Allison 3000 problems

I bought a 2000 Newmar Dutchstar with a Cat 350hp engine and an Allison 3000 6 speed transmission. It only has 26,000 miles on it so it has been sitting for quite sometime down in Florida. I picked it up in Ohio from a guy that bought it to flip. I paid half of what one generally goes for. (Should have known then it was too good to be true although I knew it had some interior issues from a roof leak). It had a recent oil change and fuel filters and runs great. On our way home about 100 miles into our 500 mile trip the transmission started acting up when we came to a stop and started to go again. It shifted hard through the gears and got to 3rd and it suddenly downshifted back to first and the check transmission light came on. I pulled over, put it in neutral. Put it back into gear and it just stayed in neutral. After shutting it off and starting again it went into gear. We had to stop about 6 times before making it to a spot to stop for the night. It never downshifted like that again, it just had the check trans light come on and it stuck in whatever gear it was in. Once it got into 6th it seemed ok till we had to stop again. Checked all I knew to check and headed out in the morning. It did it several more times before it seemed to pull out of it. We made it fine till about 20 miles from home. The last 10 miles took about an hour. We had to stop several times.

Fast forward I wanted to take it to our last big race of the year. I cleaned the 3 connectors to the transmission ECU. Drove it around and it seemed good, so hooked up the car trailer and tried it again. All seemed good. Made it all the way to Memphis (400 miles without one issue). It did great until we hit St. Louis on the way home, it started again. It slowly got worse. Last 10 miles it took an hour. I learned how to get the codes from the keypad shifter and wrote them down once home. It stores the last 5. I cleared them and let it sit a couple weeks before cleaning the ECU connectors again thinking that was the problem. It seemed ok for about 10 miles and started again. Every time going into neutral, but just turning the ignition off isn't resetting it anymore. I'm having to go back and unplug the ECU every time. It might go 50 feet or 2 miles before the check transmission light would come on and go into neutral. I recorded the codes each of the 14 stops it took to drive back home the 10 miles. Now I have a total of 19 codes. 7 of them came up twice, 2 of them came up 3 times and 10 of them only came up once so it's getting a bunch of different codes. After reading a lot of the 443 page troubleshooting guide and trying to figure out if they all have anything in common, it may be an output speed sensor, turbine speed sensor, bad wiring (wires or connectors), or a bad ECU. A few of the codes have to do with the C3 pressure switch being open for one reason or another. It's inside as well as the turbine speed sensor. The ECU is $1800. I'd like to rule everything out before going there. Has anyone had any issues like this before? Any ideas? Maybe change the fluid since it's been sitting?

Sorry for the long post but one other thing I forgot to mention. Looking at the info plate on the transmission it is a remanufactured one and it looks like the date code is from 2008. The ECU was also swapped in 2008. Maybe they were having the same issues before. I wish I knew why it was all changed 11 year ago. I don't think it has very many miles on it since it was changed. Maybe why it's been sitting for so long. I've checked the voltage at the ECU (13.6), looked over the wiring best I can, and pulled out the output speed sensor. Nothing looks bad. I measured the sensor and it is 287.7 ohms. Anyway, if you have any ideas I'm all ears.

Here are the different codes:
2511 (3 times), 3233 (2x), 5412 (2x), 5423 (2x), 5432 (1x), 5445 (1x), 5587 (3x), 5611 (2x), 5622 (1x), 5655 (2x).
Thanks!

Hi probrd.

You are going to need scope, the right pressure gauge and information in order to do a good diagnostic.

It seems TCM is getting into "limp mode". That can be caused by hydraulic (valves or drain lines inside) or electronic (tcm or sensors).

Otherwise, you are going to change parts randomly

Please list the definitions of each code! Thank you

From the description, the good news is, it sounds electrical and not "rebuild time"

ScannerDanner wrote: Please list the definitions of each code! Thank you

Will do:
2511- Output speed sensor, detected 0 output rpm 1st gear

Main code 25 occurs if the output speed sensor reports a zero speed reading while both engine and turbine speeds
are approximately equal, turbine speed is above a calibration value, and neutral is not selected or commanded.
Main code 25 indicates either the output speed sensor has failed or the required oncoming clutch or clutches did not
come on. Code 25 11 can be generated by a false turbine speed reading. This may be due to crosstalk between
solenoid and turbine speed sensor circuits caused by direct wire-to-wire short or by water in the electrical
connectors. See Section 4 for corrective action.

3233- C3 pressure switch open, 3rd range

Main code 32 indicates the transmission gear ratio is correct, but the C3 pressure switch is open when it should be
closed.

5412- oncoming ratio test (after shift) 1 to 2
5432- oncoming ratio test (after shift) 2 to 3
5445- oncoming ratio test (after shift) 4 to 5

Main code 54 indicates a failed oncoming ratio test. The ratio test after a shift is failed when the ECU has
commanded the end of a shift and has not seen the transmission shift into the target range (comparing turbine and
output speeds). Erratic readings from speed sensors are a likely cause of an oncoming ratio test failure. If
conditions for a shift still exist, the shift will be retried one more time. If the ratio test is still not met, a code is
logged and the DO NOT SHIFT response is commanded. If the code is set during a direction change, Neutral with
No Clutches is commanded, otherwise the transmission is commanded to the previous range.

5587- oncoming C3PS test (after shift) N1 to R

Main code 55 indicates the C3 clutch is the oncoming clutch in a shift and the C3 pressure switch did not close at
the end of the shift. When this code is set, the DO NOT SHIFT response and Neutral with No Clutches is
commanded. On the N1 to R shift the transmission is commanded to the previous range. Additional codes could be
logged for other shifts where “X” indicates the range from and “Y” indicates the range to.

5611- Range verification test, 1st N1 to R
5622- Range verification test , 2nd
5655- Range verification test, 5th

Main code 56 indicates a failed range verification speed sensor ratio test. The ratio test occurs after a shift and
determines if a clutch has lost torque carrying capability. If output speed is above programmed output speed for a
range but the correct speed sensor ratio is not present, the DO NOT SHIFT response is commanded and a range
which can carry the torque without damage is commanded or attempted. Turbine and output speed sensor readings
are used to calculate the actual ratio that is compared to the commanded ratio.

There is more detail and which tests to do for each code. These are the basics for each. I still need to take apart the connector that comes out of the transmission and connects to the wiring harness coming from the ECU to make sure it's not all corroded. I haven't really seen any corrosion so far with any of the connectors I've taken apart. These darn transmissions are too darn smart for their own good.

I would absolutely start with replacing that output speed sensor.
I know I am suggesting changing a part, but things are difficult to test on these giant beasts lol. It's not like you are going to have 30-40 ft test leads connected to the speed sensor to watch it while driving.
Do a good visual inspection of the wires while you are down there too.

Thanks for the reply. You are correct. It is hard to work on these huge things. I’ll get it changed once I get a chance here in the next few weeks and report back. You’re videos are very helpful. I didn’t have a speedometer jumping like you did though. I’m wondering if maybe it’s possible, since it’s been sitting so long, maybe a valve or solenoid is sticking causing an issue. I know that Transynd fluid isn’t cheap and it takes a LOT. I watched you’re video on changing the filters and it was really helpful. If I decide to do it I’ll probably go a little further and pull the pan off to check the other sensor and the c3 pressure switch to rule them out. Thanks again.

Hello Probrd, would like to know if you solved your problem as I am having the 55 87 code with my md3060 Allison and was thinking it's the c3 pressure switch.