Bolt-in powder coated steel crossmember that puts the mount pad where a 4L80E needs it when you swap one into a 1978-1988 GM G-body car.
Putting a 4L80E into a Monte Carlo, Malibu, El Camino, Cutlass, Regal, Grand Prix or another 1978-1988 GM G-body and finding the factory crossmember nowhere near the transmission mount? That is normal. This bolt-in powder coated steel crossmember was made for that exact swap. It sits in the original frame perches and puts the mount pad where the longer 4L80E, 4L80 and 4L85E case actually needs it, so you are not cutting, welding or stacking shims to make a stock bar work.
A G-body left the factory with a TH350, 200-4R or 700R4 hung from a crossmember shaped and placed around that transmission. The 4L80E is a heavy-duty truck unit with a larger case and its mount pad farther back, so on the stock bar the mount simply does not land. The crossmember carries the rear of the engine and transmission, takes the torque reaction when you launch, and sets the height of the tailshaft. That height decides your driveline angle, which is why getting the pad in the right spot matters as much as making it bolt in.
The crossmember is only one piece. G-bodies are two-wheel drive, so the donor 4L80E needs a 2WD tailhousing and output. The output speed sensor matters too, because the controller reads vehicle speed from it, and GM dropped that sensor and its exciter ring on 4x4 trucks after 1994 while 2WD units kept them. If your donor came out of a 4x4, read 4L80E input and output speed sensor symptoms before you trust its speed signal. Because a swap runs on a standalone controller, a clean solenoid circuit saves a lot of chasing; 4L80E shift solenoid symptoms covers how to check the A and B solenoids on the bench.
This crossmember fits the GM-4 transmission group, 4L80, 4L80E and 4L85E, in 1978-1988 G-body cars: Chevrolet Malibu, Monte Carlo and El Camino, GMC Caballero, Oldsmobile Cutlass, Pontiac Grand Prix, LeMans and Bonneville, and Buick Regal and Century. It is steel with a black powder coat, measures 48.82 x 9.72 x 5.43 inches overall, and ships with mounting hardware and instructions. G-body frames were not all built the same, and factory TH350 cars and 200-4R cars did not share an identical crossmember, so compare your frame perches with the product photos or send us your year, model and VIN before you order. You can find the matching parts for the build on our 4L80E parts page.
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Doing this repair right usually means replacing these at the same time. Same transmission, ships together.
1978-1988 GM G-body cars: Malibu, Monte Carlo, El Camino, Caballero, Cutlass, Grand Prix, LeMans, Bonneville, Regal and Century. Frames varied by model and by original transmission, so compare your perches with the photos or send us your year and VIN.
Yes. It is built for the GM-4 transmission group, which covers the 4L80, 4L80E and 4L85E. They share the same case mount layout.
Usually. The 4L80E output does not sit where the TH350, 200-4R or 700R4 output did, so measure from the tailshaft seal to the pinion yoke with the car at ride height and have a shaft built to that length.
No. The crossmember ships with its mounting hardware and instructions. Use a 4L80E transmission mount.
Not without changing parts. A G-body needs a 2WD tailhousing and output shaft, and many 4x4 4L80E units from after 1994 have no output speed sensor or exciter ring, which a standalone controller needs for vehicle speed.
