope i helped
 

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Problems

If this is the machine in question then I'm not sure it's a friction disc unit:
http://www.managemylife.com/mmh/lis_pdf/OWNM/1108151L.pdf

This looks like a transmission unit (Never heard of that in a MTD before). If I'm reading the schematic right, there's only a couple places I'd expect something like you're describing. Look at the trans mounting, insure they're tight, along with the shaft to gear #22. I would look to a bad mount or one of the drive bushings. Look at parts 22, 23, 28 & 29 along with any pins like 21 to see if anything is worn or missing.

On bigger Craftsman blowers with transmissions, it's the area around #22 (loose or missing step bolts) that can do what you're describing. If it is, get it fixed before you damage the transmission mounts.

Let us know how it turns out.
 

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thats the same schematic i came up with. only a few spots to make it jumpy like he is describing. hopefully an easy fix
 

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Discussion Starter #9
Ordered a new transmission and installed it. Works like new again!

For any lurkers out there attempting to do this - it's not too hard to replace the transmission. Make sure you have a punch to drive the roll pin out of the shaft with a hammer. Also, use a pair of pliers to squeeze the black plastic part that retains the clutch cable in place in the transmission piece.
 

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just in time for winter. I know the hard part for me would be to bite the bullet and buy the trans. never know if something else will be wrong.
 

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Same problem, here's what I found

For any lurkers/info seekers out there: I had the same problem with my MTD / Yard Machines 31AS3DDE729. At first it looked like just the roll pin on the drive gear had sheared, but after replacing that I found the wheels still wouldn't go if there was any pushback (snow, me holding it, etc.) whatsoever. And I could hear grinding somewhere.

I determined it was the transmission (part 618-04296), removed it and disassembled just in case it was user-repairable (why not, when a new one is $130+) As it came apart a rich, beautiful golden fluid poured out - turns out, the brass worm gear was totally chewed away, and as the unit is sealed the fine particles mixed with the lubricant and basically made gold paint.

I haven't determined yet if I can just replace the worm gear, or if I should just replace the whole thing - replacing the gear, relubricating and sealing the transmission successfully may be beyond my skill level :)
 

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Same deal here! Was wondering what that gold stuff was, the gears were completely destroyed.
Here is a pic
I have never seen a transmission like that on a snowblower before. Most are friction disc. Perhaps yours is a single speed and this was cheaper than putting the rest of the parts in?

I have seen pictures of destroyed auger gear box gears and the gold stuff in the grease is the shavings that came off of that bronze gear. Hopefully you can source a new gear for that as I assume the whole transmission assembly won't be cheap.

You might be better off looking on craigslist for a new machine. To save some money you can get a broken one. Switching your engine to a machine with a broken engine should be easy assuming the HP is about the same. You can also look for a machine with a broken front gear box if yours is able to swap over. That would take some more studying. Could be if you get another MTD you can switch the complete scoop.

I wonder if this was caused from lack of lubrication or if it was from working the blower too hard. Remember, this is a snow blower and not a plow. The transmission is only designed to move the blower around and not for the extra weight of pushing piles of snow. Let the front end do the heavy lifting. Slow and steady wins the race.
 

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yes it is a single speed machine (Craftsman 31am32ad799)
I bought a trans on ebay for $126....much cheaper than replacing the snowblower.
I really didn't push it too hard, I don't know what happened other than is just wore out.
From reading this and several other blogs, it sounds like a common issue with this snowblower.
Bronze gears? Seems like you are just asking for this with such a soft metal
 
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