Brake). The power brake is a scaled, self-contained unit that fits on the firewall between the hanging type pedal and master cylinder. Engine vacuum is used to provide the pedal pressure assistance. The power brakes, are suggested with the metallic linings, since the metallic brakes require much higher pedal pressures.

The GTO uses a modified (control arms instead of leaf springs) Hotchkiss rear end with a hypoid ring gear and pinion. Component parts have been beefed up since '63, and should give no trouble even under severe competition at the drag strip. Assuming normal maintenance, of course. The differential case is a one-piece ' unit, with a cover Plate at the rear. Steel axle housing tubes are pressed and welded into the cast case., The semi-floating rear axles are big enough for very rough usage and are supported at the outer ends by pressed-on heavy duty ball bearings.

The pinion shaft is also big and is located by two tapered roller bearings.

There are seven different axle ratios available for various model cars. Identification of a ratio is froni a code stamped on the rear of the right hand axle tube adjacent to the carrier or on the left rear brake drum surface. There will be two letters in this code identification, the first identifying type of rear end (W-Standard, Y-Safe-TTrack, X-Standard with metallic brakes and Z-Safe-T-Track with metallic brakes) and the second denoting ratio. There are 9 axle ratios listed, but only 8 of them generally appear in print.
They are: B-2.56, D-2.93, E-3.08, F-3.23 G-3.36, H-3.55, K-3.90, and L-4.33. Th( ninth is a 4.11 to 1 ratio, normally listec as an optional option, along with th( 4.33. Pontiac calls its limited-slip differential the Safe-T-Track, and lists it as optional on all '65 Tempests, regardless of axle ratio. A tag attached to one of the third member cover plate bolts identifies such an option. Very similar to the standard differential, the Safe-T-Track has an additional set of cone clutches and pre-load springs. In use, this assembly transmits power to the wheel having most traction, unlike a standard differential which does just the reverse.

The Safe-T-Track is an extremely free running unit, with no apparent binding on tight corners or deceleration. When the 335 horsepower engine is ordered, standard axle ratio will be 3.23. With the 360 bhp engine, the ratio will be 3.55. This holds true for both the 3 and 4 speed manual and automatic transmissions.

The interior, finished in pressed-pleat red vinyl and red carpet, is just austere enough to highlight the competitive theme. Special simulated wood steering wheel has spoke placement ideal for full gage view. Engine redlines on optional tachometer at 5500. Photos by Pat Brollier A three-speed synchromesh transmission is listed as standard equipment in all Tempests. A cast iron case is used for the 3-speed, enclosing helical gears made from drop-forged steel blanks, heat treated and shot peened. The GTO offers the Hurst floor shifter as standard appointment, and two ratios can be purchased in the 3-speed configuration. The first is 2.58A, 1.48A, and direct.