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Overdrive 4L65-E Transmission - Bionic Transmission

Inside GM's Stronger, Faster 4L65-E Transmission

By Barry Kluczyk

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 Corvette Z06 LS6 engine's powerband 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."


Making 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 700R4 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 700R4 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.

Here are a few additional transmission swap considerations:
* The two-piece case of the 4L65-E is bulkier than, say, a TH350 or TH400, which means the transmission tunnel may need massaging.

* The L65 is relatively long (approximately 3 inches shorter 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 to indicate vehicle speed, a mechanical speedometer won't work without a signal converter, such as AbbottEnterprises' Cable X (see sidebar story).

GM supplies the torque converter with the L65, and most shift linkages from older GM vehicles can be made to work with it. In fact, several aftermarket companies, such as Shift Works (www.shiftworks.com), offer conversion kits to adapt stock-type shifters of many '60s-vintage Powerglide applications to modern GM transmissions. Year One offers similar products.

When ordered through a GM dealership, the 4L65-E has a list price of $2,595, not including the necessary controller. We're told an inclusive kit is on the way, but in the mean time, you'll have to use the L60 controller (PN 12497316).

Yes, you could probably upgrade an L60 for less, but we think the thoroughness of 4L65-E's revisions make it an attractive alternative. It also offers the benefits of being brand new and warranted.

Besides, you can tell everyone who asks that you've got the "Bionic Transmission."


What about the 4L80-E and L85?
Yes, the 4L80-E and 4L85-E offer the same electronic controlled advantages of the L65 and L60. After all, the L80 and L85 boast 440 ft-lb and 460 ft-lb torque capacities, respectively.

By Barry Kluczyk
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