Hot tranny oil d180

[tommyg 152]

Well, I'm finally accepting the fact that my hydraulic pump is gong bad. Less and less power as the transmission warms up. But I was wondering if anyone knew if the temperature of the fluid is a byproduct of a worn pump or the reason for the decrease in power. My transmission gauge is borderline yellow zone, about 200 degrees. What causes the temp to get up so high? I'm just mowing the lawn, not working it hard at all. I'm just trying to figure out if the two are related. Anybody?

[73-18 automatic 8]

I would think they would be related. have you changed the oil and tried that

[Trouty56 567]

Here's my "definitely not an expert" thought on this subject. As the pump or motor starts to wear over time the flow of the oil becomes inadequate for the proper cooling to take place. As the oil overheats and gets hotter/thinner the more the power loss occurs at the wear points causing less oil flow and more heat and on and on.

If I am wrong at least it sounds good for now...... :)

[73-18 automatic 8]

Here's my "definitely not an expert" thought on this subject. As the pump or motor starts to wear over time the flow of the oil becomes inadequate for the proper cooling to take place. As the oil overheats and gets hotter/thinner the more the power loss occurs at the wear points causing less oil flow and more heat and on and on.

If I am wrong at least it sounds good for now......

That is correct

I have heard of guys going to 70 or heavier weight oils and lasting 1 year or more

[squonk 41,345]

You could try synthetic motor oil. Higher tolerance for heat and doesn't shear like regular oil.

[73-18 automatic 8]

I am using amsoil 30w and it works really good

[tommyg 152]

Well, I did change the filter an refilled with synthetic hoping for a better result, but alas, it didn't help. I was wondering about a heavier weight oil, but wasn't sure what to try. 70 weight seems pretty extreme. What is amsoil 30 wt? The "definitely not an expert" opinion does sound plausible. Maybe I will try something a bit heavier. I just didn't want to risk damage to other components. If I decided to get the thing overhauled, anyone know of a good repair shop?

[Trouty56 567]

This has been brought up before by others on the forum. Some members have found places to have the pumps rebuilt at a very high expense I might add, but, mostly it is advised to find a replacement pump and motor from another machine being parted out. There are a couple members dealing with what you are at the present time. Look in the tranny forum or the restoration forum for posts by Hodge71.

[Hodge71 664]

Tommy heres what I can tell you from my experience. With a hydro pump and motor operating normally what happens is the pump has pistons with brass feet on them called slippers, these ride on a brass plate called a swash plate. The pump builds pressure because the swash plate is an an angle and converts this pressure to flow. The flow in turn travels through your lines back to the hydro motor mounted on your transmission where that flow is converted to motion to turn the transmission. In the hydro motor there is another swash plate and slipper set up. There is a certain amount of heat inherent with the process. As these brass parts wear due to lack of maintenance and oil contamination, grooves get worn in them and oil starts to sneak by them causing pressure to drop and therefore you lose efficiency causing more heat to build. As the heat builds the oil thins causing it to slip by the slippers and swash plate easier continuously compounding the problem. Our machines have no way to get rid of the the heat build up. Even with the metal lines it doesnt leave quickly. There actually was a fan set up offered by Wheel Horse that mounted under the seat and was pointed at the lines to help cool better. I was going to go as far as cutting my low pressure line and installing an automatic transmission cooler with a built in fan and temp control on it to cool the oil on my 18 auto.

Now, as far as your options, You can add the 70 or 80 weight oil that other members have suggested , but its merely a bandaid on a bullet wound. Your hydro is shot and needs a doctor. Also adding synthetic oil at this time is a total waste of money. The damage is done already and cant be fixed with synthetic oil. You can buy a used motor and pump on fleabay and hope its in better shape than yours are. You can also take your stuff apart and check the slippers and swash plate for scratches and scarring and then with a micrometer for thickness. You can take the slippers and swash plate and polish out the scratches with crocus cloth as is instructed in the Sundstrand repair manual. Be sure to install the swash plate correctly when complete though as if I remember correctly if you put it in backwards, your motion controls operate in the opposite direction (forward is reverse and revese is forward) You gotta make the decision bud. I can tell you that even with buying a pump and motor off the net, I would tear both apart and check/recondition the slippers and swash plates. Once theyre in it s too late and I must say plan on spending about 4 hours disassembling the front of the tractor to get the pump out. It is an absolute nightmare and you will bleed... You also will not find anyone to rebuild these. The parts arent available through Sudstrand, all that can be done is check tolerances and hope you cn polish out the wear. Good luck

PS: I can also say with certainty, dirt is the ENEMY of the hydro. My Dads 1973 12 Auto has 2500 or more hours on its Sundstrand, the hydro oil and filter are changed with regularity and it has just as much power now as it did when he bought it new. They will last forever when taken care of.

[pfrederi 17,885]

Here is the sundstrand diagnostic for over heating.

If you try 70 w oil i doubt you will be able to start her let alone move when it is cold out. There is no disconnect on the D hydro like the C sundstrand and eatons.

[Trouty56 567]

If you try 70 w oil i doubt you will be able to start her let alone move when it is cold out. There is no disconnect on the D hydro like the C sundstrand and eatons.

Good point Paul.....

[tommyg 152]

Jeff, that's a lot to ponder. I'm curious, as a guy that's not a stranger to things mechanical, is this an impossible project if I wanted to tear her down, inspect, buff, etc? Should I have seals and gaskets on hand to put it all back together? Right now, I'm thinking that I limp along with what I have, look for a used pump on ebay or somewhere, and when I find one, tear it down as you suggested and "experiment on that one first. That way, I can still use my tractor if I screw it up. I did find someone who can rebuild it if the parts were available (in his words) for about $1100. I paid $1350 for the tractor. It makes sense to take my chances on a used one, but of course, there's no guarantee that one's gonna work. Flip a coin I guess.

Thanks for the Sunstrand overheating flowchart. Problem is, I can inspect those things, but I'm not sure what I'm looking for other than dirty cooling fins. That's a no brainer. I did find a Sunstrand repair manual. I might just add it to my current reading list and do a bit of studying before I take the plunge. That's how we learn right?

[tommyg 152]

Paul, what did you mean by "There is no disconnect on the D hydro like the C sundstrand and eatons."

[Trouty56 567]

Tommyg.....here's the manual.....

What Paul means is that the pump and motor are connected at all times unlike the other hydros that have a belt that drives the pump. When turning over the D engine you are also turning the uncooled oil in the pump. In a C160 hydro, for example, there is a belt release so the engine starts but the pump is stationary until the operator engages the belt.

[Trouty56 567]

Sorry...I see now you already have the manual.....

[wheeledhorseman 574]

So here we are again – the merry band of ‘D’ owners and the like .

I’ve noticed from some posts that I’ve made that few are prepared to put their head above the parapet when it comes to hydro problems though to be fair some have taken the trouble to offer me what help and advice they can.

I’m certainly no expert but having spent hours studying the Sundstrand manuals and diagrams (and for what it’s worth) here are my thoughts on the subject and feel free to shoot me down in flames for anything I get wrong here……

For my sins perhaps I have two tractors with hydrostatic transmissions – a ‘C’ and a ‘D’

Automatic transmissions are notorious for the fact that they are less efficient than a manual counterpart. In short, a small but significant amount of the energy from the engine gets lost in the transmission and never makes it to the rear wheels. Energy lost in this way is converted to one thing – HEAT.

The Sundstrand is no different in this respect and I can hear the extra effort that the engine of my C-120 has to produce when I take the parking brake off which also engages drive to the hydro pump even when the tractor is not moving anywhere yet.

This heat is dissipated via the casing of the pump which has fins to increase the surface area and also through the transaxle casing which also contains hot oil. The C-120 has a crude fan as part of the drive pulley to help with the cooling process.

The transmission on my C-120 runs noticeably cooler since cleaning all of the greasy dust that builds up and lowers the efficiency of the fan itself and also removing the similar grease and grass cutting dust that covers the cooling fins on the pump unit. It still runs much hotter though than the manual transmission in my C-100.

Cooling for the pump on a ‘D’ is provided by the air being drawn into the engine as part of the engine cooling system. It’s easy to see any greasy debris on top of the pump unit but I found lots of it between the fins on the underside of the pump that’s only easily accessible when the tractor side panels are off though you can sort of inspect it from underneath the tractor.

The other potential cooling issue I found on the ‘D’ was that the little holes that form the flywheel grille mesh where air is drawn into the flywheel fan were pretty blocked up in fact they were far worse than I had thought from an initial look. Both the engine and hydro pump cooling systems must have been impaired as a result. I didn’t find much stuff in the actual engine cooling fins but it’s worth taking the tin off to check.

What I’m basically trying to say is that although the cooling systems on a ‘C’ and ‘D’ are different they are both important and help to keep the oil temperature lower than it would otherwise be. Even multi-grade oil gets thinner the hotter it gets though the effect is less than with single weight oil.

Having got the cooling system as good as it gets then if loss of power as the oil heats up is still an issue then pressure is being lost somewhere. Low oil pressure as an automobile engine heats up sometimes points to a worn oil pump but more usually indicates worn crankshaft / big end bearings. When the oil is cold and thick the pump can keep up with the loss but when the oil gets hot and thin it can’t.

The problem in a hydrostatic transmission is that the loss of pressure caused by oil bleeding from the high pressure circuit to low can happen in a number of places. I believe you can check the main charge pump with a pressure gauge but as the pump in a ‘D’ also powers the lifts which are on a different circuit then it can be pretty much eliminated if the lifts continue to function normally when lifting a load even though the motive power is poor.

If the loss is in the drive system only, then it could be happening in the pump unit behind the engine or it could be happening in the motor unit on the transaxle. Unfortunately you could swap out the pump only to find the fault is actually in the motor. As Jeff suggests it could be due to worn / scored parts in the pump (or motor) particularly if it affects both forward and reverse. However, it could also be caused by a poorly seating valve. Some valves are linked specifically to forward or reverse – if the ailment affects one direction only then one of these is a likely suspect - the case with my D-200. If it affects both directions then it could even be a poorly seating push valve.

When they are working well they’re great – when they don’t work properly they can be a real pain!

I'm not sure I'd want to try using a heavy single weight oil which would be ok during warm weather but incredibly thick in very cold weather. I think as a first step down this route I'd try 20-50. It would only be marginally thicker in the cold (20 weight) but have the properties of a 50 weight oil when hot.

Well done Jeff for being prepared to have a go at a hydro - I'm looking forward to seeing some pics.

As I said earlier - feel free to shoot me down on any of this but it's up for discussion.

Andy

[Trouty56 567]

For some reason I feel very small right now.....lol

[wheeledhorseman 574]

I hope that was a tongue in cheek comment Bob. You're making me feel guilty of something bad :hide:

[Trouty56 567]

Hahahaha....well...that was a heck of a post...hats off to ya Andy. Really....a great post in fact. I couldn't put a post like that together...well..I just couldn't. I'm glad you are here is all I can say!!

[tommyg 152]

All I can say is my head is still spinning. Maybe even overheating a bit!

I think I'm going to go the route of a heavier weight synthetic gear oil as a band aid til I sort out what I'm going to do. Symptoms are indeed sluggish forward and reverse along with slow implement lift, which if I understand what you're saying, points to the pump. I've re-seated the push valve a couple times, and it seems to seat well but I have not removed anything to inspect it. Simple stuff first.

Thanks for everyone's insight and thoughts!

[tommyg 152]

Jeff, by the way... What the heck is "crocus cloth"!?

[wheeledhorseman 574]

Symptoms are indeed sluggish forward and reverse along with slow implement lift, which if I understand what you're saying, points to the pump.

Tommyg, please accept that I'm no expert but from the symptoms that would be my deduction as well. At least it indicates that swapping out the pump unit at the front end for a known good one is likely to be the most cost effective solution in the long run.

If owners elsewhere have found that using a high weight gear oil lets you get a bit of extra life out of the pump them who am I to say it won't work but as has been mentioned a couple of times in this thread, I would also be concerned about starting and cold performance. We know these pumps in good condition will run on ATF which is pretty thin and, if using oil, the OEM spec is for 10W-30 or 10W-40, the latter behaves as a 40 weight oil when hot but a 10 weight (thin oil) when cold. If I needed to climb the 'weight tree' I would stick with a multigrade hence for example going initially for 20W-50. It's just a thought.

What ever you decide to try do keep us posted - it's how we all learn a bit more on a tricky subject.

Andy

[Hodge71 664]

Tommy,

Crocus cloth is a very fine abrasive cloth that is used for polishing. McMaster Carr sells it.

[pfrederi 17,885]

So here we are again – the merry band of ‘D’ owners and the like .

I’ve noticed from some posts that I’ve made that few are prepared to put their head above the parapet when it comes to hydro problems though to be fair some have taken the trouble to offer me what help and advice they can.

I’m certainly no expert but having spent hours studying the Sundstrand manuals and diagrams (and for what it’s worth) here are my thoughts on the subject and feel free to shoot me down in flames for anything I get wrong here……

For my sins perhaps I have two tractors with hydrostatic transmissions – a ‘C’ and a ‘D’

Automatic transmissions are notorious for the fact that they are less efficient than a manual counterpart. In short, a small but significant amount of the energy from the engine gets lost in the transmission and never makes it to the rear wheels. Energy lost in this way is converted to one thing – HEAT.

The Sundstrand is no different in this respect and I can hear the extra effort that the engine of my C-120 has to produce when I take the parking brake off which also engages drive to the hydro pump even when the tractor is not moving anywhere yet.

This heat is dissipated via the casing of the pump which has fins to increase the surface area and also through the transaxle casing which also contains hot oil. The C-120 has a crude fan as part of the drive pulley to help with the cooling process.

The transmission on my C-120 runs noticeably cooler since cleaning all of the greasy dust that builds up and lowers the efficiency of the fan itself and also removing the similar grease and grass cutting dust that covers the cooling fins on the pump unit. It still runs much hotter though than the manual transmission in my C-100.

Cooling for the pump on a ‘D’ is provided by the air being drawn into the engine as part of the engine cooling system. It’s easy to see any greasy debris on top of the pump unit but I found lots of it between the fins on the underside of the pump that’s only easily accessible when the tractor side panels are off though you can sort of inspect it from underneath the tractor.

The other potential cooling issue I found on the ‘D’ was that the little holes that form the flywheel grille mesh where air is drawn into the flywheel fan were pretty blocked up in fact they were far worse than I had thought from an initial look. Both the engine and hydro pump cooling systems must have been impaired as a result. I didn’t find much stuff in the actual engine cooling fins but it’s worth taking the tin off to check.

What I’m basically trying to say is that although the cooling systems on a ‘C’ and ‘D’ are different they are both important and help to keep the oil temperature lower than it would otherwise be. Even multi-grade oil gets thinner the hotter it gets though the effect is less than with single weight oil.

Having got the cooling system as good as it gets then if loss of power as the oil heats up is still an issue then pressure is being lost somewhere. Low oil pressure as an automobile engine heats up sometimes points to a worn oil pump but more usually indicates worn crankshaft / big end bearings. When the oil is cold and thick the pump can keep up with the loss but when the oil gets hot and thin it can’t.

The problem in a hydrostatic transmission is that the loss of pressure caused by oil bleeding from the high pressure circuit to low can happen in a number of places. I believe you can check the main charge pump with a pressure gauge but as the pump in a ‘D’ also powers the lifts which are on a different circuit then it can be pretty much eliminated if the lifts continue to function normally when lifting a load even though the motive power is poor.

If the loss is in the drive system only, then it could be happening in the pump unit behind the engine or it could be happening in the motor unit on the transaxle. Unfortunately you could swap out the pump only to find the fault is actually in the motor. As Jeff suggests it could be due to worn / scored parts in the pump (or motor) particularly if it affects both forward and reverse. However, it could also be caused by a poorly seating valve. Some valves are linked specifically to forward or reverse – if the ailment affects one direction only then one of these is a likely suspect - the case with my D-200. If it affects both directions then it could even be a poorly seating push valve.

When they are working well they’re great – when they don’t work properly they can be a real pain!

I'm not sure I'd want to try using a heavy single weight oil which would be ok during warm weather but incredibly thick in very cold weather. I think as a first step down this route I'd try 20-50. It would only be marginally thicker in the cold (20 weight) but have the properties of a 50 weight oil when hot.

Well done Jeff for being prepared to have a go at a hydro - I'm looking forward to seeing some pics.

As I said earlier - feel free to shoot me down on any of this but it's up for discussion.

Andy

Andy That is a marvelous summary. Thank you.

I have overhauled a hydro motor for my d and this week Jeff may come over and we will each work on our hydro pumps. The biggest PIA here is the only way to test a unit is to install it and run it. Swapping out the entire hydro system is a D is a major and messy project. Once I have a pump overhauled then I will deadline her remove the FEL. and replace the whole system.

The guys who designed the D series obviously never planned on working on them. An example I made up a hydro test guage to check my charge pump pressure/. To use it you have to remove the battery then rig up long battery cables so you can get it started. do the cold pressure test then put the battery back in work the tractor to get the hydro hot then take the battery back out to put the guage in...

[Trouty56 567]

Paul....this sounds a bit odd but....If you had a spare tranny you put the pump and motor together like the C series....maybe use the old O ring set....and power it off the pto of another tractor....take a lot of hassle I guess.