Frequently Asked Questions

Short answer: You can run 15×7 wheels front and rear, but choose front tires carefully (a 235/60-15 might rub at full lock). These cars came with 14×6 (and optional 14×7); many members run 15×7 or 16×7, some 8″ in the rear. The bigger you go, the more critical offset and tire size become — measure your car.

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Short answer: Whether 255s fit a 15×7 Rally II depends on how the car sits (sag/lowering). The catch is mostly tire height — check your clearance first. Tire diameters:

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Short answer: All 1967–69 Firebirds used the 8.2″ 10-bolt (a “BOP” Buick-Olds-Pontiac rear) — the size has nothing to do with posi. From ~1970–71 on, Firebirds used the corporate (Chevy) 8.5″ 10-bolt.

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Short answer: Pontiac rear-axle housings can be identified by year using their date codes, stamped codes, and a few physical features. The 1969 axle ID codes differ from 1967–68 — the full table is below.

When identifying a rear end, check the cast date codes (same style as engine parts), the axle code (rear of left tube), spring-perch depth (1967 Monoplates are shallow), the extra traction-bar brackets (1967 only), and the flattened spots on top (1969 only).

Short answer: On the Billing History card, the axle-ratio sales code appears in box 74 (1967) or box 37 (1968). The codes are the same both years:

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Short answer: The axle-ratio sales code on the Billing History is in box 74 (1967) or box 37 (1968). The codes are the same for both years.

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Short answer: The billing-history line “F70x14 RL FG / TMT / $57.93 / $41.80 / $2.93” decodes as: the tires originally installed were F70x14 Redlines, Fiberglass-Belted; “TMT” is that tire’s sales code; the dollar amounts are tire cost plus final destination/handling charges.

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Short answer: Bench-bleed the master cylinder first; if the pedal still sinks to the floor afterward, suspect the master cylinder itself — even a brand-new one.

If the pedal still goes to the floor: test the master cylinder by plugging the brake-line outlets and pressing the pedal; if it sinks, fluid is bypassing the internal seals. (One member’s new master was the culprit — the old one bled fine.)

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Short answer: The brake-system valves explained:

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Short answer: A pedal that nearly hits the floor with a weekly need to re-bleed, plus a tiny leak that seems to come from the metering valve, can actually be the calipers — one member chased a phantom “leak” for years (the front disc section kept emptying and fluid appeared at the master) until rebuilding the disc calipers fixed it. Air was getting in through the caliper seals and pushing fluid back out the master, mimicking a leak there.

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Short answer: The pedal is pushed back up (to release the brake-light switch) by the pushrod from the booster/master — not just a spring. If the lights won’t shut off, remove the clevis pin, unthread the clevis to lengthen the rod a quarter-turn at a time, and recheck until the pedal returns far enough to release the switch.

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Short answer: If clamping the front flex lines gives a solid pedal (and the warning light then works), the problem is at the front calipers — and the master cylinder bore size is not the issue. The likely cause: the 4-piston calipers are reversed side-to-side, trapping big air pockets.

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Short answer: No — you can’t keep the drum master cylinder. Drum systems use a residual check valve (5–7 psi) to keep the wheel-cylinder cups seated; a disc/drum system only keeps that valve in the rear (drum) circuit, because residual pressure on discs would drag and overheat them. So use a disc/drum master cylinder (or a 4-wheel-disc master for 4-wheel disc), plus the proportioning/metering valves and warning-light switch appropriate to the system.

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Short answer: The calipers mount toward the rear of the car. If they’re hitting the stabilizer bar, they’re on the wrong sides — swap the caliper, backing plate, and caliper bracket left-to-right (the spindle is machined the same either side, so it doesn’t matter).

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Short answer: Rebuilding a caliper is just replacing the seals — unless the piston bore is corroded/damaged, in which case it must be re-sleeved (~$35/piston, pricey). To bleed air from behind the pistons:

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Short answer: All 1967–69 (and early 1970) Pontiac Rally II caps are black centers with red letters (PMD). Late 1970 and 1971–72 switched to red centers with black letters; 1973 went to polished aluminum with the Pontiac arrowhead.

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Short answer: The classic bolt-in front disc swap recreates a factory 1969 Firebird disc setup using GM A-body or X-body donor parts. Shopping for everything as “1969 Firebird with factory disc brakes” simplifies sourcing. Pieced together from a salvage yard it can run as little as ~$100–500; a complete kit is ~$350 used or ~$795–825 new.

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Short answer: For a 1968 Firebird with factory disc brakes, the correct Rally II code is “JC” — the same as drum brakes. You do not need a special disc-brake wheel. (The “JA” you were quoted is the GTO disc code, not the Firebird’s.)

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Short answer: The 1968 Custom Trim option (554) included: Custom seat covers (Morrokide + stitched knit vinyl), custom molded door and quarter trim panels, the assist bar above the glovebox, dual horns, deluxe wheel covers, deluxe steering wheel, custom pedal trim, front & rear wheel-opening moldings, drip-rail moldings (coupes), and windshield-pillar garnish moldings.

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Bulletin 68-I-15 — Pontiac Motor Division Dealer Service Information Bulletin, Section 4, dated October 16, 1967. Attention: Service Manager.

Subject: Safe-T-Track Rear Axle Lubricant.

Short answer: Differential chatter on low-speed turns in Safe-T-Track equipped units is cured by a lubricant change; only Part No. 1050081 [Z] (Gp. No. 8.800) is approved — no substitute is recommended.

A number of cases of differential chatter on low speed turns have been reported in recent years on Safe-T-Track equipped units. Investigations prove that lubricant change is still the recommended fix for axle chatter.

Bulletin 68-I-37 — Pontiac Motor Division Dealer Service Information Bulletin, Section 5, dated January 31, 1968. Attention: Service Manager.

Subject: 1968 Tempest Rear Brake Drums.

Short answer: Some early-production 1968 Tempests were built with Kelsey-Hayes rear brake drums stamped “F” instead of the specified “KH” identification. Future drums will use the combined code “KH-F.” All three codes (“KH,” “F,” or “KH-F”) represent acceptable Kelsey-Hayes drums — a variation between right and left drums is not a concern.

Bulletin 68-I-47 — Pontiac Motor Division Dealer Service Information Bulletin, Section 5, dated February 28, 1968. Attention: Service Manager.

Subject: Complaints of Low Brake Pedal.

Short answer: Many low brake pedal complaints on power-brake-equipped vehicles are psychological in nature — the depressed floor area directly below the pedal is a design feature. Pedal height should be measured as described below; pedal height must not be adjusted, and if it does not meet specification, a full brake system inspection per the 1968 Pontiac Service Manual is required.

Bulletin 68-I-50 — Pontiac Motor Division Dealer Service Information Bulletin, Section 5, dated March 19, 1968. Attention: Service Manager.

Subject: Brake Drum Turning — Front Hub and Drum Assemblies.

Short answer: When turning a front brake drum on a lathe, the drum must be torqued securely to the hub using five flat washers and five stud nuts torqued to 35 lb. ft., eliminating any movement between drum and hub during the turning operation.

See the figure in the original bulletin for the proper method of mounting the front hub and drum assembly on a drum lathe.

Bulletin 68-I-51 — Pontiac Motor Division Dealer Service Information Bulletin, Section 10, dated March 25, 1968. Attention: Service Manager.

Subject: Premature Tread Wear — Wide Oval Tires.

Short answer: Over-inflation causes Wide Oval tires to wear prematurely in the center rib. Maintain 24 PSI cold (front and rear) unless carrying a full-rated load.

Bulletin 68-I-69 — Pontiac Motor Division Dealer Service Information Bulletin, Section 5, dated May 13, 1968. Attention: Service Manager.

Subject: Service Procedures — New Type 1968 Tempest and Firebird Front Brake Drums — Limited Production.

Short answer: A new separable front hub-and-drum assembly is being installed on a limited run of 1968 Tempest and Firebird models. Unlike standard units, the drum can be removed separately from the hub; the alignment index mark on the drum web must line up with the hole in the hub on reassembly. Approximately 10,000 sets are being installed at each plant.

Affected Vehicles

Brake Drum Turning or Replacement

Hub Bolt Replacement

1. Remove the hub bolt(s) with a press or hammer. These bolts are not peened into the hub. Use care not to damage the wheel mounting surface on the hub flange.
2. Install new serrated bolt into the hole in the hub. Tap lightly with a hammer to start bolt serrations into the hole, making sure that the bolt is square with the hub flange.
3. Press bolt into the flange until the head is fully seated against the hub flange (see Fig. 2).

Front Hub Bearing Replacement

The procedure for replacing front bearings and races is the same as that shown in Section 3, page 3-5, of the 1968 Pontiac Service Manual.

Parts Information

Bulletin 68-I-75 — Pontiac Motor Division Dealer Service Information Bulletin, Section 10, dated May 31, 1968. Attention: Service Manager.

Subject: Wheel Balancing — Disc Brake Equipped Vehicles.

Short answer: Some dealers have had difficulty balancing front wheels on disc-brake-equipped vehicles using on-the-car balancers because the brake pads rub the disc and prevent the wheel from spinning fast enough. Two solutions are available: a two-motor balancer or the Kent-Moore tool J 22801 Disc Brake Pad Spacer.

Bulletin 68-I-Special — Pontiac Motor Division Dealer Service Information Bulletin, Section 5, dated November 22, 1967. Attention: Service Manager.

Subject: Warranty Policy Clarification for Brake Drum Turning.

Short answer: This bulletin establishes uniform warranty policy for brake drum turning: grooves under .020″ deep need not be turned; out-of-round drums should be turned a maximum of .010″ per side before replacement; hard spots need not be removed unless raised. Always measure drum diameter and eccentricity before cutting.

Short answer: Yes — you can convert to front discs and keep 14″ Rallys. The roadworthy choice is the 1969 Firebird/Camaro single-piston system (shared with 1969–72 A-bodies and 1969–~74 Nova X-bodies); most 14×6 and 14×7 Rally II wheels clear it (a couple of wheel codes are noted incompatible — ask the group for the specifics).

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Short answer: A badly worn yoke usually means the inner tailshaft bushing is worn out — it’s a ~2″ softer (sacrificial) bushing pressed into the tailhousing, and replacing it requires removing the tailshaft. A new yoke alone won’t fix it if the bushing is shot.

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Short answer: Two ways. Read the code: the two-letter code on the rear of the driver’s-side axle tube (halfway between the drum and the “pumpkin”) — wire-brush to read it. Or count turns: chalk-mark the driveshaft yoke and diff housing and the tire; rotate the tire and count driveshaft revolutions — ratio = driveshaft turns ÷ tire turns (e.g., 17 ÷ 5 = 3.4:1).

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Short answer: GM’s own names are inconsistent, which is why this valve has several. The rear valve on the frame rail of V8/AC cars is called both “rear brake pressure proportioning valve” (parts book) and “rear brake pressure regulator” (illustrations catalog); tech textbooks call it the “proportioning” valve.

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Short answer: Two common gear-ratio questions — how to measure the ratio you have, and how to choose one.

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Short answer: 15×8 won’t fit inside the stock wheel wells. The front and rear handle up to a 235/60-15 without trouble; the rear can take a 255 if you roll the quarter/wheelhouse lip. Rim offset is critical.

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Short answer: They’re all the same type of unit — a limited-slip differential. Each GM division just branded it differently (with slight design variations): Pontiac called it Safe-T-Track, Chevy called it Positraction — both are “limited slip.”

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Short answer: On an unaltered 1967–69, the biggest practical tire is about 235/60-15 on 8″ wheels (members report 245 on an 8″ being too big). For more aggressive fitments, Car Craft (March 2000) published maximums for 1967–69 Camaro/Firebird:

15-inch: 15×8 with 4.5″ backspacing front and rear. With some tires the rear shocks must be mounted inboard; then some 9″ wheels work with 5.5″ backspacing.

16-inch: 16×8 with 4.5″ backspacing front and rear (rear shocks relocated inboard). Use aspect ratio 50 or less, section widths 245–250.

17-inch: 17×9 with 5.5″ backspacing front and rear. Possible lower-control-arm contact with some steering gears. Aspect ratio 40 or less, 245–255.

18-inch: 18×9 with 5.5″ backspacing front and rear. Aspect ratio 35 or less, 245–255 front and 275 rear.

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Short answer: The “round piece” under the master cylinder is the metering valve (front) — it holds off the front discs until the rear drums engage. A separate proportioning valve (rectangular, on the frame rail under the driver’s seat) was fitted only to 1967–69 V8 + A/C + disc cars to limit rear pressure and prevent the nose-heavy car’s rear wheels from locking.

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Short answer: The round metering valve under the master cylinder can fail (leaking, or sucking air) — one member went through four rebuilt units. Members who bypassed it reported the pedal felt firmer and they couldn’t tell a difference in normal street driving (on dry pavement). There’s a safety/originality debate, though — the engineers fitted it for a reason.

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Short answer: Original 1968 Firebird tires were Firestone:

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Short answer: Clean them up and brush on POR-15 (a rust-killing coating that bonds to bare metal and acts as primer + color — comes in black, gray, silver), then a clear coat. Two coats plus clear looks great.

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Short answer: Yes — all 1967 Firebirds have the eyelets on top of the pumpkin (they used the A-body GTO/Tempest rear), and the backing-plate-to-backing-plate width matches a 1968. Whether you got none, one, or two radius rods (traction bars) depended on engine, transmission, and (in one case) axle ratio. Per the 1967 service-manual supplement (which calls them “radius rods”):

* One rod is used if the ratio is 3.23:1. All 1967 Sprints came with factory traction bars. They can be adapted to a 1968, but the 1968’s staggered shocks and multi-leaf springs are a better setup — posi was an extra-cost option (except later on the Trans Am).

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Short answer: Replacement boosters often have the wrong pedal-rod length (e.g., 7.75″ vs the correct ~5.75″ for a 1969). One member’s fix: a section of thick-wall tubing sized to the rod’s OD — cut the rod ~2″ from the end, set the master/rod-end at the correct length with the tube joining them, mark, and weld both ends — which let him fit a smaller-diameter ’84 Z28 booster/master (clears the valve covers nicely).

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Short answer: The booster was cadmium plated — a silver with a slight gold hue (“yellow cad”), not as yellow as some other GM boosters (Jim Mattison discusses the correct color in the magazine articles on his 1967). The spray-can “cadmium” paints are only a look, take 5–6 cans and several steps, and don’t match real plating.

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Short answer: If the master cylinder is bolted directly to the firewall, it’s manual. If it’s bolted to a saucer-shaped vacuum booster with a hose running to the top of the engine, it’s power.

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Short answer: A car that pulls or fishtails under hard braking, with all brake parts already replaced, usually comes down to the front drum brakes being out of adjustment (they’re not self-adjusting in front on 1967–69 and aren’t forgiving) — or a front-end issue.

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Short answer: For a 1968 Firebird with disc brakes, the correct Rally II wheel code is “JC” (the same as drum brakes) — per the 1968 Service Manual, 1968 Parts Book, broadcast sheet, and verified original cars. The widespread “JA for disc” claim is a technical error carried over from the 1967–68 GTO / 1967 Firebird.

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Short answer: Original-match Rally II paint codes (use lacquer, not enamel — the factory finish wasn’t very shiny):

#475      6 Units
#490    106 Units
#400    272 Units
#487    442 Units
#415    447 Units
#476    457 Units
#491    477 Units
#495    497 Units
#499   1000 Units

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Short answer: The cap has 3 clips that snap into the round center hole, plus 3 more that fit the 3 notches on the older (larger-hole) wheels to keep it from rotating. On the newer small-hole wheels those 3 positioning clips just don’t engage — the cap still snaps in fine. (Year One’s catalog has a good rear-view drawing, plus locking caps to deter theft.)

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Short answer: Not ideal — the JA (GTO) wheel offsets inward ~1/8–1/4″ per wheel, narrowing your Firebird’s track. Better to trade the JAs to a Tempest/LeMans/GTO owner and find the correct JC wheels (unless you’re stepping up to 7″ wheels).

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Short answer: Pontiac wheel/Rally II codes are confusing — per a 1971 parts book, 1967 used JA (disc brakes) and JC (drum brakes), while 1968 used JC for all (even though the disc parts were the same for 1967 and 1968). The full application/code table is below.

More detail on decoding the codes stamped on a rim: the Classic Pontiac Server wheel page and Wallace Racing’s rally-wheel date-code page.

On the 1968 Rally II, the wheel rim code is on the outside of the rim, right next to the valve stem (see below). On the inside of the rim (the flat part connecting the inside and outside) you’ll find the date code, plant code, inner-wheel code (JJ), and size (14 x 6).

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Short answer: Rally II wheels came in 30–40 varieties — the only way to know what you have is the two-letter code at the valve stem (that’s the WHEEL code the parts book uses: rim + center + offset). A code stamped inside the rim is just the rim type; the larger center hole is a non-issue (caps fit), but offset matters.

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Short answer: One member’s assembly-line method for stripping Rally wheels (he’s done 30 at a time):

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Short answer: The two-letter axle code is stamped on the driver’s-side axle tube, facing the rear, roughly 6″ from the differential cover (near/to the left of the brake clip). It’s often rusty — expect to wire-brush/sand to read it.

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Short answer: Not from 2.56 to 3.23 or 3.73 with your existing differential case. Per the factory service manual, there were three case types (by ring-gear mounting): one for 2.56/2.78, one for 2.93/3.08/3.23, and one for 3.36/3.55/3.90/4.33 (the 3.90/4.33 used only the 4-pinion locking case).

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Short answer: Swapping gears to switch between “highway” and “around-town” ratios is possible but impractical — a proper gear change needs skill (setting backlash and tooth contact), special tools (dial indicator), and time (~$250 gears + $100 tools, or ~$250 shop labor; a weekend the first time). For two ratios, a second complete rear end (faster to swap) or an overdrive transmission makes far more sense.

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Short answer: Two excellent write-ups for the 2nd-gen-into-1st-gen swap: the Classical Pontiac restoration section, and member “geebjen’s” detailed report (angelfire.com/on/geebjen/rearswap.html). Members confirm both are accurate.

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Short answer: You can change the upper rear main rope seal with the engine in the car by rotating it out with the crank (no crank removal), but getting the pan off in-car is a miserable fight — most members agree it’s better to pull the engine and do it right.

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Short answer: Per the 1967 Firebird supplement, the eight axle ratios are identified by a two-letter code stamped on the rear of the LH axle tube:

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Short answer: An A-body (e.g., 1969 LeMans) rear can be made to fit a 1967, but it’s a lot of bother for a 10-bolt: A-bodies use rear coil springs, so the housing is wider and you’d cut off the coil mounts and weld on leaf-spring perches (and narrow it or run offset wheels).

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Short answer: A 2nd-gen F-body rear (the 8.5″ 10-bolt) drops into a first-gen and is stronger, cheaper, and more available than the first-gen 8.2″ — but you must relocate the spring perches, match the transmission/U-joint type, set pinion angle, and shorten the driveshaft.

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Short answer: If your 1967 rides on 15″ Rally II rims with P225/60-15 (very close in diameter to the old G60-15 / F70-15), get the period Goodyear Polyglas in a 15″ size to match — or switch back to correct 14×6 rims if you want the original E70-14/F70-14. Don’t mount 14″ tires on 15″ rims.

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Short answer: For 1967–68, ordering the Ram Air engine made the Saf-T-Track axle (code 361) mandatory. For 1969 that prerequisite doesn’t appear on the Trans Am or 400 H.O. (with or without the Ram Air hood) — so if your 1969 documentation doesn’t list code 361, that’s how it was.

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Short answer: A click from one rear wheel during slow tight turns is common on GM posi units — it’s typically the clutch cones momentarily slipping/grabbing (and that jolt can ring through the driveshaft). It’s usually not alarming if backlash and pattern are good.

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Short answer: Pull the cable from the housing, clean the cable with solvent and flush the housing (brake cleaner), then re-grease the cable with white assembly grease (or a good graphite lube) as you slide it back in. That stops the minor needle jumping.

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Short answer: A speedo that reads off after a rear-end swap or a tire-size change usually just needs the correct speedo driven gear (the colored plastic gear on the cable at the transmission) to match the new ratio/tire size. It’s an easy, ~$8 part at a GM dealer (Classic Industries sells them too — give your trans type and rear ratio), or a shop can recalibrate. If originality matters, fitting reproduction original-size tires is the other route.

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Short answer: A rear thump that fades at speed — check, in order:

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Short answer: On a 14×7 Rally II, a safe all-around size is 225/60-14. A 235 fits the front (close) and is no problem in the rear; the rear can take a 255 or 265 depending on offset. All of these fit a 7″ rim. (Many members have moved away from a mismatched front/rear look on a street car.)

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Short answer: 1968s didn’t have traction bars. For 1967, what you got depended on engine, transmission, and rear-axle type:

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Short answer: The original early Rally II (and some Rally I) trim ring — GM #9781480 (brushed) or #475019 (polished), both 4-clip 14×6 — was discontinued years ago and sets fetch up to ~$500. Several reproductions exist but vary in clip design, outer-ridge profile, finish, and fit, so quality is hit-or-miss.

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Short answer: When freshening a junkyard 1969 disc setup for a 1968: vacuum-test the booster (if it leaks, use it as a core); use the master cylinder and calipers as core exchanges for reliable rebuilt/new parts; replace the flex hoses (old ones fail when you need them most); and replace pitted/rusted caliper pins/bolts (parts-store “HELP!” line).

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Short answer: For a safety upgrade, the 1969 F-body single-piston front-disc setup is the practical choice (the correct-for-1968 4-piston system is more work than needed; 4-wheel discs are nice but unnecessary). Get the master cylinder, booster, and valves from a 1969 Firebird/Camaro, and the disc spindles from the same car or a 1969–72 A-body (Chevelle, Skylark, GS, LeMans, Tempest, GTO, Cutlass, F-85, 442) — A-body spindles are the same, just bolt your Firebird steering arm onto them.

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Short answer: Yes — on a 1968 with power brakes the booster vacuum line runs through a small clamped bracket attached to the throttle-cable bracket (as on 1967s), and members confirm this appears original. The pre-formed hose attaches at about the 9 o’clock position on the booster (the valve points toward the right side of the car, not straight up).

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Short answer: A 50-mph resonance that disappears by 65 mph, felt in the wheel and pedals regardless of gear or accel/brake, is almost always a balance or driveline issue — check the easy/cheap stuff first.

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Short answer: Whether a wide wheel/tire fits depends on backspacing and tire size, and every car differs slightly — so measure rather than guess. Factory 14×7 and 15×7 wheels are ~4″ backspacing; on a wider wheel, keeping 4″ pushes the extra width outboard, while more backspacing (e.g., 4.5–5″) splits it inboard.

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