Hello . 2004 Trailblazer LT 4.2 L . When I put TB in 4 Lol or 4 wd then go into reverse I get a clicking maybe gear meshing kind of noise from what seems to be below the driver's door. If I put foot on brake while sitting still in reverse and press gas pedal noise gets worse. Car drives and shifts fine . Reverse works fine in AWD and 2wd . Drive works fine in all settings . Help please , I'm confused .
Welcome to the Nation. What has the maintenance of the transfer case been like? The fluid has to be replaced with smurf blood (AutoTrak II fluid) every 50k miles.
How long have you owned this truck? Is it possible that it's just binding on a solid surface? Does it make the noise while moving or stopped?
In 2WD and AWD, there is no power being sent to the front wheels. In AWD, it would engage the front only if there is rear wheel slippage detected.
It puzzles me because those two positions are far apart from each other in terms of where the cams that control the transfer case are. Were it only in 4lo I would say the encoder position sensor was worn amd the 4lo position is just a fuzz away from neutral such that if not fully engaged it might slip. But 4hi is totally different being adjacent to the A4WD range of cam travel.
Edit/addendum: Is it possible the noise you hear is actually from further up front and not the transfer case area?
It puzzles me because those two positions are far apart from each other in terms of where the cams that control the transfer case are. Were it only in 4lo I would say the encoder position sensor was worn amd the 4lo position is just a fuzz away from neutral such that if not fully engaged it might slip. But 4hi is totally different being adjacent to the A4WD range of cam travel.
Edit/addendum: Is it possible the noise you hear is actually from further up front
UPDATE!! I I changed transfer case fluid . When it came out it was blue and I refilled with advance Trac 2 which is also blue. I just went to gravel area, 1: I stopped then accelerated in drive and reverse in 2wd and no noise just spun as expected . 2: I put in 4 hi and four lo in drive and left front and rear tires spun for a second then hooked up again as expected . 3 I put in reverse while In 4 lo and 4 hi and same thing but this time with noise again. I have a better description of noise now . It sounds almost like a fan hitting a shroud or if you ever tried to push and old manual pickup into gear when clutch is bad ? Its that kind of noise . It sounds like it is coming more from front wheel area. Oh ya , I put it in AWD and got same results as 4 wd. Seems that it is engaging ok just that crazy noise in reverse. Also vehicle doesn't have to be moving to do . Parked in 4wd with parking brake on and wheels chocked , put into reverse and apply gas and same noise. All of this is just in reverse .
Welcome to the Nation. What has the maintenance of the transfer case been like? The fluid has to be replaced with smurf blood (AutoTrak II fluid) every 50k miles.
How long have you owned this truck? Is it possible that it's just binding on a solid surface? Does it make the noise while moving or stopped?
In 2WD and AWD, there is no power being sent to the front wheels. In AWD, it would engage the front only if there is rear wheel slippage detected.
It puzzles me because those two positions are far apart from each other in terms of where the cams that control the transfer case are. Were it only in 4lo I would say the encoder position sensor was worn amd the 4lo position is just a fuzz away from neutral such that if not fully engaged it might slip. But 4hi is totally different being adjacent to the A4WD range of cam travel.
Edit/addendum: Is it possible the noise you hear is actually from further up front and not the transfer case area?
Mooseman. I made a long reply but I not sure if you saw it yet. I just bought truck , I changed transfer case fluid and it was already blue . I replaced it with Advance Trac 2: Noise sounds closer to left front wheel area than transfer case .
Welcome to the Nation. What has the maintenance of the transfer case been like? The fluid has to be replaced with smurf blood (AutoTrak II fluid) every 50k miles.
How long have you owned this truck? Is it possible that it's just binding on a solid surface? Does it make the noise while moving or stopped?
In 2WD and AWD, there is no power being sent to the front wheels. In AWD, it would engage the front only if there is rear wheel slippage detected.
Hello . 2004 Trailblazer LT 4.2 L . When I put TB in 4 Lol or 4 wd then go into reverse I get a clicking maybe gear meshing kind of noise from what seems to be below the driver's door. If I put foot on brake while sitting still in reverse and press gas pedal noise gets worse. Car drives and shifts fine . Reverse works fine in AWD and 2wd . Drive works fine in all settings . Help please , I'm confused .
Have you checked the front differential fluid? To me, it sounds like the TC is working. So next suspect is either the front diff, or the front axle disconnect.
Have you checked the front differential fluid? To me, it sounds like the TC is working. So next suspect is either the front diff, or the front axle disconnect.
I would get under the front and grab each part of the driveline up there and see what movement you get. Look for looseness anywhere and everywhere. In particular check out the passenger side cv axle to the disconnect (that's the part bolted to the passenger side of the oil pan). That is a well known wear spot, the bearings fail.
I just went back out and checked both axles , everything is tight with no play at all. What's inside the axle disconnect? Could it be that unit? It only does it in reverse.
I took your advise and tried that . With 4wd engaged I can't turn front drive shaft or wheel . It's def engaging, I don't understand the crazy part that it does this noise wether the car is moving or stationary when it's in 4wd and reverse . Forward is fine , just reverse and it has to be 4wd . I'm completely baffled. I would say transmission but it's only when front axle is engaged .
But if you're not moving, nothing is moving in the transfer case or anything else in the driveline. I'm thinking something is getting torqued in 4x4 reverse and rattling. You know like when you put it in reverse and the engine will move to the right from the transmission torque.
I took your advise and tried that . With 4wd engaged I can't turn front drive shaft or wheel . It's def engaging, I don't understand the crazy part that it does this noise wether the car is moving or stationary when it's in 4wd and reverse . Forward is fine , just reverse and it has to be 4wd . I'm completely baffled. I would say transmission but it's only when front axle is engaged .
I am sorry, I missed a big part of the diagnosis above..
When the truck in 4wd, and all 4 wheels in the AIR (on jack stands!), truck in park, then try turning the driveshaft. It should not turn. Then try turning the CV axles, the wheel on the other side should spin in the reverse direction. now put the drivers side front wheel on the ground, try again, turn the steering wheel full turn one direction, try again, turn the steering wheel full turn the other direction, try again. Now put the drivers side wheel in the air, put the passengers side wheel on the ground, and repeat the instructions above.
Edit: I guess the rear axle does not have to be in the air, but the front needs to be as outlined above
But if you're not moving, nothing is moving in the transfer case or anything else in the driveline. I'm thinking something is getting torqued in 4x4 reverse and rattling. You know like when you put it in reverse and the engine will move to the right from the transmission torque.
I was kinda thinking about that myself .I will try again to post it . I thought for a second possibly a motor mount and the fan spinning against the shroud. Tomorrow I will unlug the fan and see if it still does it . I'll have to have the wife help me so I can be out front to try to pinpoint better.
I was kinda thinking about that myself .I will try again to post it . I thought for a second possibly a motor mount and the fan spinning against the shroud. Tomorrow I will unlug the fan and see if it still does it . I'll have to have the wife help me so I can be out front to try to pinpoint better.
Thats about the only thing I hate about you guys with the 4.2 LL8.. Those motor mounts are EASY!!!!! Now me, with the 5.3 LM4 V8, lets just say I rather pay to get it done.. Which is why it has not gotten done!
Thats about the only thing I hate about you guys with the 4.2 LL8.. Those motor mounts are EASY!!!!! Now me, with the 5.3 LM4 V8, lets just say I rather pay to get it done.. Which is why it has not gotten done!
I bet , you have zero room down in there. I'm still trying to load video but it's an mp4 video , whatever that is and forum says it has to be pdf or zip , no idea what that stuff is.
Thats about the only thing I hate about you guys with the 4.2 LL8.. Those motor mounts are EASY!!!!! Now me, with the 5.3 LM4 V8, lets just say I rather pay to get it done.. Which is why it has not gotten done!
Maybe the gears in the encoder motor? But again, why only in reverse? Maybe it's not quite moving enough to fully engage and works forward but slips in reverse? Quite puzzling this one
What about taking the encoder motor out and moving it manually?
I do not think it is an encoder as the noise appears to be modulated (volume & timbre) by pressing the gas pedal. I would expect the encoder to make a consistent sound regardless of throttle position.
When viewed from the left side, the reverse torque reaction would make the front diff want to rotate counterclockwise. Points above the diff would move up and/or forward.
A simple way to test the fan shroud theory would be to look for signs of wear on the shroud and fan blade tips. Fresh plastic surfaces or shiny fan blade tips should be pretty easy to spot.
I don't know anything about the 4wd system, but could it be one of the heat-shields vibrating on the exhaust or something? Noise doesn't sound like plastic to me.
Hello . 2004 Trailblazer LT 4.2 L . When I put TB in 4 Lol or 4 wd then go into reverse I get a clicking maybe gear meshing kind of noise from what seems to be below the driver's door. If I put foot on brake while sitting still in reverse and press gas pedal noise gets worse. Car drives and shifts fine . Reverse works fine in AWD and 2wd . Drive works fine in all settings . Help please , I'm confused .
UPDATE!!!! After much crawling underneath and scratching my head . I found it ! The engine fan clutch assembly is bad . Why just in reverse 4wd IDK !! I disconnected and reconnected fan 7 or 8 times this morning to confirm it . Wheeeew am I glad I found it with the help of all you people .. Next stop was AAmco , that would have been expensive , I'm quite sure they would have wanted to pull front diff. Thanks for all your help and input.
UPDATE!!!! After much crawling underneath and scratching my head . I found it ! The engine fan clutch assembly is bad . Why just in reverse 4wd IDK !! I disconnected and reconnected fan 7 or 8 times this morning to confirm it . Wheeeew am I glad I found it with the help of all you people .. Next stop was AAmco , that would have been expensive , I'm quite sure they would have wanted to pull front diff. Thanks for all your help and input.
I am suspicious. Elsewhere online you said that the fan clutch feels tight, no looseness, right? I am thinking a bad engine mount or maybe even both of them.
