Guide to the Automatic Transmission Mount for 1978-1984 GMC G1500 Vans
Stop the clunking and shaking by choosing the right new transmission mount for your classic G-series van.
- A clunking noise when shifting from park to drive is the most common sign of a bad mount.
- For a quiet, factory-like ride, choose a standard rubber mount from a brand like Anchor or Pioneer.
- For heavy-duty use or maximum durability, a polyurethane mount from Prothane is a good option, but expect more vibration.
- Replacing the mount is a simple DIY job for most owners and can prevent damage to other drivetrain parts.
Is Your GMC G1500 Transmission Mount Failing?
After more than 40 years, the original rubber on your transmission mount has likely seen better days. Age, heat, and fluid leaks cause the rubber to crack, collapse, or turn to mush. When this happens, the transmission can move excessively, leading to a number of noticeable problems. Ignoring these symptoms can lead to extra stress on other parts like your driveshaft U-joints, exhaust system, and even the transmission seals.
Key Symptoms of a Bad Transmission Mount
- Clunking or Banging Noises: The most common sign is a loud "clunk" or "bang" when you shift from Park into Drive or Reverse. You might also hear it during hard acceleration or sudden braking as the transmission shifts and hits other components.
- Excessive Vibrations: A worn mount can no longer absorb drivetrain vibrations. You may feel a new or worsening vibration through the floor, seat, or gear shifter, especially when accelerating.
- Visible Drivetrain Movement: With the van safely secured, you can often see the problem. Have a helper hold the brake, shift into gear, and lightly press the gas. If you see the engine and transmission assembly rock or lift excessively, the mount is likely bad. You can also check for excessive play using a pry bar when the vehicle is off and safely supported.
Known Issues, Recalls, and TSBs
As of this writing, there are no active recalls or widespread Technical Service Bulletins (TSBs) from the NHTSA specifically for the automatic transmission mount on the 1978-1984 GMC G1500. Given the age of the vehicle, any original defects would have been addressed decades ago. Most issues today are due to normal wear and tear.
Choosing the Right Aftermarket Mount
Since new OEM GM parts for this van are generally not available, you will be choosing from aftermarket brands. The choice comes down to your van's use and your preference for comfort versus durability.
Brand Tiers & Quality
Standard Replacement (Rubber):
- Brands: Anchor, DEA, Pioneer Cable
- Best For: Daily driving and maintaining a quiet, comfortable ride similar to the original factory feel.
- Honest Assessment: These brands provide an affordable, direct-fit replacement. Forum discussions show mixed reviews on the longevity of budget brands like Anchor and DEA, with some users reporting premature failure or poor out-of-the-box quality. However, others have used them for years without issue. They are a functional, budget-conscious choice for a standard van.
Heavy-Duty / Performance (Polyurethane):
- Brands: Prothane, Lakewood
- Best For: Work vans, camper conversions, or any G1500 that is heavily loaded or used for towing.
- Honest Assessment: Polyurethane is a much stiffer and more durable material than rubber. It will resist oil and chemicals better and last longer under stress. The main trade-off is a significant increase in noise, vibration, and harshness (NVH) felt inside the cabin, as the polyurethane transmits more drivetrain vibrations. Prothane is a well-known brand in polyurethane components. Lakewood is known for performance and racing parts. Choose this option only if you prioritize durability over a quiet ride.
Pro-Tip: Check the Crossmember
While you are replacing the transmission mount, take a moment to inspect the transmission crossmember it bolts to. These can develop cracks from stress over the decades, especially if the van was driven for a long time with a failed mount. A quick wire brushing and visual inspection can save you from future problems.
Cost of Replacing Your Transmission Mount
| Item | Estimated Cost |
|---|---|
| New Aftermarket Part | $7.93 - $34.29 |
| Shop Labor | $120 - $225 |
| Total Professional Replacement | $128 - $260 |
Frequently Asked Questions (FAQ)
Can I drive with a bad transmission mount?
You can drive for a short time, but it is not recommended. The excessive movement can cause damage to other components, including the driveshaft, U-joints, exhaust pipes, and even the transmission housing itself. It's best to get it replaced as soon as possible.
Is this a difficult job to do myself?
No, for a mechanically inclined person with the right tools, this is a relatively easy job. It typically involves supporting the transmission with a floor jack and a block of wood, unbolting the mount from the crossmember and the transmission, and swapping in the new part 🎬 Learn how to diagnose and fix a bad mount yourself.. It can usually be done in 1-2 hours.
Rubber or polyurethane: Which is truly better for my G1500?
For 90% of owners, a standard rubber mount is the better choice. It will provide a ride quality that is quiet and comfortable, as the van was originally designed. Only choose polyurethane if your van is a dedicated work vehicle that sees heavy loads, or if you are willing to accept a much louder and more vibration-prone ride in exchange for maximum durability.
Do I need to replace the engine mounts at the same time?
It's a good idea to inspect them. The engine and transmission mounts work together. If the transmission mount has failed, the engine mounts have likely been under extra stress. If they are cracked, soaked with oil, or collapsed, they should be replaced as well.
Helpful Videos
Technical Specifications
OEM Part Numbers: 22188145 17990778
The mount is typically a single-bolt design that attaches to the transmission's tail housing and bolts to the vehicle's crossmember. Construction is either a rubber block vulcanized to steel plates or a polyurethane block with a steel inner sleeve.
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.
- 🎬 Helpful Videos
- 🛍️ Shop This Part
- Is Your GMC G1500 Transmission Mount Failing?
- Key Symptoms of a Bad Transmission Mount
- Known Issues, Recalls, and TSBs
- Choosing the Right Aftermarket Mount
- Brand Tiers & Quality
- Pro-Tip: Check the Crossmember
- Cost of Replacing Your Transmission Mount
- Frequently Asked Questions (FAQ)
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