2-3 Clunk....I know, again

[biochemist]

Hey guys ...OK, as I am sure some or maybe most notice, when your truck shifts from 2-3 and sometimes 3-2 you hear a clunk. I would absolutely love for somebody to explain why this occurs other than the TSB that is floating around (although the latest version would be good to post). I even understand the 05 models do this too! Now, to explain what I hear (since day one BTW)...when accelerating, right at the shift I hear a clunk...sometimes going around a corner drop to second, clunk, then up shifts to third, clunk...nothing I can feel really, just a noise. Seems to be more pronounced in those situations where you are slowing down and then speed up again going from 3-2 back to 2-3...I am not talking about stepping on and off the gas quickly and getting a clunk, more of slowing down in traffic then accelerating back to a higher speed. I have had everything checked out numerous times, all normal. This happens in normal driving too away from lights and such...funny thing is sometimes it will not do it! It only happens at certain acceleration speeds...sort of predictable, but sometimes not. Just when I think I have a pattern, it will do it when I would have guessed it would not and vice versa. Additionally, I really only notice it with the windows down and the radio off, or windows up and everything off...so it is not that loud although sometimes it is louder than other times. Most of the time it is a small little clunk, most people would not notice this...my ears are good which I think is my real problem ...other times a little louder, most would notice, nothing I can feel though, just a noise (not the Thump that Snarkee was feeling and hearing). I would say it clunks ~40-45% of the time when not tuned by westers, so I can just retune and rid most of this. As stated, the Westers Tune did help a lot, but the dealer re-flashed the ECM last time I was in so I need to “reload” as they say. It is interesting that since the dealer re-flashed me and put the new driveshaft in (snap noise fixed BTW) with new joints and yoke that it seemed to quiet the clunk down for a couple weeks at least, but has returned slightly in the last few days...is this because of fresh grease on the yoke? Is it really that simple? Do you guys think it is the shift timing or the yoke sticking? I know Lyndon can get most if it out of there with a tune, but not all of it, so it may be a combination of timing and yoke issues...

 

As far as drivetrain lash...When in neutral I can twist the driveshaft a bit...ujoints are fine no movement in those at all. The total amount of driveshaft twist travel between R and D with the engine running and parking brake on, is ~3/4 inch...measured where the shaft was when in R then put in D...I do not think that is the issue with the clunk...Anyway, my service guy understands and says most all trucks do this...I am the type that cannot ignore these types of noises, they grate on me...he says they build in lash to keep from breaking parts and gears have to have clearance hence the clunk when going from P to R or D, which I understand completely...just wondering how much is normal. I have hear other trucks make these noises too...which help a little, but would like to understand what is going on a bit better, hence the post. The truck drives just great, I just hate noises that I cannot fix! I guess the re-tune will help again, just wondering how widespread the clunk really is!

 

So, how many hear this noise(s)...does it bother you? My truck has the new yoke and the joints are fine...what have your service departments said about this? Have you contacted Chevy? If it truly is just a noise and some of you have heard since new and have 150k on the clock with nothing going wrong, then I suppose I can just "ignore" it ...but it is not my nature. I love my truck, I just would like to rid it of anything that will not be good down the road. I prefer preventitive strikes, not waiting until later (esp. when the warranty runs out ).

 

One more thing, do you guys notice a slight whistle sound while accelerating at certain speeds...sounds electronic to me. I was thinking it was the intake or something...not sure. There is another post on this recently and I guess I have noticed it to once in a while since new.

 

Anyway, I know this has been talked about extensively, and the theme is that it is a noise and will not cause harm...but let us share our experiences and see if we can get something accomplished, or at least an understanding...For those that always have the radio on or a real loud exhaust, the poll may be skewed a bit as you would not notice this noise...do the best you can though, my guess is that if you notice it at all, it does it more than on might think...just depends on how much you listen for it. Please list truck age and how many miles you have notice the clunk. Later guys,

[Rammer]

My '02 X cab did it and now my '05 Crew cab does it also. Everytime I took the 02 in to the dealer, they must have gave me a deaf technician, as they never could hear it.

[Rammer]

Some how this double posted.

[biochemist]

Some how this double posted.

 

<{POST_SNAPBACK}>

 

 

My service is great actually, they know it does it, but the tsb says no issue...from the poll looks like ~2/3 have this...the other third must be 2x4 or they just do not notice it, I guess it may not be there, maybe just not real noticable by some people...interesting that a couple serivce guys estimated that 60-70% of the trucks exhibit this...they were right on so far...later man,

[MS3DALE]

I guess I'm lucky,My '99 never did it (w/92,000 miles) and so far my '04 is quiet (at 11,000 miles)

[biochemist]

I guess I'm lucky,My '99 never did it (w/92,000 miles) and so far my '04 is quiet (at 11,000 miles)

 

<{POST_SNAPBACK}>

 

 

Hi MS3...yea, some people will not notice it, I mean it is not like you can hear it from a mile away or something like that...and with your exhaust and programming, you may have removed it or at least covered with the exhaust...I know when Lyndon tuned me the occurance went way down...just depends on how you drive to...you, I would guess, get on it frequently...you would not hear it as much then at all...later man,

[MS3DALE]

Yea,Your right,I do tend to "get-on-it" a bit

I don't beat the truck but I do run it

On another note,I do have superman like hearing you wouldn't believe the things I hear,nor do you want to know!

Later man

[biochemist]

Yea,Your right,I do tend to "get-on-it" a bit

I don't beat the truck but I do run it

On another note,I do have superman like hearing you wouldn't believe the things I hear,nor do you want to know!

Later man

 

<{POST_SNAPBACK}>

 

 

Thought so...I tend to take of slowly...which will cause it more than the way you drive...guess I will have to get on it a bit more , when I get re-tuned and the outlaw intake... ...In know what you mean about hearing, which is my problem, I hear everything! On a side note (no punn intended), do you guys stock those new chrome gas tank covers...? I notice that Chevy is really starting to push "aftermarket" style accessories for the trucks esp...which is cool IMO. They can make a ton of $$$ on that stuff and the wheels they sell, which are awsome, but here in MA would not be too useful ...later,

[mcreyaufmiller]

I used to notice it a lot, then I added the exhaust adn other mods and now i do not hear it.

[MS3DALE]

biochemist,No I haven't seen the chrome fuel door covers yet,I know GM offers them,I just haven't had anybody lookin' to order one yet.

[facn8me]

First things first Bio. Turn up the radio your driving your dealer crazy

 

 

 

 

It's a joke people.

 

 

Actually mine was real quiet when I bought it, but the lift and bigger tires make's the slack/noise seem more noticable. To take care of this I installed a sub woofer to cover it.

 

My girlfriend keeps pointing out little noises and I keep tellin her stop turning down the radio and you won't hear them.

[5.3almnblk]

A/T - 2-3 Upshift or 3-2 Downshift Clunk Explanation

 

File In Section: 07 - Transmission/Transaxle

 

Bulletin No.: 01-07-30-042A

 

Date: December, 2002

 

INFORMATION

 

Subject:

Information on 2-3 Upshift or 3-2 Downshift Clunk Noise

 

Models:

2003 and Prior Light Duty Trucks

with 4L60E or 4L65E Automatic Transmission (RPOs M30, M32)

 

This bulletin is being revised to add the 2003 model year as well as information about 3-2 downshift Please discard Corporate Bulletin Number 01-07-30-042 (Section 07 - Transmission/Transaxle).

 

Some vehicles may exhibit a clunk noise that can be heard on a 2-3 upshift or a 3-2 downshift.

 

During a 2-3 upshift, the 2-4 band is released and the 3-4 clutch is applied. The timing of this shift can cause a momentary torque reversal of the output shaft that results in a clunk noise. This same torque reversal can also occur on a 3-2 downshift when the 3-4 clutch is released and the 2-4 band applied. This condition may be worse on a 4-wheel drive vehicle due to the additional tolerances in the transfer case.

 

This is a normal condition. No repairs should be attempted.

 

I hear it but after i read this it stop bothering me.

[pastorscott]

Hey I have a 5.3 04 burb and mine did it bad so I ran it down to the dealer with that TSB number and they did reprogram somthing. It was gone for a while and now its back again, I dont like it either.

 

 

Pastor Scott

[hoorders]

Yup............my 2000 has the 'normal clunk' crap going on............nice selling feature on GM's part.. ........all I do is lube up my yoke every few months and that seems to make it alot better.

 

I have been considering putting a zerk fitting on my yoke to make this service easier........im not sure if this would potentially screw anything up like throwing it off balance.

 

Anyone have any thoughts on that before I attempt this??.......

[ken1mod]

Does it do this at every stoplight acceleration? Almost any automatic can be made to make this noise when the drivetrain is lightly/unloaded as when decending a hill and the vehicle shifts.

 

Mine is silent but I have had vehicles that did this hundreds of thousands of miles with no problems.

 

If it makes this noise under normal acceleration, there is some problem, maybe even engine mounts. That would be intolerably annoying.

 

Ken