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Thanks for the input on learning. Since my last post I have swapped the engine ECU, transmission still shifts late as before. No sign of any improvement in shifting as result of learning after about 7 trips/drive cycles.
Had a chance to chat with the lead mechanic at a local Volvo dealer, intriqued by the problem he invited me into the shop and then into his locked back room, the inner sanctuary with the complete library of Green Books, special tools mounted on the walls that we only see in pictures but can never get to have. And yes they do have a secret personal cache of spare parts such as MAF's, ECU's etc for use in diagnosing. He let me loose on the library where I started to read about the how the TCU works and how it talks to the ECU and the tranny itself. He also made an offer to photocopy anything I want. Before I could get too far however word came around that the owner was on his way and I had to leave the inner sanctum and shop area. He invited me back any Saturday morning to hang out and look at the library material.
Here is where I think I stand.
There are 4 main signals that would affect shift points and lock up as the car gains speed:
1. MPH. originates at diff sensor and goes to ABS, speedo, cruise and TCU
2. Throttle position sensor on throttle valve
3. Converter output rpm. (comes from a sensor on tranny)
4. Engine rpm and load. (Combined signal from ECU)
Other inputs are such things as brake signal, selected gear, mode, full throttle switch etc that I have checked and double checked. These are all off/on type voltages that do not directly affect shift points.
I have confidence that all is well mechanically inside the tranny as it simply shifts when told to by the TCU. I know this from watching the voltages to the 4 solonoids.
My prime suspect
now is the speedo signal to the TCU. I am not sure if it is correct. It originates as an AC signal from a sensor on the diff and is sent to the ABS unit, from there it branches off and disappears inside the speedo. Outputs from the speedo go to other places such as cruise control, radio and to the TCU. I do not know if the speedo processes the signal to a DC pulse or just passes it through. I am now pursuing this.
Please..... ideas, thoughts, suggestions from anyone no matter how stupid it sounds, I am in brainstorming mode and will consider anything.
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David Hunter
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960 AW 30 transmission shifting- desperate and frustrated. [900][1993]