A closer look at the Borg-Warner T5

July 1, 2010 | By Richard Prince


When I had a 1955 Chevy 210 (in 1961) I was under the impression that it was a car, not a truck. Didn’t their series numbers always start with “5” and go four digits? You mention that an overdrive kick-down switch bracket is available new for all models equipped with a 2-barrel carburetor, but I understood Mr. Sullivan (December Mechanic on Duty) to state that his is a 235 (not a 283), which in stock form always ran a one-barrel carburetor, not a two-barrel. Back in the day, I replaced Powerglide transmissions in my cherry 210 sedan and ’55 Nomad with standard GM 4-bolt side cover three speeds with overdrive, and got 25 honest highway mpg on regular in both. This was with the standard equipment 3.56:1 rear end gears and 15" radials. I wired both without the kick down and ignition-kill features, instead using a toggle on the dash—which allowed gear splitting on mountain grades. I searched for several years for the Saginaw three-speed (a heavy-duty, fully synchronized transmission) with overdrive that was produced up until about 1973 for fleet applications, but never was able to purchase one. Supposedly the Borg-Warner type overdrive could be swapped onto a Saginaw 4-speed.

Now I look for Borg-Warner T5 units, cheap at U-Pull yards, when you can find them. I have a T5 from an Astro van in my 1972 half-ton (yep, this is a pickup truck) behind the 350 cid engine, and though it took some adapting, it works fine. I did get stuck with a 14-spline clutch disk of only 10-inch diameter, until I can locate something more like the heavy-duty 11-inch disk. I bagged two S-10 T5s that bolt right up to any standard Chevrolet bell housing, but their input shaft is too short by about an inch, alas. The T5 from the Astro van is perfect. I want to put T5s in my son's 1951 two door with a 350 cid engine, and in my daughter's 1967 Chevy Deuce with a 250 six-cylinder engine. It should really make a difference on the latter car!

Let me know if you ever find a definitive article on T5 identification and specs. Most of those on the net are not really very helpful.


Your 1955 Chevy 210 was a car, not a truck. Chevrolet’s light duty trucks were classified by a four-digit number that began with “3.” For example, a 3100 Series was a common light-duty truck that usually took the form of a pickup or panel delivery. Whether Mr. Sullivan’s car had a one or two-barrel carburetor is irrelevant. I cited the fact that an overdrive kick-down switch bracket is available for all models equipped with a two-barrel simply to illustrate that this is a source for a bracket that Mr. Sullivan can make work on his car.

There were two main generations of Borg-Warner T5 transmissions and the second generation is more desirable for most applications because it was improved in a number of ways.

The counter shaft rode on stronger, tapered roller bearings instead of straight roller bearings and the first, second and third main shaft gears all had bearings while those in the first generation T5 did not. The synchronizers in the second design T5 were also improved. The earlier transmissions used one-piece brass blocker rings on all gears while the later units used improved three-piece rings on first and second, and longer lasting friction lined steel core rings on third and fourth.

First generation T5 transmissions used a plain, pressed-in plug to close the bore hole for the forward countershaft bearing while second generation gearboxes used a sturdier steel plug with bearing maker “Timken” written on it.

All Borg-Warner T5 transmissions left the factory with an identification tag attached. The tag reveals several things, including the original application for the transmission and its gear ratios. British V8, which calls itself the online journal of the modified British sports car community, has an extremely comprehensive chart that deciphers the information on the tag and you can find the chart here: http://www.britishv8.org/Articles/Borg- Warner-T5-ID-Tags.htm.

Of course, knowing the original application doesn’t guarantee that the gear ratios or other internal parts of the transmission weren’t changed somewhere along the line. Also, knowing the original application and gear ratio still leaves a lot of unanswered questions about important characteristics, including case dimensions, input shaft diameter and length, input shaft’s spline count, shifter location, and so on.

I am not aware of a single source for all of this information but you can learn a lot from gathering together several resources. A good starting point is the Borg-Warner T5 Transmission Service Manual, which is available from various sources, including carburetor-manual.com, which sells a digital version.