Product Summary

Chevy LS V8, Many Transmissions, 1.75" Tube O.D., Steel

  • Easily install a modern LS engine and transmission into your Tri-5 with this bolt-on transmission crossmember specifically engineered to fit with engine swaps
  • Simple no-weld installation only requires drilling a few bolt holes for assembly saving you time versus fabricating a crossmember from scratch
  • Compatible with a wide variety of GM and aftermarket transmissions, both automatic and manual, so you can install your choice of overdrive transmission
  • Includes two 3/16” thick spacer plates which are used to accommodate for variances in frame width that is common for this era of vehicle
  • Sturdy 1-3/4" OD steel tube construction with .108” wall thickness ensures rigidity even in the most extreme environments

Key Specs

MFG. Part #91655572
BrandSpeedway Motors

Need To Know

Free Shipping on Orders Over $149

Shipping Policies & FAQs

Quick and Easy Returns

Return Policy


  • Compatible with most modern automatic and manual transmission used in LS swaps
  • Fits 1955-1957 “tri five” Chevy model frames and include 3/16-inch spacers for frame variances
  • No welding required, bolts to frame once mounting holes are drilled and tapped
  • 1-3/4-inch round steel tubing with .108-inch wall thickness
  • 1/4-inch thick welded end plates and 3/16-inch thick transmission mounting pad
  • Includes hardware to mount crossmember to frame and trans mount to crossmember
  • Specifically engineered to work with our tri five LS motor mount kit for your LS swap
  • 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 for Your Tri Five Chevy LS Swap

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.

We offer thousands of parts to keep your tri five Chevy running and on the road. Now you can repower your tri five Chevy with another iconic part of GM history, the LS engine. No doubt one of the most swapped engine platforms around the globe, powering all manner of hot rods, classics, muscle cars, trucks, and more, the LS swap is a terrific way to keep classic vehicles on the road with performance that will allow modern road speeds and the safety of keeping with today’s traffic flow. No matter what LS swap transmission you decide to bolt to the rear of your LS swap engine though, we have a bolt-in solution to support your trans of choice in the tunnel of your ’55-’57 Chevy.

Tubular Steel Transmission Crossmember Supports Auto and Manual Transmissions

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 an LS swap to your tri 5 Chevy you not only have to convert to standard side engine mounts (our tri five LS mount kit is perfect for this) but you need to add a traditional transmission crossmember to your ’55-’57 Chevy’s frame.

Our ’55-’57 Chevy transmission crossmember is specifically designed to support all the popular LS swap transmission options capable of being bolted up to an LS engine. Crafted from 1-3/4-inch round tubing with .108-inch wall thickness and CNC bent for precise transmission location, heavy duty 1/4-inch thick end plates are welded on along with a 3/16-inch thick transmission mount pad. 3/16-inch frame shims are included to accommodate frame variances and mounting hardware for the crossmember, and your transmission mount, (available separately) is included as well.

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

Our tri five transmission crossmember for LS swaps sits atop your ’55-’57 Chevy’s frame and bolts to your LS swap transmission mount of choice. We offer both a standard rubber mount, as well as a urethane mount option. Once secured to your transmission and mount the mounting holes of the crossmember are used to mark on your frame where to drill and tap for the included mounting hardware to secure the crossmember.

Designed for popular automatic and manual transmission applications found to work behind the LS engine, 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 LS swap ’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.



MFG. Part #91655572
BrandSpeedway Motors
Transmission Mount IncludedNo
Tube O.D.1.75"
Material TypeSteel
Sold in QuantityEach