Transmission Dyno test

[DEMike]

Does anybody know a facility that can do a full stall test on a 980H transmission? Apparently there is two types of dyno test, which was news to me. A lot of shops can only spin them and check pressures and run it through the gears. I need somebody that can load the transmission with a load cell to check if the converter is functioning correctly.

 

[bccat]

Cat Dealer

 

[Nige]

Cat Dealer

Probably your only hope. Even then it would need a pretty large dealer rebuild shop to have a transmission test bench.

 

[pittsburgh cat man]

We had test benches but not one that would load the transmission they would just turn them

 

[Tyler d4c]

We had test benches but not one that would load the transmission they would just turn them

Does Indiana have a trans dyno?

 

[pittsburgh cat man]

I’m thinking they still have the one we had

 

[DEMike]

Every cat dealer I’ve talked to can only spin them. They are looking into who has a bench that can load the transmission. Not easy to find apparently.
Long story short is the transmission was rebuilt and when put back into the machine it won’t pass a stall test. Engine won’t get past 1200rpm. It was pass with old transmission, but tranny was getting hot, which is why it was rebuilt. Engine has power to maintain 1700 rpm when deadheading the hydraulics, which is within specs. When the loader goes into the pile it falls flat. All pressures check out and solenoids calibrated.
We sent the transmission back to the rebuild shop so we didn’t avoid warranty saying it’s got to be a torque converter issue. They pulled it apart and said it all looks good. They put it back on their test bench and spun it. Pressures look good, but it doesn’t show me flow rates. I don’t want to put it back in into we have a definitive test to see if we have problem the transmission build or if the problem on my end. I don’t think we have an engine power issue.

 

[pittsburgh cat man]

The first thing that comes to my mind is wrong wheel are the parts listed on invoice?

 

[Nige]

Does the converter on that particular machine have a lockup clutch.? If so my first thought would be that the torque converter stator sprag clutch has been reassembled incorrectly.

Was the converter overhauled when the transmission was rebuilt.?
Why was the transmission removed in the first place.?

 

[DEMike]

Nige, yes it has a freewheel clutch. Our initial thought was the springs were installed backwards and that was creating the low stall. Rebuild shop took it apart and said they were correct. I’m skeptical at this point.

 

[Nige]

Nige, yes it has a freewheel clutch. Our initial thought was the springs were installed backwards and that was creating the low stall. Rebuild shop took it apart and said they were correct. I’m skeptical at this point.

Judging by your described symptoms that is the first place I would be looking. It sounds very much like either the sprag clutch assembly is installed backwards (meaning the ratchet mechanism fails to latch and lock the stator in position) or maybe something more subtle such as the roller return springs installed sideways. Seen that before.

Somewhere I have some photos. I’ll try to find them. Stand by.

 

[Nige]

Study this photo closely of an incorrectly assembled sprag clutch mechanism then compare it with the illustration from the service manual showing how it should be assembled. NOTE that the photo is taken from the opposite side.

1. All the springs are on the wrong side of the rollers. The springs are supposed to push the rollers towards the NARROW end of the ramp, not towards the wide end.

2. Three of the springs (3 o'clock, 8 o'clock and 11 o'clock) are installed SIDEWAYS.

 

[pittsburgh cat man]

I didn't think about it having a clutch. A long time ago we had some stators that would strip the spline in the aluminum stator and cause low stall speed only other thought is if the guy that built it wrong in the first place looked at he would probably think it was right

 

[DEMike]

That is very helpful to understand. They are supposed to be sending me some photos of when they took it back apart. Thanks

 

[Nige]

only other thought is if the guy that built it wrong in the first place looked at he would probably think it was right

Exactly my point. It's not until you try to ratchet the sprag mechanism that suddenly the penny drops that the stator won't stop turning on the hub whichever direction you rotate it.

That is very helpful to understand. They are supposed to be sending me some photos of when they took it back apart. Thanks

Say nothing to them initially but upload the photos here first. They may well be quite useful.

 

[DEMike]

I’ll push for the photos on Tuesday. Monday is a holiday

 

[John C.]

Did the H model 980 have the piston pump hydraulics or were they still using the vane pumps? I've done machine inspections on lots of 980H machine and stall tests are mandatory. Generally as I recall most torque stall at around 1,700 RPM. The hydraulics with the load sensing systems don't drop RPM more than fifty. I have to pick up boom from the ground and do a running read of the RPM drop and then it is usually less than 150 RPM. I do the same when doing full stall against the transmission and the hydraulics at full lift of the boom. Even at that if the engine speed is below 1,500 it is flagged in the report.
The lockup should not be engaged at all when doing stall tests. It isn't hard to put a torque converter together wrong. It wasn't long ago that I was involved with a D6T that wouldn't move because someone left out a part of the torque divider. I'm with Nige on this as something is obviously assembled wrong.

 

[Nige]

I suppose the next logical question would be to ask exactly what parts of the sprag clutch mechanism were replaced when the converter was overhauled.? It is a known weak point and the internal parts should be considered as consumables.

 

[Nige]

Any update on this.?