been a while since I posted.

I am having a new issue with my 01 Blazer.

i noticed it the other day while driving to work. the torque converter is coming unlocked after a while. It happens after the temp gauge is at normal operating temp. I am driving at 50mph and the rpm jumps from 1400 to 1700 and I can feel it let go. Then i get onto the interstate. After I accel to 70mph, the converter lets go again. RPM jumps from 1900 to 2200. I only noticed it happening after the weather cooled off. Actually it got up to about 65 yesterday and I did not notice it happening on the way home. I will watch it closely today to see if that is the case.

I have no idea what to look for. I found one other thread here about this. It seems related to temp but I will not know for sure until today. I only have one temp sensor in the left head. It is a 2 wire sensor. My gauge reads 180 or so when it is warmed up.

Any ideas????

 

180 is not hot enough, but that shouldn't cause the transmission to do weird things unless the transmission temperature is too low. Do you have an addon transmission cooler? If so, what type is it? If it does not have a viscosity bypass, you should cover it up in the colder months to keep from over cooling the transmission fluid.

 

I do not have an after market cooler. It has all the OEM stuff on it. It did not do this last year during the winter. Is the converter controlled only electronically or is the fluid involved? I may have the tranny serviced and see where it goes from there.

I just thought of something. This started after i put my skid plate back on. I drove all summer with it off. Could changing the air flow cause this?

 

I doubt that the skid plate changed anything.

The torque converter is a fluid coupling, but lockup is controlled by an electronic solenoid that controls fluid pressure to the clutch itself.

I would go ahead with the transmission service, but would add a new t-stat to the equation. 180*F is not high enough and if the coolant in the radiator is staying too cold, the transmission fluid could be overcooled there as well.

 

I will start there and report back. Thanks Kyle.

BTW. Is there something else I could check in the mean time. The controller circuit perhaps. And where does that live?

Does anyone know where the transmission control solenoid lives?

 

Ok I have an update. fluid change and still the same. I realized the engine temp is more like 195 not 180 like I stated. It is just shy of the 210 mark which is straight up.

I made sure to pay close attention to how it is behaving the last couple of days. When I start out in the morning, the converter locks as it should. Even after the temp reaches normal. After a few miles of driving at 50 MPH in stop and go traffic, i can feel the converter unlock. The rpm jumps up and I can feel it slip as I press on the gas pedal. If I sit at a light for a bit, the converter may (sometimes) lock for a mile or so and then let go again. I then have to stop before getting on the interstate. I get up to highway speeds 65-70 and can feel the converter lock. Then very shortly letting go. It then stays unlocked for the remainder of my trip to work. I have a 26 mile trip one way to work, so this is starting to affect mileage.

From what I understand there is a controller that locks the converter. Is this a work fail thing or could it be intermittent as it is in my case? It is pretty cheap to replace. I am not sure where it lives though.

Any thoughts?

 

Ok. So temperature in the other direction sounds like it is the cause. Your transmission may be dropping line pressure once up to operating temp or it could be a weak TCC solenoid in the valve body. There are also other possibilities, but all of these would start off with a line pressure check. Something that a transmission shop would be best qualified to do.

 

What should the temp be? It has always run the same. I will have the trans line pressure checked.

 

200-210*F is normal for a 195*F thermostat.

 

OK,
so here is one for the books. I have been noticing a miss and low throttle mostly in the mornings. I also started to feel a los of power all of the time. I decided to check this out and I replaced the cap and rotor as they looked a little rough. Well the truck runs great. Starts easier and is smooth on take off. What I also noted was I did not need near as much throttle to get the truck moving or maintain speed. This in term seems to have resolved the torque converter issue. The converter stays locked and all is well in the world.