What I Learned Changing Brakes on a 2020 GMC Denali, and Where I Got Beat

This is a Field Notes post, not a service we offer. It is me working on my own truck, getting some of it wrong, and measuring it honestly. If you are weighing whether to do your own brakes or pay someone, the numbers below are the useful part.

The short version

I changed the brake rotors and pads on my 2020 GMC Denali. The front axle went perfectly. The rear has an electronic parking brake, and that is where I lost most of my time and money. We would have quoted this job at about 5 hours. It took me 20 to 30 hours, and roughly three quarters of that was not wrenching. It was figuring out the electronics and hunting for parts and instructions for my exact truck.

Status as of October 13, 2026: the front is done and the rear is not. Parts for the rear arrive today, and a mobile mechanic is coming to help me finish it. I will update this post when the truck is back on the road.

Where it went right: the front

Front brakes are the part of this job a patient person can do in a driveway. Pads, rotors, a clean hub, a little grease where it belongs, torque everything, and test grip before you trust it.

New drilled and slotted front brake rotor mounted on a truck hub, supported by a jack stand on cardboard — New front rotor on the hub, before the caliper went back on.

Front brake assembly with new silver rotor, caliper and hub, with the strut and spring visible above — The front assembly finished. The only mistake here was a little too much grease.

Where I got beat: the rear electronic parking brake

Newer trucks do not let you simply push the rear caliper piston back. The parking brake is run by a motor on the caliper, and the truck has to be told to put it into service mode before you touch anything. A basic code reader cannot do that. I needed a scan tool that speaks to the ABS and brake modules, and I did not have one until partway through the job.

Innova 5610 scan tool screen showing a GMC ABS fault code C116B-5A with a failed status — The ABS code that stopped me. A tool that could command service mode was the missing piece.

Handheld Innova 5610 scan tool held in a gloved hand, showing an ECU information screen — Talking to the truck's modules instead of guessing.

Close-up of a gloved hand holding a small black electrical connector from the truck's rear brake system — The small connector at the heart of it. Learning to release it without breaking it took real research. I bought two versions of the part to get the timing right, and I am returning the more expensive one.

The second time sink was search. Most guides, forums and AI answers hand you something close to your truck, not your exact make, model and year, so you chase the same question in circles. A part that is nearly right is a part you return.

Opened boxes on a garage floor showing a new brake rotor and pads above a used rotor and old pads — Old against new. Getting to the right box took longer than opening it.

Cleaned rear wheel hub and studs with the old rotor removed and the brake backing plate visible — A cleaned rear hub, ready for the new rotor.

Rear brake mid-job with old pads, hardware, spray cleaner and tools laid out beside the open caliper — Mid-job on the rear. Old pads, hardware and a lot of cleaner.

Matt kneeling beside the rear wheel well holding a new drilled rotor in his gloved hands — New rear rotor in hand. The rear is still not finished, and the calipers and pistons may need replacing too.

Estimate versus actual

We write estimates for customers, so I held myself to one. Our estimate for this job, both axles with rotors and pads and the electronic parking brake service step, is about 5 hours for someone who has done it before.

Our estimate: about 5 hours
My actual total so far: 20 to 30 hours, call it 25, with the rear still open
Hands-on wrench time: roughly 6 hours, close to the estimate
Research, diagnosis and parts hunting: roughly 19 hours
The first wheel alone took 8 to 10 hours

The estimate was not wrong about the work. It was wrong about the first time. A first-timer on this truck pays for the learning, and a customer should never pay for ours. That is the whole case for hiring someone who has already done it.

Buy or build: what it really cost

Cash I spent so far, not counting tools I already owned or ones that will be reused on other jobs:

Rotors, pads, connector and other parts: $751.93
Scan tool that can command service mode: $377.69
A separate mobile inspection and brake bleed: $393.19
Total cash: about $1,523, before a return on a duplicate connector

Then the part most DIY math skips: time. I value mine at $125 an hour, our standard rate, which sits just above the low end of the $120 to $159 band where almost half of shops price labor according to AAA. Twenty five hours is about $3,125. All in, building it myself has cost roughly $4,650 so far, against a job we would price in hours, not weeks. Time is money, and opportunity cost is a real line item. Hiring help to finish the rear will add to that total, and I will include it in the update.

Floor jack lifting the underside of a truck in a garage, with the rear axle and suspension above — Lifted, supported, and about to learn something.

If you want to do your own

Assume something will break, and add time for it.
Do everything in pairs: both rotors, both pads, both sides of an axle.
If your truck has electronic rear brakes, buy or borrow a good scan tool that can put them in service mode before you start.
Confirm the exact make, model, year and trim before you order a part.
Test your grip at low speed before you trust the truck on the road.

Our take

I enjoy this work and I would do it again, with the right tool on day one. But if your truck has electronic brakes and you do not have the tools, pay a pro. Brakes are the last place to learn on the fly. We are not a brake shop. We tell you where our lane ends and who to call next.

This is a personal project and general information, not advice for your vehicle. Photos were checked for personal and location details before posting.