General InformationYear: 1968Make: ChevroletSeries: 94Model: CorvetteEngine: 427ciHorsepower: 435Transmission: Four-Speed MuncieEngine Code suffix: IU
BlockCasting No. 3916321 or No. 3935439Main: Four-bolt
Cylinder HeadCasting No. 3919842* (aluminum)Intake/Exhaust Valve Size: 2.19/1.72Combustion Chamber: 106.8*While all 1968 L89 Corvettes used this cylinder head from the factory, the car now uses the No. 3946074 open-chamber head.
Intake Manifold (Aluminum)Casting No. 3919850 or No. 3919852 or No. 3937797Carb Type: 3x2-bbl Holley
CarburetorHolley 2300 Series 2-bbl, GM No. 3902353 (front or rear)Holley 2300C Series 2-bbl, GM No. 3925517EV (center)
Exhaust ManifoldsCasting (Lefthand) No. 3880827 Casting (Righthand) No. 3880828
DistributorStamping No. 1111296Engine/HP: 427/435hpHousing: Cast-iron external adjustmentPoint: Mag PulseNotes: Tach drive, vacuum advance
Alternator1100696, 42-amp, all with TI
TransmissionFour-Speed Close-Ratio Muncie M21Maincase: AluminumExtension Housing: AluminumType: Synchromesh, all forward gearsGear Ratios:First: 2.20:1 Second: 1.64:1 Third: 1.28:1 Fourth: Direct Reverse: 2.26:1Maincase Casting No. 3925660Extension Housing Casting No. 3857584Sidecover Casting No. 3884685Special Information: Carryover from 1967 except for maincase casting number change.
1968 Rear Axles All '68 Corvette rear axles are stamped with an alphanumeric identification code. The seven-digit code contains the axle-code prefix, the month and day build code, an axle-plant letter suffix code and, on Posi-traction axles, a letter code stamped below the axle code to provide source information.
On the '68 Corvette IRS rear suspension, the differential code is stamped on the bottom of the differential-carrier housing just forward of the rearend cover. The axle code reads from left to right. The two-letter prefix designates the gear ratio and any other specific information about the axle. The calendar month is designated by a two-number code from January (01) through December (12).
Plant Codes* G = Detroit Gear & Axle* B = Buffalo NY* K = McKinnon Industries (unverified)* W = Warren, MI
Posi-traction Codes* D = Dana Posi-traction differential* E = Eaton Posi-traction differential* W = Warner Posi-traction differentialExample: AL-04 09 W
E* AL = Axle Prefix: 3.08:1, Corvette standard Posi-traction axle* 04 = Month: April* 09 = Day: 9th day* W = Assembly Plant: Warren* E = Posi-traction Source: Eaton
| 1968 Corvette Rear-Axle Codes |
| Gear Ratio | Code |
| 3.36:1 | AK |
| Posi 3.08:1 | AL |
| Posi 3.36:1 | AM |
| Posi 3.55:1 | AN |
| Posi 3.70:1 | AO |
| Posi 4.11:1 | AP |
| 3.70:1 | AS |
| Heavy-Duty Posi 3.08:1 | AT |
| Heavy-Duty Posi 3.36:1 | AU |
| Posi 3.08:1 | AV |
| Heavy-Duty Posi 3.08:1 | AW |
| Heavy-Duty Posi 2.73:1 | AY |
| Heavy-Duty Posi 3.55:1 | AZ |
| Posi 3.70:1 | FA |
| Heavy-Duty Posi 4.11:1* | FB |
| Posi 4.56:1 | FC |
*The Harvey-Bailey L89 Corvette used this rear-axle ratio.
From Corvette By The Numbers by Alan Colvin, published in 2002, used with permission of Robert Bentley Publishers.