4L60E Vs. 4L80E Transmissions: What Are The Differences?

With their debut in the 1990s, GM's 4L60E and 4L80E transmissions reveal some of their differences –- and similarities –- right in their names. The "4" and "L" respectively refer to the number of gears and the longitudinal orientation of the unit itself, while the "e" means they are electronically controlled. The "60" and "80" relate to gross vehicle weight ratings. (We previously covered GVWRs in our quick guide for RV and truck owners.)

The 4L60E can be used in a vehicle with a GVWR of up to 6,000 pounds, and the 4L80E raises its limits to 8,000 pounds. The naming strategy isn't universal, though, as the similarly-named 4L85e variant can handle a GVWR of up to 16,500 pounds.

Another basic difference comes from the applications in which the two transmissions were used. The 4L60E was typically a top choice for small-block Chevy engines at the time, and it carried over to rides with the Gen III and Gen IV LS V8 motors. Yes, a variant was used on some trucks, but that was more of a role for the 4L80E, which actually premiered with GM's 1991 C/K Series trucks. Nowadays, both transmissions are popular for aftermarket swaps, and the following details about their differences can tell you why.

Physically, swappers need to keep in mind that the 4L80E — engineered specifically and originally for trucks — is the larger and heavier of the two transmissions. It's approximately 26.4 inches long and weighs 236 pounds. while the 4L60E is 23.5 inches and 150 pounds. This would obviously make a big difference in your next build, and so would the fact that the gearboxes have different bolt patterns for being attached to engines. The smaller transmission features a 16-bolt setup while the larger one uses 17 bolts. They have differently shaped transmission fluid pans, as well. With the 4L60E, the pan is shaped like a rectangle; the pan of the 4L80E looks like an oval.

Remember how that "e" meant both transmissions relied on electronic controls? Well, they do, but even those controls have differences. The 4L60E only has a single speed sensor and the 4L80E has a pair of them. The two transmissions' wiring harnesses aren't compatible either — although rats may love chewing away at both.

Finally, right at the heart of the matter is a significant difference in the gear ratios. The four forward gears for the 4L60E, going from first to fourth, have ratios of 1:3.059, 1:1.625, 1:1.00, and 1:0.0696. In contrast, the 4L80E's ratios are 1:2.482, 1:1.482, 1:1.00, and 1:0.750.

The GM 4L60E and 4L80E transmissions ultimately go back to GM's famed Turbo Hydra-Matic family. This family was introduced in 1940 by Oldsmobile, becoming the first modern-style automatic transmissions. More specifically, the 4L80E is an evolution of the TH400 three-speed automatic. The big upgrades for the newer transmission included an extra forward gear with overdrive for enhanced efficiency, electronic controls, and a lock-up torque converter — which transfers engine power to the drive shaft and plays a vital role in how your automatic transmission knows when to shift. 

It's also worth pointing out that the 4L80E features a built-in bell housing. This is a protective metal covering that bolts onto the transmission in a specific pattern. This can limit swaps because it will only attach directly to engines with the same pattern. The same setup also was used for early 4L60E transmissions.

The 4L60E was originally conceived as a replacement for the light-duty variant of the TH400 called the TH350. That particular gearbox had been followed by the TH700R4, which boosted performance and efficiency with overdrive and a different first-gear ratio. Then, in 1990, the transmission was renamed the 4L60 without major changes before welcoming electronic controls in 1993. A removable bell housing with a different bolt pattern debuted in 1997. Both the 4L60E and 4L80E were replaced by the six-speed 6L80E in 2006.