GMC G3500 Automatic Transmission Mount: A Complete Guide for 1985-1990 Models
Stop the clunking and shaking in your G3500 van by understanding and replacing its transmission mount.
- Listen for clunking when shifting and feel for new vibrations; these are the most common signs of a bad mount.
- For most owners, a standard aftermarket rubber mount from brands like Anchor or Westar provides a good balance of cost and performance.
- This is a DIY-friendly repair that can be done in about an hour or two with basic tools, a jack, and jack stands.
- While driving is possible with a bad mount, replace it soon to prevent damage to other driveline parts.
Is Your G3500's Transmission Mount Failing?
After decades of service, the original rubber transmission mount on your G3500 van has endured significant stress. These heavy-duty vans put a lot of strain on drivetrain components. Over time, the rubber can become brittle, crack from age, or get soft and weak from exposure to engine oil and transmission fluid. When the mount fails, it can no longer properly support the transmission, leading to a number of distinct problems.
Common Symptoms of a Bad Transmission Mount
If you notice any of the following signs, your transmission mount is the likely culprit. A visual inspection can often confirm the diagnosis; look for cracked, torn, or collapsed rubber in the mount.
- Clunking or Banging Noises: This is the most common symptom. You may hear a loud clunk or bang when you shift from Park into Drive or Reverse. The noise can also occur during hard acceleration or braking as the transmission shifts and hits the frame.
- Excessive Vibration: A worn-out mount loses its ability to absorb vibrations. You'll feel this as a new or increased shaking in the floor, seats, or steering wheel, especially when idling at a stoplight with the van in gear.
- Drivetrain Movement: In severe cases, you might see the engine and transmission visibly move or lurch when shifting gears or revving the engine. This excessive movement is a clear sign the mount has failed.
Choosing the Right Aftermarket Mount for Your G3500
For a vehicle from this era, finding original OEM parts can be difficult and expensive. The aftermarket offers several affordable and readily available options. These brands are generally grouped into standard replacement and performance categories.
| Brand Tier | Brands | Description |
|---|---|---|
| Economy / Standard | Anchor, DEA, Westar, Pioneer | These brands provide a cost-effective solution that restores original performance. They are designed to mimic the factory mount's feel and vibration absorption. While some professional mechanics and DIYers have noted inconsistent quality or shorter lifespans compared to original parts, they are a popular choice for budget-conscious repairs. |
| Performance / Heavy-Duty | Lakewood, Energy Suspension | These mounts often use polyurethane instead of rubber. Polyurethane is much more durable and resistant to fluids and degradation. The trade-off is a noticeable increase in vibration felt inside the cabin, as the stiffer material transmits more of the drivetrain's natural vibrations. These are best for heavy-duty use or performance applications where durability is more important than ride comfort. |
Pro Tip: While replacing the transmission mount, it's a good idea to inspect your engine mounts as well. They are made of similar materials and fail for the same reasons. Replacing them at the same time can save you from doing a similar job down the road.
Frequently Asked Questions
Can I still drive my G3500 with a bad transmission mount?
You can, but it is not recommended for an extended period. Continuing to drive with a failed mount puts extra stress on your engine mounts, driveshaft, U-joints, exhaust system, and even wiring or hoses. This can lead to more expensive repairs in the future.
Is an aftermarket mount as good as an OEM one?
For a 1985-1990 vehicle, a quality aftermarket mount is often the only practical choice. While some budget brands may not last as long as the original part did, they are significantly more affordable and will restore proper function. Given the age of the G3500, an aftermarket part offers the best balance of price and performance.
How do I know for sure the transmission mount is bad?
The easiest way is a visual inspection. Safely raise the vehicle and look at the mount, which is located on the transmission crossmember under the van. Look for obvious cracks, tears, or separation in the rubber. You can also have a helper shift the van from Drive to Reverse (with the brake pedal firmly pressed) while you watch the mount for excessive movement.
Are there any recalls on the G3500 transmission mount?
No, there are no specific recalls or Technical Service Bulletins (TSBs) from GMC for the transmission mount on the 1985-1990 G3500. Searches of the NHTSA database show recalls for other issues on these vans, but none related to the mount itself.
Technical Specifications
OEM Part Numbers: 22188145
The standard mount for the 1985-1990 GMC G3500 is a rear, two-wheel-drive style mount, typically consisting of a rubber block bonded to a steel base with a single mounting stud on the bottom and two bolt holes on top. Aftermarket part numbers include Anchor 2672, DEA A2508, and Westar EM-2515.
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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.
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