B7200 HST Transmission shot-replaceable by novice?

[ram042400]

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MY B7200 is now experiencing issues moving. Loader hydraulics are fine, will pick the front of the tractor up at idle with the B1640 loader. Can't get up the smallest inclines in high, especially after it is warmed up. I took it to my local dealer and pressure tested the transmission. The charge pump was good at 80lbs at half throttle. The forward direction port was only hitting 1800lbs upon initial forward momentum, and then dropping down to about 1000 while moving on level ground. Should be about 3800lbs I was told. We switched the reverse and forward relief valves w/ the same outcome. Anways, I've been told, I need a new tranny, as I guess, the most likely issue is that the internals are not sealing against some plate and maintaining a tight seal to build pressure.
I'm not anxious to pay the dealer's hourly shop rate, to swap the tranny's, and I am contemplating doing it myself. They were quoting me about three days of labor. I do have a good mechanical ability(I believe anyways), just wondering if this is doable w/ that, or if a specialist/knowledgeable person is actually necessary. I am a novice to hydraulics through. Assuming it to be pretty cut and dry as far as unbolting and separating and putting back together.
Does anybody know if I have to separate from the clutch area back or does it come out from the back, keeping the main frame area attached to the front of the tractor?
I just am not in the market right now for a newer tractor.
Any words of encouragement or advice? Thanks in advance,
Rick

 

[texasjohn]

sorry HST tranny is shot, haven't heard of many such problems.

This is a repair task I would not tackle although I do lots of my own mechanic work and have a shop.

I'd recommend getting a shop manual for the tractor, looking at the HST repair section and judging if you have the tools, skill and patience to do the work yourself.

 

[brain55]

A couple of things I see. First of all that pressure test should be done with the tractor blocked up against something, a moving reading tells you next to nothing. I would then check to make sure that it is not the clutch slipping, I have replaced far more clutches in that model machine than I have rebuilt HST's. The easiest way to see if the clutch is slipping is to drive the machine up to an immovable object like a tree or heavy post set in concrete. Put the machine in high gear at full throttle with the rear PTO engaged and lock the brakes. Have someone behind you watch the PTO shaft, when you push the HST pedal forward and the machine does not move, either the PTO shaft will continue spinning or it won't. If it stops spinning the clutch is slipping, if it still spins and the machine is not moving or spinning the tires then I would suspect the HST. This is when the pressure test should be done also. Maximum relief pressure occurs when the machine meets an immovable object, not on initial movement or when the machine is traveling.

As far as you being able to do the HST swap yourself, I think I would leave it to someone with more experience. Same with the clutch if that is what is needed instead. They are a little high on the time, 20-24 hrs is about what it should take to rebuild your HST not to R&R it. I would guess closer to 12 hrs for the R&R depending on the experience level of the repair facility. I could do the clutch in a day depending on any problems, I would quote 8-10 hrs.

Brian

 

[dfkrug]

I do have a good mechanical ability(I believe anyways), just wondering if this is doable w/ that, or if a specialist/knowledgeable person is actually necessary.

I would say go for it, Rick. Brian's and John's suggestions are excellent:
get the manual and run those tests first.

If your HST is toast (due to low or dirty oil most likely), then you can buy
the important parts from Kubota. The hardest part about disassembly is
getting the tractor split in two. These units are much much simpler than
an auto trans on a car. I have fixed a few. If it is damaged, you will need
new valve plates, and possibly the pistons/cyl assemblies for the pump and
motor. The latter 2 assemblies are not sold piecemeal.

BTW, my B21's initial failure was probably a failed seal that spewed oil
all over the clutch.

 

[ram042400]

The easiest way to see if the clutch is slipping is to drive the machine up to an immovable object like a tree or heavy post set in concrete. Put the machine in high gear at full throttle with the rear PTO engaged and lock the brakes. Have someone behind you watch the PTO shaft, when you push the HST pedal forward and the machine does not move, either the PTO shaft will continue spinning or it won't. If it stops spinning the clutch is slipping, if it still spins and the machine is not moving or spinning the tires then I would suspect the HST. This is when the pressure test should be done also. Maximum relief pressure occurs when the machine meets an immovable object, not on initial movement or when the machine is traveling.


Brian

I did put the tractor against a tree, in low and it will not break the tires free, even in 2wd. I had the transmission cover off when I did this, and I watched the "prop" shaft. It did not stop spinning, just got a lot of pump whine up front. When I brought it too a shop, they did check the free play on the clutch, which they said it was fine. And as far as pressure testing it, I was there when they broke out their service manual for the 7200, and did it according to specs. I too was hoping it was "just" a clutch issue. On those tranny's there is no break down to the individual internal parts, so I ordered up a whole new transmission, along w/ a service manual. Can anyone lead me to if the tractor has to be split at the clutch, or can I leave the clutch connected and disconnect the driveshaft and the prop shaft, and pull the tranny/rear end out the back of the frame. Thanks for the replies.

 

[BrierPatch]

If you got the WSM from the dealer it will have all the info I think you are looking for and asking about. I had the WSM for my 7200 and it covered it in great detail especially the HST. By the way there are 2 screens in the hydraulic resiviour, I don't know if you have checked and cleaned them both? I believe one is for the tractor hydraulics and one is for the HST.

I say get the WSM look it over real good and then decide if you have the time, place and tools to do it.:thumbsup:

Good Luck !

 

[aczlan]

Can anyone lead me to if the tractor has to be split at the clutch, or can I leave the clutch connected and disconnect the driveshaft and the prop shaft, and pull the tranny/rear end out the back of the frame. Thanks for the replies.

How much is a clutch? I would look into replacing the clutch while I was in there (unless it looks like new). Might be a few hundred more, but cheaper than pulling things apart again in a few hundred hours to replace the clutch.

Aaron Z

 

[brain55]

To R&R the HST you can leave the clutch housing attached to the engine and just remove the HST, trans., and diff. together.

Brian

 

[ram042400]

To R&R the HST you can leave the clutch housing attached to the engine and just remove the HST, trans., and diff. together.

Brian

Thanks for the reply, that is what I was looking for. I have standard mechanic's tools, and hoping that will be adequate to tackle this one. Thanks again, it will be a few days before the parts come in.
Rick

 

[RobertN]

My first question would be if you tried new filters, fluid, and cleaned all the strainers?

If you have not, I would at least try that before going to the effort to split the tractor.