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Practicing What We Preach

By February 14, 2011Uncategorized

Our Crusher Camaro Heats Up With a Gearstar 4L85E, an Aeromotive Fuel System, and Other Tune-Ups in Preparation for Adventure.

When we last left the Crusher Camaro it ran and drove…but not well enough for a trip of a few hundred miles. We’re going to solve that.

At HOT ROD, we spend much of our lives ramrodding guys to get out there and really use their cars in glorious and punishing ways. We hock Power Tour®, Drag Week™, the Top Speed challenge. We needle in general. But we’re like monkeys throwing poop from a tree while never leaving our branch; we lead a corporate life of desk riding more than you’d think, and more than we like. While wearing those shackles we’ve formed a number of private and public excuses for not finishing our cars, many of which you’re tired of hearing. We’re sick of them, too.

Things are changing. The company has allowed us to hire extra hands, and if you saw the recent episode of Garage Mahal on the DIY Network, you know we’ve got a shop in the back of our office building that’s stocked with an obscene volume of Snap-On tools – and naturally, a bar. It’s not like working in a real car-guy garage anymore, but sometimes the salespeople leave it long enough for us to get something done, and that something has been a focus on making our project cars roadworthy. Hallelujah! We haven’t scored a 100 percent completion rate yet, but it’s a goal.

Those two paragraphs of self-challenging smack talk in front of nearly a million readers were designed to motive us, which brings us here: Our longtime Crusher Camaro project car is being revamped, and while wintertime means we won’t get to drag-test it right now, we are going to hit the road with it.

You’ve seen the Crusher on and off in HRM since 1994. It’s on the cover of the Mar. ’95, May ’03, and Dec. ’09 issues. In that most recent episode, we tore off the ’67s Pro Touring guise and reshaped it as a late-‘70s/early-‘80s street machine. Auto Drags, Sport Comp tach, 8-71, velocity stacks, the whole hee-haw. It looked perfect. The burnouts created legends.

Behind the scenes, the front fenderwells smacked the tires upon decal and locked ‘em up. Ouch. The old small-block’s torque converter in the TH400 stalled somewhere around Venus when hit with the grunt of the 650hp, 650 lb-ft, 489ci blown Rat. We never installed an exhaust system because the electric fuel pump was in the way – it was a hangover from a previous life – and the 4.57 gears had the crank humming at 3,500 rpm at just 60 mph. The gas tank leaked, and there were moments when we were ready to toss a match. Yup, the typical magazine project car.

Here’s the rescue: new CPP front springs, a whiz-bang fuel system with Aeromotive and Rock Valley parts, and a super trickadero Gearstar 4L85E auto-overdrive trans that promises the best-of-both-worlds street and strip performance while laughing off the power of this or any future engine the Crusher may swallow.

You can follow our project car tribs nearly daily at Facebook.com/HotRodMag, and /DavidFreiburger, and /MikeFinneganNews. If you’ve been doing that, then you already know of the scheduled debacle of an adventure we’ve planned as a Crusher road trip. As we write this, we really don’t know if we’ll survive. If we don’t make the national news, you’ll have to wait and find out next month. Meanwhile, here’s the tech dirt on how we made the car roadworthy.


The 4L85E transmission has ratios of 2.48, 1.48, 1.00, and 0.75:1. Compare that with the TH400 numbers: 2.52, 1.52, and 1.00:1. In addition to the extra gear, the modern trans also features a lockup torque converter, which means that on the highway, the input speed from the engine and the output to the driveshaft is 1:1. That’s unlike the TH400, which has inevitable slippage that gets worse the higher the stall rpm of the converter. With the lockup converter, the 0.74:1 overdrive, 3.50 rear gears, and 28-inch-tall tires, the Crusher’s Rat will spin 2,362 rpm at 75 mph. The same setup with the TH400 would net about 3,400 rpm.

Finally, the computerized Gearstar 4L85E brings new levels of turning, as you can adjust shift points (which can be different in every gear), shift firmness, and much more.

Making the switch from the three-speed TH400 to the four-speed 4L85E in a ’67 Camaro required modifying the passenger side of the trans tunnel right below the firewall (arrow) to accommodate the wider case of the new trans. The 4L85E is 2 3/8 inches wider at the bellhousing than the TH400, which required a few hits with a dead-blow hammer to give enough clearance for the tranny cooler line fittings to clear the sheetmetal. We were able to reuse our old flexplate.

A hammer wasn’t our only trick to make the trans fit. The factory GM ¼-inch NPT trans cooler fittings (at right) have a female outlet. Add a 90-degree male fitting to these and they flare out too far to clear the trans tunnel, even after we persuaded it with a deal-blow. Sweet Performance makes these cool 90-degree -6 AN adapter fittings (at left) that thread -6 female hose ends onto the trans and clear the tunnel with plenty of room to spare. The unique long-tube fitting goes into the rear of the trans, and the short one threads in up front, saving nearly an inch of space.

We added a Lokar dipstick to the Gearstar unit prior to stuffing the trans in place under the car. We also hooked up the tranny cooler lines at this time because it’s really tough to access them once the trans is in place.

A Hayden transmission cooler and fan assembly are mounted ahead of the core support and plumbed with stainless steel-braided line. Gearstar says a hard-core cooler with a fan is an absolute requirement to keep this transmission alive.

Aside from the mechanical differences between the TH400 (foreground) and 4L85E (background), there are other physical differences that must be considered when making this swap. The TH400 is 31/4 inches shorter than the 4L85E, so we had to shorten our existing driveline and build a new rear tranny mount.


The 4L85E OD transmission is a tough box, especially after a company like Gearstar builds it. Having another gear and a lockup torque converter will make highway cruises easier on your wallet and ears, but you still have to stuff this monster into your car. Here’s a breakdown of the critical dimensions of the GM 4L85E and a TH400. All measurements are listed in inches.


GM engineers transmission to last 100,000 miles under normal operating conditions. Normal isn’t in our genetic code, and the Crusher will brutalize whatever slush box is bolted behind the current powerplant or whatever we plan for the future. Gearstar has sold these transmissions to a group of supercharged racers and is confident that it will stand up to 1,000 hp and 1,000 lb-ft of torque. So what makes this $7,995.00 4L85E so special? Well, there are zero stock parts inside it, and it’s handbuilt by a single technician and then dyno-tested before it leaves the facility. The hard pars are burly, as well.

• The aftermarket input shaft (at right) is forged from 300M material, a low-alloy, vacuum-melted, very high strength steel. It’s the same stuff aircraft landing gears are made of. The intermediate shaft and forward hub are also 300M pieces.

Transferring power repeatedly and efficiently without fading isn’t easy with a blown big-block spinning the input shaft. Our trans was built to Level 4 specs, which include Raybestos Blue Plate Special Gen 2 clutch discs. These discs are designed to engage quickly and positively with low wear.

The development of this trans occurred over a several-year period with racers trying to break them. This billet forward drum is the result. Gearstar says it has customers putting 1,200 hp to this drum without fail. Someday we hope to find that out for ourselves.

The ProYank 10-inch race converter is planned to stall at 3,500 rpm with our 650-lb-ft big-block and lock up at a user-programmable speedo to drop our cruising rpm substantially. The lockup feature should reduce our cruising rpm approximately 300 rpm after Fourth gear kicks in.

A TPS is a must. It sends a 0-5-volt signal to the transmission controller, which alters the hydraulic line pressure inside the trans to prevent slippage of the clutch discs. If your engine has EFI, you can simply piggyback the wiring off the existing TPS. Carbureted engines will need a TPS connected to the throttle linkage that will accurately show idle to full-throttle movement. This trick TPS mount is from Compushift, and it’s designed to bolt on to a 4150-style carburetor mounting pad. The Acculink is fully adjustable, so getting the throw perfect is easy in single-carb applications. Holley also makes a kit for electric-choke models. Since we have a blower and two carbs, our linkage system prevents us from using the Acculink or the Holley setup. We’ll have to fab our own mount.

A FAST transmission controller will serve as a stand-alone module in our application and give us the ability to tailor nearly every function of the transmission to suit our needs on the street and at the strip. The wiring looks intimidating but it’s not; 90 percent of it plugs right into the transmission. The rest of the connections are for power and ground connections, a tach signal, the throttle positions sensor (TPS), and plug-in accessories.

The FAST T-Com software is Windows-based and straightforward. Screen prompts will walk the user through baseline setup, like inputting the tire diameter, rearend gearing, and so on. After that, it’s possible to tweak shift points, firmness, and almost every other transmission feature, all the while data-logging the performance of your hot rod. In the next issue of HRM, we’ll report back on the Gearstar’s performance and how it responded to our programming inputs.


Two iterations ago, the Crusher Camaro was stuffed with a mild, 632ci, all-aluminum big-block and huge, ground-mauling, dragster-style Borla collector mufflers on custom headers. That arrangement eliminated rear-mounted mufflers, so someone stuck an Aeromotive A1000 fuel pump where the righthand muff should hang. Obstacle one. Also fubar was leaky, modified OEM fuel tank without baffles to keep the gasoline pointed to the pickup.

Happy solution: a new, custom stainless steel fuel tank with an intricate baffle system from Rock Valley Antique Auto Parts, available via Detroit Speed & Engineering. The tank uses an Aeromotive Stealth setup that places the fuel pump inside the tank, making it run quieter and cooler (for longevity) and also solving mounting problems. The Stealth setup is available with the killer Eliminator pump (PM18669, good for 1,400 to 2,300 hp, depending on induction) or the one we’ve got, the A1000 (PM 18668, works up to 1,500 hp naturally aspirated, or 1,200 carbureted and blown).

Here’s the Aeromotive Stealth setup, and in-tank pump with an integral 100-micron pre-filter screen. It mounts in a thick billet ring that’s bolted to the inside lip of the tank, and it sips from a dedicated fuel well that ensures ample fuel supply for extended g-forces in any direction.

The Aeromotive pump uses an AN-10 requiring an O-ringed, cutoff-style fitting. It’s a tight fit to the truck floor, but it will clear if you use this kind of low-profile, drilled, 90-degree fitting.

The top of this custom tank has a dropped centersection that holds the pump (A), the return-line (B), and the fuel-level sending unit (C). Unfortunately, the height of the pump means that this is as deep as the dropped section can be without lowering the bottom of the tank.

For the Crusher’s anticipated many-horsepower ‘plants, we really wanted a tube-style hose end on the pump for superior fuel flow – same for the return line. As a result, we violated our virgin trunk floor and made this clearance box to accommodate the taller fitting for maximum fuel-system performance. After the hacking, we discovered that XRP makes a low-profile, full-flow, 90-degree fitting that would have prevented this. • The stainless tank is very well fabricated and semipolished. Stainless straps are also provided, and they worked in the stock mounts. This is more Pro Touring than throwback street machine, but we’re now prepped for any future powerplant. • We hit the modern Aeromotive PN 13204 fuel-pressure regulator and PN 1230110 10-micron post filter on the frame behind the right front tire. It uses a -10 AN feed line, -8 return, and -6 outlets feeding Y-blocks on the engine, splitting fossil fuel delivery to the twin Holleys.

The stainless tank is very well fabricated and semipolished. Stainless straps are also provided, and they worked in the stock mounts. This is more Pro Touring than throwback street machines, but we’re now prepped for any future powerplant.

We hid the modern Aeromotive PN 13204 fuel-pressure regulator and PN 1230110 10-micron post filter on the frame behind the right front tire. It uses a -10 AN feed line, -8 return, and -6 outlets feeding Y-blocks on the engine, splitting fossil fuel delivery to the twin Holleys.