LMTV Allison Stall Test issues

[Ronmar]

Cool info. but just neat to know, as it is difficult to pin down absolutes(actual torque produced and multiplication factor) mid power band without adding some fancy instrumentation

Where this becomes useful is when you reach a slope that takes you to the end, TC stall point near peak torque point. You can simulate this of course doing a stall test. stand on the brakes and depress the throttle pedal and see where it stalls at. If they did it right, it should be around 1450RPM for your 3126... Stall adds a lot of heat to the trans fluid, so a brief test is advised. if things are working right This should tell you if your engine is capable of producing peak torque...

 

[MatthewWBailey]

Cool info. but just neat to know, as it is difficult to pin down absolutes(actual torque produced and multiplication factor) mid power band without adding some fancy instrumentation

Where this becomes useful is when you reach a slope that takes you to the end, TC stall point near peak torque point. You can simulate this of course doing a stall test. stand on the brakes and depress the throttle pedal and see where it stalls at. If they did it right, it should be around 1450RPM for your 3126... Stall adds a lot of heat to the trans fluid, so a brief test is advised. if things are working right This should tell you if your engine is capable of producing peak torque...

Hmmm. I tried this on the back drive to my barn which is 7-8 degrees, with the brake held, at temp. Rpm did not "stall", kept going up to 2100+ and I backed off throttle. Truck was flexing, trying to go. Only a couple seconds elapsed. What does this mean?

 

[Ronmar]

Could be something slipping...

 

[MatthewWBailey]

Could be something slipping...

The Allison mechanics' tips manual says

ALLISON TRANSMISSION 3000 MECHANIC'S TIPS Pdf Download

View and Download Allison Transmission 3000 mechanic's tips online. 3000 microphone system pdf manual download. Also for: 4000.

www.manualslib.com

 

[Ronmar]

Yep.

 

[MatthewWBailey]

Yep.

Did you break my transmission!? jk

 

[Ronmar]

Did you break my transmission!? jk

No, the army probably did that…

 

[Ronmar]

Any TCU codes?

 

[MatthewWBailey]

Any TCU codes?

I'll have to check tomorrow. I never owned a vehicle that didn't blow a trans during my ownership. So this would be par. Backhoe's at 6000 hrs and that trans is starting to go. Track loader is immune since it doesn't have one.

Items 3 and 4 above don't make sense since the truck drives fine especially downhill in 3 lockup. I'm thinking either 1 or 2. Worn clutch plates in there would follow from military maneuvers I'm guessing.

 

[Skyhawk13205]

Could be something slipping...

looks like a C1 and C5 for range 1 and C1 and C4 for range 2, I would also imagine he would get a failed ratio test code. There are codes for ones below lockup, do you think the TC stall test outside of limits would cause a ratio test failure.

 

[coachgeo]

looks like a C1 and C5 for range 1 and C1 and C4 for range 2, I would also imagine he would get a failed ratio test code. There are codes for ones below lockup, do you think the TC stall test outside of limits would cause a ratio test failure.

starting to look like this is going off topic of this thread. Maybe admin or mod can split off the post from this one and form an all new thread on this adventure.

 

[Ronmar]

looks like a C1 and C5 for range 1 and C1 and C4 for range 2, I would also imagine he would get a failed ratio test code. There are codes for ones below lockup, do you think the TC stall test outside of limits would cause a ratio test failure.

Yes. you have input/engine RPM pulses, turbine RPM pulses and output/speed RPM pulses. Turbine and output should be locked together with gears and clutches, so any slipping in the trans would allow turbine to rotate and provide a signal, but with the truck stationary you would produce no output/speed pulses.. You can get this if you disconnect the transfer case connector and drive as that is where the output speed signal comes from...

And GEO is correct, probably need to start a new thread on trans troubleshooting it was relevant to Eco hubs up until the stall test anomaly...

 

[MatthewWBailey]

Any TCU codes?

Would the Clutch codes only show up during power on? I checked today and the Wtec shows no stored codes. All registers are "-". I previously deleted all stored codes months ago after the starter/overvoltage debacle. So there's been no stored codes since then.

 

[Ronmar]

I think it may reset them, it typically locks you in the current gear until you cycle the power, but I thought it held the ratio error. Are you sure you were not spinning a tire?

 

[MatthewWBailey]

I think it may reset them, it typically locks you in the current gear until you cycle the power, but I thought it held the ratio error. Are you sure you were not spinning a tire?

No I checked the video bc I was in front of the security camera lol. It was trying to push thru the breaks. I could hear it. Front flexes/lifts a little. I do the rapid warm up procedure a lot in winter so the response is within expectations but I only go lite throttle when I do that.
Is it possible that the ECM knows the foot brake is on? and is making the TC dump fluid? I'm just swinging in the dark here.
See audio below. Video is grainy sorry.
The growling was less above 1500rpm

Stall test

youtube.com

 

[GeneralDisorder]

What is the stall speed rating of the torque converter? I can hookup CAT ET to my truck and do a stall speed test. Stall speeds are not a hard number - they are subject to engine performance also. I know the TC has a 1.9:1 effective reduction when fully loaded (stalled)...... although I wouldn't think you could get anywhere near redline or shouldn't be able to anyway unless the transmission is slipping or the converter is damaged internally. I've seen a turbo 400 converter in a CUCV disintegrate internally - wouldn't transfer ANY power once that happened though. And it unbalanced it when all the vanes detached and fell to the bottom.

 

[Ronmar]

Ideally it should stall very near peak torque on the engine.

 

[GeneralDisorder]

Ideally it should stall very near peak torque on the engine.

Ideally - but it's locked in every gear except 1 and 2 - did they pick some absurd stall rating? Because mil-spec? IDK but if his trans was slipping I would think there would be codes stored.

 

[Ronmar]

Yep, ideally, should be in the peak range for installation behind a diesel, which would be ~13-15 hundred RPM? The only spec I have found for our TC part number found in the -24P manual is from Xcalibur, and they refer to that P/N as a TC-418 with a 1.98:1 conversion ratio at stall. TC-418 is referenced in the 3070/3700 brochures, but again no other info beyond the conversion ratio… I suspect the available power output would have a say in the final stall RPM…

If the turbine was spinning and the output was not, it should have posted a ratio fault and locked it in gear. I have seen this same fault when I left my transfer case cannon plug disconnected. Was a 22 series code. I would,say it would also theow a code for a incorrect ratio(57?)… So either the mismatch wasn't present long enough to fault or his TC stall is that high. I don’t have a tach so have not been able to plot mine yet…

 

[Ronmar]

And of course this discussion reminded me i did replace the flywheel sensor and I do have a frequency counter… freq in HZ X 60 = cycles per minute / 133 teeth = revolutions per min…

I ran 5 stall tests, 2nd gear in mode, full pedal and allowed about 5 seconds for the RPM to stabilize after it peaked. All 5 fell between 1725-1750 RPM, which is 175-200RPM above the 3116 advertised peak torque of 1550RPM. I could see the heatwaves these created, push the temp gauge from the 195F thermostat temp to ~205, but the fan never kicked on. I allowed it to settle back to 195 between tests…