VV Pump Failure?

[tlb]

Moving stumps today and the PT425 was working fine for several hours, then when moving a large stump up an incline, there was a loud back from the engine compartment. Forward and reverse motion not working. Lift arms and steering working fine. Looked at the tram cable and it is moving fine.

It is not clear to me in my copy of the PT425 manual what controls forward and reverse motion. I am assuming the VV pump?
I have attached two pics of the rear pump(s) and forward pump. If someone knows which is which please let me know (pump 1, pump 2, vv pump?).
If VV pump control forward and reverse, is there a slotted key that may have sheared or lovejoy connector failure?
Thanks,
-Tim

 

[MossRoad]

In your pictures:
Pump 1 is the AUX PTO pump that powers your steering, FEL and Quick Attach.
Pump 2 is the MAIN PTO pump that powers implements.
I make this assumption by the size of the hoses coming out of the pumps.

VV pump provides fluid to your wheel motors for forward/reverse.
Your Variable Volume pump has the hydroback cable attached to it. That's the cable that the treadle operates.
In neutral treadle position, that lever on the top of the VV pump holds the swash plate in neutral.
Push the right pedal, it moves the cable, that moves the lever, that moves the swash plate to forward.
Push the left pedal, and it moves the cable in the other direction, lever goes other direction, swash plate goes reverse.

So, yes, you may have one of several problems if the cable is moving the lever on the VV pump when the treadle pedals are depressed.

Since you heard a BANG and then it stopped moving, I'd suspect something snapped (yes, I'm captain obvious).

- There could be something internal to the pump that is damaged.
- The key in the motor shaft that keys the lovejoy to the pump could have sheared or come loose.
- The teeth in the lovejoy could have sheared.
- The pump side of the lovejoy could have come loose.
- There's two shafts on the engine. One is the main crankshaft that I believe powers your 2 PTO pumps.
There's a stub PTO shaft on the opposite side of the engine that I believe powers your VV pump. That stub PTO shaft could have broken.

I'd call Terry at PowerTrac on Monday for advice before tearing into it.

Also, don't attempt to roll the machine without opening the tow port.

 

[tlb]

Thanks for the quick response and explanation. I'll call Terry tomorrow.
This is the first major mechanical failure in 18 years. All other were just wheel motors so not that hard to fix.
A few electrical issues involving bad key switch and blown fuse, so I can't complain (too much).

 

[MossRoad]

No problem. That's why this forum exists. Mutual assistance and commiseration. :laughing:

Your machine looks very much like mine, except I have a Kohler muffler and your's looks like a PowerTrac muffler. But my pumps are laid out the same and I also have the same hydroback cable/treadle arrangement, so I'm pretty sure we're on the same page.

Good luck. Please let us know what Terry suggests. Thanks.

 

[tlb]

MossRoad,
I'm giving an update on my PT425 in the hopes that others can use the info. It's not completely back together yet, but should be done in the next few days.

So, I talked to Terry at PowerTrac about 3 weeks ago and he thought the Lovejoy connector had broken, which requires removing the VV pump (never done this before). Terry mentioned I would need a pry-bar to remove the Lovejoy connector from the pump shaft.

First step was to remove gas tank (Pic1) to get access to pump bolts. The bolts require a large Allen wrench. After removing the pump bolts, it was clear the Lovejoy connector was loose on the pump shaft and would turn freely by hand (not supposed to do that). I was able to slide the Lovejoy connector off the VV pump shaft without using a pry-bar (Pic2).

Inspection of the Lovejoy showed it was intact but the shaft key (Pic4) had come loose and damaged the inside of the Lovejoy (Pic5, Pic6). There are two (Allen type) set screws that help hold the Lovejoy onto the pump shaft, so neither set-screw was making contact with the shaft. The (half-moon) key (Pic4) was damaged as well as the pump shaft where the key sits (Pic3, Pic7). Looks like this may have been loose for some time and just finally failed when the pump was under heavy load.

I called Terry and discussed what I saw. He knew (without me mentioning details) the key had slipped and damaged the inside of the Lovejoy. Seems this may be a known issue. I ordered a new Lovejoy ($136+shipping) on Tuesday and received it the same week on Saturday.

Inspection of the new Lovejoy showed it was larger in diameter than the old Lovejoy, by about 1/8 inch (Pic9). No problem, so I thought. When I tried to fit the new Lovejoy through the VV pump mounting hole (Pic8), it would not fit, not even close. So I called Terry back and discussed. He assured me it would fit and I assured him it would not. The new Lovejoy was exactly 4-inches in diameter, but the old one was about 3 7/8 inches. He said not possible as PowerTrac has never made a Lovejoy less than 4 inches. Long story short, I sent old and new Lovejoy back to PowerTrac, and 3 days later received them back, with the new Lovejoy milled down to 3 7/8 inches. Now it fits. My guess is when the tractor was initially built, the VV pump pilot hole was not exactly 4 inches round so someone just milled down the Lovejoy until it fit. Close inspection of the pilot hole shows it is not perfectly round. The pilot flange on the VV pump is 4 inches in diameter, but it has 4 cutouts for the mounting bolts which allows the pump to fit even though the mounting hole is not exactly 4 inches in diameter all the way around.
-Tim

 

[tlb]

Forgot to mention one other aspect of the change out, when removing or installing the Lovejoy, the VV pump needs to unbolted first, then slide it back as far as possible, then slide off the Lovejoy connector, then move the pump out of the way, then slide the lovejoy connector through the VV pump mounting bracket hole. I initially thought (and tried) to remove pump with Lovejoy still connected but there is not enough room to do this, at least in my vintage PT425. Same thing when reinstalling, I initially tried to reinstall pump with lovejoy already connected but no room to do this.

Reinstalling the Lovejoy was similar, in reverse order. With the pump out of the way, slide the lovejoy through the mounting bracket hole, then slide the pump into the hole, then slide the lovejoy back onto the pump shaft. Make sure the key on the pump shaft is lined up with the key in the lovejoy before starting. I had to use a mallet to get the lovejoy to go onto the pump shaft. Before mating the pump to lovejoy, make sure pump shaft is rotated until key slot is top-dead-center, then place the new key in key slot on pump shFT, then slide lovejoy back onto pump shaft, making sure the key slot in lovejoy matches up to key slot on pump shaft, them tap lightly with mallet to seat. Easy-peasy.......not

 

[MossRoad]

Excellent write-up. Thanks! :thumbsup:

Glad it was the lovejoy and not the pump.

 

[cqaigy2]

Yes, nice write up and picts!

 

[ldabe]

Very Good "tlb".
Thanks for putting this on the forum, BUT, I hope I never need it, lol.
Since I am not all that mechanically inclined, it is posts like these (and of course all the people of the forum) that help greatly for a guy like me.
Thanks again.