C-121 auto. What's normal?

[woodys3b 0]

I'm working through some small issues with my new 78-79 C121. This is my first experience with a WH Hydrostatic transmission so what I'm experiencing may be normal.

When mowing, I seem to be adjusting the speed all the time. The tractor slows considerably going up hills and in turns. Then speeds up considerably going down hills. There seems to be a very high amount of driveline lash. I don't think the drive belt is slipping. This thing would pull out a stump if it could keep the front tires on the ground. It isn't making any unusual noises. It doesn't get too hot and the fluid level is good.

When I bought it, the PO said that they work better with 10-30 motor oil. That statement and the color of the fluid lead me to believe that's what's in it. Any truth to that?

[woodys3b 0]

Come on guys, throw me a bone.

:thumbs:

[pfrederi 17,866]

OK I will throw the first bone and probably get heat from the hydro lovers here.

Up until two years ago I was strictly a gear guy. Yes, they have some issues (e.g.2nd is too slow and 3rd to fast for mowing in some conditions....but they don't change speed much at all uphill or down.

Now I have 3 hydros. The charger 12 is a 1 previous owner tractor and I believe he was careful with it and maintained it. It has a Sundstrand gear hyro and is running ATF.

The D200 has a Sudstrand piston to piston and was not well maintained. I have replaced the hydro pump and the hydro motor. (uses 10w-40)

418A has an Eaton and I think she also had a hard life previously. It was the first hydro I had and it did the same as yours speeding up downhill slowing on the up. I replaced the pump on it, it made little change. Most of the time I have to mow with my hand on the speed control lever as frequent adjustments are need.

The D200 when she is using her finish mower also need adjustments as you mow.

The Charger 12 is probably the best when it comes to maintaining speed but it requires tweeking on turns and hills.

The adjustable speed is nice but it is not a free lunch requiring frequent tweeking of the lever.

FYI my wife uses a John Deere 235 that we bought new. It has a foot pedal speed control so it is easier to use and frankly it need some what less tweaking than the WHs...but it is a lot younger.

Finally, I have spent a fair amount of time and money replacing hydros...3/8 speeds are a whole lot cheaper to work on and once you fix them they will outlast you. My 43 yr old L-107 has had her rear end oil changed 2 times and still works like new

[woodys3b 0]

Thanks Paul,

So, how do I figure out what transmission my tractor has?

I'm used to my old B-80 4 speed. While constantly adjusting the speed on the auto is a bit of a pain, I still think it is a big improvement over the manual for my situation. I have lots of trees to mow around. I have to use reverse a lot too. I was always shifting my old B-80. Now I just move the lever. If I had a big open area to mow, the standard would be better.

BTW, my old B-80 standard has a lot of driveline lash too.

[C-Series14 15]

It is gonna be a Sunstrand. Your VIN is either 81-12KS01 for a 1978 or 91-12KS01 for a 1979.

C-121 Automatic

[woodys3b 0]

Well, the plot thickens.

Here's what is on the ID tag on the steering tower.

91 16BS02

So it seems that I have a 161 with a 12hp transplant

[woodys3b 0]

After lots of reading and talking to folks at WH shows about this, I even test drove a different tractor with same transmission, I was convinced that my tranny needed work. I planned to do it this fall and just use it in the mean time. The transmission oil looked new so I didn't see much point in changing it or the filter. What I did do was add Sea Foam to the transmission a few times over the summer. The improvement was almost immediate but it wouldn't last more than a few tanks of gas. I kept adding it as needed and each time it would be good longer. Now, I think I can just change the oil filter and have a really nice working hydro.

If you have not used this stuff before, you are missing out. It works wonders to clean up fuel systems when added to gas. My recent experience with it shows it works wonders on our hydros as well.

[Sparky-(Admin) 21,405]

Hmmm.....never heard of putting an additive in a hydro unit. So any crud the Sea-Foam loosened up is hopefully in the filter your about to change . Keep us posted as to how well this fix works and how long it really lasts.

Mike.....

[squonk 41,321]

Did you add Sea Foam engine treatment or the transmission treatment?

[Lane Ranger 10,992]

The Seafoam engine treatment can has instructions that describe placement in the gasoline, diesel fuel tank or oil crankcase -not specifically in a transmission.

But seafoam is a very good product and works well in small engines. We have used it in about everyone of our tractors.

Woodys3b experience with this leads me to beleive that a hydro transmission treatment -cleaning of the oil - over several treatments is also a good use.

I am glad you mentioned this treatment being used for this purpose.

I think we can try it on our C-121 hydro that sat outside for 15 years. The transmission works fine with new oil in it but it has to be pretty dirty iside and we have not opened up the transmission to do any work onit.

Woodys3b - Thanks for posting this information.

:thumbs:

[kpinnc 12,429]

Just my two cents here...

Before adding ANYTHING to the transmission, I would try tightening the friction on the Direction Control Lever, or DCL. Of course I can't be 100% sure what is going on with your tractor without being there, so I'm just going off what you've said in your post:

1. Most important- You say the tractor is very strong pulling against a load. That tells me that you're not losing pressure in the hydro (as in bypassing), meaning wear is at least probably is not the culprit- so long as the transmission is warmed up.

2. Some folks say that when a hydro starts "free wheeling" on a descent, it's a sign it is beginning to show wear. While I understand the thought process here (bypassing in the pump can just as easily show up as slowing up hill AND speeding up downhill), I do not agree completely with it. I have 5 hydros- 3 Sundstrands and 2 Eatons. All of them "free wheel" in varying degrees, and all of them are strong units that do not lose power as the fluid warms up, which is the best way to tell the hydro is on it's way out to pasture. I can mow, drag a turn plow, or push gravel all day without a loss of power with any of them.

3. The design of both types of WH hydrostatics is that when the transmission is used under load, the internal forces acting on the hydro "push back" against the DCL. In other words, the lever on the pump itself pushes back against the DCL when you go up hill. This is the whole purpose of the friction adjustment on the tractor. It keeps the DCL in the last place you put it until you move it by hand. If you have to keep pushing the lever forward on an incline, you need to check and see if it was where you left it last before starting up the hill. I would suggest (as long as it is safe to do so) that after the tranny has reached operating temperature, try driving up the hill while holding the lever all the way forward during the climb. Of course, please take care not to flip the tractor- a small but steady climb should be enough to check it. If it slows down without pulling the engine RPM down, you've got a pump that is bypassing or some type of slippage in the belt/ pulleys. If not, it's probably the friction setting on the DCL.

Again, I'm just going off what you've said. Good luck!

Kevin

[woodys3b 0]

Just my two cents here...

Before adding ANYTHING to the transmission, I would try tightening the friction on the Direction Control Lever, or DCL. Of course I can't be 100% sure what is going on with your tractor without being there, so I'm just going off what you've said in your post:

1. Most important- You say the tractor is very strong pulling against a load. That tells me that you're not losing pressure in the hydro (as in bypassing), meaning wear is at least probably is not the culprit- so long as the transmission is warmed up.

2. Some folks say that when a hydro starts "free wheeling" on a descent, it's a sign it is beginning to show wear. While I understand the thought process here (bypassing in the pump can just as easily show up as slowing up hill AND speeding up downhill), I do not agree completely with it. I have 5 hydros- 3 Sundstrands and 2 Eatons. All of them "free wheel" in varying degrees, and all of them are strong units that do not lose power as the fluid warms up, which is the best way to tell the hydro is on it's way out to pasture. I can mow, drag a turn plow, or push gravel all day without a loss of power with any of them.

3. The design of both types of WH hydrostatics is that when the transmission is used under load, the internal forces acting on the hydro "push back" against the DCL. In other words, the lever on the pump itself pushes back against the DCL when you go up hill. This is the whole purpose of the friction adjustment on the tractor. It keeps the DCL in the last place you put it until you move it by hand. If you have to keep pushing the lever forward on an incline, you need to check and see if it was where you left it last before starting up the hill. I would suggest (as long as it is safe to do so) that after the tranny has reached operating temperature, try driving up the hill while holding the lever all the way forward during the climb. Of course, please take care not to flip the tractor- a small but steady climb should be enough to check it. If it slows down without pulling the engine RPM down, you've got a pump that is bypassing or some type of slippage in the belt/ pulleys. If not, it's probably the friction setting on the DCL.

Again, I'm just going off what you've said. Good luck!

Kevin

I like your two cents. I'd probably even give you four cents for it.

I'll pay more attention to what's going on with the lever when I'm working on slopes. I think the friction on mine is about right but I could be wrong. For the record, I'm an old Air Force F-15 mechanic so I'm pretty familiar with piston to piston systems as they are common in aircraft flight control and hydraulic systems. One of the symptoms that I have been trying to correct is the harsh starting and stopping characteristics. When I study the schematic for my tranny, I see that it has valves that soften this. My theory was that these valves were worn or dirty and were not moving freely. The Sea Foam was added mostly to try and free them up and I believe it has. The past few days, I have been working my horse hard pulling a heavy trailer full of fire wood up and down some pretty good hills. Going up is hard to keep enough weight on the front wheels to maintain steering. The transmission feels plenty strong in this regard and really always has. The change that I have noticed is that the transmission is getting smoother when starting and stopping which I can only attribute to the Sea Foam. Perhaps the change I've noticed in it maintaining it's speed better on slopes is caused by the friction on the lever increasing in the cold weather we are having.

None of the symptoms I'm describing here are miraculously cured. They are just noticeably better than they were before the Sea Foam.

[woodys3b 0]

The Seafoam engine treatment can has instructions that describe placement in the gasoline, diesel fuel tank or oil crankcase -not specifically in a transmission.

But seafoam is a very good product and works well in small engines. We have used it in about everyone of our tractors.

Woodys3b experience with this leads me to beleive that a hydro transmission treatment -cleaning of the oil - over several treatments is also a good use.

I am glad you mentioned this treatment being used for this purpose.

I think we can try it on our C-121 hydro that sat outside for 15 years. The transmission works fine with new oil in it but it has to be pretty dirty iside and we have not opened up the transmission to do any work onit.

Woodys3b - Thanks for posting this information.

Hmmmm........

I'll have to go check the can but I swear I thought the can said it can be used in transmissions as well.

BTW, one of the reasons I decided to try the Sea Foam is because I had a conversation with a fellow at a tractor show about this transmission. He said his did the same thing as mine did so he decided to take it apart and see if he could find anything wrong. Once apart, he said everything looked pretty good so he just cleaned everything and put it back together. After that, he said it worked perfectly and has been flawless ever since. So I thought I'd try to clean it without taking it apart.