Frequently Asked Questions

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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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.

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

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

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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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