TH125 Trans problems

Hello I have some questions about my '88 GA with a 2.3L Quad4 and TH125 trans. I have recently been having problems with it stalling intermittently unless I two foot it. I already know that means the TCC is staying locked when it's not supposed to. Also the SES would come on interm. and I pulled a code 26. A friend gave me some GM diag pinpoint tests that pointed to replacing the TCC solenoid. Been there done that know I don't have converter lock up most of the time and on occasion it wil surge at highway speeds. My other half refuses to call his friend and ask Questions. Also this car was a freebie that had sat for 2 yrs. because of a failed fuel pump. I changed the fluid and filter when I replaced the soleniod, everything else seems to work ok. If anyone can help, please feel free.Thank you.:banghead: :banghead:

Welcome to AF.

So you replaced the TCC ?

Diagnostic trouble code 26 Quad Driver(QDM)Circuit malf.

This could be many things.
Thiers no certain thing to look at but I would suspect that its something to do with the TCC .

Might try some Seafoam Trans tune up and see if the surge doesnt clear up and will help clean the inside period.
After a car sits for that long the inside of the trans gets varnish biuld up and things get clogged.

The above treatment should clear this up, after another trans fluid & filter change.

Thanks for the welcome. I have never heard of Seafoam trans tune up, but at work we use BG products, and I haven't yet flushed the trans. I have other things to worry about like a blown head gasket. I would like to fix that before driving it too much. Another thing is I am not a GM tech, however the person I talk to before that gave me the info is. That and the symptoms I was having are the reason I replaced ithe TCC soleniod. I would like to know exactly what a Quad Driver Module is. Is it a term for part of the PCM or is it maybe part of the ignition module? The surge seems to be the converter locking and unlocking at speeds higher than 40mph, and it only happens for a short period after the solenoid has been removed from the valve body and put back in. I had the trans apart again to check the connector was seated and that there was no fluid blow by past the o-ring on the soleniod. Aftter the surging stops I have no converter lockup at all.

You could have a shorted wire on the trans.
I had a 93 GA that did this surging when going down the road at a constant speed. Was one of the trany wires grounding out .

As for the quad driver, just because you have a Quad driver code doesn’t mean the Quad driver is bad.
All a Quad driver code means is that an expected value is not present when it’s suppose to be.
Also a Quad driver is a techy name for 4 on-off switches arranged in a group, hence the name Quad driver.

The computer watches the voltage values on each switch and knows that if the switch is on, a voltage value will be seen.
When the switch is off the opposite voltage value will be seen. Simply put, light on, light off.
So what can set a quad driver code?

You’d be surprised. How about a bad bulb? How about a bad fuse? The answer is yes to both questions. Yes, a bad bulb or failed fuse can set a Quad driver code. Start with checking your fuses. There can be up to 3 fuses that supply power to circuits controlled by the Quad drivers.

If the fuses are good the next check would be of all or some of the following, depending on how your vehicle is equipped: Up shift light bulb, coolant hot bulb, shift to drive bulb, A/C relay, coolant fan relay, EGR solenoid, Canister Purge solenoid, even a speedometer output signal goes to one of the switches on the Quad driver.

What I’m saying is, that it is unlikely you have a computer problem. It’s more likely that the Quad driver code is present because the computer is not seeing the information that it expects to see at one of the switches.

Hope that clearifies the Quad Driver :)