Cub Cadet 154 transmission problem

[brdfrd]

So, I scoured the forum pretty well before posting this, but my 154 runs great, but won't move...

I was using it a couple years ago, and while going up a slight hill behind the house it slowed to a stop, and if I hadn't use the brake it would've rolled backwards. There was no big event, no big noise, no significant change in RPM.

I'm finally getting to look at it now. The clutch is adjusted properly and functioning fine, and when I spin the flywheel the gears in the trans spin--so it isn't the pin holding the flywheel on the input shaft. I had guessed it might be a shifting fork issue but when I opened it up they seem to be fine/tight, and not bent. I haven't found a good blow-up of the parts in the trans or diff, so I'm at a loss to guess where a pin or key might have fallen out.

Any advice would be very appreciated. I'm hoping I don't have to split the whole thing. We moved last year and the cub is buried in the barn--I could probably manage to drive it out, jockeying carefully. But I can't get anything near it to pull it out--without trying to get a couple other projects running and moved first.

Thanks, Brad

[John *.?-!.* cub owner]

Put it in gear and jack up rear wheel one at a time and while looking through the oil fill hole rotate the wheels by hand. I suspect you will find one will spin differential and one will not. The one that does not most likely has a broken shaft going from the differential to the final.

[brdfrd]

Thanks--will do. Is that common, and will it happen without an obvious, catastrophic event/sound?

Brad

[gitractorman]

No, what John described is not common and I think it would have been quite an event if that happened. I'd be willing to bet that the rear bolt is broken where the drive shaft attaches to the transmission. This is VERY common. What happens is the bolt wears and eventually breaks but the ends of the bolt often stay in place because they are rusted there. So, when you inspect, it looks ok. I've seen several do this. What's even trickier about this is if you are sitting at idle, trying to diagnose, the engine will spin the driveshaft and turn the transmission, but if you put the tractor on the ground, there will be enough resistance that the driveshaft will begin to spin inside the coupling. I've even seen this where the tractor will drive around in the shop or on flat concrete, but if you get in the grass there is enough resistance to make the slippage occur. Good news, easy fix if this is the problem.

[brdfrd]

Thanks, for the second opinion--I was pretty sure that the previous scenario would have been an obvious catastrophe. It did occur to me that the bolt you mention could have sheared and left a burr and enough friction to seem okay turning by hand. I hope you're right. I'll check that first in the AM.

Thanks gentlemen.

[brdfrd]

No, what John described is not common and I think it would have been quite an event if that happened. I'd be willing to bet that the rear bolt is broken where the drive shaft attaches to the transmission...

Bingo--we have a winner. You were right gitractorman: bolt sheared, but had enough friction to hold when turned by hand. It's a pain to get at, but about the simplest fix I could hope for. Can I just put a grade 8 bolt in there?

Thanks, Brad

[seahaul]

The prevalent thinking is to put a grade 8 bolt where the rear flywheel bolts to the transmission input shaft and put a weaker bolt in the forward end of the driveshaft (where it bolts to the engine flywheel). Then if one breaks, it will most likely be the front bolt that is easier to get to and replace.
Charlie

[brdfrd]

That makes sense--the front one broke once, and I just put in what I had, not grade 8, so I'll put that in the back and I should be good.

Thanks very much for the help going out to pick one up now.

[gitractorman]

Glad to hear you found it! The transmission and rear-end components are away stronger than the driveline in the number series tractors, and those two bolts are the weakest points. Not a particularly bad design. The bolts are fairly easy and cheap to replace, so I'd much rather do that than tear up a transmission!

Thanks,
Bill

[brdfrd]

Yeah, the back one is more of a pain than it should be though. I got in and we're running. To think it sat 2 years waiting for me to find time to do into the transmission...

Thanks guys, Brad