OK. Help again. My O/D is cutting off after normal highway driving. Yes I can cut the engine off and it resets. This is after I have changed out the radiator, water pump, hoses, not the heater core though, the check valve in the return line of the tranny cooling line. I have also dropped the tranny pan with a filter and oil change. I have also changed out the timing set, oil pump and pick up tube. When y'all helped me before you stated that the O/D would kick off to prevent the tranny from over heating. The temp gage now never goes above normal range even in this fabulous 90 -95 degree heat we're having. I have been driving back and forth to work for about a month now about 40 miles round trip with no issues. After about a two hour drive yesterday the O/D kicked off. I am not towing anything. Also I was having issues with the A/C cutting out from dash to defrost vents. Cleaned the check valves in the vacuum lines and it semi cured the problem. Meaning it will cut the dash vents off sometimes but not every time I accelerate. I was using cruise control the first time it kicked out. The second time, I was not using cruise control. I've searched the threads as best as possible and couldn't find anyone having the same issue. Thank you all so much in advance for any suggestions!!!

 

Would be interesting to see what PCM thinks trans temp is doing when O/D drops out.

If the PCM is doing it on purpose, it *should* set a code.

Did you remove the check valve in the trans line? Do you have an aux trans cooler between the radiator, and a/c condenser? If there isn't one, might consider adding one.

 

For your vacuum issue do you have a check valve in the AC/Heater vacuum line that goes through the firewall? If not add one and the report back. For your tranny issue the snapring in the OD unit may have went bad (common problem). But as HeyYou said add an auxiliary cooler is you don't have one. Eliminate the check valve in the tranny line (FYI I still have mine with 170,000 miles with no issues on factory trans) if you haven't (I think you did by reading your post but a little confusing). Also if you have a scanner read the tranny temperature.

 

On my cheapie code reader I only see two temperature reading components, ECT and IAT. The manual doesn't really explain all the acronyms on the scanner. I'm assuming the ECT is engine core temp as it reads 190 at idle at operating temp. It does however explain how to perform a run cycle for the scanner to perform a check. I will start this cycle tomorrow. I do not have an auxiliary cooler but have a new radiator and check valve in the tranny cooling line.

 

As telling the same to Heyou, I don't know if my scanner reads the tranny temp. ECT or IAT. I posted a pic of the check valve for the vacuum lines that run through the firewall. The check valve has the white ring around it. which I removed and cleaned. I have two that run through the wall. One goes beside the a/c line the other, with the check valve, goes in up higher by the wiring harness. If I can figure out the tranny temps, and they are high then I guess installing an auxiliary and removing the check valve in the tranny cooling line will be next. is there an overdrive band in the tranny that may be overheating? Thanks for your help!

 

ECT: Engine coolant temp.
IAT: Intake air temp.

Might need a better scanner to read trans temp.

I was referring to the check valve in the trans cooler line. If its still there, get rid of it.

 

You have the correct vacuum check valve so you might have another leak. Did you check your plenum? No band in the OD unit that I'm aware of. As HeyYou said eliminate the tranny check valve and install an auxiliary cooler

 

I plan to eliminate the check valve in the trans cooling line, even though it's new. Will also search for a better scanner. Maybe a temp gauge for the tranny temp too. I was also talking about the check valve in the vacuum line that controls the blend door with MoParFanatic21. I thought I read somewhere on here where it was in connection with the cruise control which I think is located under the battery box. Then again at my age I may have this confused with something else. Will advise of progress. Thank you!!

 

From what I understand installing a check valve in the cruise control line will have the opposite affect. I'm not to sure though if I'm being honest. I couldn't see how it would hurt, but I've been wrong before

 

Doesn't the vacuum line for the cruise attach to the throttle body? That should be 'ported vacuum', so, higher the airflow thru the throttle body, the higher the vacuum is sees.