keepon truckin

Hi All--

My two-month old Silverado is making a clunk when I lift off the brake
to go--it sounds like the automatic transmission.

I bought a new 2005 Silverado 2wd Reg Cab shortbed with 5300 v8,
automatic transmission and locking differential. It also has the towing
package and ABS brakes.

I took the truck back to the dealership service dept, they kept it
overnight but said it was normal for these trucks to make that
noise. I thought 'WTF'? I've been around cars and trucks for a
long time and never had this experience.

I'm not 100% sure its the tranny-- it could be the locking differential
or the ABS brakes, but the only way I could tell for sure is if I could
plug in some kind of scan tool or laptop software to show what gear
I'm in (since the tranny is a 4-speed electronic, it should be possible)
then I could see if, when at a stop, my tranny was still in 2nd gear.

Anyway, I just wanted to post to see if any of you guys have heard
of this problem.

thanks!
chris

keepon truckin

Bump. I have read on another forum that a 'clunk' sound sometimes
is due to driveshaft slip yoke binding, and that the fix is to pull the driveshaft
and grease the spline. Has anybody done this? Thanks!

Trotorx2

Mine does the clunk when I'm in slow traffic and give it some gas from a coast. I've read here and other forums that it is a problem with these trucks. The slip yoke problem you are talking about I thought was fixed when GM changed the type of yoke a couple of years ago. I had my truck at the dealer to change the tailgate straps and mentioned the clunk to the trans tech and he said greasing the splines might help but also said GM leaves a lot of clearences in the drivetrain too. I'm going to pull the shafts on mine this week and re grease them to see if it helps. Also I didn't really notice it till after my tune which changed some of the shift points and line pressures and removed some torque management.

keepon truckin

Thanks -- mine is usually only from a dead stop, and I don't think it's the suspension
or slip yoke because it just has that sound and feel of a transmission dropping down
into 1st gear.
But I can't be positive its not the suspension or ABS because I had Chevy install two
coil spacers on the drivers side fron coil, and had a frame shop de-arch the pass. side rear leaf, due to my truck leaing left 1". That's why I think the possiblility exists that
the geomery somehow changed and affected the ABS brakes or ???. The frame shop
said they did an alignment after and I have no reason to doubt them-- they had the
truck for 4 days!

Also, i read this truck had an adaptive algorithm that adjusts the shift points in the tranny based on the drivers driving habits, and maybe that got screwed up. I wish
I had the time and energy to fight the dealership, but they are all in bad moods these days due to GM's recent financial troubles and seem not to care about the customer.

chris

Trotorx2

With the suspension work you've had done it could be that. Have a friend stand out side the truck and see if they can locate the sound. And yes the pcm controls the shifting of the trans and will learn your driving habits some.

Also this might have been better posted in truck drivetrain & suspension.

keepon truckin

Trotorx2-- thanks...not too many friends around as I'm stuck in San Jose for another month, but since the transmission is electronic, I thought for sure some company made a plug-in digital display tool to see what gear its in, so when I'm at a stop I could see its still in 2nd gear--nothing like that exists apparently according to the guy at Napa Auto parts.

Trotorx2

Your Welcome....keep lookin around here there is lots of good people with lots of info. Someone else may chime in here with more other ideas.

Gran Patron

The problem started in the 03's. I bought my truck brand new and it made that clunk over and over only from a complete stop. It was driving me nuts and ask a service coordinator at chevy WTF? He said the same thing "its normal" so I just ignored it. 2 yeas later with 28K It occasionally does it not as bad has it was tough. I still cant belive this is still happening. I tought they were suppouse to resolve that problem in 04 and the piston slap in 03 but same 'ol crap!!!

keepon truckin

runin9s-- sorry to hear you have it too- but its a relief to know someone else has this problem. The thing is, its made me modify the way I drive--now I have to take my foot off the brake and wait a second for the tranny to drop into 1st-- not exactly why I bought this loaded LS! But I still like this truck-- the way it looks and no rattles, and the 5.3L engine is more fun to drive than the '70 SS 396 Chevelle I had 20 yrs ago!
chris

Gran Patron

Oh yeah man I love my truck. They run great and I have no worries. I drive mine like I would all other vehicles. That clunk is no biggie and I stopped paying attention to it and now I cant remember the last time I heard it. You shouldn't worry drive it normal the truck will adjust with more miles on it.