55-57 Chevy LS Trans Mount Adapters

Tri five Bel Air, 210, 150 and Nomad owners running an LS with a modern GM gearbox can bolt one of these adapters to the tailshaft. They suit the TR-6060, CTS-V T-56, MG9, 6L90E, 8L90E and 10L90E and give the transmission a standard mount pad.

Fits 4 late model GM gearboxes
Crossmember brackets bolt through drilled frame holes
T-56 needs the tunnel seam flattened

Bracket heights and drilling steps are in the 1955-1957 Chevy LS install guide. Engine mounts, radiators and tanks are on the 1955-1957 Chevy LS swap page.

$39.99 Cadillac CTS-V T-56 / standard TR-6060 Trans Mount Adapter

$39.99 MG9 high-torque TR-6060 Trans Mount Adapter

$39.95 Cadillac CTS-V 6L90E Transmission Mount Adapter

Tri five LS transmission mount adapters

Six speed manual adapters

Late model automatic adapters

Which bracket for your tri five

For a CTS-V T-56 or standard Camaro TR-6060, pick the jig welded bracket that comes with its bolts.
The MG9 version of the TR-6060 from the CTS-V LSA gets a different bracket, also with hardware.
Pick the 6L90E bracket for a 2009-2014 CTS-V six speed automatic.
Eight or ten speed: the 8L90E and 10L90E share a single bracket.

1955-1957 Chevy transmission notes

With a T-56, relief cut the body seam in the tunnel and flatten it with a hammer and dolly first.
The tri five crossmember brackets need 1/4 inch pilot holes, opened to 25/64 inch on the inner frame wall.
A 1 inch hole saw on the outer frame wall gives socket access to the crossmember bracket bolts.
The guide gives bracket heights of 1 3/4 inch for a T-56 and 2 1/2 inch for a 4L60E, measured from the frame bottom.
BRP lists its 1955-1957 Sure-Fit crossmember for every body except the convertible.
Low mount LS A/C compressors hit the frame, so the compressor has to be relocated up top.

Notes from the 1955-1957 Chevy LS install guide and the crossmember listing.

1955-1957 Chevy LS transmission mount FAQ

Does a T-56 fit a 1957 Chevy tunnel?

The tri five guide says to cut relief slots in the tunnel body seam and flatten it before a T-56 goes in.

How high do the tri five crossmember brackets sit?

The guide gives 1 3/4 inch for a T-56 and 2 1/2 inch for a 4L60E, measured from the bottom of the frame.

Is there a tri five crossmember for a convertible?

The 1955-1957 Sure-Fit crossmember listing excludes the convertible. Check with BRP for a convertible car.

Do the automatic adapters need a BRP crossmember?

The 6L90E and 8L90E adapter listings say they are meant to be used with BRP transmission crossmembers.

1955 - 1957 Chevy LS Transmission Mount Adapters