2002 4x4 1500, rattles at 40 - 45 mph?

[jalex11]

I have a 2002 4x4 1500 that has a rattle everytime I hit about 40-42 mph.  It occurs when the overdrive kicks in and the rpms go to about 1200.  Usually on an easy accel.  Sounds like an exhaust or transmission problem right under the cab.  Its been back to the dealer twice (only 1200 miles) and they replaced the muffler and tailpipe assembly, but the probelm persists.  I tightened the heat shields, but the problem persists.  Does anybody have any other ideas?  Thanks.

[RyanbabZ71]

Sounds like a driveline vibration (growl as gm calls it).  I had that and there was a programming fix however about a yr ago they stopped this cause of decreased MPG.  My suggestion if you are driving around town drive in 3rd and not Drive.  OD wont kick in and you wont feel the vib

[jalex11]

Though I think that you're right, the higher RPM's would eliminate the vibe, I can't help but want it fixed.  It seems as though a brand new truck should be able to drive in "drive".  Thanks though for your thoughts.

[RyanbabZ71]

I had the reprogram done which fixed the problem.  However this was back in 2000.  They stopped the program because people reported their mpg dropped off.  GM didnt want this i guess so they pulled it

[Shaners]

I had my '00 Silverado reprogrammed for the same thing... it raised the shiftpoints and delayed the "lock-up" of the torque converter.

 

I wasn't aware that the reprogram was no longer available...

 

What I heard was more of a harmonic vibration as the engine/drivetrain lugged around 40 mph.  The reprogramming wouldn't allow the torque converter to lock untill about 45 mph.

 

Your only other option is to by a "hypertech" or something similar and then reprogram your shift points yourself.

[RyanbabZ71]

I wasn't aware that the reprogram was no longer available...

 

Shaners back last yr around this time i had a lengthy discussion with the shop foreman.  I was having a problem with the torque converter locking up way to early (it was like a lugging at 35mph).  Told me he would look for a program.  He said i had the latest update which i did.  He then told me that program is no longer offered in their system.  Reason being was decreased fuel economy.  

 

After about a month the lugging stopped and hasnt returned.  It was wierd.  Kinda like a bug and it worked itself out

[Stepside Z]

Mine same the same thing. I took it in to the dealer and got nothing resolved. I think it is drivetrain vibration from the engine lugging. Now I just give it more gas so the tranny downshifts. It is better to rev the engine then to lug it down.

[jalex11]

Well, the dealer had it again today.  I discussed the idea that the shift point needed to be increased by about 5 mph, but the dealer insists that the vibe isin the muffler.  They're going toorder muffler weights and install them tomorrow.  We'll see if it has any success.  Thanks for your input.

[RyanbabZ71]

muffler weights?  Better have him check the muffler bearings also (joke)

[jaslo]

I have the same rattle. The service guy told me it was something in the muffler too and that was about 13,000 miles ago, So i left it alone and I still have the rattle, oh well, I thought better not worry about it and just enjoy my truck.

[y2kz71]

Could be the heatshield that is above the muffler, that is a common problem. Check to see if the bolts are tight or if it could be the problem.

[jalex11]

Heatshield was tightened on the first trip to the dealer with no positive results.  The "muffler weights" didn't arrive today, so its back to the dealer tomorrow (even though they had my truck all day today).  I asked the "service consultant" what did the muffler weights actually do and where are they installed.  He said that he had never heard of them, but he would check with one of the techs.  He also told me that he had heard of this problem, and that one of the techs told him mine was the worst he had heard.  Oh well, I'm hoping for positive results.

[jalex11]

Tightening the heat shield didn't work, replacing the muffler and tailpipie didn't work, all of the technitions took it for a drive, several phone calls to GM, all to tell me what you guys already have, it needs a programming update to change the shift point where the torque-convertrr locks.  The fix is still available, however they stated that I would lose about 4 MPG.  Is this right?  That seems like a steep drop.  Thanks for your help.

[Shaners]

You won't lose 4MPG!!!  You might lose 1/2 mpg but that would be about it.  The nice thing is, if you don't like the new programming, they can always put it back to stock...

[jalex11]

Programming change was made and [/b]no more vibration! thanks to everyone for their help.