How A Rare LS6 Chevelle Became A TREMEC Transmission Test Mule

This story begins in October of 1969 when young Denny Smith saved enough dough to buy one of the badest street machines coming out of Detroit a 1970 LS6-powered Chevelle. However, Smith was only 18-year-old and needed his mother to sign the paperwork so he could purchase the car.

At the time, GM was the biggest automaker and largest employer in the world. Things were looking good for the Bow Tie crew. More people were buying American cars and trucks and there was plenty of petroleum available on the market. Sporty passenger cars with more power were the dream of the car-buying public.

Here’s the full story of how Don Rogers’ 1970 LS6 Chevelle became a test mule for TREMEC transmissions’ latest new product design – the TKX five speed.

The Order Gets Delayed

Smith ordered his car from Berger Chevrolet — a process which would normally take about seven weeks from start to delivery — then he returned home to wait for his purchase. Berger Chevrolet was a nationally known outlet for all of Chevrolet’s high-performance cars and parts, having been featured in numerous muscle car and enthusiast magazines.

Unfortunately, UAW Local 598 was on strike. The workers at the Fisher Body plant had walked off the job at 4:45 p.m. on September 24, 1969 – roughly 15-minutes after the start of the second shift. This was a local strike, but the plant on strike built bodies for Chevelle and the new Monte Carlo passenger cars under the same roof where light trucks were built.

The strike caused a huge delay in production as the workers held out for 136 days. After all involved resolved their differences, cars were once again assembled at the plant beginning February 6, 1970. Smith finally got his LS6 Chevelle in April of 1970. Later, during the OPEC gas crisis, a more economical 350ci V8 was put into the car, and eventually, the car was reduced to sitting in the corner. However, he knew the value of the car and it was well maintained even as it was lightly used.

What Was Special About The LS6 Chevelle?

Chevrolet was caught off-guard when the muscle car market took off in the early ’60s, but it didn’t take long for them to catch up. The SS 396 Chevelle challenged the Pontiac GTO for a race to the top in an effort to catch up with Mopar’s Hemi.

By 1970, The Chevelle SS 396 actually carried 402 cubic inches, capable of 375 horsepower with the L78 engine package. If you checked the Z15 box on the order form, you got the big-block 454 that was rated at a conservative 360 horsepower with an option of a four-speed Muncie or three-speed automatic. Those in the know opted for another option, the LS6.

The LS6 was the 450 horsepower version of the 454 that packed 500 lb-ft of pavement crunching torque. The price tag for the additional LS6 was a whopping $750 more, a fairly large amount in those days. In terms of 2021 dollars, that is roughly valued today at $5,188 with inflation figured in. While most figures agree that Chevrolet produced 4,475 LS6 Chevelles, there is no breakdown in coupe, convertible, and El Caminos in that total number.

The LS6 engines came with an 800cfm Holley carb mounted on an aluminum intake manifold. The block supported four-bolt mains with a forged-steel crankshaft and connecting rods with forged aluminum pistons. The compression ratio was 11.25:1, and to turn over the high-compression engine, GM included a heavy-duty battery from the base LS5 package.

Rogers’ Chevelle currently has a modern Gen VI big-block engine giving motivation, but the original 454 is sitting on the shelf ready to install when needed.

RPO Z15 SS 454 Package

Deep groove front accessory drive pulleys were necessary due to the higher redline. The RPO Z15 SS 454 package also consisted of bright engine accents, dual exhaust with bright tips, a painted black grille that was split horizontally and had a large SS emblem in the center. The body featured sculpted lines above the wheel openings with moldings at the openings.

Early emission laws required an air pump (Air Injection Reactor) that injected air into the exhaust manifold to reduce the hydrocarbon and CO2 emissions. Almost every new owner pulled these items off as soon as the car was parked in the driveway. The M22 Muncie manual transmission was an additional $221.80, or the M40 Turbo Hydra-Matic automatic transmission was $290.40 for mandatory options. There was a special “tuned” rear suspension to complete the package.

The tell-tale cowl induction hood badge. Photo from www.ecklers.com.

For appearances, the rear bumper sported a black insert and a “power bulge” hood was added. The hood featured cowl induction that offered a vacuum-operated door at the rear of the hood. It was designed to feed air from the high-pressure area at the base of the windshield directly to the Holley carb. The hood and deck lid featured wide “rally stripes” that were becoming fashionable in high-performance cars.

The black insert in the rear bumper with SS badge and stereo rally stripes on the deck lid give away the performance identity under the hood.

Inside A Stock LS6 Chevelle

Nothing said sleeper like a front bench seat, and this beast came standard with a bench — no matter what transmission was installed. Bucket seats were an extra option, and you could add a center console too. Unlike the typical Chevelle model, the LS6 version received the newer Monte Carlo style larger instrument panel and gauge package. There were basically three circular gauges for the tachometer, speedo, and a clock with a few smaller gauges surrounding them.

Rogers has kept the interior pretty stock with the exception of an aftermarket Autometer RPM gauge mounted on the steering column and the TREMEC shifter.

Yes… a cigarette lighter was standard equipment, but you had to pay extra for the AM pushbutton radio. The LS6 package with options would hit the invoice somewhere between four to five grand – and it was worth every penny. Hindsight being 20/20, the LS6 Chevelle SS 454 is a prominent piece of automotive history. If the Chevelle was the bread and butter car for General Motors, the LS6 Chevelle was the jelly on top.

Back To Our Story

The story of this Chevelle picks back up in 2000, when Don Rogers got a lead on a one-owner, original LS6 car for sale. Tom Hilding of Tom’s Automotive in Oregon, Ohio, had been the car’s mechanic for its entire life. Hilding arranged a viewing for Rogers and a deal was made. Fortunately, Hilding was also able to help Rogers track down the original 454 big-block and restore it.

Don Rogers is the kind of guy that respects a numbers-matching LS6, but he also understands there is no replacement for displacement. So Rogers initially put a 502ci big-block crate engine in the car. Unsatisfied, he sought something a little bigger —572 inches of Brian Thomson (of Thomson Automotive in Wixom, Michigan) built asphalt buckler. Thompson’s 836 horsepower big-block engines are legendary for power and the ability to deliver decent street manners when needed.

A Brian Thompson prepared 572 cubic-inch monster currently resides in the engine bay.

All this time, Tom Hilding was still the car’s regular mechanic. Hilding is well known in Ohio and Michigan car circles, so he’s one of those guys that “knows a guy.” As it turns out, Hilding introduced Rogers to Mike Kidd at TREMEC Transmissions. Always looking for the next great idea, Kidd asks Rogers if he is interested in trying out a toploader transmission from the company. The caveat is the floorpan will have to be cut for the new trans to fit properly.

Unwilling to cut the original floorpan of the LS6 Chevelle, Rogers turned down the offer, which led Kidd into the next great product: A TREMEC five-speed that could be swapped into classic muscle cars without too much cutting, if any. The engineers at TREMEC went to work on a new slimmer case design. The test mule for the new design? Don Rogers’ 1970 LS6 Chevelle of course.

The new TKX five-speed manual gearbox gets installed in the Chevelle at the TREMEC shop.

TREMEC’s TKX Five-Speed Transmission

At this point, we’d be negligent if we didn’t discuss the new transmission that is the heart of this story. In fact, you can read all about the new TKX by clicking here. After TREMEC developed the TKX five-speed and Rogers had successfully tested it out fully, Mike Kidd gave us a “heads up” on this great car they had used to design and refine its latest product.

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According to Kidd, in addition to making a transmission that was easier to swap into classic muscle, there were a few criteria the new package had to meet. One: It must have excellent shifting performance. Two: It had to be universal to many different classic muscle car models. Three: It had to exhibit extreme durability.

“The end result is superior shift-ability with smooth shifts at high RPM through the use of multi-cone synchronizers and hybrid synchronizer rings,” said Kidd. “At the same time, noise, vibration, and harshness performance are optimized with a gear layout to best control stress levels, while providing structural stiffness with a ribbed, three-piece aluminum housing. Durability is further optimized with oversized gear widths, gaskets at all flanges, and caged needle bearings in all gear positions.”

Without further ado, here are the features of the TKX five-speed gearbox:

  • 600 lb.-ft. of torque capacity; capable of engine speeds of 8,000 rpm with shifts at 7,500 rpm.
  • Available in multiple gear ratio configurations.
  • Designed for multiple applications with three possible shifter locations.
  • Compact, end-loaded design provides clearance in most transmission tunnels without floor modifications.
  • Increased case strength with three-piece aluminum housing provides outstanding structural stiffness.
  • Gaskets at all flanges simplify installation and eliminate fluid leaks.
  • Superior shift-ability through the use of multi-cone synchronizers and hybrid synchronizer rings made of sintered bronze and carbon.
  • All gears and shafts made from special grade steel (ASTM 4615), providing increased torque carrying capacity.
  • Equipped with a high-performance short-throw billet aluminum shifter that isolates road noise, while providing clean, crisp shifts.
  • Robust design with internal three-rail shift system and a combination of aluminum and steel shift forks.
  • Wide gear width increases gear life and torque capacity.
  • Separate GM and Ford case patterns and input configurations. Integrated GM and Ford transmission mount patterns

No modification needed to fit the TKX five-speed in most classic muscle cars.

To find out more about TREMEC’s TKX five-speed transmission, visit them online at TREMEC.com.

About the author

Bobby Kimbrough

Bobby grew up in the heart of Illinois, becoming an avid dirt track race fan which has developed into a life long passion. Taking a break from the Midwest dirt tracks to fight evil doers in the world, he completed a full 21 year career in the Marine Corps.
Read My Articles

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