GMC Jimmy Transmission Filter Kit Guide for 1970-1981 Models
Keep your classic Jimmy's automatic transmission shifting smoothly with the right filter kit.
- You must identify your transmission (TH350 or TH400) by its pan shape before buying a kit, as they are not interchangeable.
- Symptoms like delayed shifting, whining, and fluid leaks are serious warnings that your filter may be clogged and needs immediate service.
- For this vehicle, quality aftermarket brands like Wix or ATP provide a reliable and cost-effective alternative to unavailable OEM parts.
- Always replace the transmission filter when you perform a fluid change, typically every 30,000 miles.
Why Your Transmission Filter is Critical
For a classic truck like the 1970-1981 GMC Jimmy, the automatic transmission relies on clean fluid to operate. The filter is the only line of defense against contaminants that can clog narrow passages and damage sensitive shift control valves. A clogged filter can starve the transmission of fluid, causing it to overheat and wear out prematurely. Regularly changing your transmission fluid and filter is one of the most important things you can do to ensure a long life for your transmission.
First, Identify Your Transmission!
Before ordering a transmission filter kit, you MUST identify which automatic transmission your Jimmy has. During this period, GMC used two common transmissions, and they require different filter kits. The shape of the transmission pan is the easiest way to tell them apart:
- Turbo-Hydramatic 350 (TH350): The pan is almost a perfect square, but one of the corners is cut off at an angle.
- Turbo-Hydramatic 400 (TH400): The pan has a more irregular, complex shape, sometimes described as looking like the state of Texas.
Visually inspect the pan on the underside of your truck. Ordering the wrong kit will mean the filter and gasket will not fit.
Choosing the Right Aftermarket Filter Kit
Original OEM parts for these trucks are no longer available from dealers, so the aftermarket is the primary source for these kits. Quality varies between brands, but all provide the necessary components: a filter and a pan gasket. Here’s a breakdown of common brand tiers:
- Top-Tier (Wix): Wix is widely regarded as a high-quality aftermarket brand that often meets or exceeds OEM specifications. They are known for good fitment and reliable performance, making them a trusted choice for many mechanics and DIYers.
- Mid-Tier (ATP, Premium Guard): ATP has a long history and is a popular choice, with some users in fleet maintenance using them for decades. They are sometimes noted for innovative gasket designs that can help with installation. Premium Guard positions itself as a high-quality alternative, engineering its parts to meet OEM fit and function.
- Economy (Pioneer Cable): Pioneer is often seen as a budget-friendly option. While generally functional, they are a standard replacement part without the premium features or reputation of the higher-tier brands.
Pro Tip: Gasket Installation
The biggest cause of leaks after a filter change is an improperly installed gasket. Make sure both the transmission housing and the pan's mating surfaces are perfectly clean and dry before installing the new gasket. Some kits from brands like ATP come with gaskets that have smaller bolt holes to hold the bolts in place, making it easier to align the pan. Regardless of the brand, do not overtighten the pan bolts, as this can warp the pan and cause leaks.
Cost of New Aftermarket Transmission Filter Kits
| Brand Tier | Estimated Price Range |
|---|---|
| Economy (Pioneer) | $11.74 - $25.00 |
| Mid-Tier (ATP, Premium Guard) | $20.00 - $40.00 |
| Top-Tier (Wix) | $30.00 - $56.59 |
Frequently Asked Questions
How often should I change my transmission filter?
For a classic vehicle like the 1970-1981 Jimmy, it's best to replace the filter every time you change the transmission fluid. A general guideline is every 30,000 miles or every 2-4 years, depending on how you use the truck. If you do a lot of towing or heavy hauling, consider changing it more frequently.
Does the kit come with everything I need?
Yes, a transmission filter kit will include the filter and a new pan gasket. You will need to purchase transmission fluid separately. The TH350 and TH400 transmissions typically use a DEXRON-III/Mercon compatible fluid.
Can I reuse my old gasket?
No. You should never reuse the old transmission pan gasket. The heat and pressure cycles cause the old gasket to become hard and brittle, and it will not seal properly a second time. Always use the new gasket that comes in the kit.
Are there any recalls for the transmission filter on my Jimmy?
No, there have been no specific recalls from GMC or the NHTSA for the transmission filter on the 1970-1981 GMC Jimmy. This is considered a standard maintenance and wear item.
Technical Specifications
Kit must match transmission type: GM Turbo-Hydramatic 350 (TH350) or GM Turbo-Hydramatic 400 (TH400).
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.