mtd transmission works in reverse but not forward

danny_2010June 23, 2010

MTD 46" model 13AN771H729 (2007)

drives ok in reverse only. Won't move in forward and grinding noise coming from gear box. Removed gear box and dismantled. All looks ok, seems fine on the bench but when reinstalled same thing.. Also checked linkage to make sure it was going all the way into forward. Not sure if problem is with the differencial, gears or slide. When I turn the drive pully by hand on the bench and shifted between neutral, forward and reverse it looked fine. Trying to decide what parts to replace, gears, differential or what.

Anyone have any ideas? Thanks

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Take it back apart. Refer to the image below, or better yet, get your free copy of the online manual from MTD.
Look at items # 15. These are the two 42 tooth bevel gears that actually provide the means of selecting forward or reverse, depending on which one of the gears item # 16 (clutch collar) is engaged to. Here's what you need to look for.
The clutch collar (#16) rides and slides on item # 17 (called the drive shaft by MTD) and has internal splines that match the external splines on the drive shaft.
You need to check the splines on the clutch collar and on the drive shaft to see if the is a small section of splines missing (worn off or sheared off) from both parts.
If you do not see any damage to the splines, you need to examine the engagement "cogs' on the clutch collar and the coresponding mating cogs on each of the 42 tooth bevel gears. If you find wear or rounding off of the cogs on the clutch collar and/or either of the 42 tooth bevel gears, that is why you hear the the racket.
One more item that needs looking at is # 20. MTD calls this a "detent shaft assy"...........yeah well right! But I calls it the "forward/neutral/reverse shift fork".
If this fork does not shift the clutch collar equally as much in both directions, that could cause partial engagement in one direction (in your case this would have been FORWARD) and that could have caused the clutch collar cogs and the forward 42 tooth bevel gear cogs to round off to the point of slipping.

    Bookmark   June 24, 2010 at 1:40AM
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Well, if it works well in reverse--install a big rear-view mirror, and get to the mowing! ;0)

    Bookmark   June 24, 2010 at 7:23PM
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Mowie: Thank you, wish I could buy you a beer. I think I'm just going to order all those parts and replace them, except for the differential (the way that gizmo works is confusing to me) I really can't tell how worn they are without a new part. I'm somewhat obsessed with this project because I think It's a conspiracy to make these machines disposable. I just can't see throwing this thing away. I'm a marine biologist, let me know if you have a question about fish...least I can do. Just kidding.
Rusty: Can't engage blades in reverse or I would.

    Bookmark   June 25, 2010 at 1:39PM
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Hi Danny,

After you changed the parts inside the differential, did that fix the grinding noise? I have the same model ride mower and I cannot find anything wrong with the gear parts either.

Thanks for your help

    Bookmark   June 9, 2013 at 1:05PM
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