Tahoe 6-Speed T56 Conversion

[digitalfiend]

I will never have a daily driver that is an automatic if I can help it. It is my strongly held personal belief that this mod is a requirement as it fixes the biggest flaw of the NBS Tahoe: an automatic transmission. I did an auto-to-manual swap on my last vehicle (2003 Toyota Tacoma) so this is just a natural progression of making this Tahoe to be MY TAHOE.

With that said, I have to pay credit to where it's due. I'm standing on the shoulders of giants by doing this to my Tahoe because this conversion was not my original idea. The biggest reason I decided to buy a Tahoe is because of vanillagorilla's thread over at performancetrucksDOTnet that covers his Official A4 to M6 (T-56) Thread . vanillagorilla's thread covers all the necessary information, so I'm not going to go too far into the build detail. My aim is to show that the conversion is possible in an NBS Tahoe, show what it costs, then point out what I had to do that wasn't a direct bolt-in.

Parts

• $2300 T56 GM/LS1 rebuilt to withstand 750 foot pounds of torque
• $220 lightly used LS flywheel/clutch/pressure plate
• $160 abused & used LS T56 Bell Housing
• $35 Arp-330-2802 Flywheel Bolts
• $24 Arp-134-2201 Pressure Plate Bolts
• $25 Grade 10.9 M10x1.5x40 Fasteners
  For Bell housing to engine & transmission to bell housing
  From McMaster
• $176 Slave/Master/Hydraulic-Line CC649034 (Rockauto)
• $4 Brake pedal pad 15706041 (Rockauto)
• $47 Shipping (Rockauto)
• $18 Pilot Bearing (O'Reilly Auto Parts)
• $135 used crossmember from a 2003 Silverado with manual transmission
• $75 used clutch pedtal from a Silverado
• $52 Throwout shim kit (TICK Performance)
• $300 HPTuners (used)
• $100 HPTuners credits for my single vehicle
• $130 Driveshaft shortening (1") and balancing
• $0 used t-shirt for prototype shifter boot
• $20 Genuine leather for shifter boot

My Process At A High Level
Items in red are not direct bolt-ins

• remove the old tranny/flywheel
• install the pilot bearing
• install the flywheel/clutch/pressure-plate onto the engine
• install the bell housing onto the engine
• remove the entire center console (temporarily)
• cut the hole in the floor for the shifter
• install the transmission onto the back of the bell housing
• cut the hole in the firewall for the clutch pedal
• install the clutch pedal and master cylinder and run the hydraulic line
• cut the brake pedal to be the size of a manual brake pedal
• buy or fabricate a shifter arm, then install
• buy or fabricate a short throw shifter, then install
• alter the center console to allow a spot for the shifter
• buy or make a shifter boot, then install
• reinstall the center console
• measure the driveshaft then have it shortened or lengthened then balanced
• install the driveshaft
• rewire the park/neutral switch to be in drive so that the speedometer and cruise work, and that the Tahoe will start
• wire up the reverse lockout into the brake pedal switch
• wire up the reverse lights
• correct the speedometer with HPTuner
• retune the throttle flollower with HPTuner so that the throttle falls faster and makes shifts smoother
• remove error codes due to the manual transmission being removed with HPTuner

Pros

• When I don't hammer the gas pedal and bang through the gears after every stop light I see an increase of 2MPG across the board
• IT'S FUN TO DRIVE THIS WAY
• You get to command your Tahoe when and how to shift. Since the 4L60e is compter controlled this means there's one less computer in control of my destiny. SCREW YOU SKYNET!!!
• The truck is instantly more responsive thanks to not having a torque converter any longer
• This was the way this truck should have come from the factory.

Cons

• There is a lot of work involved to make this happen. For me this was a labor of love, so it was just another fun mod to do to my Tahoe...others may see this differently.
• There's quite a bit of cost involved with this mod. If you don't need a new transmission and/or you're not sure you'll own your Tahoe for a long time then this mod is not for you.

This transmission shifted fine...but I strongly dislike automatic transmissions, so it's got to go:


Here she is, 750 foot pounds of torque handling beauty:


Here's the master cylinder, hydraulic line, and slave cylinder:


Here's the shifter before the installation of the short throw kit:


Before:


After:


Todo Items

• Finish tweaking the custom short throw shifter
• Tweak the custom shifter arm so that the shifter is in the sweet spot for my comfort
• Create a refined shifter boot in real leather
• Wire the clutch pedal to interrupt the cruise control
• Wire the clutch pedal to interrupt the starter when not depressed
• Ditch the stock 3.73 rear end gear and install a 4.10 gear

Things I'd Do Differently If I Did It Again

• Use a SPEEDWAY Clutch remote bleeder line
• Use a new bell housing. The used one I bought had three bolt holes stripped, so I had to ream them out and thread them to use M12X1.5 fasteners. With this added cost I saved less than $20, and bell housings cost $200 new.
• Budget for a stronger clutch because the weight of the Tahoe is a little too much for the clutch to last long term.

 

[1sickz71]

talk about something out of the ordinary lol good for those whose truck are supercharged or has other mods a friend of mines went through 3 trannies within months apart due to his supercharger

 

[95escahoe]

Looks great

Sent from my HTC One X using Tapatalk

 

[dcarver]

How does the short throw feel in a truck as opposed to a small car? Reason I ask is I've only driven cars with a short throw and trucks and jeeps with the long shifter

 

[yukondoit]

This is awesome, I would love to this mod in 02.
Makes me glad I have the 5 speed manual in my 94 Yukon.

 

[08grey]

750 lbs of torque. I wanna see a burn out video. Nice work!!!

 

[Gzes]

looks damn nice. yep i hate dd autos aswell

 

[yukondoit]

750 lbs of torque. I wanna see a burn out video. Nice work!!!

+1, we need a video

 

[Goodinblack]

Dang. Nice.

 

[Wake]

Very cool...

I must be getting old though, I'm pretty content with an automatic on my commute. I drove stick shift on my 100 mile commute for 3 years and I've had enough of that. LOL.

I still have my 6spd Corvette for my fun car when I feel like rowing through the gears, so I haven't totally walked away from manual gear selection.

Four speed automatics were a great improvement over the previous 3 speeds but were pretty fragile and they're antiquated now when you see what's out there.

My STS-V and my Audi A6 have 6 speed automatics in them and those two extra gears really make a difference. I had a Mercedes with a 7 speed auto for a month as a loaner car and even with a four cylinder the car was always in the right gear for what I needed from it. I believe Mercedes is working or has an 8 speed automatic now.

Your conversion is definitely a clean job from appearances, glad it work out for you.