• If you currently own, previously owned or want to own an Avalanche, we welcome you to become a member today. Membership is FREE, register now!

"Clunky Shifting" On An 03

teksavy

SM 2011
SM 2010
SM 2009
SM 2008
SM 2007
SM 2006
SM 2005
SM 2004
SM 2003
Full Member
Joined
Jan 23, 2003
Messages
1,131
Location
San Jose, CA
I now have 1700 miles on my '03 1500 Z71 and have noticed slow shifting and clunking at times. The clunking is almost always on the 3-2 downshift and sometimes when I shift into/out of reverse.

I notice the slow-shifting mainly under load (with lots of people in the truck).

I've checked the trans fluid and its fine. Is this something I should take it in for right away, or just see how it goes. It doesn't happen all the time, so I'm not sure what the dealer could do. Would a fault code be posted?

-Ed
 
I have a 2002 green Av Z71.It has also had a problem with shifting.It does it on the 1-2 upshift.Most of the time it only does it after driving for about 30 minutes.I would describe it as clunky shifting.The truck now has 12000 miles on it.It does not happen every time i drive it.Looking for some answers.
 
I have an '03 Z66 with only 1850 miles, and I have the same problems. Most of the time I am the only one in the beast with no cargo so the load isn't an issue. There were a few times at a stoplight when the light turned green, I would push the gas pedal and the truck would drag for a second then a loud "clunk" and then I would lunge forward. I also encounter the shifting issues you two have. I wonder if these could cause a big problem in the future?? :cautious: Well, if it does I hope it happens before 36,000 miles :rolleyes:
 
I have been reading about this with '03's and '02's here for quite some time now. I just got my '03 and low and behold it does the same thing. I was actually expecting it as I had heard so many reports of it. It is minor and seems to happen after coasting a bit and then accelerating...like the transmission is trying to "find the gear"...kinda hiccups for a second.

AFAIK, GM has said that this is normal for this tranny. Someone correct me if you know or heard otherwise.

Rich
 
Now I have a clunk, only sometimes, and then when I slow down it is making weird noise. It sounds like a whine in the tranny. The service department said it was normal. It seems kinda funny I didn'y have the noise for the first 2200 miles. I have a 4x4 1500. Is this normal?
 
And I have been only driving my AV in 2 wheel. I have never put it in 4 wheel yet.
 
I was told by my service manager that they get this complaint alot and he gave me this explanation in my lehmans terms.........the tranny was built to go from 1st to 2nd at a higher rpm, to be easier on the transmission, when it goes from 1st to 2nd it has a longer way to go (gave me a bunch of ratios) so when you are going slower it doesn't sit right in there right away. But going from 2-3, 3-4, etc. the gears do not have to go so far and you are at higher speeds so you do not feel the setting in of the gears??? Made sense to me and I do not ever notice it when accelerating through it and not babying it.
I do however notice, when downshifting I feel a clunk going from 3-2, or 2-1st. Might be the same thing but didn't ask him that one.

I apologize for not using the correct terms on this post, I am not a mechanic so if anyone wants to elaborate or tell me that my service manager is full of poop and I should check it out somemore, please feel free to post. I will not take offense.
But his explanation did make sense and he said he gets the question alot.
 
I have an '02 Z71 with about 10,000 miles on it. It was built at the end of January - 2002. I have only taken it in for service once for two issues:

First, was a complaint I had regarding "slow" shifting from 2-3 gear. I guess the official term for how long a shift takes is called overlap. There seemed to be some intermittent delay when upshifting from 2-3 especially under medium acceleration or when going up a hill. The dealer kept the truck for a couple of days and said they noticed the delay only a couple of times but since there were no bulletins out regarding the issue that there was no repair necessary or recommended.

Second, was a problem with the bow-tie on my front grill. One day when I was powerwashing the front to remove some bugs the water pressure actually flaked some paint off from the inside of the bow-tie. The dealer replaced that.

Other than those two issues I have been very happy with my truck.
 
sounds normal, especially the 3-2 downshift part. I've read about this enough and now experienced enough with my Av to just accept the fact that it is normal. Other than this "clunk", the transmission feels pretty normal.

I'm not saying don't have a service department check it just in case, I'm just saying be prepared for them to likely tell you that it is normal.
 
Just talked to my buddy who is asst service manager at local dealer. He says the 3-2 shift is a known problem and they do have an update in the form of a computer flash that is supposed to remedy the problem. Will find out next week. Damn, just had a custom tune made for the diablo, gonna have to get a new one with the new data.
 
Inherently, it is due to the design of the transmission....

The 700R4/4L60E transmission has a design flay that will rear it's ugly head if it is in a heavy vehicle with a long drive shaft. No matter what the calibration, etc, etc.... If something is changed and one tries hard enough, the noise can be found.

When the trans shifts from 2nd to 3rd, it's very busy. It first has to release the 2/4 band and then apply the third clutch. In an automatic transmission using planetary gears, one can never use three seperate holding devices.......unless you want a hydraulically controlled Park! To prevent the main shaft from locking to the case, there has to be a bit of time-delay built in.

Now look at the stackable tolerances from the crankshaft to the wheels......gears in the trans, u-joints (albeit very minimal), and finally in the ring/pinion. Under certain circumstances (namely a 2-3/3-2 shift) all of those tolerances are unloaded, then loaded with a lot of mass. This unloading/loading can be heard through what is inherently a very large speaker.......the big ole hollow driveshaft. Don't think for a minute that GM added the rubber floor mat for Avalanche owner convenience.......it's a huge sound absorber trying to minimize the noises heard through the prop shaft.

There are numerous TSB's and PI's in the GM system that addresses this. However, there are really no known cures for it. Some are worse than others due to differences in stackable tolerances, specifically what the backlash is set to in the rear diff. By no means try to have that tightened as it almost always turns into a rear axle whine around 30-60MPH that is REALLY annoying! If it REALLY REALLY bothers you, one can take the propshaft to a very good machine shop, have the end cut off and install a press-fit cardboard sleeve, put the end back on and hope for the best. Some folks will advise to foam the prop shaft, but usually ends up with a nasty vibration as nobody really gets it done right....

Bottom line, a change in calibration will only hide it, and it can eventually be found again if one is anal enough. Nothing is being hurt and actually tells you that the third clutch is not slipping a bit! (or the 2/4 band is holding great, depending on if up or down shift).

However, if anyone hears it in a 2500 Av......take it straight to the dealer and ask them to look at the sprag which is getting ready to puke.


Enough of my incessant ramblings.....lol.
 
Not sure if this helps, but my 1994 Camaro does the same loud *CLUNK*, and apparently this is normal.

Hasn't happened yet to my '03 Av, but will keep listening for it.
 
Back
Top