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GTO Automatic to Manual Transmission Swap

The most difficult thing in doing this swap is probably finding all the parts needed.  Most stuff is being reproduced, but some things still aren't.  Converting can also be tricky depending on what year GTO you have.

In my searching for parts, I've found out some things about the '67 as well as other years which might be of interest:

  • Pilot bushing: Most if not all 60's and 70's Pontiac cranks are machined to accept a pilot bushing, unlike some other makes of cars.
  • Z bar: 64-66 cars share the same Z bar, clutch rod components, and pedal assembly. 1967 uses unique one year only Z bar, rod components and pedal assembly.
  • Pedals: When putting in clutch and brake pedals, you don't need the pedal housing; the clutch and brake pedals will bolt right in where the automatic brake pedal was.
  • Driveshaft: 64-66 2 speed automatic and manual trans 2 dr cars (also 1967 2 speed auto 2dr Lemans and Tempest) use the same driveshaft which measures 60" from U joint center to U joint center.  1967 GTO's with the TH400 automatic (otherwise known as the M40) used a slightly shorter driveshaft, at 59.34" from U joint center to U joint center.
  • Crossmember: 64-72, You can keep your existing crossmember; there's no difference between an automatic from a manual equipped car, but read on for its location....
  • Crossmember location: 64-66 GTOs Lemans Tempests crossmember location is the same for 2 speed automatic cars and manual trans cars. 
  • Crossmember location: 67 Hardtop:  Frames have two sets of holes for the crossmember.  The TH400 auto crossmember sits back about 6 inches from the manual trans crossmember location.  For hardtop cars, just move the crossmember forward to the front set of holes. 
  • Crossmember location: 67 GTO convertible: It's not that easy for convertibles or for hardtops with the heavy duty frame option:  The factory welded tabs to the inside of the frame rails to mount a special narrow crossmember.  You'll have to weld new tabs 6 inches forward.
  • Crossmember location: 68-72 cars also have two sets of holes, and the convertibles don't use tabs, so no welding is necessary for either frame type.
  • Z bar tab 64-67 cars will need a tab welded to the frame to mount the outboard ball stud for the Z-bar.  Note the exploded view below to see the tab.
  • Z bar tab 68-72 cars have a bolt on tab.

Parts needed:

(See the exploded views.  Click on them to view large size)

Clutch linkage for 1967 GTOsteering column detail for 1967 GTO

  • the hump, bellhousing inspection cover and yokeTransmission.  I got a muncie but if you're on a tight budget, consider a 3 speed manual.  They're super cheap and later you can upgrade as your budget allows. Get a yoke with it if you can. 
  • Driveshaft, needed only for 67 and later.
  • Flywheel.  There is a large I.D. model and a small I.D. model.  I'll post as soon as I find out what is what.
  • Clutch.  Stock is 10.4 inch
  • Bellhousing and clutch fork.  Bellhousing was the same from about '65 to '77 (#9785581)z bar and clutch rods
  • Z bar and rods that go from pedal to z bar and z bar to clutch fork.
  • to be cont.

Frame / Crossmember information

67 H.D. GTO frame detailMy GTO is a 1967 convertible.  This is probably the most difficult combination to convert.  Regular frames have two sets of holes; a rear set for a TH400 automatic, and a forward set for a manual trans.  The heavy duty frames can't use these sets of holes so Pontiac welded tabs to support the crossmember.  The tab only had one set of holes so if you want to swap to a manual, it is necessary to weld new tabs in front of the original tabs.  In the first picture you can see the 8 holes on the left are for the hard top style frame.  You can also see where the inside frame rail (heavy duty or convertible option) is welded on and the location of the tab. 

1968 GTO frame detail (heavy duty frame)1968 and later GTO's have two sets of holes also, but they drilled access holes in the bottom of the frame and mounted the crossmember on top.  So no welding is necessary for new tabs.
Of course, hardtop owners with regular frames need not worry about any of this, they only need to move the crossmember up and bolt it down.

Home | About | Links
GTO Main | Auto to Manual Swap | Muncie Rebuild
Jeeps | Minibike
Dave Miles
November 14, 2004

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