[miketexas]

hello everyone this is my first post here. i recently picked up my first Trailblazer 4x4 LTZ 2002. the vehicle runs great and rides great, but this being my first Trailblazer i have nothing else to compare to. my transmission started acting funny, still getting all my gears but it just seems like the shift points are late. on a cold engine its more noticeable like almost 3k before a shift. at normal operating temp i can see 2k on a shift which feels normal with easy throttle, but if i give heavy throttle its shifting at 2500, this is operating temp. also others have said feels like overdrive is coming in late. on heavy acceleration im reaching 60 MPH and shes still shifting, this does not feel normal. i checked the fluid level and its full and doesn't smell burnt. i thought about taking her in to have the fluid/filter changed, but i keep reading about shift solenoids and them being common problems. i have no SES light and the transmission pulls strong so IDK what to think if im looking at a rebuild in the future. everything else on this vehicle works great AC, heat, 4x4, awesome LED headlight mod very little rust for a Michigan 17yr old SUV thats why i wanna make this work. any thoughts?

Changing the fluid will not have any effect on it. If the shift solenoid(s) were bad the trans would take off in third gear all the time. it is possible one is leaking a little, but it's rare. You might suspect the TPS but at this point it's all guess work. One easy thing to do is clear the battery then reconnect it and drive it around easy and let it relearn and see what happens.

 

[miketexas]

if the TPS was bad wouldnt i get a code? ill try disconnecting the battery, see what happens

You would usually get a code yes, but in the real world things don't always work like we expect.

 

[miketexas]

how do i test the TPS to see if it working correctly?

The only way I know to test them is to use a digital oscilloscope. I have one and they do work, but you can get a good idea from reading the voltage coming from the tps with a scan tool. usually at closed throttle it will read about .5 volts or so up to about 4.5 or so at wide open throttle. The voltage should rise steadily but not go up and down. What did clearing the battery do? Anything?

 

[miketexas]

i do have a scanner that displays live data and this is what the throttle position said at idle

i noticed the TPS come built in the throttle bodies so if i have to do it i gues i have to replace the whole throttle body?

On that model I believe you can change just the TPS. So, did clearing the battery have any effect?

 

[miketexas]

ok i left the battery positive and negative off for a couple hours. when i went to drive again there was no change in shifting

Sorry but it's hard to say. A situation like this would call for someone with experience to check it out. If I understand correctly it shifts through all the gears good, right? If so, and seeing how this vehicle is new to you it may be normal or the beginning of something. So you either have to keep driving it as is, start throwing parts at it, or let someone check it out. Good luck.

 

[miketexas]

Two notes I want to make here from my own experience.
1) Be aware that if the transmission hasn't been regularly serviced since its beginning, that fluid may be the last line of defense to keep it from failing. The density of the fluid surrounding the gears may partly be what is letting it shift correctly. I had to have my tranny rebuilt a year ago or so because I did have someone do a drain and fill with filter replacement on my transmission fluid and shortly after got hard shifts from first to second. Ended up having to rebuild very shortly after that.
2) Be aware of heat, have had weird shift intervals before too when driving a lot and tranny heated up.
My Two cents

The thing you say about the fluid is false sir. I reality it never had anything to do with the gears. Ford used to use square cut seals back in the 60's and 70's and they would become hard an brittle. With no Lip type seals which GM uses today, the new fluid would blow past the old seals. It wont happen on a 4l60. Fake news in other words. Your tranny had problems before you changed the fluid.

 

[miketexas]

i trust you Mike, you seem very knowledgeable on these transmissions. thats kinda a relief. when he posted that i remember about 10 yrs ago i called a Ford dealer to schedule a transmission service on mu 89 Mustang and thats exactly what he told me and suggested just change the filter. he said new fluid might agitate the transmission and give me more problems. shortly after i sold that car but didnt really have any transmission problems. any way thank for the info man.

to update everyone i still have not heard back from my mechanic yet but i drive by his house and i see my Trailblazer moved around in different positions quite a bit as if he is driving her so IDK. maybe ill stop by and see how shes doing

Thank you. Unfortunately most car dealerships know very little about transmission repair and spread the same stories around that they have heard. Ford no longer uses the square cut seals either and your Mustang would probably have been fine to have the fluid changed.

Here is a analogy for people to consider. Many many times when people have problems with an automatic transmission the first thing they want to do or have recommended to them to do is change the fluid and filter. I look at it a lot like this: If you change the problem to the motor of the vehicle, will changing the motor oil fix a bearing knocking, or a misfire, or a no start condition? Nope it won't. Tests have been done on trans filters that show after a 100,000 miles they still have over 80 percent flow. And if the filter does get stopped up, it's stopped up with clutch and gear parts from failed parts in the trans. When the fluid turns black it is from being contaminated with burnt up clutch plates.

Good luck on it.

 

[miketexas]

well i got a call shortly after my reply earlier this morning, he dropped the pan and changed the filter and fluid. he took her for a long drive after also scanning for codes and said the transmission is working as it should be and shifting great. so it seems maybe since i had nothing to compare to thats just how the 4l60 is supposed to be

Good deal.

 

[miketexas]

i got another call from him today telling me the lower ball joints were bad since a set of Moog lower control arms were included when i purchased the vehicle i just gave them to him to put on. i probably could have done it myself but with recently moving and losing my garage, having to do this in my driveway while it has been raining past couple days didnt really appeal to me. i have been busy anyway taking care of my fathers final affairs im too busy to do it.

he did say when he drained the transmission fluid it was dark but no clutch buildup inside. the vehicle is shifting better now but i still get to 60MPH and shes still shifting must just be how she is

To know if it's working as it should, depending on the rear ratio at 70 mph rpm should be a little below 2000 RPM, or real close to 2000.

 

[miketexas]

this is my RPM at 70

Lookin' good!