Sorry, can't help you with firmware versions, but typically if the firmware worked fine before and a problem has come up, new firmware is NOT going to fix the new problem, that might be from wear or a malfunction. But, yes, I could be wrong, perhaps there was a common problem that firmware changes did address, and a little wear was enough to induce the problem that newer firmware would fix.
Fresh Fluid and Filter never hurts. If its been a while and you're tough on your trans its always possible degraded fluid, changed viscosity and greater pressure drops across filters is contributing to extra shifting.
I "thought" there was a TSB on the 545RE for filters installed at the factory cracking, don't remember what the symptoms of the crack filter were, but just more reason to do an oil and filter change if you haven't done one. I think the 545RE has two filters, the typical pick-up filter and pressure filter that looks like a small engine oil filter. Its the small engine oil like filter that cracks, and I think it is inside the trans, NOT on the outside, but accessible by dropping the pan. There are youtube videos about changing that filter.
I'd be more concerned with the trans overheating, the biggest problem with the OD automatics is the tall OD gear, you get into conditions where the trans keeps shifting in and out of the OD gear, and the constant shifting overheats the trans, and then the cascades of effects from that which shortens the life the trans greatly.
That is why there is a towing mode for OD trans.
For the Brick Like Aerodynamics of the Commander, I wouldn't be surprised if 65mph the aerodynamic load is enough that its at the edge of downshifting out of OD.
Do you have cruise control on when you get the shifting/tc unlock?
Have you changed the tires or at least checked they are at proper pressure?
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Last edited by Mongo; 07-29-2014 at 08:56 AM.