Subscribe to a magazine

Building The Bombproof Gearstar TH400 Transmission

Jerrod Jones | Writer
Posted July 1, 2011
Photographers: Courtesy of Gearstar

Immortal Transmissions

Iadmit it. I’m a little hard on transmissions, and if you read this magazine often enough, you might have already noticed. In fact, it’s so bad that I was dubbed “The Tranny Killer” long ago, and the name has stuck ever since. And before you start to think I have some sadistic hatred for cross-dressers, I’ll come clean and confess to at least 19 transmission murders…and I’m sure I’m forgetting a few.

Knowing about my luck with transmissions, an ex-editor of OFF-ROAD magazine turned me onto Gearstar Performance Transmissions out of Akron, Ohio. It seemed a little far to go for a transmission build, but I’m always eager to learn about shops with claims like “unbreakable” or “world’s finest.” Besides, at this point in my tranny-killing career, I’m game to try just about anything if someone thinks it might hold up.

Over the last couple years, I have been nursing a well-ridden TH400 transmission in a ’74 K5 that probably should have been rebuilt after ripping the torque converter in half. It’s been patched back together a few times and kept sort-of running until the back of the housing actually broke off this last time out. It was time to look up Gearstar.

I found Gearstar online ( and clicked on the “TH400” link. There were three levels of TH400 builds: Level 2 ($1,395) will hold up to 450 hp; Level 3 ($2,195) up to 550 hp; and the Level 4 ($4,395) package will handle up to 850 hp. They come with bottles of ATF, fluid coolers, heavy-duty aluminum pans, and new dipsticks. Did I mention that all of this comes in a crate shipped free of charge within the continental United States? Oh, and there is no core charge. Admittedly, I was a bit skeptical—the prices and the quality of the build specifications seemed too good to be true.

I got on the phone and called Mark, one of the technicians at Gearstar, and the answer to my transmission issues. Mark and I talked about the way the truck is built, what kind of powerplant is sitting in front, what I have behind the transmission, my driving style, and how I like to use the truck. Though I could have gotten away with a Level 2 build, he recommended the Level 4, since I’ll be adding some more power to the fuel-injected big-block in the future.

Of course, I had to ask Mark what the deal was. And he told me the tale: The company was started by Zack Farrah after he chose six top builders (many working with Zack since the ‘80s) to join him at what would make up Gearstar Performance Transmissions—an employee-owned company where each transmission is built by a single technician from start to finish. Each torque converter is built to match the specific transmission it’s going in and each transmission and torque converter is run on a dyno before being shipped out. All this makes for low overhead, excellent customer satisfaction, and no returns…and this is how I can buy a complete high-performance package shipped free of charge for a great price.

I bit. How could I say no?

A couple weeks later, a crate with “Gearstar” stamped on all four sides showed up at South Bay Truck in Hawthorne, California, where a K5 Blazer was waiting to accept the new TH400. After a fairly laborious install (dual transfer cases and three crossmembers will do that), South Bay Truck had the transmission back in the truck, and I was ready to start putting the Gearstar TH400 to the test.


View Photo Gallery


Gearstar Performance Transmissions
Akron, OH 44308
South Bay Truck and 4x4
Load More Read Full Article