1955-57 Chevy Tri-5 Transmission Crossmember, Bolt-In, Steel

• Compatible with most modern automatic and manual transmissions
• Fits 1955-1957 “tri five” Chevy model frames, not for use with truck frames
• No welding required, bolts to frame once mounting holes are located and drilled
• 1-3/4-inch round bare steel tubing with .108-inch wall thickness
• 1/4-inch thick laser cut and press bent frame brackets
• 3/16-inch thick crossmember end plates and transmission mounting pad
• Includes hardware to mount crossmember brackets to frame and crossmember to brackets
• Fits TH350, TH400, 700R4, 4L60E, and 4L80E automatic transmissions
• Fits Saginaw 3/4-speed, Muncie 4-speed, and aftermarket Tremec manual transmissions

A Bolt-In Transmission Crossmember Conversion for Your Tri Five Chevy

Chevrolet’s iconic 1955, 1956, and 1957 models, affectionately referred to by enthusiasts as a “tri-5 Chevy” or “tri five Chevy,” are one of the most recognizable classic cars on the planet. From usage in dozens of movies and TV shows over the decades to magazine project cars like the famed Project X (which itself was also a movie car at one time), their body lines and classic styling work well for everything from straight axle gassers to pro touring builds and everything in between. Thankfully, we offer thousands of parts to keep your tri five Chevy running and on the road no matter the build theme.

The original engine and transmission fitted to the tri five Chevy had what some would refer to as “reverse motor mounts” with two mounts straddling the side of the transmission bellhousing area and one mount at the front of the engine. When performing a later small block or big block Chevy engine swap it is usually a good idea to upgrade from the standard single front mount to the later side mount configuration, which allows easier accessory drive fitment, but you need to add a traditional transmission crossmember to your ’55-’57 Chevy’s frame to complete the driveline support.

Tubular Steel Transmission Crossmember Supports Auto and Manual Transmissions

Our ’55-’57 Chevy transmission crossmember is specifically designed to support all the popular transmission options capable of being bolted up to a small or big block Chevy engine. Crafted from 1-3/4-inch round tubing with .108-inch wall thickness and CNC bent for precise transmission location, heavy duty 3/16-inch thick end plates are welded on along with a 3/16-inch thick transmission mount pad. 1/4-inch thick frame brackets are included to accommodate allow for bolting the crossmember in. The frame brackets are position on the upper inside edge of the frame rails and used as templates for drilling the mounting holes required into the inner frame wall. Mounting hardware for the crossmember and frame brackets is included as well.

Installation Couldn’t Be Easier with Basic Hand Tools Found in Any Garage

Our bolt-in tri five transmission crossmember frame brackets sit atop your ’55-’57 Chevy’s frame and are secured via self-tapping bolts once you drill the mounting holes. Then our crossmember bolts to these frame brackets. The crossmember is setup for standard two bolt GM transmission mounts. We offer both a standard rubber mount, as well as a urethane mount option.

Designed for popular GM automatic and manual transmission applications, including popular overdrive models, your options run from the old school tried and true TH350 to one of GM’s electronically controlled overdrive automatics. If you prefer your tri five with three pedals our ’55-’57 Chevy transmission crossmember will support all the modern Tremec aftermarket 5-speed and 6-speed variants, as well as classic manuals like the Muncie 4-speed and others. Note that the Tremec manual transmissions may require a spacer for proper driveline angle correction.

Transmission Crossmember Instructions (PDF)

• End to end width = 32-7/8"
• Center to center width (mounting holes) = 3"
• Drop of top of tube to top of plate = 2-3/4"
• S-bracket drops the mount surface for teh crossmember 2" down from the top of the frame
• S-bracket is 4" wide- slotted holes for crossmember mounting are 1" to 1-3/4" long