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2003 Chevy Trailblazer LT
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Well its 2800 $ Heavy duty clutches and torque converter flush lines and remove and install $2800.00 Apparently Trailblazers are known for bad transmissions ? I only have 125,000 miles on it. I never knew that I thought people get over 200,000 miles out of one I stayed ontop of my fluids. I guess ill see if my shop can scan it and see if any trans codes come up before I spend 2800 $
 

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Well its 2800 $ Heavy duty clutches and torque converter flush lines and remove and install $2800.00 Apparently Trailblazers are known for bad transmissions ? I only have 125,000 miles on it. I never knew that I thought people get over 200,000 miles out of one I stayed ontop of my fluids. I guess ill see if my shop can scan it and see if any trans codes come up before I spend 2800 $
Not just Trailblazers, it's the 4L60. GM never has fixed the built in failures. Every trans they make has them.
 

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2006 chevy trailblazer_ls
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Most of these model vehicles are now old enough so that you would not want to do a flush; only do a fluid partial replacement. That is the beauty of what I did on my '06 TB. I replaced the factory pan with a Dorman pan with the plug and drain it every 5000 miles into a graduated bucket from Lowes, so I know how much to put back in. The only problem I have had is the leaky washer, copper material, that comes with the Dorman pan. I replaced that washer with Dorman #65269 washer, which has a rubber gasket bonded to a metal washer and which allows tightening without the worry of overtightening. A full flush will shock a transmission and can cause much debris to plug the solenoid valve passages, and then you have big problems. A drain and refill makes for a gentle cleansing of the internals and is what most transmission rebuilders recommend,
 

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the reason people opt for the fluid exchange is you get the majority of the 7-10 quarts out, not the 3 or so by dropping the pan. The only reason to drop the pan is to get the filter replaced, but if the trans is acting up, the majority of the time is because the screens behind the shift solenoids fill up with aluminum and clutch dust and restrict the fluid from getting to where it has to go. If you are dropping the pan, consider removing the shift solenoids and trying to look at the passage. Some years had screens to stop big chunks, but those screens are what fill up with dust and are easily cleaned. If you dont want to do it again, consider rockauto and just get replacement solenoids, they are not that expensive. Of course, running diagnostic codes will tell you for sure, but if the solenoid is functioning and has blocked passages, it wont throw codes.
We tried to clean those tiny screens and were never successful. Once they are contaminated it's not a job for a transmission shop to clean them: it's a cleanroom process at minimum, or new parts.

I'd buy reman'd units and they might be OK... or not.

OTOH ....... the trans filters did a fantastic job of keeping contaminants out of the pump ...... that's where cleanliness IS next to godliness.

But dropping the pan gives you a very good view on the health of your transmission. You cannot see thrust washer debris, sprag or planetary parts in a cooler line.

If you service your transmission on a decent schedule ... and NOT WHEN IT ACTS UP ... which is too late ..... you're gonna get the most out of it.
 

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I drove her to the shop and dropped it off yesterday It drove completely fine so I have no idea what's going on. Ill report back when I pick it up. Im wondering if I should just do another pan drop and fill ?
 

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2004 chevy trailblazer_ls
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I have an 03 trailblazer with the 4.2 vortec inline 6, idk much about transmissions but mine is just acting goofy. I have 238,801 on the odometer and I need to change the fluid in the tranny, just looking for tips when changing fluid and filter.
FWIW: You might also look into the valve body shift kit if the fluid change doesn't do it. I did mine a few years back when my 04 started acting up; around 150k miles. It would drop out of 4th - Overdrive while driving (lockup?), much more severe in hilly areas. It never threw a code. There's a steel piston that moves back and forth inside the aluminum valve body so it wears down the bore over time. Maaco couldn't duplicate the problem and diagnose. I think there are a couple good threads here and at least one youtube video that shows the process in good detail. It was tedious but doable in a few hours - I couldn't get out the servo on the side and make the changes needed there but the lockup problem stopped with the valve body changes. It does shift a little differently - more firmly, from when it was new. Also replaced the 1-2 and 3-4 accumulator pistons while I was in there. The most scary part was making sure the check balls didn't go anywhere when I was putting everything back together. I've probably driven 75k miles since; including towing a car on a two axle trailer.
 

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Not just Trailblazers, it's the 4L60. GM never has fixed the built in failures. Every trans they make has them.
Precisely why I lean a tad on the "overkill" side of things with transmission service schedules. My TB has been serviced every 30k since we bought it and I'm at 175k miles on the original trans. I also rarely tow and while I consider myself a "spirited driver" I don't try to lay rubber at red lights.
 

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Precisely why I lean a tad on the "overkill" side of things with transmission service schedules. My TB has been serviced every 30k since we bought it and I'm at 175k miles on the original trans. I also rarely tow and while I consider myself a "spirited driver" I don't try to lay rubber at red lights.
I got 220,000 out of my TB before the 3-4 clutch failed.
 

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Most of these model vehicles are now old enough so that you would not want to do a flush; only do a fluid partial replacement. That is the beauty of what I did on my '06 TB. I replaced the factory pan with a Dorman pan with the plug and drain it every 5000 miles into a graduated bucket from Lowes, so I know how much to put back in. The only problem I have had is the leaky washer, copper material, that comes with the Dorman pan. I replaced that washer with Dorman #65269 washer, which has a rubber gasket bonded to a metal washer and which allows tightening without the worry of overtightening. A full flush will shock a transmission and can cause much debris to plug the solenoid valve passages, and then you have big problems. A drain and refill makes for a gentle cleansing of the internals and is what most transmission rebuilders recommend,
The flush won't do anything to it. It doesn't blow through like a power jet wash or anything.
 

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I drove her to the shop and dropped it off yesterday It drove completely fine so I have no idea what's going on. Ill report back when I pick it up. Im wondering if I should just do another pan drop and fill ?
Story of my life lol my failblazer has 210,000 and my mech would never recommend a flush, period. Towed the 3-seater at least 4 times to and from the lake, and even the jet boat a few times. I replaced solenoids and have only ever done the filter/fluid never a flush, sometimes it shifts hard and sometimes it is smooth as butter. We could go on and on, my horn worked when I locked my doors this morning, but not when the girl was sitting at the green light with me stuck behind her. Take it with pride when it is issue free, and try not to overthink when its acting up. Good luck and I am curious to see what they tell you.
 

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I've seen flush jobs not able to drive out of the service bay .... I've seen flush jobs make it as far as the driveway, leaving various shops. I even helped push vehicles that wouldn't motivate, back into the service bay ... but since this shop didn't "do transmissions " they'd be calling for a tow truck to take the crippled car to a "reputable place like AAMCO" (pardon me, I just barfed a little lot there).

The last general auto repair shop I worked at before I retired, bought a flush machine with an instruction book that warned about flushing older cars (which was totally ignored) ... and saw dozens of vehicles start doing strange things.

Like: Park, a little bit of R, N, an almost Low gear in OD and lots more Ns ... or Park, no R, 4 Ns ... or P, N, N, N, N, N, Low ... or P, N, N, N, 3, 2, L ... or things like that.
Park never failed though ... and I may have misspoken here ... if the rear planets barfed and blew the reaction ring.​

The shop owner ... totally sold on his latest toy ... would always tell the customers that the transmission would "figure it out in 200 miles and that's because new fluid needed new calibrations and the transmission would do that all by itself" ... uh huh.
Later on, he just let the service writer handle those problems. After a few screaming fights in the waiting room ("You're standing here, telling me that, although I DROVE my car into here, that now I cannot drive it OUT AGAIN" type things ... for which the service writer demanded a serious pay raise for this abuse).​

When I retired ... I got recruited to write work orders in a friend's transmission shop (thanks Steve "Mister Butthead" McConichie, wherever you are now) ... until my retirement and SS got started ... where we got a steady diet of screwed up transmissions from not only that "other" shop, but also many shops around us ... selling the idea that flushes are good for your car.

So ... yeah .... as a retired mechanic and having been a transmission shop (or two) owner in the past ... please DO FLUSH YOUR TRANSMISSION!

You can't make me mad slapping my face with money.
 

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Do you find the 3-4 clutch pack failure or the 2-R shell breaking more often?
A toss up I think.

Abuse (see Note) will kill either one equally. The 2 Shell is a serious weak link that I always replaced with a hardened version.
Note: in some situations, turning the ignition to START is considered abuse.​

I wish there had been hardened shells for the 200R4s too! In my time, we never got them from 3rd party companies.... although the 200 wasn't really gonna be around for long .... it would have been nice to have to keep comebacks away while they lasted.
I think the Baby Cadillac Deville had them for a while ... I may be wrong there ... or was that a Cadillac Seville?​
Either way ... it was a Cadillac in the same size as the Nova .... remember? I digress.​
 

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Just for kicks -------> does anyone have any war stories about the THM125C transmission?

Let me start this ball bouncing with: I DO!
 

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A toss up I think.

Abuse (see Note) will kill either one equally. The 2 Shell is a serious weak link that I always replaced with a hardened version.
Note: in some situations, turning the ignition to START is considered abuse.​

I wish there had been hardened shells for the 200R4s too! In my time, we never got them from 3rd party companies.... although the 200 wasn't really gonna be around for long .... it would have been nice to have to keep comebacks away while they lasted.
I think the Baby Cadillac Deville had them for a while ... I may be wrong there ... or was that a Cadillac Seville?​
Either way ... it was a Cadillac in the same size as the Nova .... remember? I digress.​
We had hardened shells for those.
 

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You can't make me mad slapping my face with money.
Preach it, brother!

I get lots of work from "another shop". Two of 'em actually. They all mysteriously have nice, shiny, and fully loaded parts cannons.

Before I scare all the DIY'ers on the forum, please understand that I'm generalizing (ranting) here.

There are good mechanics, great mechanics, and bad mechanics. Just like their is good pizza, great pizza, and terrible pizza.
There are good honest shops and there are poorly run shops.
There are shops that sell you services on a menu board like you are at Wendy's and there are shops that sell diagnosis and repair.

But holy bat guano Batman, does anyone in this industry take pride in their work anymore? Is everybody beholden to the friggin' flow charts that all wind up at "Replace PCM"? I'm tired of cleaning up other people's messes, although it has put one kid through college. I'd much rather... and I often recommend on this forum... a DIY'er who is in over his head bring me the car to diagnose and let them replace the parts if they want to. I've even been known to bring them in to the shop and show them how I arrived at my diagnosis.

And don't even get me started with the quality of the parts supply... Dorman? AC Delco Advantage? Please please please folks... the guy at AutoZone is NOT A MECHANIC. He job is to sell you a part. Pick a part. Any part. He'll sell it to you.

Rant over. Feeling much better and with a strange craving for pizza now.

My top five tools / tips with almost every vehicle brought in where the customer complaint starts with "ever since...". DIY folks, pay attention.
  1. Scan tool. Only gives me a starting direction. Look at codes. Look at live data. Maybe look at mode 6? Understand what the data should be by looking at it when nothing is wrong. I have fancy expensive scan tools. But I can do ALOT with a $200 code reader from Amazon.
  2. Service data. First stop for me is always TSBs and Bulletins. Next stop is understanding how the component or system works. If there is a DTC code, I want to know what makes that DTC set. I rarely use the diagnostic flow charts. Finally, usually a wiring diagram is studied and then printed. Folks, if you are a serious Saturday afternoon driveway warrior, invest in a Mitchell DIY or Alldata DIY subscription for your specific vehicle. Spend some time exploring, reading, learning.
  3. Eye balls. Now that I know what or at least where to focus on, I look for anything obviously wrong. Get a great flashlight and an extending mirror. No touching!!
  4. Test light. Okay, now you can touch the car. I know you want to. Nothing fancy here. Just a computer safe test light. Thanks, Jeff Bezos, for delivering mine in two days.
  5. Digital volt-ohm meter. I think mine is an OTC, but invest in a good one and a good set of probes. Make or buy a set of long meter leads with banana jacks on the ends. Get some alligator clips and t-pins. Eventually invest in a full set of automotive test leads. You'll thank me one day.
 
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