There’s no doubt that the LS and LT engines are a vast improvement over the small-block Chevrolet. With more horsepower, reliability, and an aftermarket jam-packed with goodies for these engines, it’s easy to see why these swaps are so popular. However, when you hear about someone doing an LS swap, one key component usually gets left out of the conversation, and that’s the transmission.
One reason enthusiasts may not choose to upgrade the transmission is that there may not be a need with the LS. After all, companies offer flexplates that allow the use of non-electronic transmissions like the Powerglide, TH350, TH400, 200R4, and 700R4 transmissions. However, like the LS and LT engines, transmissions have gotten more efficient over the years and offer numerous advantages over the older versions.
First Things First
There have been some significant innovations since the release of the first four-speed electronic transmission when it comes to technology. The 4L80-E was the first to debut in 1991 and followed up by the 4l60-E in 1996. Since then, we’ve had a couple of variants like the 4L65-E and the 4L85, which are more robust versions of the originals. But GM didn’t stop there, as it also introduced more four-speed transmissions along with six-, eight-, and 10-speed units as well.
To get the scoop on Chevrolet Performance’s latest transmissions, we spoke with Blake Nye, Design Responsible Engineer, and GM Propulsion Engineering at Chevrolet about the differences between the six-, eight-, and 10-speed units over older electronic four-speed transmissions like the 4L60-E. Nye said, “The biggest change has been the advent of the clutch to clutch technology. This was introduced with six-speed automatics and continues with eight and 10-speeds. This technology is much more efficient than the ‘freewheeling’ designs of the four-speeds.”
Another difference that is probably obvious for most is that the six-, eight-, and 10-speed transmission cases have grown in size to accept larger clutches, making the transmission stronger capable of higher torque ratings. But, that hasn’t stopped the consumer from figuring out how to fit these modern units in a project. “Customers see the value in the higher speed transmissions even with the need to modify transmission tunnels in some cases,” Nye explained. “The higher gear ratios in these transmissions allow for better launches with lower rear end gears and the overall performance is a plus.”
Why More Gears Are Better
When you think about a four-speed transmission versus a six-speed, two more gears may not seem like a big deal. But when you start looking at the gear ratio differences between a 4L60-E and the 6L80-E, we get a clear picture of its advantages. The 4L60-E comes from Chevrolet with a 3.059 first gear, 1.625 second, 1.00 third, and a .69 fourth for overdrive. The 6L80-E, in comparison, offers a 4.02 first gear, 2.36 second, 1.53 third, 1.15 fourth, .85 fifth, and a .67 sixth.
So what does all of this mean? Nye said, “The higher speed transmissions allow the engine to stay in its power band longer for better performance and fuel economy.” So basically, the lower first gear ratio will allow the vehicle to accelerate quicker in most cases while staying in the engine’s powerband since the gear ratios are closer together.
As you can imagine, the 8L90-E and 10L90-E offer even better gearing with a super low first gear. The 8L90-E offers a 4.56 first gear and a 2.97 second, while the 10L90-E utilizes a stump-pulling 4.70 first gear and a 2.99 second which are both considerably lower than the 3.059 first gear in the 4L60-E. And while everyone loves the 4L80-E transmission, you might be surprised to know that the transmission has a higher first than the 4L60E with a 2.482, which is a far cry from the 10L90-E’s 4.70.
LS Vs. LT Transmission Options
Choosing an LS or LT powerplant for your vehicle will determine what kind of transmission you can use. If the LS is the mill of choice, you will be limited to a four- or six-speed transmission if you go with an electronic unit. The Gen III ECU can operate any of the 4L60-Es along with the 4L80e variants. A Gen IV ECU can step it up a notch and open up some possibilities by including the 6L80-E.
The LT is superior to the LS, even though some will argue otherwise. With direct injection, among other notable improvements, the LT can also be packaged with just about any transmission, thanks to the aftermarket. You can also run a four-, six-, eight-, or 10-speed transmission from Chevrolet Performance.
Currently, if you want to run an 8L90-E or 10L90-E transmission with an LS engine, you’re out of luck. Nye said, “The eight and 10-speed transmission controls are part of the transmission kit and not sold separately. Each eight-speed and 10-speed controller is matched to its transmission due to the complexity of the software. Supermatic crate transmissions will only function properly with Chevrolet Performance engine control systems. They should not be used with production vehicles.”
A Popular Choice
You might think that the most popular transmission choice would be the 4L60-E due to the overdrive and small size, but this is somewhat of a gray area. Nye said, “Four-speeds outsell the six-speeds by a very slim margin. However, both of the 6L80 variants in the Chevrolet Performance portfolio singularly outsell any one of the individual four-speed units, including the 4L65, 4L70, 4L70 4WD, & 4L75.
Even More Options
While we focused on the Chevrolet’s six-, eight-, and 10-speed transmissions in this article, the company has many more to offer. On its website, you can find five different variations of their 4L transmissions, along with Their 6-speed Super Magnum manual transmission. Chevy even offers crate engines with transmission packages called the Connect and Cruise, with plenty of LS and LT engine and transmission platforms to choose from. So, If you’re looking for a new GM transmission, crate engine, or both, now would be an excellent time to buy. Nye said, “We currently have a $250 rebate on the purchase of a Chevrolet Performance transmission within 180 days of the purchase of any Chevrolet Performance Crate Engine as well as our Connect & Cruise rebates.”
With more transmission options than ever from Chevrolet Performance, we expect to see more of the six-, eights-, and 10-speeds to be on the road soon. And with all of the advantages of the advancements in clutch design, engagement, and added gears, hot rods and classics will only get better with time.