Gearstar Performance

Custom Transmission Build Team

  • torque converter matching
  • dyno testing
  • transmission installs
  • GM performance automatics
  • Ford performance automatics
  • Mopar performance automatics




Gearstar Performance Transmissions has been hand-building high-performance automatics in Akron, Ohio since 1996. Every unit is assembled start to finish by one builder, matched to the customer's engine, gearing and intended use, then dyno-tested before it ships. The build team writes here about transmission specs, install procedures, torque converter matching and what actually holds up behind real power.

How Do I Know if My Transmission Solenoid is Bad?

How Do I Know if My Transmission Solenoid is Bad?

Gearstar Performance 10 minute read

A bad transmission solenoid causes delayed or erratic shifting, slipping, harsh shifts, or a flat refusal to shift at all. Other warning signs are...

Are 4L60E and 4L65E Interchangeable? Understanding the Differences and Compatibility

Are 4L60E and 4L65E Interchangeable? Understanding the Differences and Compatibility

Gearstar Performance 10 minute read

Physically, yes. The 4L60E and 4L65E share the same case, the same bellhousing bolt pattern, the same mount location, the same tailhousing, the same cooler line...

Can You Drive with a Bad Transmission Valve Body? What You Need to Know

Can You Drive with a Bad Transmission Valve Body? What You Need to Know

Gearstar Performance 7 minute read

Driving with a bad transmission valve body can cause serious damage to your vehicle’s transmission, harm your driving experience, or even result in avoidable...

TH350 vs. TH400 Performance: Which Transmission Offers Better Power and Reliability?

TH350 vs. TH400 Performance: Which Transmission Offers Better Power and Reliability?

Gearstar Performance 10 minute read

The TH400 holds more power. The TH350 is lighter and shorter. That is the whole comparison in two sentences, and everything else is about matching one of...

What is the Difference Between a 4L70-E and a 4L75E? Key Variations Explained

What is the Difference Between a 4L70-E and a 4L75E? Key Variations Explained

Gearstar Performance 7 minute read

The 4L70-E and 4L75-E transmissions are both upgrades of the 4L60 series, but they differ in strength and design features. The 4L70-E includes an added...

Prolonging the life of your automatic transmission

Gearstar Performance 7 minute read

Your car's transmission is one of its most vital parts. Without it, your vehicle wouldn't move. Keeping it in good shape can save you from costly repairs...

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