Allison slow shift into 4th.

4 or 5,00 series # 6610370843 in a Mack GU813 #024766
It had a code for low trans fluid but it was not low. This would derate the truck to about 15 MPH. We replaced the fluid level sensor #29549755 which requires R & R valve body. The electric harness stand pipe was broken so we also replaced that. It includes a new harness. The derate and code is fixed.
Now it has a new problem. When it shifts out of 3rd it goes to neutral for 3 seconds. Then shifts firm. If driven normally the RPM jumps and the accelerator is let off. RPM is still a little high in 3 seconds and it shifts hard. If driven with very slight acceleration the truck slows down to much and it shifts back into 3rd, in 3 seconds. If 3rd is manually selected, run it up to 2150, select 4th and let of the pedal it shifts smoothly, in 3 seconds. No trans codes but a J1939 data link message. All other shifts are fine including the all down shifts.
Also replaced the filter kit, and fluid. Harness was # 29549578.
Any knowledge of these appreciated. Which valves in the body way control this.
Thanks in advance.

 

I am sure you understand this is a fully automatic transmission unlike a automated manual transmission.
Saying that so all others hopefully follow. It is kind of like a turbo 400 but a 6 speed and may have a built in retarder. ( Transmission brake ).
We decided to run it a bit and see if it corrected itself. Have an operator that works around the problem well but it has not gotten better.
If calibrations are possible I am not sure I have the software to do that. If you have any information about that and or places to look for that information I would appreciate that.
Mack wont work on it and the Allison dealer is several hours away. Allison dealer sounds way backed up.
Thanking if we can schedule a day or two will drop the valve body. Double check our work and spools related to these gears.
Have really been wondering if this J1939 deal could be related. It was there before the shift problem.

 

Thanks: I will look into that.