Bop 400/t-56
May 7th, 2019, 11:44 AM
#1
Registered User
Thread Starter
Join Date: Sep 2018
Posts: 122
Bop 400/t-56
Does anyone have an idea how a T-56 works behind a 77 or 78 Pontiac 400? Adapters needed, bell housings, clutch options, cross member requirements? I'm currently running a T10 4-speed with a manual clutch.
Thx.
Thx.
May 7th, 2019, 01:45 PM
#3
Gary
Join Date: Feb 2014
Location: Gillespie County Texas
Posts: 2,075
This is a fun project and will work out fine; there are a few steps to it, but everything is do-able.
- Buy a T-56 with adequate torque rating for your engine.
- Some transmissions are rotated. I bought one that was straight-up.
- The length and diameter of the input shaft must be machined to match your pilot bearing. Your trans supplier should do this for you. The proper length may change depending on your choice in point 5.
- Your existing mechanical clutch and linkage should work perfectly with the T-56.
- Instead of an adapter plate (which works OK otherwise), you could consider buying an SFI bellhousing with the correct bolt patterns on both ends; that way you also get protection from any possible clutch disintegration.
- Your cross-member will need to be relocated or perhaps replaced. Ask your T-56 supplier for advice. I got my T-56 from D&D in Wixom MI, and the stock crossmember in the T-400 position fit perfectly.
- Check your driveline angle after installation. I found I needed adjustable rear upper control arms (on an A-body) to get relative angles back in range.
- An A-body will require a larger transmission tunnel. This is major surgery as it requires cutting through one of the integral floor supports. I rolled 6 x 1/4" plate to form a driveshaft loop and welded this to the integral floor support to restore the floor strength. You can fabricate the new trans tunnel or purchase one made for this swap. This requires welding or bonding to complete.
- I put thick bubble wrap over the trans before finalizing the new tunnel position, that way I was sure I had adequate clearance everywhere.
- The taller and wider transmission tunnel will require custom carpet (if you have a console, you can cut the carpet lengthwise underneath it to gain the extra width).
- Connect the reverse solenoid to the car's brake light circuit. That will release access to reverse when you have your foot on the brake.
- Figure out the position of the shifter and determine if this needs to be changed (by buying a trans with a tailshaft from a different supplier or availing yourself of an alternate shift position on a special tail-shaft). I found my shifter was 3" back from the Muncie position. It worked OK with bucket seats. It would not have worked with a bench seat. I had to adapt the Cutlass center console to accommodate the different shifter position.
- Make sure the shift adapter will bolt to a Hurst stick so you can choose from an assortment of stick styles, heights, and offsets.
- You will need a floor boot and a console boot for the shifter. I used a floor boot from a 2000-ish Camaro.
- I used a 3.5" driveshaft, so I had to heat and stretch a 12" area of the driveshaft tunnel to allow room at full jounce.
- You can see some pictures of an install in one of my albums.
Last edited by VC455; May 7th, 2019 at 02:30 PM.
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