129 transmission leak/running away
 

I have a slow leak somewhere in the front of the hydrostatic transmission on my 129, but the more concerning problem is that the transmission will pull itself into full forward on its own while driving.

It doesn't matter going up or down hill, it just works its way up to full speed and takes off. The brake will take it back to netural, or you can hold the control lever down.

What should I be looking for? I'm not very experienced in fixing things like this, so I'm wondering if this is major project or something easily fixable.

Don’t panic, happens to a lot of them. It’s an adjustment. Under the dash, or maybe under the tunnel cover.
Download the manuals from here or just poke around under there with the engine off, and move the handle, you will find the friction adjustment.
If there wasn’t a blizzard going on I would go out and take a pic of mine.

Friction nut is always on the dash tower on a Cub Cadet.
On a 129 it's not much fun to get to. It's in the manual.

You will have to clean off your dirty trans and find the leak. Could be several places. Leaks happen around gaskets and seals.

Good advice from the both of you guys.

The pivot point is at the bottom of the shaft, bolted to the cross member. The early ones, serial #425999 and lower were a cast iron arm that is split where it tightens and contains a tiny bushing that may be worn out and NLA. Be VERY careful, or the arm will break and then you will be screwed.

Hopefully, it will be the later one in your case and will just need to be snugged up some.

You can find the parts page here

http://www.cubcadet.com/webapp/wcs/s...0-A/0020100014

Good luck!

It is the earlier one with the split arm. I’ll be careful!

I've had this on a couple of my cubs. Tightening the friction nut always fixed the problem. It prevents the runaway situation, but it doesn't help the speeding up downhill and slowing uphill--that requires new trunnion springs and perhaps some repairs to the linkages/trunnion arm.