Allison 4000MH Failure after fluid change
We had the fluid (Transyn) and filters changed in the transmission by a mobile RV service. The transmission seemed to work fine before the service. We warmed it up before the tech showed up, idling it in forward, shifting into reverse and back to forward. We got enough torque movement to cause an uproar by the wife who was doing her face at the time.
After the tech finished he started the engine to warm it up so that he could tweak the final level. He idled it in forward and soon got a trans warning light. The long and the short of it is that the transmission fluid would never warm up and we never felt the torque surge when he engaged it. It is like the fluid was not circulating at all. The original diagnostic code was 25-11 which for the output speed sensor in 1st gear. I tried putting it into reverse at one point and a second code started to show up, 55-17 which is Oncoming C# pressure test (after shift). Now both codes seem to come on the moment we start the engine, with D1 being the 25-11 and D2 being the 55-17. Allison suggested that we let the fluid set over-night and check it both before and after running the engine. The thinking was that the dip stick fluid level would drop if the transmission were circulating. We did that and the level did not change. We will try again with Allison Monday morning but perhaps someone here has some thoughts. Their (Allison's) tendency seems to be to pass it off to a distributor.
We have checked the sensor connections at the transmission and they seem sound. Can anyone guide us to the location of the ECU? That connection needs to be checked for sure.
We have kept up with the maintenance on the transmission and the fluid removed appeared clean and did not smell burnt. The removed filters appeared normal. The current milage is 70,000.
Any thoughts or experiences you can share would really be appreciated. Let's just say that we are in a horrible position for a tow and must work every angle to get this going in place.
Texas Hill Country
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