GMC G1500 Automatic Transmission Mount: A Complete Guide for 1973-1977
Stop the clunking and shaking in your classic GMC van by understanding and replacing your transmission mount.
- Symptoms of failure are hard-to-miss: loud clunks when shifting and heavy vibration.
- Replacement is a simple, DIY-friendly job that takes 1-2 hours with basic tools.
- Standard rubber mounts (Anchor, Westar) are very affordable; polyurethane mounts (Energy Suspension) offer more durability at the cost of increased vibration.
- Since OEM parts are unavailable, a quality aftermarket replacement is your only option.
Is Your G1500's Transmission Mount Failing?
A transmission mount is a simple part, usually a block of rubber bonded between two metal plates. Over 50 years, that rubber gets hard, cracks, and can even separate completely from the metal. Oil and transmission fluid leaks can speed up this process. When it fails, you'll know it.
Common Symptoms of a Bad 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 braking as the transmission shifts and hits the frame.
- Excessive Vibrations: If you feel new or heavy vibrations through the floor, steering wheel, or the seat, especially while accelerating, the mount's rubber is likely no longer absorbing the impact.
- Drivetrain Movement: In severe cases, you might feel the whole engine and transmission assembly lurch forward or backward. A helper can often see the transmission physically move or rock excessively when you briefly put the van in gear with the brakes held firmly.
A Warning on Severe Failure
If a transmission mount fails completely, the transmission can move enough to put stress on other parts. This can damage driveshaft U-joints, exhaust pipes, and even coolant hoses or wiring. It's a simple, cheap part to replace, so it's best to fix it before it causes more expensive problems.
Choosing the Right Aftermarket Mount
Finding a genuine GM "New Old Stock" (NOS) part for a vehicle this age is nearly impossible. The good news is that the aftermarket offers several options that fit your G1500, which likely has a TH350 or similar GM transmission.
Tier 1: Standard Rubber Mounts
These are direct, OE-style replacements made of rubber and steel. They are very affordable and will restore the original ride quality.
- Brands: Anchor, Westar, DEA, Pioneer.
- Quality: These brands are budget-friendly. Many owners use them without any problems for daily driving. However, some forum users have reported issues with fitment or a shorter lifespan compared to original parts. For a stock van that sees normal use, a standard rubber mount is usually sufficient.
Tier 2: Polyurethane Mounts
For heavy-duty use or just for a longer-lasting part, polyurethane is a great upgrade.
- Brands: Energy Suspension, Prothane.
- Quality: Polyurethane is much tougher than rubber and stands up better to oil, heat, and stress. Many performance-oriented mounts also have an interlocking metal design that prevents the transmission from separating from the frame even if the polyurethane fails. The trade-off is that you will feel more vibration in the cabin, as polyurethane is stiffer than rubber.
Pro Tip: Check Your Engine Mounts Too
The transmission mount works together with your two engine mounts to hold the entire drivetrain in place. If your transmission mount has failed, your engine mounts have likely been under extra stress and may also be worn out. It's a good idea to inspect them at the same time and replace them as a set if needed.
Estimated Replacement Costs
Replacing the transmission mount on a '73-'77 G1500 is a straightforward job. The part itself is not expensive.
| Item | Estimated Cost |
|---|---|
| Aftermarket Rubber Mount | $10 - $25 |
| Aftermarket Polyurethane Mount | $35 - $100 |
| Shop Labor | $100 - $225 (1-1.5 hours) |
| Total (Shop Installed) | $110 - $250 |
Frequently Asked Questions (FAQ)
Is this a difficult job to do myself?
No, this is a great DIY job for a beginner. It requires basic hand tools, a jack, and jack stands for safety. The process involves supporting the transmission with the jack, unbolting the old mount, and bolting the new one in. The job can typically be done in 1-2 hours.
Do I need a special type of mount for my van?
Most 1973-1977 G1500 vans use a standard GM-style rear-wheel-drive transmission mount that is very common. It fits transmissions like the Turbo 350 and Turbo 400. Always confirm the fitment for your specific vehicle before purchasing, but you should have no trouble finding the correct part.
Will a new mount make my van ride rougher?
If you choose a standard rubber mount, it will restore the original, smooth ride. If you upgrade to a polyurethane mount, you can expect a slight increase in vibration felt inside the van because the material is stiffer.
Were there any recalls for the transmission mount on my G1500?
No, searches of the NHTSA database show no specific recalls for the automatic transmission mount on the 1973-1977 GMC G1500.
Technical Specifications
The standard mount for this application is a rear-wheel-drive style, typically made of rubber vulcanized to steel plates. It attaches the tail housing of the transmission (e.g., TH350, TH400) to the frame's crossmember.
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.