Weird fan clutch + transmission issue.

[Niklaus]

Hello all,

Posting this one for my dad's 2002 Trailblazer EXT with about 175,000 miles on it.
He seems to be having a problem with his fan clutch but I can't be sure why or how or if it really is the fan clutch or not.
He is on his 3rd fan clutch, the first being OEM which died and was on the full stuck on position, then he bought a cheap chinese made fan clutch (big mistake I know) which helped the problem but there was still something wrong for it's entire life. It came with the infamous ticking sound which I believed was the fan clutch trying to engage/disengage but failing to do so. The biggest problems were that it took very long to go away at first start, like sometimes it needed a full minute of driving, even in winter on cold days. As he put more miles on the car, we started getting SES lights which threw codes for a bad fan clutch. We took an 8 hour drive to North Carolina last summer and over there it seems like it died totally. When we slowed down on the highway due to traffic, the fan would get stuck on the full on position and it wouldn't stop, especially with the AC on and even more with the AC running in the back (EXT version so it has the roof vents). With the AC running it would not turn off at all. The gauge read 210 temperature.

When we got back home, he replaced it with a Dorman or Hayden fan clutch which seemed to be fine for a little bit, and better quality then the old one, but it still had the issue of taking a very long time to turn off at first start. I know this isn't normal because my 2002 Envoy never does this, it turns off in seconds at most.

Now after months of driving, the fan clutch turns on and off rapidly and cycles over and over again when cruising at highway speeds. It sounds annoying, like someone is turning a vacuum on and off and repeat. This happens without AC on but with the AC on it happens more frequently or gets stuck on the full on position.

Next, my dad also has a transmission problem. When cruising highway, especially going up on a hill, the transmission is almost as if stuck in 3rd gear. It never kicks into 4th or overdrive unless he lets go of the throttle completely, but even when he pushes it again just a little bit, it jumps right back to 3rd with high RPM every single time. He claims this started happening when the fan clutch started failing or screwing around. Coincidence?

For me, it seems hard to believe that both fan clutches died in such a short amount of time and both have the same problems from the start. Is it possible that the PCM could be screwing my dad over and also messing with how the transmission works? I know the PCM controls the fan clutch and it can be tuned to change how the transmission works. I also read that flashing the PCM is not necessary and will only improve AC idle performance. But maybe in his case it will do something more? Or is this what he gets for getting a non OEM fan clutch? Will a better quality or OEM GM fan clutch help? Does the transmission have any correlation with this?

Any thoughts would be appreciated.
Thanks for reading.

 

[The_Roadie]

It's too bad about the fan clutches, but they are unrelated to the tranny issues. Good news in all that is the fan was effective, and kept the gauge temps to 210. That is good, and contributed to tranny longevity.

Of the 175K miles, how often has the transmission been serviced? Any towing involved?

Was the transfer case fluid changed religiously every 50K?

Plugs and all other fluids done at 100K?

Any other maintenance history?

 

[BRomanJr]

"We took an 8 hour drive to North Carolina last summer and over there it seems like it died totally. When we slowed down on the highway due to traffic, the fan would get stuck on the full on position and it wouldn't stop, especially with the AC on and even more with the AC running in the back (EXT version so it has the roof vents). With the AC running it would not turn off at all. The gauge read 210 temperature."

Sounds somewhat normal to me, When running the A/C, especially when not moving, the fan clutch will be commanded on, it pulls air through the Condenser (and Radiator) to allow the A/C to cool properly. The A/C system REQUIRES a flow of air over the Condenser whenever A/C Compressor is running.

IIRC the clicking was usually fixed by a PCM update in the early years up to 2004, or 5?

The brand of clutch probably makes a difference in proper operation and longevity, I use the adage, "You get what you pay for"
I occasionally go cheap and In those instances I am sometimes rewarded with long life.

FYI, I recently replaced my fan clutch with a Hayden 3201 when I replaced a leaky water pump, Both work great.

 

[KNBlazer]

Didn't have time to read the replies, but did you update your PCM firmware after installing the fan clutch? The fan speeding up with the AC on I believe is normal... and on a cold start, my fan also stays elevated for about 20-30 seconds....

 

[Niklaus]

It's too bad about the fan clutches, but they are unrelated to the tranny issues. Good news in all that is the fan was effective, and kept the gauge temps to 210. That is good, and contributed to tranny longevity.

Of the 175K miles, how often has the transmission been serviced? Any towing involved?

Was the transfer case fluid changed religiously every 50K?

Plugs and all other fluids done at 100K?

Any other maintenance history?

The tranny is rebuilt, my dad bought the car used 5 years ago and it was rebuilt when we got it. The mechanic at that time did a flush which was a terrible idea considering we didn't know if the transmission would 'handle' it since it could make it worse and we didn't know how long the transmission has gone flushed or not flushed. It might've helped or done nothing wrong but it might've hurt it as well. Plugs have been changed, TC fluid has been changed about 20k miles ago I believe, and all the other maintenance was done. The car had never done any towing and we don't plan on it.

Didn't have time to read the replies, but did you update your PCM firmware after installing the fan clutch? The fan speeding up with the AC on I believe is normal... and on a cold start, my fan also stays elevated for about 20-30 seconds....

The PCM firmware was NOT updated, which is why I was wondering if this could help solve the issues the car is experiencing.
The fan stays elevated for an average of 30 seconds but it's weird since my Envoy and other GMT360's I've been in shut it off very quickly.
____

The real issue at hand is why does the fan clutch screw up every time driving highway. The fan clutch seems to engage and disengage rapidly in cycles, this happens even when the AC is NOT on and more frequently when it is. The temps outside are moderate too, like around 60s. This happens driving normal highway speed. When we slow down due to traffic, the fan clutch is fully on and doesn't turn off unless we get back up to 50MPH or more only for the on/off cycling to happen again. The cycling doesn't happen all of the time but it happens like 50% of the time when highway driving. -ALSO, there is an SES light but I feel like it's unrelated to the fan clutch because cruise control doesn't work as well and the code hasn't turned off after a few drives even when the fan clutch was behaving normal. It feels like the fan clutch is fine but the computer is screwing up the engagement/disengagement (if that's possible). Maybe the fan clutch is just bad and we need a 4th one, . Damn the bad luck?

That long drive I wrote about, we had a SES light that gave a code for the fan clutch. The weird thing is that it seems like the fan clutch is fine but the code appeared when it didn't want to turn off when it should've. The fan clutch seemed to work fine even in high temps, but once it engaged once (after the engine temps reach 210) then it wouldn't turn off at all. Then we replaced the fan clutch which fixed the problem but now we are experiencing what I mentioned above.

 

[IllogicTC]

The transmission issue, I'm wondering if it's in the transmission or in the PCM. The transmission of course houses all the hydraulics and clutches and does the actual job of shifting, but it's the PCM that tells it when to shift. The only reason I'm curious about the PCM is because of the reported symptoms of just barely touching the accelerator it goes bananas.

Thinking of it, what is the possibility of an APP acting up and not scaling linearly as intended? So a tiny bit of throttle is read as more than it actually is?

 

[seanpooh]

Just remember, the PCM also changes shift points of the transmission after driving after so many miles.

When you reset the PCM by disconnecting the battery when doing work or just cleaning the throttle body, it goes back to the factory settings and the PCM adjusts itself with the shift points.

It might be a good chance to give it a try and clean the TB while you wait the 30 minutes.

I also noticed that you have the 2002 version just as I do. However when I replaced my fan clutch, I put in the 2008 version which is term ally activated, no more PCM controlled. Maybe that's something to look into if you think your current clutch is failing again.

 

[Niklaus]

Huge issue.

My OBDII scanner finally came in from Amazon and I got to check the SES code that my dad had for the past few days.

P0741. Ouch.

From what I read, "If the solenoid is stuck in the off position, the only thing you would notice, is a decrease in fuel mileage. When the Torque Converter Clutch(TCC) solenoid fails, it prevents the converter from going into lock-up(or 4th gear). So initially you wouldn't really notice anything, except that the rpms are a little higher when at highway speeds, thus burning a bit more gas."
The TCC turns off to prevent further damage from the transmission. The TCC may also be slipping.

This is exactly what my dad was experiencing, but when he lets off the pedal it seems like 4th gear engages since the RPMs drop a lot but as soon as the throttle is pressed then it can't get into 4th and is stuck in 3rd. I feel pretty sorry for him as this calls for a transmission rebuild or a new tranny in general. Dad says he feels no difference when driving other than the 4th gear issue.

And after reading more in depth, it seems like it will only get worse till the tranny sh*ts on itself. Weird thing is that he's driven like this 2 weeks ago and there was no code. This time there is a code and so far there have been 200mi+ driven with this issue. 100mi with the code.

Any thoughts? Does this definitely call for a new tranny or rebuild? I think he will take it in to the mechanic soon.

PS.Seems like the fan clutch is ok then.. but there's still that weird issue when cruising.

 

[MJRBrooks]

Huge issue.

My OBDII scanner finally came in from Amazon and I got to check the SES code that my dad had for the past few days.

P0741. Ouch.

From what I read, "If the solenoid is stuck in the off position, the only thing you would notice, is a decrease in fuel mileage. When the Torque Converter Clutch(TCC) solenoid fails, it prevents the converter from going into lock-up(or 4th gear). So initially you wouldn't really notice anything, except that the rpms are a little higher when at highway speeds, thus burning a bit more gas."
The TCC turns off to prevent further damage from the transmission. The TCC may also be slipping.

This is exactly what my dad was experiencing, but when he lets off the pedal it seems like 4th gear engages since the RPMs drop a lot but as soon as the throttle is pressed then it can't get into 4th and is stuck in 3rd. I feel pretty sorry for him as this calls for a transmission rebuild or a new tranny in general. Dad says he feels no difference when driving other than the 4th gear issue.

And after reading more in depth, it seems like it will only get worse till the tranny sh*ts on itself. Weird thing is that he's driven like this 2 weeks ago and there was no code. This time there is a code and so far there have been 200mi+ driven with this issue. 100mi with the code.

Any thoughts? Does this definitely call for a new tranny or rebuild? I think he will take it in to the mechanic soon.

PS.Seems like the fan clutch is ok then.. but there's still that weird issue when cruising.

I'd love for someone to chime in on this, as well. I'm having the same issue with my tranny when traveling up a hill (WV mountains when heading to Cincinnati). My temporary fix is pulling over, turning the TB off, waiting 5 mins, starting her back up and getting back on the road. Allows access past 3rd gear, but I'm sure it's not doing any good in the long run.

Furthermore, had the tranny rebuilt a couple years back. I'm fearing that this thing is going to give out on me at the most inopportune time (which is technically any time ever).

 

[KNBlazer]

When there's a transmission problem, I recommend that you call a few transmission shops in your area and ask if they offer a free diagnostic... Their computers are expensive computers that allow the tech to run various tests on solenoids and sensors... They will tell you with certainty whether your transmission is shot or you only need a solenoid.... Take it to at least a couple of shops so you can compare the results...