You didn't insult a witch, did you?


Hitting Intermediate/2nd gear hard is a sign of bad calibration, a broken spring in the valve body, bad shift timing, a leak in the valve body or a broken accumulator spring in (either) the band cap or the pistons in the valve body --- notice I said: "piston(s)" in the valve body .....

Someone could have stuffed the accumulator bore with pinless pistons or a spacer or a (now) broken accumulator Shift-Kit spring (which usually isn't a factory policy ... TTBOMK!).

It's not uncommon for the first shift-of-the-day to 2nd/Intermediate - in the morning or not - to MAYBE be somewhat harsh; I don't think I've owned a THM700R4 or a 4L80E that doesn't do that from time to time.

Sometimes, having the HVAC at a very LOW MODE (or DEFROST) --- and the compressor is also running, CAN cause a /partial throttle shift to hit a little hard too. It happens.

Now --- Cruise Control has very little --- maybe nothing --- to do with the transmission shift quality.

C/C is dependent upon clean-pure-unwavering 5VDC to be available all the time it operates - and it shares that 5VDC with several (or all --- this is out for discussion yet) of the 5V supply from the ECM.

There ALSO appears to be a pair of 5V outputs, but they may be from the same source --- I dunnow for sure but am wildly interested in learning the truth.

Up for consideration ---> the cooling fan appears to be a big bugaboo.

 

So I know that doesn’t seem possible but I am traveling through three states. When I left AZ it shifted hard into second. I then hit the highway and no cruise control. Drove 80 miles stopped for gas took a break. Got back on the road no hard shift to second and cruise control is back. I have been traveling all on highways and every time I start off from a stop mostly for gas or a rest area If it shifts hard into second I do not have cruise control. If it doesn’t have a hard shift. I always have cruise control. If I lose cruise control and a leave the vehicle off for at least 10 minutes it shifts smoothly and I have cruise control. Today I lost cruise control when it was on cruise control and I stopped along the road for just a few minutes and when I took off it hard shifted and no cruise. I drove like that till I got gas. When I left gas station it shifted smoothly and had cruise. ??? lol

 

OK --- where would you like to start? You need to make a plan to solve one or the other.

 

The cheapest. lol. Probably the cruise control first. I took it to someone and was going to change the transmission fluid and he advised against it. The mechanic said it would make it worse or make it fail faster. I bought this car about 3 months ago with 100,000 miles. Not sure what the maintenance was. The inside is pristine.

 

BS on the new fluid ruining a transmission --- it won't FIX it ass no transmission service will --- but it won't actually hurt anything that is already dead or dying.

Every time I had a customer come in and request a transmission service --- I asked a lot of questions.

Why? was the biggest question.

Most people who request a transmission service think it will repair all the bad stuff inside the unit and make it whole again --- like a visit to Lourdes.

 

Ok that’s good to know. I thought it was kinda stupid myself. He said you just have to drive it till it fails. So will I have a code on my trailblazer even if I’m not getting a check engine light. For either of my problems?

 

Ultimately? Mebbee ... but it depends on what fails and how the computer interprets it.

Slipping friction materials in the transmission will be tattled upon because of the RPM differences of the expected values after a shift is attempted.

The input RPM as read from (maybe) the crankshaft sensor, will send that metric to the ECM and then the output shaft will also relate its RPM and they have to meet the plotted hard-coded values from the engineers at the factory.​

Yeah - a CEL should pop if there's a (multiple) late shift, an incomplete shift, or any component(s) are slipping and letting the engine rev higher than normal.

But - realistically --- we live until we die and cars drive until they cease to motivate. Mechanical things will die ultimately.

Drive it with an eye to transmission failure since you've already rocked that boat - and save your Krugerrands for the day it won't back up or won't shift above 2nd gear. It happens.

 

I wish there was a way to check and be sure before failure. It’s like saying smoke cigarettes till you get lung disease then stop. If I knew for sure I’d just change it out.