John Deere 955 won't move.

[Alumalite]

I had the bolt that holds the drive gear to the hydro break in my old JD 955. (I guess this is a fairly common problem). Following the service manual I pulled the hydro, replaced the bolt, fished out the broken bolt and washer out of the transaxle and put the whole thing back together. After replacing all the fluid I started the transmission bleed procedure, but the tractor will not move in forward or reverse now! I tried moving the shift lever to both fast and slow several times and it didn't do anything. It just acts like it's in neutral.
The rest of the hydraulic functions seem to be acting normally, the power steering is working, the bucket raises/lowers, etc. Is there anything I can check or try before tearing into it again?

 

[Williy]

Did you recheck to see if you have enough fluid??
Is it possible to have air in the system??

willy

 

[Alumalite]

That's what I originally thought it was too. I was working on bleeding the system when I discovered it wouldn't move. The service manual says to check the charge pump pressure, but I don't have the correct gauge. I did open the screw where the pump pressure is tested and bled the air out of it.
I also checked the charge relief valve, which looked fine.
The service manual also recommends checking the charge pump flow, but I don't have a gauge for it either.
I am stumped. The original repair was pretty straight forward (but a ton of work to squeeze the hydro out of the frame rails) so I am not sure why I have a new problem now.
I will go through the bleed procedure again and see if I can find any hidden air pockets. Thanks for the suggestion.

 

[Alumalite]

So, I can push the tractor forward and backwards in all 3 settings: slow, neutral, and Fast. I don't know if that will give any clue as to what's going wrong. I don't know enough about how these work to diagnose the problem.

 

[rScotty]

That's what I originally thought it was too. I was working on bleeding the system when I discovered it wouldn't move. The service manual says to check the charge pump pressure, but I don't have the correct gauge. I did open the screw where the pump pressure is tested and bled the air out of it.
I also checked the charge relief valve, which looked fine.
The service manual also recommends checking the charge pump flow, but I don't have a gauge for it either.
I am stumped. The original repair was pretty straight forward (but a ton of work to squeeze the hydro out of the frame rails) so I am not sure why I have a new problem now.
I will go through the bleed procedure again and see if I can find any hidden air pockets. Thanks for the suggestion.

Pressure gauges are pretty inexpensive. Check Amazon. Less than $20 and about that much again for fittings. A gauge would at least let you know if the pump is making pressure. Without one, I'd just be guessing.
Flowmeters are real expensive and even a lot of medium size tractor dealer shops won't have one. But there are ways around that if you know the pressures.

 

[Alumalite]

I will get a gauge ordered, I have been wanting one anyway. I will update you on pressures when I know. Thanks!

 

[gstrom99]

Which bolt broke? I don't have a repair/parts manual handy. Following, and awaiting your findings... Good luck.

 

[Alumalite]

Bolt "A" seen in this photo. The later models switched to a castle nut since it was a common failure point.

 

[rScotty]

Is that an output gear or does it drive the HST pump? It almost looks like an output. Would a lose nut cause enough gear slop to break the bolt? Maybe a larger exploded parts diagram would help.

 

[gstrom99]

Ouch! Thanks for the pic. I see where that failure would be bad...