Before the first hot rods were regularly fitted with automatic transmissions, rodders rowed and speed-shifted their manual transmissions with great precision and enjoyment for decades. Today, for a number of reasons, installing an automatic transmission in a rod or custom is no longer the automatic decision (no pun intended) it was in the last few decades. Whether it is for added mileage, performance, or just the pure nostalgia of three pedals, rodders have been opting to use manual transmissions in great numbers lately.
The addition of a Fifth or Sixth gear and the wide selection of gear ratios in the modern manual transmissions have made this choice much more appealing. We will focus on the popular GM T5 unit found in many S-10s, Camaros, Firebirds, and Astro vans. Some swapping of parts may be required for a more friendly installation, but the pieces are readily available used or brand-new at your local parts counter.
The T5 five-speed was originally manufactured by Borg Warner Automotive in 1982 and is still being manufactured today by Tremec. The T5 is the only American-made standard transmission to span almost 20 years of production (GM's Muncie four-speed previously held that honor). Because of the large quantities of T5s produced, many parts are interchangeable, allowing one to create interesting five-speed combinations.
The commonly found S-10 and Camaro gearboxes are getting a lot of attention and interest because they all include a Fifth-gear Overdrive and use the standard GM bellhousing bolt pattern. The T5s can also be found under many late-model Ford Mustangs, as well as a few different Jeeps and other brands (each with their own mounting pattern). The Ford pattern was also used by AMC and Nissan.
Many internal parts are interchangeable, but there are two basic grades of T5s: World Class (WC) and Non World Class (NWC). WC is a later version with many upgrades for smoother operation and improved reliability.
There are several T5 applications to consider. NWC T5s were introduced in 1982 in S-10 Blazers. Those used in the GM S-10 pickups from '83-87 are good candidates, but they do require some modification to work with the earlier clutch and flywheel packages. By 1983, Ford started using them in the Mustang, GM had them in the F-body (Camaro and Firebird), and AMC had them in the Eagle and Jeep lines. AMC dropped the T5 by 1985 to make room for cheaper Peugeot and Toyota boxes. By late 1985, the first WC boxes were used by Ford and had First, Second, and Third gears riding on roller bearings instead of solid shafts. The counter gears saw an upgrade to tapered bearings. Fiber-lined rings and dual cone-designed rings replaced the bronze synchro rings to improve ring surface area. GM started using WC boxes as early as 1988 in the Camaro/Firebird line but still kept NWC boxes in S-10s and Astro vans. Most of the GM T5 installations were all World Class by the mid-'90s.
RatiosThe close-ratio T5 gearbox uses a 2.95 First gear and is the best choice if you desire a performance-oriented setup. Information from the Chevy dealer shows two ratios available from '85-90 in the S-10, though there may be others; ML2 code in the glovebox is 4.03 First and 2.37 Second; ML3 is 3.76 First and 2.18 Second.
An early box with mechanical speedo is a plus since it's very expensive to change from electronic to mechanical speedo drive. S-10 boxes can be found for $50 to $100 at swaps, but the V-8 variants with 2.95 First will run more (around $200)-but crafty hunters can always find them for much less.
Before You InstallBefore you purchase a used transmission, it's a good idea to take a peek inside, or at least before you install it. You can't just pop a cover off to inspect these; you must pull off the tailshaft housing and shifter to get the top cover off. You may as well re-shim the endplay off the main shaft while you're doing this. These transmissions use tapered roller bearings and any endplay will result in sloppy bearing clearance as in sideways play. One might also consider bearings and synchros at this time, along with changing the speedo drive gear, if necessary. Also remove the C-clip from the rear of the output shaft so there is no interference installing your new driveshaft.