Yardman lawn tractor stuck in forward wouldn't shift to Neutral

[carusoswi]

I have a 1987 Yardman lawn tractor (Model 135607-7) which has been operating flawlessly since an engine replacement last fall. This afternoon, towards the end of mowing my 3/4 acre lawn, the tranny seemed to stick in forward and attempts to shift to Neutral or holding in the pedal did not stop forward motion. I had to shut down the engine to avoid a collision. After shutdown, I lifted the rear end slightly (slightly is all this 70 year old could manage) in order to pull the machine backward from the object into which we faced imminent collision. That action plus some 'exercising' of the 'gear' selector (fwd/n/rev) seemed to free it up.

I finished up my cutting, and pulled her up to the garage door, put her in neutral and reduced the throttle to idle. Opened the garage door, and, while I was removing the rear deflectors, she jumped into gear on her own. I had to shut her down to stop her. Lift and 'exercise' again restored normal shifting operation.

I was able to use the gear selector to fwd/rev in order to park her inside my garage.

What could cause this and what should I do to fix it?

Thanks.

Caruso

 

[Rivets]

First thing I would be checking is the belts and the idler pulleys. When were they last changed? When you step on the brake/clutch pedal and lock the parking brake the drive belt should be loose, which stops the transmission pulley so you can shift. Would you double check your model number, as I’m not finding the one you posted. I’m assuming we are talking about a rear engine rider.

 

[carusoswi]

First thing I would be checking is the belts and the idler pulleys. When were they last changed? When you step on the brake/clutch pedal and lock the parking brake the drive belt should be loose, which stops the transmission pulley so you can shift. Would you double check your model number, as I’m not finding the one you posted. I’m assuming we are talking about a rear engine rider.

We are talking about a front engine rider. The model number 13607-7 (my bad). It was delivered with decals describing it as a 12 HP model. The engine sported decals describing it as a 12.5 HP model. My local dealer replaced that engine with an 11.5 HP B&S engine. I have no problem with that. Sorry for this error in reporting the model number. I cut my entire 3/4 acre lawn without incident until the last 20 sf when I noticed the problem. I do as much cutting in reverse as I do in forward due to the layout of my lawn. When I received this mower (back in 1987, oh my!), the first thing I did was to alter the electrical connections to defeat the ridiculous setup that the mower would not run/cut in reverse. That has never been an issue, and I doubt it has anything to do with this current issue.
Thanks for the reply. Any advice welcome.

Caruso

 

[Rivets]

There is an adjustment on the speed shift rod, but you will have to remove the deck to access it. When was the last time the you had the variable speed belt and the drive belt changed. Various speed belt is part number 954-0281 and the drive belt number is 954-0280A. They need to be replaced as a set.

 

[carusoswi]

All:
Cut my lawn two days ago and experienced no problems. Will have to keep an eye on this. Thanks for the replies.
Caruso