LMTV Allison Stall Test issues

[GeneralDisorder]

@MatthewWBailey - How sure are you of the accuracy of your tach? Isn't it running off the VR?

Just trying to reconcile a seemingly functional truck, no codes present, and the stall test results.

CAT ET or any J1939 setup will read the tach from the ECM also.

 

[MatthewWBailey]

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…

Did it peak well above 1750 then come down, or just go there and stop? Mine went up to 2100 then I backed off bc I was unsure of going too high.

 

[MatthewWBailey]

@MatthewWBailey - How sure are you of the accuracy of your tach? Isn't it running off the VR?

Just trying to reconcile a seemingly functional truck, no codes present, and the stall test results.

CAT ET or any J1939 setup will read the tach from the ECM also.

It's running off the pulses from the new delco alt. The "R" terminal. Shows 700 at idle and 1350 at high idle. I've driven it around, seems to be accurate based on driving results. Showing up shifts at ~1800, down shifts at 1100-1200ish.

maybe I should get that ET software. I have an old Windows 10 machine

 

[Ronmar]

Did it peak well above 1750 then come down, or just go there and stop? Mine went up to 2100 then I backed off bc I was unsure of going too high.

Nope, never went past 1750…

 

[MatthewWBailey]

So either the mismatch wasn't present long enough to fault

Could this happen if the internal speed sensor on either the input or output is flaky? The strange shifting issues I had previously went away the moment I redid those chassis grounds. But I'm wondering if those intermittent overvoltages from the bad alt damaged sensors in the trans? Leading to lack of fault sensing? Again, more swinging in the dark.

 

[GeneralDisorder]

Could this happen if the internal speed sensor on either the input or output is flaky? The strange shifting issues I had previously went away the moment I redid those chassis grounds. But I'm wondering if those intermittent overvoltages from the bad alt damaged sensors in the trans? Leading to lack of fault sensing? Again, more swinging in the dark.

I woudn't think so - if the sensors are damaged the TCM is going to detect open/shorted circuit, or not see the RPM pulse. I can't envision a scenario where the sensor would read but at a shifted frequency resulting in inaccurate readings but not throw off the slip detection algorithm in the TCM. Multiple sensors would have to have failed in the same way and shifted the same amount. Highly improbable.... probably impossible.

My money is on the assumption that your tach is accurate. The truck drives normally and the TCM isn't pissed off about input/output speed correlation - that's two facts that seem to have more credibility than the observation that the tach "seems about right".......

 

[MatthewWBailey]

I woudn't think so - if the sensors are damaged the TCM is going to detect open/shorted circuit, or not see the RPM pulse. I can't envision a scenario where the sensor would read but at a shifted frequency resulting in inaccurate readings but not throw off the slip detection algorithm in the TCM. Multiple sensors would have to have failed in the same way and shifted the same amount. Highly improbable.... probably impossible.

My money is on the assumption that your tach is accurate. The trucks drives normally and the TCM isn't pissed off about input/output speed correlation - that's two facts that seem to have more credibility than the observation that the tach "seems about right".......

So where can I download the CAT ET software so as to read the rpm? I assume I'll need a serial to canon cable to interface to the truck. Seems like everything needs it now, even my golf carts connect to my laptop.

 

[GeneralDisorder]

So where can I download the CAT ET software so as to read the rpm? I assume I'll need a serial to canon cable to interface to the truck. Seems like everything needs it now, even my golf carts connect to my laptop.

Well..... you can't. Not *legally* without paying for it anyway. And it's prohibitively expensive. The military has a somewhat reduced functionality version of CAT ET that doesn't require registration, etc but getting a copy typically involves offline methods due to size and potential for anything hosted online to contain trojan software, viruses, and spyware.

What you can do that's free (software wise) is pickup a used dearborn protocol adapter (DPA) 3, 4 or 5 and the software for it (free on the Dearborn website) has a generic diagnostic application that will read every system on the truck and pull most all of the live data that conforms to the J1939 standard.

I think @Suprman has some surplus DPA 4's for sale that he mentioned recently in another thread.

Alternatively I do build laptops and I have a SWICE kit available. But that's the Cadillac of options.

 

[shawnspeak]

So where can I download the CAT ET software so as to read the rpm? I assume I'll need a serial to canon cable to interface to the truck. Seems like everything needs it now, even my golf carts connect to my laptop.

Or grab a Bluefire Adapter . It's a very easy way to get at the J1708 (and J1939) data flying around the bus.

 

[MatthewWBailey]

Or grab a Bluefire Adapter . It's a very easy way to get at the J1708 (and J1939) data flying around the bus.

Can they be setup as a continuous monitor, while driving?

 

[shawnspeak]

Can they be setup as a continuous monitor, while driving?

Yes.. you can create "dashboards" on a phone/tablet and monitor whatever you like while driving.

 

[MatthewWBailey]

Yes.. you can create "dashboards" on a phone/tablet and monitor whatever you like while driving.

I'm looking

 

[GeneralDisorder]

Yeah the Bluefire dongle seems to be a good option for basic monitoring. Note that for some strange reason they don't make it compatible with the 24v J1939 powered port on our trucks so you have to either modify your plug or add a second interface plug that's 12v so it doesn't damage their dongle.

Besides that, it's only capable of generic J1939 data display. It doesn't do any two-way communication so it can't run component tests, and doesn't know about unique data streams that aren't part of the generic protocol. It's the equivalent of a $25 scan tool for a '96 and newer OBD-II car. Compared to CAT ET/Allison DOC, etc.... it's like comparing the $25 Amazon scan tool to the $5,000+ dealer level diagnostic tools. Nothing wrong with having it or with having both but important to note it's limitations. It's a monitoring device - not a diagnostic tool. You can't do a cylinder cutout test, injection pressure control tests, or see any of the proprietary data streams specific to HEUI CAT engines (somewhat unique in the diesel world).

 

[Third From Texas]

Yeah the Bluefire dongle seems to be a good option for basic monitoring. Note that for some strange reason they don't make it compatible with the 24v J1939 powered port on our trucks so you have to either modify your plug or add a second interface plug that's 12v so it doesn't damage their dongle.

The way I installed mine was to add a "Y" cable that created two ports. One I attached into the OEM hole and it acts as my diagnostic port. The second I clipped the 24v wire and sealed it, then I ran a 12v wire from a fuse panel and attached it to the port.

The Bluefire lives permanently behind the driver kickpanel. And the diagnostic port is unaffected.

 

[MatthewWBailey]

My money is on the assumption that your tach is accurate. The truck drives normally and the TCM isn't pissed off about input/output speed correlation - that's two facts that seem to have more credibility than the observation that the tach "seems about right".......

I checked it with the strobe I have. Matches up at 1500 and 2000. When doing a pedal to the floor accel on flat road, it revs to 2400 before shifting to 3, then 2100 before shifting to 4.

based on the feedback and also the Allison "tips" manual, I'm wondering if it's worth dropping/replacing the fluid and having a fluid test. Maybe I have fluid issues? not like Midwest would've changed it. I guess that still doesn't account for lack of codes thou? ...

Odd since it drives quite powerfully. Even with 3.07s and ECO, shifting into D from N at a dead stop with no brake on makes the truck lurch forward noticeably at idle. Going up the 10* slope took 1150 rpm today from dead stop.

 

[Guyfang]

This about got it?

 

[MatthewWBailey]

This about got it?

You da man!

 

[Guyfang]

I was sweating bullets!

 

[hike]

I like the Bluefire while driving, though it doesn't pickup a lot of information that could turn an iPad or Surface into a glass dash. No air pressures, voltages, CEL, for example. A lot of potential, though with limited information shared on the J1708/1939 from the CTIS, chassis, CAT ECU and Allison ECM not as useful as it could be.

In my spare time I am hoping to see if we can add new functionality, but there are more pressing items on the list. As usual–