Site hosted by Build your free website today!
1975-79 GM X-Car Manual Tranny Hump Assembly

Ever since there have been websites for 75-79 GM X-Cars - no one has ever seen a factory setup of a floor-shifted manual tranny in a GM X-car before.  The pics below is proof that GM actually produced floor-shifted manual tranny X-cars after 1974.

(pic courtesy of

Upon winning an auction on eBay where a manual tranny hump assembly, this will be the first time where X-car enthusiasts have seen a 75-79 tranny hump assembly.  The hump - the sheetmetal piece seen in the pic - has a footprint identical to the one in a 1973/74 X-car; however, the 73/74 X-car part has a different shape with a 'tower' for the shifter boot.  Here's a pic of a 73/74 hump (as seen on the 1975-79 X-Car Facts):


Note the shape of the tranny hump - the 'plateau' seen in the background has a smaller hole - which uses a shifter boot from a 1967/68 GM F-car (Camaro/Firebird).  It is possible to use a 73/74 hump in a 75-79 X-car; both the 73/74 and 75-79 humps are not available from the aftermarket.  The only tranny hump being reproduced is for 1968-72s only.

Here's a shot of a 75-79 X-car tranny hump - these pics were snapped right after it was cut (see the existing pic above - all of the spot welds were drilled out):


The C-shaped sheetmetal piece is the remains of a transmission tunnel from a 77 Nova with a factory 4-speed - the missing pie-section is in fact the location of a floor crossmember sandwiched underneath.

The green line seen in the pic above is in fact, the opening in the tranny tunnel where the shifter hump is located - below are a few pics (snapped 9.8.04) where the tranny tunnel was hacked.


The upper LH corner pic is what a factory 75-79 GM X-car would look like where a manual tranny hump was installed.  A majority of manual tranny 75-79 X-cars came with Saginaw trannies, either the 4-speed (RPO M20) and/or the base 3-speed (not too many floor-shifted 3-speed Novas exist - these are a rare option).  No Borg-Warner Super T10s were factory-installed in a 75-79 X-car (unless it was dealer-installed).

As depicted in the pics - here's the revelation:

The lower shifter boot seen in the top pic, as well as the shifter boot and ring, is similar to the one used in 1973-81 Camaros (also 70-81 Firebirds and Trans Ams) with the exception of the lower screw position.  A second-generation F-car (70-81) factory shifter boot, lower boot, and boot retainer ring can be used if the boot retaining hole on the bottom (facing south) is redrilled.  To date, no reproduction 75-79 X-car shifter boots are available from the aftermarket. Here’s the P/#s for the OEM shifter boot assembly (all of which are discontinued):

  • chrome ring (#364994 – discontinued since 1990)
  • lower boot (#327544)
  • upper boot (?)
  • For 1973/74, the tranny hump also positions the floor console (similar to 68-72 Novas); this also holds true for 75-79 X-cars with a manual tranny console.

    Both console and non-console applications used the same tranny hump for 75-79, regardless of the seat options (bucket or bench seat).

    Floor-shifted 75-79 X-cars were not only for coupes and hatchbacks, regardless if it was an SS or Nova Rally (including the Pontiac Ventura Sprint or Omega SX4).  4-door X-cars also had a 4-speed option - here's a weblink.