So I have a 95 blazer, and recently whenever it shifts into 4th/OD/the torque converter locks up, it will shift into it, but not all the way. It will then shift back out of it, then back int. It will do this several times and then fully go into 4th. Sometimes its shifts hard into it too, not slam into it but you can definitely feel the shift, which I never really did before. It will go into OD at less then 40 mph sometimes too, like around 37-38. I thought it wasnt supposed to until 45. Ideas?

 

Is the problem when it shifts to overdrive, or during the torque converter lockup? I found out recently that if I'm low on ATF, it will have difficulty going into lockup. It'll lockup, unlock several times, until you get to a little higher speed.

 

It only happens in OD, so during torque converter lockup I presume. The fluid is fine. I added a bottle of Lucas Transmission fix and it went away... Going to do a transmission flush when it gets a bit warmer out.

 

Alright, it started doing it again, and now more frequently. It's really driving me nuts and I don't know what it could be. I haven't done the transmission fluid change yet.

 

Alright, 95 blazer, after around 40mph the rpms will fluctuate a couple hundred rpms, like its shifting in and out of OD, but it does it in D too at higher speeds. I've read it could be the torque converter solenoid, bad fluid, bad valve body, temperature sensor, etc. How can I narrow it down? I had codes ran and all it gave me was a bad egr, o2, and emissions. could the egr be doing this???

 

If it is shifting normal into 2nd and 3rd and TC locks up while it is cool(engine and trans) but shifts hard and TC wont lock when it gets hot it will prob be the valve body, my Blazer did this and now works perfect after installing a valve body. Look for VB at Amazon

 

It shifts into 2nd and 3rd fine, the problem happens when both cold or warm. usually after a few minutes of driving above 45 it doesn't do it anymore. If I stop or slow down below that it will do it all over again.

 

Sounds similar to what mine was doing. I removed and cleaned the brake light switch to fix a cruise control issue and accidentally also fixed the TCC. There are 3 separate sets of contacts in the switch, 1 is for the brakelights, 2nd is for the cruise control and the third set is for the TCC.

 

Where is the brake light switch? Cruise works fine on it.

 

The brake light switch is down in the driver's foot well. Follow the brake pedal up and you will see it. I had to remove the panel to access it.