Find answers to Frequently Asked Questions for First Generation Firebirds that have been asked and answered on FGF. Special thanks needs to be given to all the FGF members who took the time to respond to other member's questions.
Codes - Drive Train Codes
Q: Axle Codes for 1967 and 1968
How do I identify the Sales Code for the axle ratio that is shown on the Billing History cards.
A: In 1967, the ratio will be shown in the box marked 74 and in 1968, it will be shown in box 37. In both instances, the codes used to identify the axle ratio will be the same and they are as follows:
C = 2.56:1
D = 2.78:1
E = 2.93:1
F = 3.08:1
G = 3.23:1
H = 3.36:1
K = 3:55:1
P = 3.90:1
S = 4.33:1
Note: Do not confuse these Sales Codes with the two-digit code that is stamped on the axle tube.
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Content last modified: January 24, 2014 at 9:50 pm
Q: Rear End Code Facts
I am confused by the codes found on the rear end.
A: After reading all the comments, I thought I’d better give some facts. The 1967 Firebird axle housings have the loops (where control arm bushings would mount) on top of the center chunk as if they were getting A-body control arms, but they also have the spring perches for leaf springs, and the brackets for the factory style “traction bars”. There should also be a date code cast into the center section somewhere. In 1968 they left off the control arm bushing loops and the traction bar mounts, but seemed to use the same codes as 1967. In 1969 the date code position moved from one side of the center section to the other, but I can’t get to my rearend housings to see which are which. Another change from 1968 to 1969 was the addition of flattened spots on top of the axle tubes where the snubbers meet the housing, 1967 and 1968 did NOT have the flat spots. Again, check your cast date codes if at all readable.
Also, all 3 years had the 2-letter stamped code in roughly the same position, about 3-5 inches to the LEFT of the center section, on the rear of the left axle tube (left being the driver’s side of the car). Many times it is obscured by the steel brake line – you’ll need to loosen the clip welded to the axle tube and raise the brake line a bit to see it.
The 1969 codes were different. Here’s the list (first the open ratio, then the posi):
1967, 1968, and 1969 Axle Identification Codes |
|||||||
---|---|---|---|---|---|---|---|
Ratio |
1967 |
1968 |
1969 |
||||
Std. Diff. Code |
Lock Diff. Code |
Std. Diff. Code |
Lock Diff. Code |
Std. Diff. Code |
Lock Diff. Code |
||
2.56 |
XB |
UN |
XB |
UN |
YB |
ZB |
|
2.78 |
XC |
UP |
XC |
UP |
YC |
ZC |
|
2.93 |
XD |
UR |
XD |
UR |
YD |
ZD |
|
3.08 |
XE |
US |
XE |
US |
YE |
ZE |
|
3.23 |
XF |
UT |
XF |
UT |
YF |
ZF |
|
3.36 |
XG |
UV |
XG |
UV |
YG |
ZG |
|
3.55 |
XH |
UW |
XH |
UW |
YH |
ZH |
|
3.90 |
– |
UX |
– |
ZP |
– |
ZK |
|
4.33 |
– |
UY |
– |
ZR |
– |
ZM |
I hope this clears up some confusion and misinformation. Whenever possible, ask about date codes (same style of codes as engine parts), axle codes (rear of left tube), spring perch depth (67 Monoplates are shallow), whether it has the extra brackets for traction bars (67 only), or if there are flattened spots on top (69 only).
Any proposed updates, changes, pictures, and/or corrections, please use our comment section below (may need to click on permalink to access comments feature). Information is subject to change and offered as is without any warranties or guarantees. Please review our Term's Of Use for more information.
Content last modified: December 8, 2017 at 4:11 pm
Q: Date Codes
While comparing the date code on my 1967 engine to the Fisher Body Tag, the dates are about three weeks apart. Should I be concerned my engine is not original even though it has the correct engine code (matches docs)?
A: As for date coding, the general rule of thumb for drivetrain components compared to Body Assy Date is anywhere from 2 weeks to 3 months. I’ve seen documented cases where some components were the week before Body Build and as distant as 3 months for things like an alternator. Generally, 6 weeks is the usual maximum. Keep in mind that there are no absolutes when it comes to date coding. Inventory Control 30 years ago was not like it is today. Most people will say that NEVER should a drivetrain component be dated AFTER the Body Build Date however, “never say never”. There have been special cases where the entire engine assy had a casting date after the Body Build Date. This could have been the result of production shortages and/or special build orders.
Also, remember that the Fisher Body Build Date on the firewall Trim Tag is not the final assy date. This Month & Week Code denotes the week that the body shell was assembled at Fisher Body. Again, in special cases, the body shell might have been pulled or put aside from the regular production flow due to a special order or part shortages. The Final Assy Date can be found on the Billing History. Listed as the “Invoice Date”, this is when the car left the final assembly line and was ‘certified’ to be shipped (bought-off). Once again, there could have been factors that delayed this date from being assigned to the vehicle or shipped. Part shortages, mis-builds, repairs would delay buy-off.
Your Firebird body shell was scheduled and assembled during the 4th week of October 1967 (23rd – 27th). This was the basic painted shell with glass, carpet, headliner, seats, some trim. From there,. it was transferred to the Final Assy Plant (Lordstown, OH) for Final Assy. This is where the front fenders, hood, bumpers, trim and drivetrain were installed. The Invoice Date on your Billing History would tell you when the car left Final Assy. The “WK” Engine Block you have (I177) was cast on Oct. 17th 1967. From there it was sent to the Engine Assy Plant and then to the vehicle Final Assy Plant where additional components were added to it before being installed to the vehicle. One could estimate that if it was cast on the 17th (Tues.) then it was probably not assembled until the 20th or 23rd. Figure another couple of days until it arrived at Lordstown for Final Assy into the car. In this hypothetical scenario, there is a chance that this particular engine COULD have been installed into a Body built during the 4th week of Oct. 1967. Variables would be how long it sat at the foundry, shipping time, scheduling and routing through selectivity banks, etc.
Often times, lower production vehicles were built according to a batch order. This would result in many of that particular model, color, engine being routed through production within the same week or period of time. This explains the Body Unit Number found on the Trim Tag and special in-plant codes found on the corner of the Trim Tag (usually found on Van Nuys or Norwood cars in late 1968 or 1969).
Hope this helped. As always, this information is from various sources and research others or myself have done. Exceptions usually DO exist to every rule.
Any proposed updates, changes, pictures, and/or corrections, please use our comment section below (may need to click on permalink to access comments feature). Information is subject to change and offered as is without any warranties or guarantees. Please review our Term's Of Use for more information.
Content last modified: January 11, 2014 at 8:39 am
Q: “Numbers Matching”
How do you know if you have a numbers matching car.
A: People still call cars “numbers matching” if all of the Part Numbers and Casting Codes are correct and pre-date the car by the correct 1-3 months (in general).
A:
Use the following web pages on the First Generation Firebird web site as a guide:
1967: https://FirstGenFirebird.org/1967-info/1967-technical-information/1967-drivetrain-id-number-information/
1968: https://FirstGenFirebird.org/1968-info/1968-technical-information/1968-drivetrain-id-number-information/
1969: https://FirstGenFirebird.org/1969-info/1969-technical-information/1969-drivetrain-id-number-information/
Any proposed updates, changes, pictures, and/or corrections, please use our comment section below (may need to click on permalink to access comments feature). Information is subject to change and offered as is without any warranties or guarantees. Please review our Term's Of Use for more information.
Content last modified: January 15, 2014 at 12:21 am
Content last modified: September 15, 2023 at 11:15 am