C3 Transmission Swap - Grabbin' New Gears, Part 2

As Promised, We Take Keisler Engineering's New T45-RS For A Test Drive

Alan L. Colvin Nov 17, 2009 0 Comment(s)
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Last month I spoke about Keisler Engineering's new 5-speed transmission that had just been released for the C3 Corvette, the T45-RS, which is based on the Borg-Warner T-45 that was used from 1996-2001 in high performance passenger cars including the Cobra and 4.6L Mustangs. Keisler provides the new T45-RS in kit form and their proprietary and patent-pending designs for this tranny include a crossmember mount bracket, rubber transmission isolator, back-up wiring harness, forged quick release slip yoke, driveshaft, 5-speed shift pattern plate, template and tunnel cover, installation hardware kit, and an installation manual.

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While I was on the 2-lane roads, I kept the car in 3rd and 4th gear most of the time and the car responded instantaneously to every shift with ease. There was absolutely no shifter vibration inside the car and I attribute that to the workmanship of the transmission, the newly designed shifter and the high quality of the rest of the assembly including the Keisler-built driveshaft. The transmission is a Double Cone transmission, with all forward gears and reverse fully synchronized, and it shifted up and down flawlessly. Even under very hard acceleration, the T45-RS easily found the next gear with absolutely no gear grinding or missed shifts.

In case you missed the last issue, Keisler buys the T-45 from reliable used transmission sources and then remanufactures each transmission in-house with a number of upgrades and custom features that greatly improves the reliability of the gearbox. The T45-RS rebuild includes new upgraded carbon fiber synchronizers, bearings, seals and gears (as required), a new high strength alloy front casting that allows the T45-RS to bolt up to the standard GM bellhousing bolt pattern, and a new super duty input shaft. As we mentioned last month, the transmission comes in two builds, 350HP and 425HP. The primary difference between the two is that the 425HP version uses the larger 26-spline input shaft while the 350HP version uses the 10-spline input. The same gear ratio is used for both versions and is as follows: 3.37 1st, 1.99 2nd, 1.33 3rd, 1.00 4th, .67 5th; 3.22 Reverse which equates to a 33% drop in engine RPM in 5th gear. Keisler also offers a choice of electronic or mechanical speedometer output for the T45-RS and uses a high strength 31-spline output shaft.

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The T45-RS also uses a custom billet aluminum short throw shifter that has been custom designed to work in all 1968-82 Corvettes, and an optional C3 replica shift handle is also available that not only gives you an original look but also places the shifter at the correct height. On a final note, each T45-RS is 100% spin tested and leak checked prior to shipment and comes with a 6-month warranty (extended warranty available at extra cost).

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As I said last month, Shafi Keisler invited me to fly up to the Keisler plant for the T45-RS install and to test drive the new transmission for myself. Our test drive consisted of some 2-lane back roads through the hills around Knoxville as well as some high speed expressway driving. When you are testing a transmission, you need to drive the car in a multitude of driving conditions to really get a feel for the car and how that particular transmission is performing in that car. Over the years, I have driven thousands of miles in Muncie 4-speed equipped cars but I had no idea what to expect since I had driven very few Mustang 5-speeds except for an '84 SVO Mustang I had bought new.

As we got out on the road, the first thing I noticed about the T45-RS was how similar the shift gate was to the original Muncie in contrast to the Tremec TKO. The T45-RS shares many internal components with the famous T-56 6-speed and because of that fact, I assumed that the gate would feel the same or similar to the TKO. But I was wrong. A TKO typically feels very "notchy" when you shift from one gear to the next where the T45-RS feels very much like a new Muncie transmission felt back when they were brand new. The T45-RS shifts very easily and can actually be shifted with one finger, even with the optional C3 replica shift handle that we used on this install. The original Muncie transmissions obviously had a much narrower (1-2) gear drop since it was a 4-speed so the gear ratio gap with the T45-RS 5-speed with the 350/350HP smallblock in this car seemed almost the perfect match.

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