Trunion Shaft Seal Leak?
 

Morning Fellas,

So i just finished the Axel seals and Cork gasket on my 129, for a first time the process was easier than i expected to split the tractor thanks to the thread about that exact issue! So i get her all back together and get her cranked up and notice i have a leak, so i investigate further and find that it is coming from the Trunion rod where it passes into the pump unit. So im kinda at a loss here on where to go and what the next move is... is this repairable? or is this something that will need to be professionally done as i assume the pump will need to be split at this point? Any input is greatly appriciated yall.

Thanks,

Matt

Is it leaking from the left or right side? Left and right based off you sitting on the tractor.

The leak is going to be on the drivers side... left side of the tractor. When its running you can see little bubbles coming from around where the trunion shaft goes inside the pump housing. Shortly thereafter ill have a slow but steady drip once the fluid runs down to the cooling fins.

Matt

The pumps going to have to come apart to replace that seal, if you haven't already you need to download load the manual. I'd also recommend messaging Sam Mac as he's pretty knowledgeable with those pumps.

If you don't have a decent set of tools and a really.... I mean REALLY clean place to work in, I'd suggest having that seal changed by a shop. However, as someone who has done it and worked at dealers before, you may not "get what you pay for" so to speak. Few "mechanics" have pulled hydrostats apart. It's not a overly complicated job, but it does require some skill. If your going to do it yourself, I'd suggest buying and changing all the seals and gaskets on the whole pump. I personally don't suggest this job done by someone with little mechanical experience, just because of the sensitivity of a piston pump. They are similar to, but somewhat more sensitive, to dirt than the inside of a motor/engine.

I cannot agree with John more!
For us who know our way around tools/equipment it is just another walk in the park.
But for those who are a little intimidated with mechanical things, it can turn into a disaster.
Do study the service manual and online videos before you decide one way or the other.

It's not that big a deal to change it. Biggest issue to things need to be CLEAN. Take your time, read the manual, then read the manual again and after you do that read it again. Look at it this way, it was assembled by a human, no reason you can't do it yourself. Take care when driving the pins out of the swash plate especially on the trunnion side. It has 2 pins and you need to be careful to follow the manual or you will be in trouble. Other than that it's not a big deal to do one. Worst case if you screw it up you can find a good used pump on Flea Bay.

Do not try this without following the manual
 

There is a critical step in disassembly where you can ruin your hydro housing if not done correctly, not to say it is a difficult job, but it is a job that has specific steps that must be followed.

Sam Mac beat me to it.

Morning fellas,

Thank yall so much for the replys! I am reasonably mechanically inclined, and have the drive to do it. I have read the manual, and the only tool i dont have is press or vise to press the spring down in the piston barrel to remove the spring retainer. We actually just moved so my garage is really clean at the moment, cluttered with some boxes, but clean. Ill have to get a set of calipers from work so i can accurately measure the slippers. After reading over the manual i think i can do this. Im going to look up some videos on the youtube to get a better grasp on the whole thing as well.

I know the seals and gaskets are avalible through CCS as they have a "rebuild kit" are the barrings avalible through them as well? i dont recall seeing them yesterday.

And when the manual says to clean parts, i assume that means use a sacrificial quart of hytran or fresh hydro fluid?

Thanks again guys! great help!

Matt

WHOA, there cowboy!!

You don't need to rebuild it! I promise, it's in fine shape inside there. No need to buy a press or mic's to measure stuff.... or even borrow them. If the slipper pads are wore, you'll be able to see it with your eyes. They don't just wear a little, they basically don't wear at all unless something goes wrong, then it's usually catastrophic. DO NOT take the springs out of the piston blocks. Just leave them alone. DO NOT take the pistons out of the piston blocks, and be very careful when disassembling to try and keep them from falling out. They need to stay in the same hole if possible. Just order the case gasket, cork gasket, o-ring for the charge pump, O-rings for any of the fittings or for the relief valves if you want to remove and change them, and the seals. No need for bearings, or anything else unless you find something once you get in there. If you do find issues.... weigh your options. Good used hydro's go for between $75 and $125, so no need to spend a bunch of money on one.


Clean the internal parts with diesel fuel, then coat with hytran before assembly. Clean the case and other parts with mineral spirits or lacquer thinner.

What J-Mech said. No need to mess with something that is working. All you need to do is to replace the seals, O-rings and gaskets. No need to disassemble the piston assembly's.

I will reiterate to be careful so as the pistons stay in the bores they are now lapped too and living in.
If they fall out, and it does happen:angry: they all are ground the same in the beginning, so the only problem you will experience will be it is more noisy then it was before you mixed them up. BTDT.
Assembly grease (trans gel or chassis grease) will keep the valve plates where you need them when reassembling.There is a your tube video with a fellow making a board jig that helps hold the unit while dis/reassembly.

When removing the pins from the shafts/swash plate pay particular attention to directions as to marking a drive pin punch and not driving it too far.
I found one that had one long pin and not 2 pins holding the shaft in the swash plate,lucky it just cleared the case when it was turned just right so the shaft would come out.
I have seen pix where a person drove the pin threw the case, that will ruin not only your day, but a good case also.:angry:
Make sure you start disassembly with a very clean case exterior it helps keep everything clean inside, just try to think of your doctor operating inside you!
Clean clean!
Have a large bench and use plastic bags to put parts in keeping them clean.
When I get one assembled, I like to pour hytrans in side so it don't start dry
on initial start up, it just makes a more happy rotating environment inside.

Good deal fellas! That puts my mind at ease a little bit with not having to take Everything apart. I saw the wood jig in the manual and im going to partake in that as well. I bought a bunch of plastic baggies for bolts and parts to stay clean with. I also finally noticed that i have a ported pump. But on a 129 i dont know what for... no lines to the front or a lift... did they just put those in random tractors?

Oh while im in there i want to clean the valves... they are a little sticky... work fine i guess but the button could be smoother. Regardless a good cleaning wont hurt right? Would i just use diesel and pb blaster... then lube with hytran before assembly?

Thanks guys... gunna order my kit friday, and get this party started!

Thanks

Matt

As others have said, it's an interesting job, and you'll learn a lot about what makes the hydro work in the process.

Work meticulously and methodically, but you will not have to clean anything inside. It will probably be spotless.

Clean the exterior very well before you start. I used a large woodworking vise to help hold the hydro as I worked on it but the manual has instructions to make a wooden jig.

Follow the instructions to remove the pins in the trunnion shafts EXACTLY.

Replace all the seals while you are at it.

I've done it a couple times. It's actually a pretty neat piece of engineering and a little remarkable that the pressure of those little slippers on the angle plates transfer power so effectively.

The one trick that Sam Mac helped me with was using grease to hold the valve plates in position on reassembly.

Also, make sure you do not pinch the O ring reassembling the charge pump. BTDT.

Oh, one more suggestion. Repair the trunnion rectangle when you have the shaft out. I welded on new rectangles on the two I reworked.

Yep, here's that high-tech assembly board you need! Have fun! As has been mentioned, clean everything real good before you take it apart, you'll thank yourself later. My shop is a farm shop, pretty darn dirty. I cleared off the work bench and put down sheets of cardboard so I knew I had a clean area to work on. Oh if all those pistons don't stay where they belong regardless of how hard you try, join the club--I still ain't figured out how I let that happen when I was TRYING not to.:bigeyes:

John - Thanks for the pic, Im going to make one of those for sure. I like the cardboard idea, and im going to clean the outside as best i can, wear gloves and all that jazz. Going to try and get everything situated in one of those big tinfoil turkey pans too that way i have something to catch misc. items if they get away from me. Only thing i guess im worried about is putting the valve plates back in appropriately, not so much switching the motor and pump plates around, but putting them in upside down or something.... granted that may not matter. Gotta find me somemore videos... the one i did see the guys wasnt using a manual and was just kinda pulling everythning out to replace a cracked case...

Thanks guys,

Matt