High Performance Transmission - Transformation

Despite these upgrades, the L65's gearing remains the same as the L60's: 3.059 for first gear, 1.625 for second, 1.000 for third, and .0696 for the overdrive.

Finally, the L65's valve body, including line pressure and shift timing, differs from the L60 by optimizing shifts based on a higher engine torque curve. Also, to withstand the higher fluid pressure of the L65, the springs in the accumulator valve are stronger than those in the L60.

Shift points for the L65 are programmed to complement the LS6 engine and, compared with the 4L60-E, the maximum shift speeds for each gear change is lowered from 6,100 rpm to 5,600 rpm

"Although the 4L65-E was originally developed for trucks, the transmission available through GM Performance is specifically tailored to cars," says Ford. "We think it offers the best compromise to a five-speed manual. It's got great strength and the gear ratios complement a car's power-to-weight ratio."

But, Will it Fit?All the improvements made to the 4L60-E to make the 4L65-E are internal, so it will bolt up to any vehicle originally equipped with the 4L60-E. And since the L60/L65 transmissions are basically electronically controlled versions of the 4L60 (which was known as the 700-R4 until the early '90s), they'll bolt up to most GM vehicles from the early '80s and up.

Of course, the 4L65-E requires the use of an electronic controller, whereas the non-electronic versions of the L60 or 700-R4 do not. These non-electronic overdrive transmissions, however, were used in computerized applications and adapting them to carbureted, non-computer vehicles requires the use of a throttle valvespring and some "just right" adjustments to ensure proper kickdowns.

That's not the case with electronically controlled transmissions like the L65. Swapping it into an older vehicle, though, requires the use of its electronic controller. And if the swap is performed with a carbureted vehicle, an aftermarket controller kit with a specialized throttle position sensor is a must. Aftermarket vendors, such as JET Performance (www.jetchip.com) or Phoenix Transmission Products (www.phoenixtrans.com) offer such kits.

You'll also want to look to Phoenix Transmission if you want to bolt up the L65 to your old Pontiac engine. They have a B-O-P kit that includes an adapter plate and converter pilot extension. TCI Automotive has a B-O-P adapter plate, too, (PN 230001).

Here are a few additional transmission swap considerations:* The two-piece case of the 4L65-E is bulkier than, say, a Turbo 350 or Turbo 400, which means the transmission tunnel may need massaging.* The L65 is relatively long (approximately three inches longer than a TH350), therefore a custom driveshaft may be required.* Depending on the vehicle, a new rear crossmember may be required to mount the tail end of the transmission.* Because the L65 uses an electronic signal toindicate vehicle speed, a mechanical speedometer won't work without a signal converter, such as Abbott Enterprises' Cable X (see sidebar story).

GM supplies the torque converter with the transmission but not the electronic controller (it uses the L60 controller, PN 12497316). Also, most shift linkages from older GM vehicles can be made to work with it. In fact, Shift Works (www.shiftworks.com) offers conversion kits to adapt stock-type shifters of vintage Firebirds, GTOs and LeMans, including Super Turbine 300 (two-speed auto) applications, to modern GM transmissions. Year One offers similar products.

Truth be told, a prepped 700-R4, a non-electronic 4L60, or even a 200-4R along with GM's throttle valvespring kit (PN 24502513), is a less expensive option than the electronically controlled L65 for a vintage, non-computer controlled car. However, if you're looking for a stronger trans for your Third- or Fourth-Gen Firebird, the L65 is an easy swap. It's also great if, say, you plan to put an LS1-based drivetrain in your old Tempest.