Floating tach needle

Gatorboy112 · May 28, 2014

I noticed on my way home from the dealer on the interstate that when in 6th gear the needle floats up and down down couple hundred rpms. Anyone else having this happen to them? It happens in other gears occasionally too.

Gatorboy112 · May 28, 2014

This truck had 490 miles on it when i bought and drove it home. I really hope that's not what it is.

TJay74 · May 28, 2014

The converter on the 6 speed transmission is constantly slipping and engaging/releasing depending on load and speed. I have seen this truck and my previous truck do this as well. Only way to fix it is via a tune and setup the TCC to lock/unlock quicker. The factory does it so you don't feel the TCC engaging/releasing like on the older 4 speed transmissions.

2strokesmoke · May 28, 2014

Here read this, this might be related to your issue.

brandon1282, on 14 Nov 2013 - 4:28 PM, said:

Just to update everyone on the rumble strip vibrations I was experiencing. I got the truck back 2 days ago and so far so good. Here is what the dealer reported:

Road tested vehicle and found possible tire/wheel vibration. Removed all four wheels and road force balanced to find one tire out of range. This tire was replaced and then vehicle was road tested again. The vibration improved but was not eliminated. Checked for TSB's and none were found that directly addressed this concern. Contacted TAC and TAC suggested to utilize TBS PIP5149B. I followed all instructions of this TSB, checking for excessive spark retardation and connecting rod oil squitter condition. There were no conditions observed. TAC then directed me to utilize DOC ID#2102430 where I checked the operation of the control solenoid within the transmission. When commended to the on position, It registered full pressure and when commanded off it registered 0 pressure. After completing all tests found that TCM could not be 'pulse-width' tested, only command on or off. With these measurements we determined that the TCM was sending an erratic signal causing the torque converter to be commanded erratically. This caused potential damage to torque converter. Therefore, I replaced the TCM (Signal) and torque converter (damaged internally). Road tested vehicle; now operating to GM specifications with no vibration when tested under the original conditions.

I have also noticed that the "floating Tac" condition I had earlier is no longer present.

fondupot · May 28, 2014

Don't listen to Won, he is the the biggest troll of this forum. He actively tries to induce panic in new forum users inquiring about an issue.

The converter on the 6 speed transmission is constantly slipping and engaging/releasing depending on load and speed. I have seen this truck and my previous truck do this as well. Only way to fix it is via a tune and setup the TCC to lock/unlock quicker. The factory does it so you don't feel the TCC engaging/releasing like on the older 4 speed transmissions.

This is the correct answer.