Common 2015 GMC Sierra Transmission Problems (Solved)

Dealing with a faulty transmission is a total misery for a busy driver. Most of the time, hearing noises when in neutral or a burning smell coming from the hood are some of the common symptoms of a faulty gearbox.

Its components continuously rub causing friction and heat. As an important part of the engine, the 2015 GMC Sierra transmission problems need to be solved in a proper way.

Don’t Worry! In this guide, you’ll discover some issues along with their fixing procedure.

2015 GMC Sierra Transmission Problems & Solutions.

GMC Sierra Transmission Problems & Solutions infographic

Due to bad sensors, air inlet grille panels, wire, and fluid leaks, the transmission temporarily gets sick. You may need to change the faulty parts and use a nice seal on the reverse servo cover. But, if the transmission is overheated, you need to replace it.

Some of the common issues which truck drivers can solve are by spending a little to treat the minor injured part. For major parts treatment, you have to pay a lot. Hope it helps!

Problem #1: Transmission Vibrates At 40-50 MPH.

Sometimes the transmission shakes or shudders when you drive at 40 MPH or more due to the torque converter clutch. This happens as the rainwater has entered the transmission part by sipping inside the dipstick.

Solution: To fix this, you need to change the air inlet grille panel to a good-quality one like the Genuine GM 25820730 as it’s reliable and fits well. Detach the old one and insert the filler aligning rightly. Then, put the exterior cover.

Problem #2: Harsh Shift When Driving.

One of the common 2015 GMC Sierra 1500 transmission problems is harsh shifting when changing gear. Not only that it shows a P0717 DTC code in the display but also shows an issue with ISS sensor wiring.

Solution: Change the white wire on the ISS sensor and the wiring. Notice if the pump cover is pointy or knife-like which sometimes causes damage to wiring. Use files to sand down the edges.

Problem #3: Transmission Fluid Leaking.

The transmission fluid can leak over time if the sealing of the reverse servo cover is out of date. This kind of thing happens due to the 20°F (6.7°C) or below temperature.

Solution: To fix the error, you need to use a better reverse servo cover seal. It will charge no more than $8 to $20. 

Problem #4: Overheating Problem.

Tire slipping during gear change is another sign of transmission issue. Sometimes it can get worse by not letting you shift at all. And, you’ll find DTC P0894 or P0218 error code on the screen. These kinds of issues arise if friction happens in the TCC (Torque Converter Clutch).

Solution: This can’t be fixed by just changing the faulty parts so you have to spend around $3,000 or more to replace the transmission itself.

Problem #5: Faulty Sensor.

The faulty sensor is one of the popular 2015 GMC Sierra 6 speed transmission problems that eventually affect transmission. During the shifting procedure, the truck integrated sensors can signal to the inner processors.

Solution: Use the OBD-II tool to fix the error code. Or, change the sensors that are affecting negatively to the transmission.


When the power system of the engine is sick, the car surely will act weak. The given solving techniques for most-occurred 2015 GMC Sierra transmission problems might cost a little but I believe it won’t be as expensive as repairing the transmission.

Hope the techniques are worth your attention and solve the troubles which you are facing in the transmission. Happy Driving!

Leave a Comment

Written By

Photo of author

William Baldwin

This Is William Baldwin, The Founder & Managing Editor of this website. Me and my team share automotive tips, tricks, and news

Fact Checked And Mechanically Reviewed By


Talha Atta

Talha Atta, a Mechanical Engineer and experienced technical content writer and editor at with a passion for the automotive industry.