4L60E Transmission Crossmember for 1959-1964 Chevy Impala

If you are putting an overdrive automatic into a 1959, 1960, 1961, 1962, 1963 or 1964 Chevrolet Impala and the tailshaft mount lands nowhere near the factory crossmember, this is the piece that closes the gap. It is a steel transmission crossmember made for the X-frame Impala, with the mount pad moved to where a 700R4, 4L60 or 4L60E actually sits. It suits a cable-shifted 700R4 behind a carbureted small block just as well as an electronically controlled 4L60E behind an LS engine.

What the crossmember does in a 4L60E swap

These Impalas left the factory with the two-speed Powerglide automatic (Turboglide was also offered in the early cars), and many have since been converted to a Turbo 350. Both of those transmissions put the rear mount in a spot the original crossmember was built around. An overdrive unit is a longer package: Novak lists the 700R4 main case at 23-3/8 inches against 21-3/4 inches for a TH350, and the Powerglide is shorter again. With the engine left where it was, the rear mount of a 700R4 or 4L60E ends up behind the stock pad. The crossmember carries the back of the transmission, sets its height, and with it the angle of the driveshaft into the rear axle. Get the pad in the wrong place and you end up with a hanging tailshaft, cut-and-weld brackets, or a driveline that vibrates at speed.

Symptoms of a mismatched crossmember

• The transmission mount bolts do not line up with the original crossmember after the swap
• Driveline vibration that builds with road speed because the transmission sits too high or too low
• Exhaust pipes or the crossmember contacting the pan or tailshaft, making a clunk on takeoff
• A homemade bracket or shimmed mount that has cracked or shifted
• Fluid leaks at the rear seal from a slip yoke running at a bad angle

Remember that a sloppy installation can hurt the transmission itself. The 4L60E family is known for burning its 3-4 clutch pack behind a modified engine, and heat from a poorly mounted, poorly cooled swap does not help. Our 4L60E common problems guide covers what to watch for once the car is driving.

How to confirm you need it

Bolt the transmission to the engine with the mount on the tailshaft and support it with a jack at the factory engine height. If the mount sits behind or off the side of the stock crossmember pad, you need a relocated member rather than a spacer. Check the length from the rear mount to the end of the tailshaft against the gap to the rear axle as well, since that tells you what driveshaft you need. If the car already runs a 4L60E and shifts poorly, rule out mounting first, then work through the 4L60E shift problem diagnosis guide, because the hydraulics and electronics are the same as in an F-body.

Fitment

This crossmember is listed for 1959-1964 Chevrolet Impala X-frame cars fitted with a 700R4, 4L60 or 4L60E. It is not a factory GM part number, and early Impalas varied by body style and options, so compare the frame rail mounting points with the product photos before ordering. If you are unsure, send us the year, body style and the transmission you are installing and we will check it. The transmission mount itself is not included, and no instructions come in the box. Other overdrive conversion parts are in our 4L60E parts collection.

Install notes

• Support the transmission with a jack and a wood block under the pan rail, never on the pan itself.
• Remove the old crossmember and mount, then set the new member in loosely with the supplied mounting hardware.
• Bolt the mount to the tailshaft first, then snug the crossmember to the frame.
• Before final tightening, check driveshaft angle, exhaust clearance and shifter linkage or cable routing.
• Plan on a driveshaft length check; the overdrive case moves where the slip yoke ends up.
• Fill a 4L60E with Dexron VI and check the level hot.

If the swap uses a fresh or used converter, a new 2307304 converter bolt set is inexpensive peace of mind. If the core transmission came from a salvage yard with unknown miles, a 4L60E master rebuild kit lets you refresh it before it goes into the car.

Will this crossmember work with a TH350 or Powerglide?

No. It is made to put the mount pad where a 700R4, 4L60 or 4L60E sits. A Powerglide or Turbo 350 is shorter, so its mount would land ahead of this pad. Keep the original style crossmember for those transmissions.

Does it come with a transmission mount?

No. The crossmember and its mounting accessories are included, but the rubber transmission mount is a separate purchase, and installation instructions are not supplied.

Do I need a different driveshaft after the swap?

Usually you need to check it. The overdrive case is longer than the Powerglide or TH350, so the slip yoke ends up in a different place. Measure with the car at ride height before ordering a shortened or new driveshaft.

Will it fit a 1965 or later Impala?

It is listed only for 1959-1964 Impala X-frame cars. The 1965 and later cars use a different frame design, so this part is not intended for them.

Does a 4L60E need anything else to run in an early Impala?

Yes. A 4L60E is electronically controlled, so it needs an engine computer or a standalone transmission controller, plus wiring, a speed signal and Dexron VI fluid. A 700R4 instead needs a correctly adjusted TV cable.

• 4L60E Common Problems, Symptoms, and What to Actually Do About Them
• 4L60E Camaro Shift Problems: Diagnosis and Fix
• 4L60E Overrun Clutch: Function, Wear and Symptoms