Built to Hold

Build guides, transmission tech, and install notes from the Gearstar shop floor. Every unit we ship is assembled by one builder, matched to your combo, and dyno-tested before it goes out the door. This is where we show the work: what holds, what grenades, and how to spec it right the first time.

E40D Transmission Swap – Hot Rod Hauler

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Check out this E40D transmission swap on this 1973 Ford f350. Read more only at www.customclassictrucks.com, the official website for Custom Classic Trucks...

6L80 vs 6L90: Devil's in the Details

6L80 vs 6L90: Devil's in the Details

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The 6L80 and 6L90 are two of the most popular rear-wheel transmissions from General Motors. So many things have been discussed about these remarkable...

6L80E and 6L90E Transmission Specs and Identification

6L80E and 6L90E Transmission Specs and Identification

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The 6L80E and the 6L90E are close enough that people mix them up constantly, and different enough that putting the wrong one in a heavy truck is an...

Sports Cars That Are Faster with an Automatic Performance Transmission

Sports Cars That Are Faster with an Automatic Performance Transmission

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Some luxury cars with automatic transmission include the Lexus ISF, BMW M4/M5, Audi S6/S8, and Porsche Panamera, to mention a few. Since there are two...

Ford C4 and C6 Transmissions: What Are the Differences?

Ford C4 and C6 Transmissions: What Are the Differences?

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Ford's C4 and C6 3 speed automatic transmissions are similar in operational characteristics; however, there are still unique differences between the C4 and...

545RFE Transmission Specs and Schematic

545RFE Transmission Specs and Schematic

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The 545RFE transmission is an electronically controlled unit that was great for its time until it was replaced bu the 65RFE and 66RFE. Read below for...