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SmokinVette.com Forums : Corvette Forums : C3 Corvette Forums : C3 Corvette General Discussion : 4 Speed to LT1 T56 6 Speed Swap
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Old 10-17-2012, 07:24 AM   #1
MIKE80
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Default 4 Speed to LT1 T56 6 Speed Swap

I posted this a while back on another forum and thought this might help some guys here looking to convert to a 6 speed.

Summer 2011 I picked up a T56 trans out of a 94' Trans Am that a guy was parting out. So I finally decided to go for the install and removed my old trans and clutch linkages and sold them. I kept my Centerforce dual friction clutch and Fidanza aluminum flywheel. I picked up a conversion kit from Weir Hot Rod Products to convert the trans from a pull type clutch to a push, so I can use my current clutch and flywheel. The kit comes with the following:

LT1 T56 Kit (converting the pull clutch to a more conventional push design)
356 T6 Cast Aluminum Heat Treated Bellhousing
Self Adjusting Hydraulic Release Bearing Assemble (which is rebuildable)
Steel Block Plate
Pressure Tubing
All Necessary Bolts
Master Cylinder
Clutch Line



Cleaned up the trans and picked up a Hurst Billet Plus Shifter.




I insulated the tunnel to cut down on heat.



I relocated the battery cable so it is out of the way of the new shifter location and trimmed the tunnel up.



I made a removable cover for the tunnel with a neoprene seal on one side and insulation on the other.





Bought a driveshaft from an 82' vette, has the correct yoke that I need and had it shortened 1", installed solid Spicer U-Joints, and balanced. Now 24" from center u-joint to center u-joint.



I needed an angle adapter for the firewall to clutch master. I received this generous donation from Keisler.



I used a rod end and bolt coupler for the clutch pedal connection.



Installed the clutch master with remote reservoir.







Bolted up the trans.



Since the new trans uses an electronic speedometer, I made a filler plate and installed this 3 3/8" Autometer Digital Speedometer/ Tachommeter Combo.





Also, I picked up all the electrical plugs I needed for the trans speedometer, reverse lockout, and backup lights from ebay.

Here's a pic of the replacement crossmember powdercoated Flame Red, the same color as my chassis.



Here's a couple pics of the undercarriage.







I had to shorten the emergency brake cable because the new crossmember positioned the cable pulley back further which added to much slack for adjustment.

Here is how to wire up the transmission sensors:

With OEM GM connectors;

Reverse Lockout
Pink - +12V (wired to power on with the brake lights at the brake pedal switch)
Green - Ground

Backup Lights (connected to the stock wiring to my 4 speed)
Green to Ignition +12V (stock blue wire)
Brown to Backup Lights (stock green wire)

VSS
Purple - Speedometer Signal
Green/Black - Ground

I took my truck out and marked off 2 miles from my house to calibrate the new speedometer in the vette. I took out the vette, calibrated the speedometer, and headed for the highway. The biggest things that I noticed the most was how much smoother shifting was. Definitely much better! Also with the stock trans in 4th gear at 60 mph my vette was at a very loud 3100 rpm. Now in 6th gear at 60 mph my vette is at a mellow 1550 rpm! This is just so much better than before. Also, I have 370 gears in the rear and 17"x9.5" wheels with Nitto 275/40 ZR17 tires all around.

A pic of the Autometer Digital Speedometer/ Tachometer installed.



Modified the shifter so it comes up through the stock console position. Here's a few pics.








A pic with the finishing touch of the shift pattern plate installed. My 6 speed swap is officially complete!



Here's some before and after pics of when I cleaned up the trans.

Before:





After:




Also, here's a couple pics of the stock T56 bellhousing (left side) next to the upgraded bellhousing (right side) that I installed.



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Old 07-22-2013, 08:39 PM   #2
AboveTheLogic
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Great read, wish mine had a 6-speed!
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'79 Chevy Corvette (C3) L48 4-Speed - Unknown cam, Crane Roller Rockers/Girdles, Double Pumper 650, Super Vic Intake, Headers, Supertrapps, VB&P Street & Slalom Suspension.
'99 Jeep Grand Cherokee (WJ) Limited 4x4 4.7L - Daily Driver - 2" Lift w/ 245/75R17s Back from the dead after rod knock.
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Old 07-23-2013, 02:33 AM   #3
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very nice
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Old 07-23-2013, 07:02 AM   #4
MIKE80
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Thanks guys! Yeah, I love having the 6 speed! I did tons of research before I jumped into this. I worked on it by myself, took my time, and it actually wasn't that bad of an install. It was definitely worth the effort.
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Old 07-23-2013, 04:53 PM   #5
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It is definitely on my list of things to do. I don't like 3,000rpm at 65 mph and I could use a shorter 1st gear.
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'79 Chevy Corvette (C3) L48 4-Speed - Unknown cam, Crane Roller Rockers/Girdles, Double Pumper 650, Super Vic Intake, Headers, Supertrapps, VB&P Street & Slalom Suspension.
'99 Jeep Grand Cherokee (WJ) Limited 4x4 4.7L - Daily Driver - 2" Lift w/ 245/75R17s Back from the dead after rod knock.
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Old 07-25-2013, 01:53 PM   #6
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Looks nice!!! (work of ART)
Congrats!
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Old 07-25-2013, 05:29 PM   #7
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Quote:
Originally Posted by david78 View Post
Looks nice!!! (work of ART)
Congrats!
Thanks David!
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Old 08-05-2013, 07:38 AM   #8
ltwayne
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Default Mike 80 - HELP !

Mike, your conversion to the T 56 , your pictures
and post are great ! I am a new member with a
'71 and have been unable to locate a trans crossmember such as the red one in your photos.
It appears to be perfect for the application...
Your crossmember eliminates pipe clearance problems and makes future R & R of the trans. , clutch, etc. easily doable.
Could you please share with me your source for the
crossmember ? It would be much appreciated !
ltwayne 440-465-4327
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Old 08-06-2013, 07:35 AM   #9
MIKE80
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Quote:
Originally Posted by ltwayne View Post
Mike, your conversion to the T 56 , your pictures
and post are great ! I am a new member with a
'71 and have been unable to locate a trans crossmember such as the red one in your photos.
It appears to be perfect for the application...
Your crossmember eliminates pipe clearance problems and makes future R & R of the trans. , clutch, etc. easily doable.
Could you please share with me your source for the
crossmember ? It would be much appreciated !
ltwayne 440-465-4327
Thanks! Welcome to the forums!

I called Bowtie Overdrives and told them what I was doing and they knew what I needed and made me the crossmember. Give them a call.

http://www.bowtieoverdrives.com/index.shtml

Is your current crossmember removable? My original one was, and I was able to just swap crossmembers.
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Old 07-01-2014, 01:25 PM   #10
Richard B
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Great read. I put a Doug Nash 4+3 in my 73 some years ago. Original car was an automatic so I had a bolted in crossmember and cooling coils in the radiator for the OD unit. Brought hwy RPM from 3500 down to 2100 on the interstate. Not unlike your modification but did not have to deal with a hydraulic clutch conversion. Adapted speedo to a cable and put in a push button for overdrive engagement.
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