4L80E Swap Transmission Crossmember for 2WD Silverado

Swapping the 4L60E out of a two-wheel-drive Silverado or Sierra for a 4L80E is one of the most popular upgrades for half-ton owners who tow, run boost or keep killing light-duty transmissions. The catch shows up the moment the bigger transmission is in the truck: the factory crossmember no longer meets the mount. This bolt-in crossmember is built for that conversion on 2000-2013 2WD GMT800 and GMT900 trucks, so the job stays a bolt-together swap instead of a cut-and-weld project.

What the crossmember does in a 4L80E swap

The crossmember is the rear support for the whole engine and transmission assembly. It holds the tailhousing up, sets the angle of the output shaft and takes the twisting load when the truck launches or pulls a trailer. GM placed the half-ton crossmember around the 4L60E, which is a smaller, shorter case. The 4L80E is a heavy-duty unit with a longer case, and its mount pad lands farther back; the listing puts the difference at roughly four inches. Bolting a stock half-ton crossmember under it means the mount either misses the holes or the transmission is pulled out of line. This member is made around the longer case and uses the factory frame holes, so the driveline sits where it should.

Problems this part solves

• The 4L80E mount sits behind the bolt holes in the stock crossmember.
• The transmission has to be forced forward or back to reach the stock bar, preloading the engine mounts.
• Vibration after the swap from a driveline angle the factory member cannot correct.
• No room for the exhaust: the bigger 4L80E pan and case push the pipe outward, and this member is shaped to leave space to route it.

Check the swap before you bolt it in

A crossmember will not fix a donor transmission that has problems of its own, so check the unit before it goes under the truck. Many donors come out of 2500 and 3500 trucks that towed hard, and the 4L80E Silverado 2500 problems guide explains what to look for. Pay attention to the speed signal too. GM dropped the output speed sensor and its exciter ring on 4x4 4L80E trucks after 1994, while 2WD units kept them, and a 2WD half-ton still needs that signal. The 4L80E speed sensor guide shows how to check both sensors. The truck's computer also has to be set up to run a 4L80E, or the swap needs a standalone controller, because the shift and converter solenoids are not the same as the 4L60E's.

Fitment

This crossmember fits 2000-2013 Chevrolet Silverado 2WD and 2000-2013 GMC Sierra 2WD trucks that are being converted from a 4L60E to a 4L80E. It is not meant for heavy-duty chassis that already had a 4L80E from the factory, and it is not listed for 4WD trucks. Specs: mild steel, powder coated, 30.71 x 10.83 x 4.53 inches, 9.53 pounds, part number VC-LYAM-499-2. GMT800 and GMT900 trucks were built in several cab, bed and frame combinations, and some later trucks left the factory with a six-speed, so compare your frame mounting points with the product photos or send us your year and VIN before you order. You can find the rest of the swap parts on our 4L80E parts page.

Install notes

• Support the transmission with a jack, then remove the stock crossmember. No instruction sheet comes with the part, so take photos of the factory exhaust hanger and brake line routing before you start.
• Set the new crossmember in the factory frame holes with the bolts loose. Raise the transmission until the mount sits flat, start the mount bolts, tighten the frame bolts, then tighten the mount bolts last.
• Route the exhaust through the clearance area and check that nothing touches the pan or the case when the engine rocks.
• Plan for a shorter driveshaft. The longer 4L80E puts the output yoke farther back, so measure with the truck at ride height.
• Before the donor goes in, a fresh 4L80E internal wiring harness or a solenoid kit with internal harness and filter removes the guesswork from used electrical parts.
• Fill with DEXRON-VI and check the level hot. GM's 2008 Express owner manual lists 7.7 quarts for the 4L80-E.

Which trucks does this crossmember fit?

2000-2013 Chevrolet Silverado 2WD and 2000-2013 GMC Sierra 2WD trucks being converted from a 4L60E to a 4L80E. It is not listed for 4WD trucks or for heavy-duty trucks that came with a 4L80E from the factory.

Why does a 4L80E swap need a different crossmember?

The 4L80E case is longer than the 4L60E and its mount pad sits farther back, so the factory half-ton crossmember no longer lines up with the mount. This member is built for the longer case and bolts to the original frame holes.

Do I need a different driveshaft?

Yes, in nearly every case. The 4L80E output is farther back than the 4L60E's, so the driveshaft has to be shortened. Measure with the truck at ride height after the transmission and crossmember are bolted in.

Does the crossmember come with hardware or instructions?

No instruction sheet ships with it. It uses the factory frame holes, so check your original bolts and have new ones on hand if they are rusted.

Will my truck's computer run a 4L80E?

Not as delivered. The 4L80E uses different shift and converter control than the 4L60E, so the computer has to be programmed for a 4L80E or you need a standalone transmission controller.

• 4L80E Silverado 2500 Common Problems and Fixes
• 4L80E Input/Output Speed Sensor Symptoms
• 4L80E Common Problems and Fixes: The Six Failures That Actually Come Through the Door
• 4L80E Shift Solenoid Symptoms and Replacement: A and B Diagnosis