A Guide to Replacing Rear Brake Drums on a 1986-1991 GMC Jimmy
Keep your classic S-15 Jimmy stopping safely by understanding when and how to replace your rear brake drums.
- No recalls or TSBs are active for the rear brake drums on this vehicle.
- Always replace brake drums, shoes, and hardware at the same time and in pairs for safety and performance.
- Premium aftermarket brands like Bendix or Dynamic Friction offer superior durability and corrosion resistance compared to economy options.
- Key symptoms of failure include grinding noises, pedal pulsation, and a weak parking brake.
Is It Time for New Brake Drums?
On a vehicle like the 1986-1991 GMC Jimmy, the rear brake drums do a lot of work. Over time, the inside surface wears down from the friction of the brake shoes. They can also become warped or out-of-round from heat and use. Knowing the signs of a worn brake drum is key to keeping your truck safe on the road.
Common Symptoms of Failure
If your brake drums are failing, you'll likely notice one or more of these signs:
- Scraping or Grinding Noises: A metal-on-metal grinding sound when you brake is a critical warning. It usually means the brake shoes are completely worn out and are now digging into the drum itself.
- Vibrations When Braking: If you feel a pulsing or vibration in the brake pedal or through the chassis when you apply the brakes, the drums may be "out-of-round" or warped. This uneven surface causes the brake shoes to make inconsistent contact.
- Weak Parking Brake: Does your Jimmy roll even when the parking brake is pulled tight? Worn-out drums can make it hard for the shoes to get a good grip, causing a loose or ineffective parking brake.
- Vehicle Pulls to One Side: If one brake drum is more worn than the other, it can cause your truck to pull to the left or right when you brake.
A Note on OEM vs. Aftermarket
For a vehicle over 30 years old, finding new original equipment manufacturer (OEM) brake drums from a GM dealer is highly unlikely. The good news is that today's aftermarket parts are often made to standards that meet or exceed the original 1980s specifications. Reputable aftermarket brands provide a reliable and cost-effective solution for keeping your classic Jimmy on the road.
Choosing the Right Aftermarket Brake Drum
Not all aftermarket brands are the same. They generally fall into different quality and price tiers. For your GMC Jimmy, here’s a breakdown of the available brands.
Brand Quality Tiers
- Premium (Bendix, Dynamic Friction): These brands are known for high-quality materials and manufacturing processes. Bendix is a long-respected name in brakes, often supplying parts to vehicle manufacturers. Dynamic Friction (DFC) focuses on meeting or exceeding OEM standards, often including features like balancing and corrosion-resistant coatings to prevent rust and vibrations. For owners who want the best durability and performance, these are excellent choices.
- Standard (Centric): Centric is one of the most popular aftermarket brands and offers a great balance of quality and affordability. They are a go-to choice for daily drivers and are known for providing good performance for the price. While most users have good experiences, it's always wise to inspect the part upon arrival to ensure quality.
- Economy (Pronto): Pronto is a budget-friendly option that provides a functional replacement for your original drums. These are a good choice if you need to get your truck back on the road and cost is the primary concern.
| Part Type | Estimated Cost (per pair) | Notes |
|---|---|---|
| New Aftermarket (Economy) | $103.14 - $120.00 | Brands like Pronto. Good for basic replacement. |
| New Aftermarket (Standard) | $120.00 - $140.00 | Brands like Centric. A good balance of price and quality. |
| New Aftermarket (Premium) | $140.00 - $159.66+ | Brands like Bendix and Dynamic Friction. Best quality and durability. |
Pro Tip: Replace in Pairs
Always replace brake drums in pairs (both rear wheels at the same time). This ensures even braking performance and prevents your truck from pulling to one side. It is also highly recommended to install new brake shoes and a new hardware kit when you replace the drums.
Frequently Asked Questions
Do I need to worry about any recalls for my Jimmy's brake drums?
No. Searches of the NHTSA database and other records show no specific recalls or technical service bulletins (TSBs) for the rear brake drums on the 1986-1991 GMC Jimmy.
Can I just replace the brake shoes and not the drums?
It's not recommended. Installing new shoes on a worn, grooved, or out-of-round drum will lead to poor braking, noise, and rapid wear of the new shoes. At a minimum, an old drum should be measured and resurfaced by a machine shop if it's within specification, but replacement is often easier and more reliable.
What is a self-adjuster and why is it important?
The self-adjusting mechanism is a set of levers and gears inside the drum brake assembly. As your brake shoes wear down, this system automatically adjusts them to stay close to the drum surface, ensuring a consistent pedal feel. When replacing your drums and shoes, it's critical to clean, lubricate, or replace the self-adjusting hardware.
What does "out-of-round" mean?
An out-of-round drum is no longer perfectly circular. This happens from thousands of heating and cooling cycles. When the brake shoes press against this uneven surface, it causes a pulsing or vibrating sensation that you can feel in the brake pedal.
Technical Specifications
Standard rear drum size is typically 9.5 inches. Always confirm fitment for your specific 2WD or 4WD model, as there can be minor differences.
We Have This Part in Stock
The information in this article is provided for general reference and educational purposes only. Vehicle specifications, procedures, and part compatibility can vary by production date, trim level, and region. Always consult your vehicle's factory service manual and verify part numbers before purchasing or performing repairs. Safety-critical components such as airbags, seat belts, and braking systems should be installed by a qualified professional.
- GMC Jimmy: