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Chevy 4L60E to 4L80E Transmission Swap - Four Wheeler Magazine

Ken Brubaker Senior Editor, Four Wheeler

This 1997 Chevy Suburban has a 5.7-liter engine, 6-inch suspension lift, and 35-inch tires. The truck is regularly used off-highway and to tow trailers. It also has a propensity for killing its 4L60E four-speed automatic transmission.

1997 Chevy Suburban 4l80e Transmission Swap garage Lift Photo 27059015

The 4L60E transmission has been used in a slew of 1/2-ton GM trucks and SUVs, and it has even appeared in some GM 3/4-ton trucks. It's a decent transmission that has proven itself a workhorse. However, if you use your truck hard, it can be a weak point that can fail-in some cases, repeatedly.

The owner of this rig could've kept paying to have the 4L60E rebuilt, but instead chose to replace it with the much beefier 4L80E four-speed automatic transmission. The 4L80E has been used in a number of 1/2-, 3/4-, and 1-ton GM trucks over the years. Upgrading from the 4L60E to the 4L80E is akin to going from a Dana 44 axle to a Dana 60--you'll add some weight, but also add durability. According to GM Powertrain information, the 4L60E has a maximum engine torque rating of 360 lb-ft and a maximum gearbox torque rating of 610 lb-ft.

The 4L80E has a maximum engine torque rating of 440 lb-ft and a maximum gearbox torque rating of 885 lb-ft. What this boils down to is that the 4L80E offers an 80 lb-ft and 275 lb-ft improvement over the 4L60E in both areas, respectively. Is there a downside? Well, the 4L80E is slightly heavier and offers a less crawly First gear ratio (2.48:1) than the 4L60E (3.06:1).

1997 Chevy Suburban 4l80e Transmission Swap comparison Photo 27059018

Here you can see the old 4L60E transmission next to the new 4L80E. The 4L80E we installed was built by Finish Line Transmissions in Wood Dale, Illinois. It's their Level 3 Street Performance unit, which features a number of upgrades and enhancements to improve performance and durability. With torque converter, the new 4L80E tipped our scales at 254 pounds dry. By contrast, the 4L60E weighed in at 182 pounds wet.

Matt Dinelli and his team at Attitude Performance in Arlington Heights, Illinois, have completed a number of 4L80E swaps on fullsize GM trucks. We recently had the chance to witness one of these swaps on the aforementioned vehicle. Here are the highlights.

1997 Chevy Suburban 4l80e Transmission Swap components Photo 28309423

Shown here are the components needed to complete the swap, sans transmission and driveshaft. There's a new inspection cover, transfer case adapter with hardware, new filler tube, reflashed ECM, transmission shifter cable bracket with hardware, 4L60E-to-4L80E jumper harness, speed sensor harness, and a larger-diameter transfer case input shaft.

Bottom Line
The total price of this particular swap was a hair under $4,200. This included the complete transmission with torque converter (about $2,300), all of the conversion components, front driveshaft, and labor. Keep in mind that this figure was for this specific rig, and costs can vary significantly by vehicle and the price of the transmission and torque converter being installed. If you're a do-it-yourselfer, a kit is available from Attitude Performance for approximately $700. It includes everything listed in the first-captioned photo at the beginning of the story.

PhotosView Slideshow

As with any transmission swap or rebuild, it's important to clean the transmission cooler lines before installing the new or rebuilt transmission. This removes the old transmission fluid as well as any dirt or metal particles. Even diluted with the cleaning solution, the fluid we removed was pitch-black and very burned, which gave us some insight into the general condition of the overworked 4L60E transmission. We continued to run cleaner through the system until it ran clear.

A few items must to be installed on the new transmission before it can be bolted in the truck. The 4L80E requires a speed sensor, which the 4L60E doesn't have. This is where the new speed sensor harness comes into play. It carries the signal from the speed sensor to the truck's ECM. One end simply plugs into the speed sensor as shown here.

The 4L60E computer harness plug is on the passenger-side of the transmission and the 4L80E plug is on the driver-side of the transmission. The jumper harness allows the 4L80E to be plugged into the factory wiring.

PhotosView Slideshow The shifter cable bracket is in the same position on both transmissions, but the 4L60E has a wider mounting bolt pattern than the 4L80E, so a new shifter cable bracket is installed to attach the shifter cable.

The shifter cable bracket is in the same position on both transmissions, but the 4L60E has a wider mounting bolt pattern than the 4L80E, so a new shifter cable bracket is installed to attach the shifter cable.

The torque converter goes in next and is seated all the way into the pump so that when the bellhousing is tightened to the block, the torque converter doesn't bind up and break the pump gears.

Here's the new 4L80E, ready to be installed in the truck.

PhotosView Slideshow Because of the way the exhaust was routed on this lifted Suburban, the inspection cover had to be loosely set in place before the trans could be bolted in-otherwise it wouldn't have been able to be put in position. Also, we were able to reuse the flywheel because it was dual-drilled and would accept the 4L80E torque converter bolt pattern.

Because of the way the exhaust was routed on this lifted Suburban, the inspection cover had to be loosely set in place before the trans could be bolted in-otherwise it wouldn't have been able to be put in position. Also, we were able to reuse the flywheel because it was dual-drilled and would accept the 4L80E torque converter bolt pattern.

The transmission is then installed, and care is taken to make sure that no wiring is pinched in the bellhousing. As the trans is tightened up, it's a good idea to check and make sure the torque converter spins freely. If it doesn't, it means that the torque converter isn't seated all the way, and this will cause transmission damage.

All of the items disconnected from the 4L60E are reattached to the 4L80E. The list includes a variety of things including a vent tube, fuel line bracket, and a heat shield. The new filler tube is also installed, and it uses the 4L60E dipstick.

PhotosView Slideshow The 4L80E can use the 4L60E neutral safety switch because it has dual mounting holes. Dinelli says he simply unbolts the switch from the 4L60E as a unit and then reattaches it to the 4L80E. He says it's a bad idea to try to unplug it because the plugs often melt to the neutral safety switch harness, and trying to unplug them usually results in breakage.

The 4L80E can use the 4L60E neutral safety switch because it has dual mounting holes. Dinelli says he simply unbolts the switch from the 4L60E as a unit and then reattaches it to the 4L80E. He says it's a bad idea to try to unplug it because the plugs often melt to the neutral safety switch harness, and trying to unplug them usually results in breakage.

The output shaft on the 4L80E is a larger diameter than the output shaft on the 4L60E. This means the transfer case input shaft must be swapped to one with a larger internal diameter bore. Here you can see the 4L60E transfer case input shaft on the left and on the right is the new 4L80E input shaft.

Here's the new input shaft installed in the transfer case. Even though the input shaft has a larger-diameter bore, it has the same outside diameter so it uses the same seal and bearing as the old input shaft. As long as this bearing isn't worn and there are no leaks, the swap only requires the new input shaft, some silicone, and fluid. However, if your transfer case needs a rebuild, now is a good time because the transfer case has to be completely disassembled to install the input shaft.

PhotosView Slideshow Here you can see the new transfer case adapter bolted to the 4L80E.

Next up, the transfer case is reinstalled, and the appropriate linkage and wiring are connected.

The original transmission mount from the 4L60E is reused on the 4L80E.

PhotosView Slideshow While we had the two transmissions side-by-side, we took this photo to illustrate the length difference between the two. The 4L80E is 1 5/8 inches longer than the 4L60E. In most situations, this means that new front and rear driveshafts have to be made. It also means that the transmission crossmember must be moved rearward.

While we had the two transmissions side-by-side, we took this photo to illustrate the length difference between the two. The 4L80E is 1 5/8 inches longer than the 4L60E. In most situations, this means that new front and rear driveshafts have to be made. It also means that the transmission crossmember must be moved rearward.

Because this frame was designed to use the 4L80E in some applications, there were already a set of holes in the perfect location for the transmission crossmember, so no holes had to be drilled. We did have to move the lift kit's compression strut mounts forward 15/8 inches to compensate for the relocation of the transmission crossmember.

The last step to the conversion is to install the speed sensor wiring to the reflashed ECM. These are the only new electrical connections needed to complete the swap. With these connections made, the computer will now have the info it needs to correctly shift the 4L80E.

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Chevy 4L60E to 4L80E Transmission Swap - Four Wheeler Magazine

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