There are a lot of options when it comes to transmissions for your LS swap. That’s one of the benefits of GM using the same bell housing bolt pattern for the majority of their V8s over the years. Choosing the wrong one can end in a lot of headaches, a project car that has to go back on the jack stands, and a drained bank account. That’s why, for our 1996 Caprice sleeper — Project ODB (Old Dirty B-body) — we decided to go with TCI’s 4L80 to get our LS-swapped Caprice shifting right.

A quick recap: Project ODB is a 1996 Caprice that we’re building into an LS-swapped street sleeper. With its mundane silver paint and about 100,000 miles of daily duty on the body and chassis, it’s perfect for the unassuming Mustang or Corvette at the stoplight. We started with a major suspension upgrade utilizing a QA1 Stage 2 Drag suspension kit, featuring adjustable coilovers front and rear. Once ride height and shock firmness were dialed in, it was then dressed in a set of new 20-inch REV wheels and Mickey Thompson rubber. Last time you saw this Caprice, we used a kit from BRP Hot Rods to swap a junkyard 5.3 into the engine bay, filled with goodies like Edelbrock’s Pro-Flo EFI, a Howards cam, some nitrous, and more. Now it’s time to transfer the Caprice’s upgraded power to the rear axle with a full manual 4L80 from TCI.

4 Speeds Of Brute Force

The Caprice came with a 4L60 from the factory behind the original Gen-II small-block. For simplicity’s sake, we could’ve easily adapted our LS to fit it, which would have saved us time and money, since we wouldn’t need a new drive shaft, shifter, transmission cross member, etc. But, we decided to upgrade to a 4L80. Why? For starters, strength.

To break down the naming of GM transmissions, the “4” stands for four forward speeds and the “L” stands for a longitudinal engine configuration, as you would find in a Corvette, F-Body, or pickup. The last two digits stand for the factory gross vehicle weight rating; 80 means it was built to support an 8,000-pound gross vehicle weight rating, while 60 means it is only rated to support 6,000 pounds. That extra capacity should be your first hint at its strength and durability. The 4L80 is filled with more robust components, like larger-diameter input and output shafts that better resist breaking under severe-duty usage, larger clutches and steels that have more surface area to hold torque, and more. TCI built our 4L80 with Alto Red Eagle clutches and Kolene steels, Kevlar bands, and their 34-element sprag assembly. This 4L80 can handle more than GM designed it to hold in our sleeper Caprice project.

Improved Gear Ratios

Another benefit of converting to a 4L80 transmission is the gear ratios. For a high horsepower drivetrain to perform, you need more than just the power; you need to have a properly geared transmission to put that power to the pavement. Compared to the smaller 4L60, the 4L80 has a closer-ratio gear set, which benefits a performance application.

The 4L80 shares its roots with its muscle car-era grandad, the TH400, and it shares the first three gear ratios with it as well, at 2.48:1, 1.48:1, 1.00:1, and 0.75:1 for the 4L80’s overdrive gear. The 4L60’s gear ratios are 3.06:1, 1.63:1, 1.00:1, and 0.70:1. The 3.06:1 first gear helped lower horsepower and mild-performance cars achieve respectable acceleration figures. Still, it can also make hooking at the local dragstrip a little more difficult once you start making real horsepower.

Also, compared to the second gear ratio of the 4L80, the 1.63:1 second gear ratio in the 4L60 is farther from first gear, which drops the RPMs lower than desired during the 1-2 shift, which can make you run slower if your torque and horsepower figures peak higher in the rev range.

Why The 4L80, But With No “E”?

Unlike the 4L60, which came in electronic and non-electronically controlled versions over the years, the 4L80 only came as an electronically controlled version from the factory. This means there are shift solenoids in the valve body controlled by the PCM that use various inputs to shift gears when needed, whether you’re cruising around town, making a wide-open throttle pass, or anywhere in between. The LS in our big B-body Caprice is still fueled with EFI, so we could have run an electronically controlled transmission if we wanted, but we opted against it. Instead, we decided to go with a full-manual valve body with a transbrake in our TCI-built 4L80.

Dallas Moss with the Edelbrock Group explained the pros and cons of a full-manual valve body setup on the street: “You will have a constant line pressure, which allows for a consistent and firm shift at all times, so the only real downside is you lose the ability to set it in drive and forget it. You do have to remember to shift it.” Driving a street car that requires constant shifting and always has a very firm shift isn’t for everyone, but this isn’t our first high-horsepower rodeo, so we decided to go this route.

You will have a constant line pressure, which allows for a consistent and firm shift at all times, so the only real downside is you lose the ability to set it in drive and forget it. You do have to remember to shift it. — Dallas Moss, Edelbrock Group

Along with the ability to manually shift our 4L80, the transbrake will give us consistent neck-breaking launches at the drag strip. A transbrake is an electronically controlled solenoid valve installed in a specially designed valve body that controls the reverse fluid circuit. When a racer places the transmission in first gear and activates the solenoid, the transmission becomes locked in first gear and reverse gear, acting as a brake for the car. Now the racer can bury the gas pedal to the floor without having to hold the brakes for the launch. The result is hard and consistent launches and improved 60-foot times.

Why a 4L80 Over a 4L60?

If the 4L80 seems to be better built as a heavy-duty performance transmission, why did GM only put it in heavy-duty trucks? The answer is size and weight. The bigger and badder 4L80 is physically larger and weighs a lot more than its 4L60 brother. The 4L80 case has more girth, making it difficult to fit in the transmission tunnel of a car. It’s also a little longer at 32.7 inches in overall length compared to the 4L60’s 30.7-inch length. As if packaging a larger transmission isn’t difficult enough for an OEM engineer, weight plays a big role too. The 4L80 transmission with converter weighs 236 pounds — that’s a whopping 80 pounds more than its little brother! Just imagine how much that would affect performance and handling in a Camaro or Corvette.

But the benefits outweigh the pitfalls in higher horsepower applications, like we have planned for Project ODB here, so it was a no-brainer to step up to the 4L80. We need a transmission that can handle the power and weight of a four-door full-size hot rod without breaking a sweat, so we’re willing to eat the price difference, physical size, and a weight penalty for our sleeper B-body to have a transmission that is capable of handling 750 horsepower with ease.

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Once the flexplate is bolted to the crank and torqued to spec, the converter hub adapter is pressed in place.

Mating The 4L80 To An LS

Due to the popularity of the 4L80 transmission and the fact that GM put them behind small-blocks, big-blocks, and LS-based engines over the years, mounting ours in the Caprice can be done with some off-the-shelf parts from TCI. The bellhousing bolt pattern bolts right up to our 5.3, but the torque converter bolt pattern to attach it to the flexplate is different from the 4L60, and the spacing is different too. TCI supplied us with their flexplate kit, which includes an SFI-approved flexplate, torque converter hub adapter, and hardware. This will get our TCI 4L80 and converter mounted up with the correct converter to flexplate spacing.

Converting All That Torque

The technical team at TCI also hooked us up with their Breakaway torque converter for the 4L80. This unit features a stall speed in the 3,500-rpm range, which is perfect for a heavyweight street car like ours, that will still see the dragstrip on the weekends. It features furnace-brazed fins, needle bearings, and a flame-hardened hub, along with a forged billet front cover. Daily-driver sleeper or street/strip weekend warrior, this torque converter can handle whatever we plan to throw at it.

Banging Gears

When converting from a 4L60 to a 4L80 transmission, you can adapt the stock shifter to work with a little effort and ingenuity, most of the time. However, due to the full-manual valve body with a transbrake, we needed something special and decided to splurge on TCI’s Outlaw-X shifter. This shifter is a cable-operated gated-style shifter that will work with our 4L80 swap and will work with forward or reverse-pattern valve bodies like ours. It also features two buttons to activate whatever you want, like a line-lock, transbrake, nitrous, or more. We will have ours working the transbrake and a little giggle-gas. It also adds a little cool factor to have a sleeper with a shifter that looks more at home in a Pro Mod instead of grandad’s land yacht.

A More Rugged Yoke

BRP supplied the transmission cross member in our swap kit, but the next step will be the output yoke and driveshaft. Not that we would want to use a stock driveshaft with our power goals, but we couldn’t even if we wanted to. As stated earlier, the 4L80 is a little longer than the old 4L60, and the output shafts are different too. The 4L60 uses the same slip yoke as a TH350: 1.500 inches in diameter and 27 splines, while the 4L80 uses the same robust slip yoke as a TH400, 1.886 inches in diameter, and 32 splines.

Keeping It Lubed And Cool

To finish out our 4L80 conversion, TCI also supplied us with a higher-capacity transmission cooler kit and a case of their Max Shift street performance ATF fluid. A transmission cooler is required in a street car to keep the tranny from overheating and to extend longevity and performance. While it is possible to use the cooler built into the radiator, TCI’s cooler will keep the temps low, even under the high loads the transmission will see behind the 5.3 LS. The Max Shift transmission fluid is specially formulated for high-performance applications like ours and exceeds the original Dexron specifications, keeping our 4L80 running cool and slip-free.

Picking the wrong transmission to mount behind the LS in your project car can make or break how it runs and drives. A transmission that isn’t strong enough will turn into a money pit that will never run right, and a transmission that isn’t built to match your project car’s performance goals can kill performance and leave you disappointed. The next time you see our Project ODB Caprice, we will show you how we installed our new TCI 4L80 and what it’s like to drive. With a little luck, we’ll soon see how well it runs at the local drag strip!