988f series 2 variable torque converter.

[komatsukid]

Hello and happy 4th! The torque converter on the loader I run is failing, Outlet relief pressure is 54psi spec is 60 to 80 psi. Our Cat dealer is going to bring a new torque converter out and swap the old one with the new one on site. Anyone know how long a job like this might take? And will the new converter increase the wheel torque? Thanks.

 

[pittsburgh cat man]

It should take about a day As far as increasing wheel torque it all depends if there was some thing wrong with the variable pitch system in the torque. other wise it will be the same

 

[Nige]

Post a machine Serial Number to find the Part Number of the correct converter.
If the dealer doesn't install the right unit then maybe performance might not be optimum.
Do you know if they measured the converter inlet pressure or pump pressure.?
I wonder if anyone looked at the cooler.

 

[komatsukid]

Serial is 2Zr01754
I believe the inlet pressure was measured but I don’t remember what the number was. There is a wheel torque control lever in the cab that allows the operator to dial in the wheel torque that best matches the ground conditions that the machine is operating in. That’s a great benefit because the pit that it works in has a sandy footing.

 

[komatsukid]

it may sound silly but I believe the machine has lost a considerable amount of wheel torque, before while digging 2 gear had plenty of torque and if you locked the clutch up in the converter and dug with it there was an extraordinary amount of wheel torque. Now you need 1st gear to dig.

 

[Nige]

There is a wheel torque control lever in the cab that allows the operator to dial in the wheel torque that best matches the ground conditions that the machine is operating in.

I hope someone proved that system was working correctly and that the cables were adjusted to specification.

Serial is 2Zr01754

According to me the converter with housing for that Serial Number is 8E-7009 or Reman 0R-4071.
There appear to be two different arrangements of converter.

 

[pittsburgh cat man]

I believe the the other torque is the load and carry quite a bit different

 

[komatsukid]

How does the lever in the cab work to lower wheel torque control?

 

[Nige]

How does the lever in the cab work to lower wheel torque control?

It is connected to a valve that varies the pressure in the torque converter impeller clutch. Reduced clutch pressure allows it to slip. For 100% traction the impeller clutch does not slip at all. From the service manual

The torque converter is a variable capacity converter. The purpose of the variable capacity converter is to allow the operator to limit the amount of torque increase in the torque converter. This will cause a decrease in wheel slippage and reduce tire wear. This also permits an increase of engine power for the hydraulic implement system.

The amount of reduction of torque converter capacity is manually controlled by the variable capacity torque converter control lever in the operator's compartment. The lever is connected to the load piston in the sequence and pressure control valve by a cable. This lever permits the torque converter to operate at any position between maximum and minimum capacity.

A switch in the lift control lever also controls torque converter capacity. When the switch is moved to the ON position, it permits the torque converter to operate at maximum capacity without any movement of the wheel torque lever. When the switch is moved to the OFF position, the torque converter capacity returns to the variable capacity torque converter control lever setting.

 

[Nige]

I believe the the other torque is the load and carry quite a bit different

The major difference is that is has a lockup clutch and a freewheel stator.

 

[John C.]

Just for general information, torque converter problems show up as over heating the transmission fluid. The overheating will cause the engine to run hot as well in machines that use engine coolant to cool the transmission fluid. Overheated fluid through any amount of time also results in cooked out seals, particularly on the torque convertor drive line output yoke if the machine has a converter that is separate from the transmission case. I've worked around and on multiple 988 model machines from the B model to the H model and done appraisals on lots more. I have found the switch on the joy stick lever always in the locked or full torque position. When I've asked the operators about it, they generally say they use the engine speed and the declutch to control bank penetration and hydraulic power to the boom and tilt functions. I don't recall Komatsu or Volvo having the variable torque function.

 

[komatsukid]

Thanks for posting, once the converter heats up it takes an awful long time to cool back down. I feed a crusher and if I’m mixing material and feeding at the same time the torque will get hot (just before the red) and stay there most of the day. As I stated before the machine just doesn’t seem to have as much wheel torque as it used to. I can use first gear with the torque button on and it won’t even try to slip a tire. Before it would spin the tires without even trying if I used first gear. Cat will be out the end of this coming week, after they replace it I’ll post an update on its performance. Thanks for all the input.

 

[aussiechunda]

Thanks for posting, once the converter heats up it takes an awful long time to cool back down. I feed a crusher and if I’m mixing material and feeding at the same time the torque will get hot (just before the red) and stay there most of the day. As I stated before the machine just doesn’t seem to have as much wheel torque as it used to. I can use first gear with the torque button on and it won’t even try to slip a tire. Before it would spin the tires without even trying if I used first gear. Cat will be out the end of this coming week, after they replace it I’ll post an update on its performance. Thanks for all the input.

That kinda sounds like you have cooked the axle oil more than it being a torque converter problem and the torque converter working harder and failing is just a symptom, do you use the clutch brake?
I do the same work as you, face loader on a fixed plant in a 988 and this is a mistake many new operators have

 

[aussiechunda]

That kinda sounds like you have cooked the axle grease more than it being a torque converter problem and the torque converter working harder and failing is just a symptom, do you use the clutch brake?

Thanks for posting, once the converter heats up it takes an awful long time to cool back down. I feed a crusher and if I’m mixing material and feeding at the same time the torque will get hot (just before the red) and stay there most of the day. As I stated before the machine just doesn’t seem to have as much wheel torque as it used to. I can use first gear with the torque button on and it won’t even try to slip a tire. Before it would spin the tires without even trying if I used first gear. Cat will be out the end of this coming week, after they replace it I’ll post an update on its performance. Thanks for all the input.

Do you always run with the torque converter locked? Because you shouldn't be if you are digging in to a face, that is more for finished product and load and carry long distance, digging into a raw face with the torque converter locked is putting unnecessary strain on the machine, use the hydraulics not the wheel power to dig

 

[Nige]

once the converter heats up it takes an awful long time to cool back down.

A few questions.

1. What temperature does the coolant normally run at once the machine is warmed up.?
2. How long does it take for the converter outlet temperature to get close to the red after starting operation, I assume from “cold/ambient” temperature.?
3. When the converter temperature gets close to the red have you tried selecting neutral and running the engine at 14-1600 RPM then observe how fast the temperature comes down.? As soon as the transmission is in neutral the temperature comes down should drop like a stone. The rate of falling temp will decrease the closer the TC Out temp gets to coolant temp.
4. Are there temperature numbers on the gauges or simply green/yellow/red sectors.? Post some photos if you can.

If the dealer is going to replace the converter then the least they should also do is to pull the cooler and inspect/clean it. If it's in bad shape it really ought to be replaced. IMO it's somewhat of a lack of planning if they rock up with just a converter and no cooler.

 

[komatsukid]

Nige, on Monday I’ll take and post a few pictures of the engine temperature and torque converter gauges and try to time how long it takes for the torque temperature to come down. The dash cluster in this machine is digital and the gauges are like a pie graph so there isn’t an actual temperature number to go by. Either way I’ll post more information Monday.

 

[aussiechunda]

Nige, on Monday I’ll take and post a few pictures of the engine temperature and torque converter gauges and try to time how long it takes for the torque temperature to come down. The dash cluster in this machine is digital and the gauges are like a pie graph so there isn’t an actual temperature number to go by. Either way I’ll post more information Monday.

Also please post axle oil temp, i am about 95% certain this is all because the axle oils have been cooked and that has caused a flow on effect on the rest of the gear, If your axle oils are cooked then it will cause exactly what you describe and it is all because you are operating the machine wrong.
Torque converter locked when digging into a raw face,
Not using the clutch brake,
Not using the gears to slow down just using the brakes etc etc
If this is the case you can expect a full transmission rebuild in the near future and a bunch of other **** that will cost more than buying a brand new cat988xe

 

[John C.]

When I do appraisal inspections on torque converter machines, I do stall tests on the converters. The stall test works best when the transmission oil temperature starts out cold. The reason is that the temp will raise and fall suddenly if the flow through converter is right. If the transmission is already warm, it will take a long time to cool off and you have to have some knowledge of what is a normal rate of cooling and what isn't. If the machine is warm and I think there is a problem, I'll stall the converter and then get out and check the cooler with an infrared thermometer. On newer machines now days that use separate transmission radiator coolers, the transmission temps almost never change unless there is something wrong and as a bonus they no longer drive up engine temps.
As far as I know, axle oil coolers were always an option on 988 machines and were usually specced on machines used for material handling and load and carry.

 

[Nige]

As far as I know, axle oil coolers were always an option on 988 machines and were usually specced on machines used for material handling and load and carry.

That is correct but the OP’s machine was actually originally built with one. On the 988FII the axle oil cooler circuit is separate to the powertrain oil circuit. It has an air/oil cooler mounted in the radiator pack. The transmission cooler is oil/water and mounted oh the side of the engine block.

 

[Nige]

To the OP.
Do the converter outlet temperature test as suggested by John C on first start up. With the coolant temp low it will give you a very good idea of the powertrain cooler efficiency.