2014 5.3L 6 Speed RPM Fluctuations

morrislee · December 29, 2015

Recently, my truck has been doing something weird. I dont think it was doing this before but it is doing it lately.

During my normal commu on highway, I notices it hovers just above 1500RPM when traveling at 100km/h. Recently, it feels like slipping or misfiring as the needle jump about 1-3 millimeters up and down when I cruise normally at 100 and after a while, it ramps up to ~1800 to stay at that speed. It takes a few more minutes of driving for the RPM to drop back to 1500, have not figure out when or how it goes back to the 1500 range but this happens at least 2 to 3 times on my 1 hour drive in the morning and also coming home. When it is at 1800RPM, the fluctuation seems to be nonexistent at this range.

I have searched some of the key terms, I can only find relevance to Torque Converter failing, I am at 56000km on my truck now, is it normal that this is failing already?

It has been cold lately too, but didnt do it last winter from what I remembered, it is -13 to -24 Celsius where I have noticed this issue.

Almost out of base warranty, just added the GM PP to 100000km.

I would like some pointers on what I can do to fix this if it is not normal.

andyhaug · December 30, 2015

I have a 2015 with the same engine/transmission. I noticed the small fluctuations a while ago, at about 5000 miles. Asked the dealer about it and was told that they all do that. For the 1500 to 1800 change, is it changing from V8 to V4 mode or V4 to V8? I have noticed that the RPMs change quite a bit when it changes.

morrislee · December 30, 2015

I have a 2015 with the same engine/transmission. I noticed the small fluctuations a while ago, at about 5000 miles. Asked the dealer about it and was told that they all do that. For the 1500 to 1800 change, is it changing from V8 to V4 mode or V4 to V8? I have noticed that the RPMs change quite a bit when it changes.

Disabled V4 AFM using diablosport, so not AFM. Tuned it back to stock, same thing. Dropping it off on Saturday.

silveradosid · January 3, 2016

mine 2104 chev has been doing this for awhile , cant wait to hear what tthey do for you morrislee

pm26 · January 3, 2016

This could be the torque converter locking and unlocking, which results in some RPM fluctuation.

ic3man5 · January 4, 2016

from: http://www.silveradosierra.com/vortec-5-3l-v8/rpms-fluctuating-t9475-10.html

#PI0680: Random Tachometer Needle Movement or Engine RPM Increase while Driving at Steady Throttle on Level Road at Approximately 50-55 MPH - (Feb 23, 2012)

Subject: Random Tachometer Needle Movement or Engine RPM Increase while Driving at Steady Throttle on Level Road at Approximately 50-55 MPH

Models: 2010-2012 Cadillac Escalade Models

2010-2012 Chevrolet Avalanche, Silverado, Suburban, Tahoe

2010-2012 GMC Sierra, Yukon, Yukon XL

Equipped with 5.3L, 6.0L or 6.2L AFM Equipped Engines (RPOs LMG, LC9, L76, L94) and 6L80 or 6L90 Automatic Transmission (RPO MYC, MYD)

Condition/Concern

Some customers may comment on a random tachometer needle movement while driving at a speed of approximately 80-88 km/h (50-55 mph) with a steady throttle on a level road. They may also comment about hearing an engine tone change as engine RPM briefly increases and then decreases. Customers may occasionally describe this condition as a surge, flare or shudder.

Recommendation/Instructions

This condition may be caused by normal Active Fuel Management (AFM) transitions. When the engine cycles from V4 mode to V8 mode, the engine will produce increased torque and as a result the TCC slip speed may increase momentarily. This increased slip speed may be visible as movement of the tachometer needle or audible as an exhaust note change. This AFM transition from V4 to V8 mode and back to V4 mode is normal operation. The resulting small increase or decrease in engine RPM is also normal.

To diagnose if the random tachometer needle movement is caused by AFM transition, shift the transmission to manual mode (M), select 5th gear (M5) and drive the vehicle under the same conditions. Selecting M5 manual mode will make AFM inactive and the engine will stay in V8 mode. If the condition is eliminated when AFM is inactive, it is normal operation and cannot be eliminated. No repairs should be attempted.

morrislee · January 4, 2016

mine 2104 chev has been doing this for awhile , cant wait to hear what tthey do for you morrislee

Most likely going in on Tuesday morning for a drive with them if they are not sure of what I am referring to as they are unwilling to drive it around for 30 minutes to 1 hour to see the problem themselves

This could be the torque converter locking and unlocking, which results in some RPM fluctuation.

I am betting this too, hoping this would be the only issue.

from: http://www.silveradosierra.com/vortec-5-3l-v8/rpms-fluctuating-t9475-10.html

Definitely not this, if you see what I have done already in my original post, it does it when I have AFM disabled. When I am hovering at V4 as the indication in the instrument cluster, it does it too from time to time.

ic3man5 · January 4, 2016

Alright how about this one:

from: http://www.hptuners.com/forum/showthread.php?28770-6L80E-TCC-info

from the gm service manual:

A torque converter with an electronically controlled capacity clutch (ECCC). ECCC was developed to reduce the possibility of noise, vibration, or chuggle caused by TCC apply. In a torque converter with ECCC, the pressure plate does not always fully lock to the torque converter cover. Instead, the pressure plate maintains a small amount of slippage. In RWD 6-Speed transmissions, this slippage can range from 0-50 RPM. Full lockup (0 RPM slip) is still available on some applications. TCC may apply in 2nd, 3rd, 4th, 5th, or 6th gears. The specific TCC apply points and the amount of clutch slippage are determined by a number of operating conditions, including throttle position, vehicle speed, gear, as well as specific vehicle application. Transmission fluid temperature will also affect TCC apply points.

ic3man5 · January 4, 2016

Some more reading:

http://www.transtar1.com/TranstarIndustries/media/Transtar1/technical/bulletins/TLT-TC-035.pdf

This is normal behaviour of the transmission and nothing to worry about.

edit: Also the difference between 1500 and 1800RPMs is the difference of your transmission being in between 5th and 6th gear. When its in 5th gear its more than likely in V8 mode applying less PWMing to the lockup.

edit2: if you really want to reproduce this "issue", just make sure the transmission is up to temperature (180F+) and you should be able to reproduce it easily.

Edited January 4, 2016 by ic3man5

robvas · January 4, 2016

Sounds perfectly normal to me.

morrislee · January 5, 2016

Alright how about this one:

from: http://www.hptuners.com/forum/showthread.php?28770-6L80E-TCC-info

Doesnt sound like mine is doing what it is suppose to be doing then.

Some more reading:

http://www.transtar1.com/TranstarIndustries/media/Transtar1/technical/bulletins/TLT-TC-035.pdf

This is normal behaviour of the transmission and nothing to worry about.

edit: Also the difference between 1500 and 1800RPMs is the difference of your transmission being in between 5th and 6th gear. When its in 5th gear its more than likely in V8 mode applying less PWMing to the lockup.

edit2: if you really want to reproduce this "issue", just make sure the transmission is up to temperature (180F+) and you should be able to reproduce it easily.

and no, I have lowered the gear to 5th when this happens, RPM jumps even higher!

ic3man5 · January 5, 2016

Doesnt sound like mine is doing what it is suppose to be doing then.

and no, I have lowered the gear to 5th when this happens, RPM jumps even higher!

what diff ratio do you have in the back? 3.42 should be around 1900RPM.

Mine jumps about +-50RPM in both directions (or 100RPM total).

Edited January 5, 2016 by ic3man5

silveradosid · January 5, 2016

mine does it all the time when i am in 6th gear, just like ic3 , it will fluctuate up and down . i have 3.08 gears

morrislee · January 5, 2016

Didnt do this before, something is definitely wrong and ever since I start seeing this, the economy went down the drain

morrislee · January 7, 2016

Dealership had to test drive it twice (after they told me they could not reproduce the issue)

They detected the torque converter slipping allowing a spike of up to 150RPM which was outside of the factory tolerance. They have agreed to replacing the torque converter.

Wish me luck!