Since its introduction by General Motors back in 1982, the venerable 700-R4 automatic overdrive transmission has found its way into more early American iron than we care to count. Part of the reason for its popularity is its gearing characteristics-low first and second for those inevitable rabbit starts, plus a very pleasing 30 percent overdrive, which significanty lowers engine rpm during freeway cruising. Now, as with anything performance-oriented, OEM equipment can come up short in certain areas, and Jet Performance Transmissions has sought out all the weak links of the 700-R4 and developed a virtually bulletproof trans with a variety of options and applications.
Jet's T-700 transmission (its modified version of the 700-R4) features all of the standard GM options, but has been improved upon to produce firmer, more responsive shifts. Jet also offers the transmission in a non-lockup version, which we will showcase here. The converter in this model is stall-matched to each individual engine. A variety of things are done to improve the transmission, such as the addition of extra (heavy-duty) clutches, a Corvette servo to eliminate band slippage, and bigger, stiffer springs throughout. The clutch band is eliminated in the non-lockup converter, and shims are used to prevent premature wear or failure.
The reason behind a non-lockup overdrive is the ability to get more out of the four-speed transmission in all gears. Instead of the 700 hunting for overdrive at certain speeds or rpms, it features positive, firm shifting throughout. Instead of being "stuck" in lockup on the freeway, you can simply press on the throttle a bit more and get responsive acceleration every time rather than having to hit it hard to drop down into third. With a higher-stall converter, launching off the line is greatly improved, as well. Basically, you get benefits on both ends of the performance spectrum. Obviously there will be some enthusiasts who prefer the characteristics of the lockup trans, which is why Jet offers high-performance versions of it as well.
Instead of rambling on about the ins and outs of the Jet Performance Transmissions T-700 overdrive, follow along with the accompanying photos and see what tricks they've perfected to get the most out of this popular transmission.
(Editor's note: Jet offers a plethora of automatic transmissions for everything from daily-use applications to high-performance race models. Rebuild kits are also available, but Jet strongly recommends that qualified professionals perform the work. )