Sliding A TREMEC TKX Five-Speed Into A Vintage GM A-Body Without Major Surgery

After years of overdrive-transmission swaps, we don’t need to waste words on extolling their highway-cruising virtues, but when it comes to adapting the popular TREMEC five- and six-speed transmissions, there have been compromises. For five speeds, the TKO-500 and TKO-600 work well with old-school small-blocks, but aren’t well-suited for the higher-revving capabilities of LS and… The post Sliding A TREMEC TKX Five-Speed Into A Vintage GM A-Body Without Major Surgery appeared first on The Online Automotive Marketplace.

KhloeKardashian

Dec 25, 2024 - 11:27

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Sliding A TREMEC TKX Five-Speed Into A Vintage GM A-Body Without Major Surgery

After years of overdrive-transmission swaps, we don’t need to waste words on extolling their highway-cruising virtues, but when it comes to adapting the popular TREMEC five- and six-speed transmissions, there have been compromises.

For five speeds, the TKO-500 and TKO-600 work well with old-school small-blocks, but aren’t well-suited for the higher-revving capabilities of LS and LT engines. When it comes to six-speeds, there are basically two choices: The production-based T-56 and aftermarket-intended and T-56-based Magnum. Used T-56 units are getting scarce, and for most vintage Chevys, the shifter location typically requires modifying the transmission tunnel. The relatively bulky Magnum also requires alterations to the tunnel to create room for the Magnum’s wide case.

Honestly, it takes more than just a little trimming to fit a Magnum six-speed to most muscle-era cars. In an early F-body, the entire tunnel must be cut out. It’s pretty much the same for A-bodies, including the subject of the project in this story: a 1969 Chevelle.

The project car is a 1969 Chevelle undergoing a comprehensive restomod makeover, including an EFI system on its big-block engine, plus brake and suspension upgrades, and more. An overdrive transmission will help make it a more comfortable and fuel-efficient highway hauler by knocking down the top-gear cruising rpm.

To address those fitment challenges, TREMEC introduced the TKX gearbox a few years ago. It’s a five-speed specifically designed for retrofit applications. It has a slimmer profile that slides into the transmission tunnel of most vintage cars with little or no clearance issues. There are even specific versions for GM and Ford applications, with unique case patterns and inputs, along with integrated transmission mounts. Even better, it was also developed to complement the higher-rpm capability of modern LS and LT engines, handling rev ranges of up to 7,500 rpm and matching that with a 600 lb-ft torque capacity.

At the Detroit-area shop Stellar Rod and Custom, we recently followed the installation of a TKX in the Chevelle mentioned above, but rather than an LS or LT, the vintage A-body was powered by an EFI-fed big-block. The engine was also backed by an automatic transmission, which added another wrinkle to the project, as this project would also include the conversion to a manual transmission, which required swapping the flexplate for a flywheel and adding a new pedal assembly. Ironically, despite the TKX being designed to help avoid floorpan modifications, the shop still had to cut into the transmission tunnel, but only because there was no shifter hole.

Next, the aluminum bellhousing is slipped into place and bolted to the engine; after making sure no wires or hoses had drooped in the way.

“It was all pretty straightforward, because apart from the shifter hole there were no other tunnel modifications required with the TKX,” said Mike McKeehan, Stellar’s chief wrench-turner. “It slips into place very easily.”

An installation kit with the requisite bellhousing, pilot bearing, throw-out bearing, slave cylinder, and other associated hardware, is also required. The installation kit sourced for this project came from Silver Sport Transmission (SST), which included those swap parts in addition to the transmission and flywheel.

SST also supplied the pedal assembly, along with a reproduction transmission hump for the interior that matched what came on original manual-transmission models. And while a shifter was included with the transmission, the project car’s owner opted for a different aftermarket version.

“All the swap parts fit as intended,” said McKeehan. “Thankfully, there were no surprises or hang-ups with the installation.”

It’s not an exaggeration to say the slimmer profile of the TKX case makes installation easier, but the conversion from an automatic to a manual transmission required a bit of follow-up trimming after the initial measurements were made for the shifter hole. It was really nothing in the grand scheme of the entire swap. A lift made the project infinitely easier and while we know many a transmission has been swapped with just floor jacks and jackstands, the details involved in converting from an automatic to a manual make a lift all but a necessity.

We’ve outlined the basics of the project with this story, but it’s also worth noting the installation was performed on a car that was also undergoing additional significant upgrades, from the wiring system to the brakes and more. That meant a road test of the Chevelle with the TKX wasn’t immediately possible.

Nevertheless, the project was surprisingly straightforward and the new five-speed transmission slid into the A-body like an old shoe—and with inclusive swap kits going for typically less than $4,500, including the transmission itself, it’s a smart resto-mod upgrade to put a muscle car-era classic into overdrive.