brandon1282

I also have a Sierra. So far the TCM and torque converter replacement seems to have solved my issues. The deal just called today to ask how it was running (bout 3 weeks and 500 miles since replacemet). The also said that GM would l like them to flush out the tranny again and check to make sure everything still looks good. Dropping it off Friday.

Yes. When the cruise was set on a steady up hill climb the tachometer would float I.e. kind of fluctuate in a range of RPMs; not hold steady.

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.

Update: Just was informed that GM has advised the dealership to change out the Torque converter and the Transmission Control Module. My truck should be ready on Tuesday. In the mean time they have given me another 2014 sierra as a loaner....I am interested to see if in the time I have this truck if I notice the same vibration. As far as tires go, I think we may be talking about two different issues here. The problem I am experiencing (as well as some others on this thread) is intermittent at speed, not a continuous vibration that occurs above a certain speed. If the later is the case, then yes I agree, the first thing I would look at is a problem with tires (or possibly the drive shaft). The problem I am having does not occur every time I am at a certain speed or operating under the same conditions (i.e. it only seems to happen under moderate power between 50 and 65, but does not occur everytime I am under moderate power between 50 and 65). As always, I'll keep you posted of the findings/results.

Yes that's it!!!! Can't say that I really noticed the lurch while shifting though. The dealer originally thought I had a problem with the tires; either out of balance or a problem with "road force" - can't say I have very heard of that. Long story short they rebalanced everything and put a new tire on, took it for a test drive and they are still getting the same issue. They just called me and said they are going to keep the truck over night to do some checks on the torque converter as well as some more diagnostics. I will keep everyone posted on the results.

I am also having a vibration issue. When it first started I was convinced it was something in the road; feels exactly like driving on rumble strips. The vibration seems to happen under light to medium power on a slight grade at a steady speed (50 to 65 mph). Only lasts for a second or two but can happen 3 or 4 times in a row. Also seems to happen mostly when in a curve (but does happen on straightaways too). Once I realized it was the truck and not the road, I tried to de-activate the t/c to see if that might be doing something but no luck. Currently at the dealer and the are trying to reproduce the problem. One concern I has is the truck is leased; I don't want to be putting a ton of miles on it driving it around trying to deal with an issue that's certainly not any fault of mine. BTW Has anyone noticed their RPMs "floating" constantly while the cruise is set? I could see this happening on a road with a lot of ups and downs but it seems to do it on a steady pull up hill too. Dealer says this is normal and the truck is doing what it can to save MPGs bit it seems counter productive to me; uses more fuel if it's constantly trying to catch up.