Crossmembers

How Do You Choose a Transmission Crossmember by Transmission Type?

Start with your transmission, because each transmission crossmember is built around a specific case length and mount location. A crossmember made for a TH350 usually won't line up with a 4L80E in the same chassis.

G Force Performance Products builds transmission-specific crossmembers that show how this works:

• RCAE-W for a TH350 in 1964-1972 A-Body hardtops with a wide frame
• RCAEC1-400 for a TH400 in 1964-1967 A-Body convertibles and boxed frames
• RCG-700 for a 700-R4, 4L60 or MD8 in 1978-1988 G-Body cars
• RCG-4L80 for a 4L80E in 1984-1988 G-Body cars
• RCF2E-4L80 for a 4L80E in 1970-1974 Camaro and Firebird models
• RCAE-4 for a THM200-4R in A-Body cars

Running a 4L60E? Confirm the listing names your exact transmission, since a 700-R4/4L60 callout doesn't guarantee fit. Plan on matching transmission mounts, and review how to install a new transmission before you set the crossmember.

Which Crossmembers Fit G-Body, A-Body, F-Body and Other GM Platforms?

Pick crossmembers by chassis platform first, then narrow by transmission. If you need a G-Body transmission crossmember, JEGS 555-640600 fits 1978-1988 G-Body cars with a TH350, and 555-640603 covers the TH400.

F-Body and X-Body owners can look at G Force RCF2L-4L80, which fits 1975-1981 F-Body and 1975-1979 X-Body models with a 4L80E. OER 691-3912573 fits 1967-1969 Camaro builds with a TH400. For 1977-1990 B-Body cars with a TH350, G Force RCB3-350 is the match.

Truck owners have options too. G Force RCS-10 fits 1982-2005 Chevy S10 and GMC S15/Sonoma trucks, and RCC-10-4 fits 1988-1998 GM C1500 2WD trucks. Planning an engine swap on one of these platforms? See our guide to LS-swap kits for S10, C10, G-Body, Nova and Chevelle builds.

What Do You Need in an LS-Swap Transmission Crossmember?

An LS-swap transmission crossmember puts the transmission mount where your new engine and transmission combination needs it. Once the engine moves, the stock crossmember often sits in the wrong spot.

Trans Dapt 969-6422 is an LS engine swap transmission crossmember kit for 1978-1988 GM A-Body and G-Body cars with a 200R4. Hooker Headers 520-71222007 is an LS engine swap transmission crossmember. Hooker 71222019HKR fits 1982-2004 S10 and Sonoma 2WD trucks.

Choose the crossmember after you pick the transmission, since case length drives mount location. Our guide to automatic transmissions for LS engine swaps compares common choices. Engine position matters too, so pair the crossmember with the right motor mount brackets & kits.

What's the Difference Between Front, Engine and Subframe Crossmembers?

A front crossmember supports the engine and front suspension, so many builders call it an engine crossmember. A transmission crossmember supports only the rear of the transmission.

OER T677203 is an original-style front crossmember for 1967-1972 Chevy and GMC C10 trucks. OER T677209 is an OE-style rear crossmember for the same trucks. If you're restoring a C10, those part numbers give you a factory-style C10 crossmember for each end.

On cars with a front subframe, the subframe crossmember is part of that assembly. If you're replacing the whole front structure, compare sub frames and K-members as well. Heidts Mustang II IFS kits are also listed here for builders converting to independent front suspension.

What Should You Check Before Buying a Tubular Transmission Crossmember?

Check the mount, driveshaft angle and exhaust clearance before you order any crossmember, tubular or OE-style. A tubular transmission crossmember, like the 555-64066 for 1963-1972 GM C Series trucks, can open up room around the exhaust.

• Confirm whether the transmission mount is included or sold separately
• Measure exhaust clearance, especially with headers or dual exhaust
• Check driveshaft angle and length if the transmission position changes
• Note whether the design is a bolt-in crossmember or needs welding

A new transmission position can call for different driveshafts & components. If you've added sub frame connectors, make sure the crossmember clears them. Shop all crossmembers above, or browse more chassis & frame parts for your build.