Hello. I have a 2002 Trailblazer LTZ. When I am driving usually I notice around the speeds of 50-60 mph my car revs up and you can watch the rpm's go up and down. There is not check engine lights on. Pushing on the brake pedal will make it stop revving up and down. Could this be something like the Throttle Position Sensor? If so wouldn't it throw an engine code? Could it be the transmission?
Rpm revving up and down while driving around 50-60mph.
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littleblazer
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From what I remember this is an issue with lockup in the torque converter. At that speed it tends to hunt under slight throttle variations and is normal I believe. Pressing the brake while still applying gas disengages the torque converter.
Jrgunn5150
Member
It is on the highway...it is mostly flat with a few slight inclines nothing major. Usually it is with cruise on but it seems like it did it once without cruise on too.
I don't think it is normal because it just started doing this within the last month. I have owned it for like 8 years and it never did it before. I am getting high miles on it now but I love it and do not want to give it up lol. But I have heard of the torque converter thing as I googled about this....my question is how do I fix it (I am affraid it will break down and we are going on vacation in two months and driving it). Thanks.
Jrgunn5150
Member
It sounds like the valve's in the transmission have worn the bores over sized and now you're falling out of lockup. A TPS is also possible, but I bet it's just worn with knowing you've had it eight year's and it's high mileage.
I use this on my 4L60's,
http://www.sonnax.com/parts/3029-the-sure-cure-kit
I use this on my 4L60's,
http://www.sonnax.com/parts/3029-the-sure-cure-kit
dkvasnicka
Member
The 4.2 has plenty of power to stay locked at 50 - 60 mph, even with the car full of family & stuff and even on slight inclines. Actually, on a few occasions I was amazed by how much "suffocating" the engine took before the computer decided it cannot go locked anymore.
Sparky
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This is what I used to cure it on my one 4L60E, and also I use it as preventative maintenance on all my 4L60E transmissions now (well I get the appropriate year, different plate for my 2007 for example).
http://www.ebay.com/itm/4L60E-4L65E...ash=item3f1166b953:g:WDkAAOSwpDdVeOGx&vxp=mtr
http://www.ebay.com/itm/4L60E-4L65E...ash=item3f1166b953:g:WDkAAOSwpDdVeOGx&vxp=mtr
littleblazer
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I dunno. I was told 400 ish rpms around 50 was normal. With cruise it doesn't really seem to do it but just using the pedal does...
dkvasnicka
Member
Only if your TC is unlocked, which at 50 it should not be unless you're towing or accelerating or going fast up a steep incline or something... My 9-7X is quite agressive when it comes to locking the TC and does it even while accelerating on a highway. If I don't accelerate aggresively enough it thinks it can handle it locked a does so, which isn't very pleasant to be honest. But whatever, the authors of the tranny software knew what they were doing I presume.
Then there is one special case where the tranny can legitimately jump up and down in RPM on a highway, even with the CC on. And that's when you are going down a slight decline, doing like 55 MPH or something and the transmission thinks locked TC would slow the car down, so it unlocks. But after a few secs it finds out that it'd have to burn too much while unlocked so it locks again... and this circle of insanity continues until you hit a level surface or a incline. There is a place on the route to my father's house where my tranny does this, even though it works perfectly OK everywhere else. You can get around this by going faster at which point the transmission computer cannot think it could handle it more economically while unlocked.
First, what is the mileage on the T.B. now ?
Second, when, if ever, have you serviced the transmission ?
Third, have you inspected the trans fluid level ?
Forth, when you say it REVS UP ..... are you talking 2,000 RPM'S or are you talking 400 RPM'S ?
Second, when, if ever, have you serviced the transmission ?
Third, have you inspected the trans fluid level ?
Forth, when you say it REVS UP ..... are you talking 2,000 RPM'S or are you talking 400 RPM'S ?
The fluid is fine...it is at like 180,000 miles. We have not had the transmission serviced in the 6 years we have owned it. I hear a lot of ppl that say do not get it serviced on high mileage cars but just as many ppl say to get is serviced. I have noticed a few things: it only happens between 50-65 mph, it only happens with going uphill even if it is just a little uphill on the highway, it does it with and without cruise control on, when it revs up it is going up and down between a few 100 rpms and it sounds like the engine is revving up and down. I just want it to be an easy fix like a sensor or something. Any thoughts?
That is one of the biggest myths out there. How can new fluid and filter ruin a transmission? If it fails after that, it's because it was destined to fail regardless of what you do. When I bought my truck in 2011, the engine was knocking and the fluid was old and brown so it was obviously neglected. 100k km and 5 year later, still have the same tranny.
Jrgunn5150
Member
I think that's where the myth comes from. People run them 150-180k on the same fluid, it start's acting up, they do fluid and filter, or worse, one of those quicky lube flushes, the trans dies anyway, they blame the fluid change lol.
hockeyman
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This, this, and this.
Better to know ahead of time before it leaves you stranded. The planetary gears decided to "go south on me" as I was about 15 miles from home and in the pouring rain. Murphy's Law seems to have a crush on me lately.
Also, if it were me, I'd do what Mooseman mentioned and change the fluid/filter. Do it while the pan is dropped and you're looking for any large metal pieces....y'know, like I recently found! ->> Look at post #12 http://gmtnation.com/forums/threads/transmission-started-grinding-in-1st-reverse.14929/#post-485210
138k on my odometer and it happened completely out-of-the-blue!
NEVER EVER DO A FLUSH AT A QUICK LUBE OR SHOP! Most of them don't drop the pan and just do a reverse flush, which moves the dirt back into circulation. There is a post here somewhere that shows how to do your own flush using the tranny's own pump so it is a normal circulation flush (more like a complete fluid replacement). @MAY03LT even has a couple videos on it.
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gmcman
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With what's been stated, I wouldn't keep driving it with it acting up unless you are 100% sure it's the TCC and not the 3-4 clutch pack. 180K is alot of miles but if this is the only symptoms, anything is cheaper than a new or reman trans so what do you have to lose?
The 4L60E is a very good trans, your symptoms are very likely from neglect... what's possibly happening is you're losing pressure somewhere and this is resulting in holding power being lost....this is more noticeable in the higher gears.
Put the selector in "3" and get it up to 60 MPH, will the converter lock? If so ( it should) does it act the same as in 4th or "D"? Also, with the cold weather, your TCC won't lock until the trans is up to temp, this takes longer when it's cold.
I would do what Matt suggested...drop the pan, change the filter (deep pan filter) get it from the dealer if you're not comfortable in aftermarket. I would use some Valvoline Max Life ATF, this is Dex 6 compatible and is great fluid.
Drive it for a few hundred miles and do it again.
Don't drive with it slipping just in case it's the 3-4 clutch pack, if you smoke that clutch pack the trans is toast.
The 4L60E is a very good trans, your symptoms are very likely from neglect... what's possibly happening is you're losing pressure somewhere and this is resulting in holding power being lost....this is more noticeable in the higher gears.
Put the selector in "3" and get it up to 60 MPH, will the converter lock? If so ( it should) does it act the same as in 4th or "D"? Also, with the cold weather, your TCC won't lock until the trans is up to temp, this takes longer when it's cold.
I would do what Matt suggested...drop the pan, change the filter (deep pan filter) get it from the dealer if you're not comfortable in aftermarket. I would use some Valvoline Max Life ATF, this is Dex 6 compatible and is great fluid.
Drive it for a few hundred miles and do it again.
Don't drive with it slipping just in case it's the 3-4 clutch pack, if you smoke that clutch pack the trans is toast.
Renato gonzalez
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If you are having this problem, I also had it and fixed it with the TCC valve replacement. You can do it with the transmission still in the truck.