I have a 96 blazer. 145,000 miles. I have used the search and didn't really see what i was looking for. My question has to due with overdrive lockup or better yet not locking. The last servicing on the trans was justa few months ago andoverdrive will still not lock.Highway mileage has dropped with the higher rpm's. What do i need tolook atto correct this? It has a shift kit and Trans works good. have had no problems with it except the overdrive issue which started about 9 months ago. looking to get my gas mileage back.

Thanks

Ed

 

Could be a TCC PWM solenoid failure, torque converter clutch failure, a wiring problem inside the transmission or a number of other things...

 

Thanks for the reply but now you have my curiosity going...."what other things". My son is in school and just starting automatic transmissions. Can you guide him where to look for the other things if the soleniod does not do the trick?

Thanks

Ed

 

Start with those things which you know need to work. If those check out good, then you move on to the "other things". Other things could be a bad seal, junk in a seal, allowing a leak, etc.

 

Is your blazer triggering 1870?

Computer controls TCC. Computer must see proper inputs before it turns on TCC (ie TPS, VSS, CTS, ect). Computer controls TCC on 96 Blazer 4L60E by grounding the TCC solenoid and controlling the TCC PWM solenoid.

Difinitive testing on solenoids is almost impossible by the DIY'er but.....

Electrical function-You can test a solenoid's electrical function by ohm checking it, but they can short or open intermittantly so your test could be a waste of time. Amp checks are better but hard to interpret on PWM solenoid. Most of the time solenoid electrical testing is a waste of time unless there is a trouble code for the solenoid.

Mechanical function-You can test a solenoids mechanical function by removing the solenoid and "jumping" power and ground to it, while blowing it it to see if it seats and unseats. But the mechanical portion of the solenoid also can stick intermittantly so this really isn't conclusive. Dont invert the polarity while you "jump" power and ground to it or you will kill the diode in the solenoid and then you'll definatly have a code.

A better check of the solenoids mechanical function and electrical function is through the use of a scope and a low amp current probe. The pattern will reflect the movement of the "pintle" in the solenoid. This would be a very conclusive test if you drove the car while the problem happened, and you watched the pattern on the scope.(.....if you had experience with interpreting the scope pattern)

Here's a short list of things inside the trans could cause no TCC.

1. solenoids
2. Valves (some in valve body andone in pump)
3. Stator bushings.
4.Crossleaks in the pump
5. Converter

As a professional I've allready been through this a thousand times. EVERY time, its been wear in the TCC regulator valve. The other things could be causing it and someday it'll happen, but for now I dont even do checks on them anymore, other than scan and verify the code and verify the TCC is slipping. I just pull the vavle bodybore the valves oversize and install oversized vavles.

The AFL valve works in conjunction with all the solenoids, and it wears also, so it needs done as well.