Transmission jerk on downshift 3nd to 2nd low Speed no pedal gas

[David T]

Maybe try your old board and see if you still have the same problem? If you don't have harsh downshifts with the old board, then you have confirmed there is a problem with the new shift computer. In a picture on I think it was post #9 you had the old governor alongside the new one. It would not be unusual for the electronics (or a solder joint) to be sensitive to temperature. You can also contact Ed and ask if he has seen this problem before and what to do about it.

[Michael]

Sully mode on : Can we all get real now?


We all have $50k+ cars. Spend 3 or 4 hundred bucks, replace the governor and put this BS behind us.

[axh174]

The more I think on this, the more I agree with Michael and David. The most likely culprit is the governor; your transmission wants to downshift but the governor is not sending the signal to do so. Using the gear select lever or forcing the kickdown switch to activate both provide an alternate means of informing the transmission to downshift, and they both work. So, it's likely not anything mechanical with your transmission that is causing the problem.

Given the heat-related nature of the problem, it's likely a bad solder joint. You could try reflowing the solder joints, as David suggested, or you can reach out to someone to see if they can fix/replace the current or old boards, as Michael suggests.

If you are still unsure of the diagnosis, you can also try to further isolate the cause. For example, try heating up the governor yourself while the car is cold and then driving it. Or you can drive the car until the shifting problem happens, park it, and somehow cool the governor down (wrap with dry ice?) and try driving again.

Let us know what you find out/choose to do. We'd love to hear the conclusion to the story!

[Michael]

Yeah just to clarify, I'm not saying the governor is 100% your problem, but I am saying it probably is. My logic is more than that though, if you do have an internal problem, then the trans most likely has to come out and apart to even diagnose, let alone rectify. A governor is 400 bucks sans fluid and gasket and 1.5 hours of your time. Even if I was only 50% sure replacing the computer would fix it, I would roll those dice vs. the alternative.

There are a few things that would be worth checking while your pan is off such as the wiring to the plug and solenoids, debris in the valve body (maybe pull the filter and check for any red flags in the element), and make sure the electrical plug connections are clean and making good contact.

[axh174]

Slightly off topic: is there a knowledge base somewhere for how the digital governor circuit works or what it's capable of doing?

If it has programmable shift points, maybe it was incorrectly programmed for when to downshift?

[David T]

Slightly off topic: is there a knowledge base somewhere for how the digital governor circuit works or what it's capable of doing?

If it has programmable shift points, maybe it was incorrectly programmed for when to downshift?

Not on the digital one. For the OEM one we have the schematic and procedures on how to resolder the joints and replace the capacitors that typically blow. To change the shift points you would have to change the resistors and capacitors to different values. For minor changes you can play with the adjustments to the shift cable. We call it a "shift computer" but it really is not doing any "computing" and is not programmable. The digital one may be programmable but you would have to get in touch with Ed. This is the point at which you need to have a conversation with your vendor as to how to proceed. Maybe he can exchange or repair your governor or at least test it to make sure it is functioning properly. Or, as I suggested in my last post, put the old one back in and see what happens.

[Ron]

Slightly off topic: is there a knowledge base somewhere for how the digital governor circuit works or what it's capable of doing?

If it has programmable shift points, maybe it was incorrectly programmed for when to downshift?

???
I'm confused -- You posed in this thread. /dmctalk.org/showthread.php-Automatic-Transmission-Governor

Anyhoo, at this point, I agree with just changing out the GC.

[axh174]

???
I'm confused -- You posed in this thread. /dmctalk.org/showthread.php-Automatic-Transmission-Governor

Anyhoo, at this point, I agree with just changing out the GC.

Hi Ron,

That thread discusses the design and function of the original OEM governor after we as a community back-engineered it. I was inquiring if there was a thread that discussed the design and function of the newer, updated Ed/DMCH governor.

In the past, I've heard rumors the shift points are programmable on the newer design. But I never really looked into it to see if that is true. I've also been really curious about the type of controller chip it uses and how it drives the shifting solenoids. But I'm guessing that information might not be generally available.

I've been half tempted over the years to buy one and back-engineer it like we did with the OEM.

[Bitsyncmaster]

I've been half tempted over the years to buy one and back-engineer it like we did with the OEM.

You would probably find (by bench testing) the new one does what the OEM one does. The micro would just input voltages and use those values to turn the solenoids off or on with those switch points hard coded in the software. The micro just drives transistors which in turn drive the solenoids.

It's more work to un-assemble the software than to write your own new software.

[Ron]

Hi Ron,

That thread discusses the design and function of the original OEM governor after we as a community back-engineered it. I was inquiring if there was a thread that discussed the design and function of the newer, updated Ed/DMCH governor.

In the past, I've heard rumors the shift points are programmable on the newer design. But I never really looked into it to see if that is true. I've also been really curious about the type of controller chip it uses and how it drives the shifting solenoids. But I'm guessing that information might not be generally available.

I've been half tempted over the years to buy one and back-engineer it like we did with the OEM.

Aaah...the new one...had a brain fart.
{Those were the days}