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.

Will a 4L60E Torque Converter Fit a 4L65E or a 4L80E? GM Converter Compatibility, Straight

Will a 4L60E Torque Converter Fit a 4L65E or a 4L80E? GM Converter Compatibility, Straight

Gearstar Performance 6 minute read

Everything below is why, plus what to check before you buy a converter for either swap. A torque converter is a fluid coupling between the engine and an...

Why Proper Cooling is Critical for GM Transmissions: Prevent Overheating in Your 4L70E, 4L75E, or 4L65E

Why Proper Cooling is Critical for GM Transmissions: Prevent Overheating in Your 4L70E, 4L75E, or 4L65E

Gearstar Performance 6 minute read

Effective cooling is essential to maintaining the performance and lifespan of older GM transmissions like the 4L70E, 4L75E, and 4L65E. Low or contaminated...

Is a 4L65E Stronger Than a 4L60E?

Is a 4L65E Stronger Than a 4L60E?

Gearstar Performance 6 minute read

Wondering if the 4L65E transmission is stronger than the 4L60E? In short, yes. The 4L65E is an upgraded, heavy-duty 4L60E introduced initially for trucks, and...

How Much Horsepower Can a 700R4 Transmission Handle?

How Much Horsepower Can a 700R4 Transmission Handle?

Gearstar Performance 9 minute read

A stock 700R4 in good condition handles about 350 lb-ft of torque and roughly 300 to 350 horsepower. GM rated it to move a vehicle up to a 6,000 pound...

Why the GM 4L75E Transmission is a Top Choice for Performance Enthusiasts

Gearstar Performance 6 minute read

The GM 4L75E transmission is a high-performance automatic transmission ideal even today for car enthusiasts seeking durability and power. Enhanced to...

TH400 vs 4L80E vs 6L80E: Which GM Heavy Duty Automatic Belongs Behind Your Build?

TH400 vs 4L80E vs 6L80E: Which GM Heavy Duty Automatic Belongs Behind Your Build?

Gearstar Performance 8 minute read

All three of these will hold serious power. The question is not which one is strongest, it is which one matches the car you are actually building. If you...

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