6 Speed Basics
The webmaster drives a B.B.H.P. conversion ( # 134) and consequently offers the following from his own archives.
First the quick and dirty -
So far I’ve learned the following:
1) BBHP is no longer doing conversions. (A company created by Josh Korsower - B-Body High Performance -was in the business of converting our Tri-9's into 6 speed cars. The conversions were performed in Rockville, Maryland - and the company was headquartered in Prairie Village, Kansas.) The T56 tranny should have several upgrades prior to installation;
a. Steel Shift Forks
b. Reverse Lock-out Solenoid
c. Upgraded gears
d. Heavy duty output shaft (because of the greater weight of the car)
e. Run only Royal Purple lubricant in the tranny
3) The rear end gears should be changed to either 3:73 (for mileage) or 4:11 for acceleration.
4) The posi unit should be changed out for a heavier unit.
OEM Tranny for 1994 - 1997 Camaro / Firebird
Bog Warner (BW / TREMEC) T-56 6 speed with flywheel / clutch assembly
The Borg Warner / Tremec T56 is a stout 6 speed manual ! It was the original equipment transmission for fourth generation Chevrolet Camaros and Pontiac Firebirds, fifth generation Corvettes, and Dodge Vipers.
There are three versions, each with different gearing and torque capacities, as outlined below.
Gear A B C 4L60E
1 2.66 2.97 3.36 3.08
2 1.78 2.07 2.07 1.62
3 1.30 1.43 1.35 1.00
4 1.00 1.00 1.00 0.70
5 0.74 0.80 0.80 N/A
6 0.50 0.62 0.62 N/A
Reverse 2.9 3.28 3.28 2.29
Torque Capacity (lb/ft) 450 400 350 350
Take a look at the above chart comparing transmissions. Due to its higher torque capacity and better gear ratios, good sense recommends A, which can be found in '94 - '97 Camaros and Firebirds. When the LS1 was introduced in '98, the T56 received a different bellhousing and input shaft which is not directly compatible with the LT1 in the Impala.
Here's a little 6 speed FAQ that answers the most common questions regarding the swap.
What parts are needed for the conversion?
A BBHP-designed clutch pedal assembly is fabricated from scratch, and they modified a factory transmission crossmember.
Since BBHO is out of existance, you have to get creative! Additionally, you need a T56 transmission complete with bellhousing, clutch assembly, and flywheel. You also need to have your PCM reprogrammed. Its possible to modify your stock center console, but likely wiser to seek out a donor from an S10.
Does the floorpan need to be modified?
The six-speed fits very nicely. The only floorpan "mod" needed is towards the back of the tranny, on top. The floor needs to be hammered a little from the bottom, to raise it up and make a little room.
Aren't there different T56 transmissions out there?
Yep, there sure are. The T56 is available in '93 and newer F-bodies (F-bodies are Camaros, Firebirds, and Trans-Ams), '97+ Corvettes, and all Dodge Vipers. Smartchoice is a complete tranny from a '94+ F-body. Here's why: the '93 F-body T56 has less desirable gear ratios, and is only rated at 350 lb/ft of torque, while the '94+ T56 is rated at 450 lb/ft. Additionally, the Corvette uses a different bellhousing, I believe, and may not share the same case. They are also not as common as the F-bodies. Besides, if it comes from a 'vette it always seems to cost more!! The Viper transmission has larger input and output shafts, and a different bolt pattern. Also, the shifter is located several inches farther forward.
What about the computer & wiring?
Fortunately, Bryan of PCM4less does great computer reprogramming at a very reasonable rate, and can make your LT1-powered B-body work with a 6 speed.
Other than the PCM, 1996 Impala's need to have 2 wires jumped to fool the PCM into thinking the auto shifter is in Park.
You should wire up a starter kill so that the car will not start unless the clutch pedal is depressed.
What about PCM trouble codes?
After the conversion, your PCM will set trouble codes, as it cannot detect the transmission. Additionally, the speedometer will not read correctly. However, the car will still run and drive fine. These problem can easily be corrected by reprogramming the PCM.
How does the shifter fit?
The BBHP shifter pops out in just the right place, so the stock shifter can be retained. However, most opt for an aftermarket shifter such as the Hurst Billet Plus, B&M Ripper, or Pro 5.0 models. The Hurst is a favorite. The B&M unit is nice, but the bends in the supplied shifter handle do not clear the center console (unless you really hack it up!)
What about my car's interior?
Either of the two different Impala center consoles ('94 - '95 version and '96 version) can be modified to work. Center console coversion by BBHP featured a custom plastic insert and a 2001 Corvette leather shift boot. Others have scavengered other GM center consoles. If you know of a specific year/make/model chime in here.
What else should I get if I get a 6 speed?
Most who convert recommend running 4.10:1 rear gears in place of the factory 3.08:1 rear. The webmasters BBHP has 4.10:1 rear.
The 6 speed is marvelously flexible - I can smoke my tires all the way through second gear, yet I turn less than 2,000 rpm at 70 mph. At a minimum, go with 3.73's, and if you really like to shift 4.56's will keep your right hand and left foot plenty busy!
Steeper rear gears will necessitate a high-speed balanced drive shaft - the stocker can be made to work, but most will prefer an aluminum driveshaft. Gears will run around $200-250. If you want to run the 4.10's or 4.56's and keep your ABS, the ABS reluctor will cost $85. A 3.73 ABS reluctor can be bought at any GM parts counter for around $5-7.
Is this reversible?
Well yes & no. The conversion requires drilling holes in your firewall and cutting a big hole in your floor. Technically, you could, at any time, replace the 6 speed with the auto and remove the clutch pedal, and everything should work fine. Additionally, the mounting points for the '96 floor shifter are removed, as that's where the hole is.