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I have a Yardman by MTD Model # 13AM772G755 bought new in 2007 and has been a good mower. It's got somewhere around 125 hrs on it. Very little done to it over the yrs, replaced belts last year and new battery. I use synthetic oil in it and so far hasn't used a drop in 7yrs. My issue is this. For past couple yrs I've noticed when going downhill it jerks a little bit more than what I thought was normal. However, after mowing a few times this year, it's getting noticeably more pronounced. I'm assuming its something in the transmission. I"ve checked for some type of adjustment but apparently there isn't one. I'm at a loss as to what the problem could be, but since I have some downhill mowing I'm almost afraid to get on it. I can go up the hill, but at some point I'm gonna have to go over the hill. I usually make a few passes up and down to give me some clearance to turn, then I start cross mowing.

My question is....is this a tranny issue? and if so, is it repairable? I'm a shade tree mechanic and can probably do this, but don't won't to explore as it's mowing season and don't have time.

First make sure there are no bad, worn, burnt spots in the belts. The other thing could be going on is, I am assuming a gear drive tranny, is the drive gears, and the shift collar are getting worn causing slop in the gears, and could be causing slippage, or slack to develop when the load changed .

ILENGINE said:

First make sure there are no bad, worn, burnt spots in the belts. The other thing could be going on is, I am assuming a gear drive tranny, is the drive gears, and the shift collar are getting worn causing slop in the gears, and could be causing slippage, or slack to develop when the load changed .

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Thanks....now that mowing season is past and a couple months till the next, thought I'd attempt to "fix" my lawn mower issue. Yes...it is gear driven. I'm thinking I'll order parts....forward drive gear and clutch dog. Since it's not doing this in reverse, should I change the reverse drive gear as well? I'm guessing when you say, shift collar, you are referring to the clutch dog? Again...I'm a shade tree mechanic and as long as I'm careful and note how the parts are positioned as I take them off, I think I can replace them. I may have to ask on here if I get lost in the repair. Thanks!!!

Technically, this is not "gear driven" , since your different gears are in the variable speed pulley system. I wouldn't buy anything before I got into it. One problem area on these tractors was the large nut and hub that holds the big pulley on the trans gets a little loose, and the pulley starts wallowing out. That may be your problem.

The hub has a raised star shape, like on the blades, and the pulley has a star shaped hole, and if you were to keep running it like this, it would get worse until the star rounded out and you would not move anymore.

So I would check this first, as it may just be the problem, an easy fix.