Part 3 - By the Numbers

After reading and researching my 1978 Trans Am on the internet and also in parts and service manuals, I decided that I was not sure if my car is a special edition Trans Am or a regular one. The paint job, the gold trim, and the pin stripes all indicate a special edition car, but special edition cars sell for much more than what I paid. I found out that there is a company in Michigan that has access to historical Pontiac records. The company is called Pontiac Historical Services (PHS). I sent them my Vehicle Identification Number (VIN) and they sent me the original dealer order form for this car. My car is not a special edition, but it does have a rare (WS6) Trans Am Special Performance Package (which is really cool), maybe I got a good deal on this car after all.

The VIN from my dashboard

My VIN Number 2W87K8L189064

VIN Interpretation: 

2 = Pontiac

W = Trans Am

87 = 2 door sport coupe

K = V8 403 6.6L 185HP 320 lb*ft Torque (L80 RPO Code)

8 = 1978   

L = Los Angeles/Van Nuys CA Assembly Plant

8-13 = Production Sequence Number 189064

PHS Services Original Dealer Order Form for my car

My PHS Documentation is shown above. The base model 1978 Firebird Trans Am cost $5889.00 plus options.  All my options are shown on the right side of the dealer order form. The suggested retail price of my car was $8838.00. The car was built in the Van Nuys Assembly Plant in Van Nuys, CA. on July 7, 1978.  The car was delivered to J.C. Fortune Pontiac in Santa Ana, CA (Just northeast of Huntington Beach) on July 22, 1978.

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UPDATE MARCH 30, 2013:

PHS Window Sticker Reproduction

My PHS services reproduction window sticker arrived today. This would be the sticker in the passenger side window of a new car. It shows the options and pricing of the vehicle.

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My engine block VIN code marking

Upon additional reading and research I discovered that cars with "Matching Numbers" are hard to come by and are worth more. Matching numbers means that all the original parts are still there because they have a portion of the VIN number stamped on them (Engine, Transmission, Firewall, and Dash) and/or the other parts on the car have the correct part number marked on them for your car's options. I decided to try to determine if my car has matching numbers. I found my VIN marking on my Oldsmobile 403 cubic engine (6.6L) engine block (shown above) right where the service manual said it was supposed to be. Just below the left front cylinder head on the block.

VIN portion on Engine Block: 28L189064

2 = Pontiac

8 = 1978

L = Van Nuys Ca.

189064 Production Sequence Number

My transmission case VIN code marking

Finding the VIN portion on the Turbo-Hydramatic 350 Three Speed Automatic Transmission was more of a challenge.  The service manual said it would be in one of two other locations (it was not), I accidentally found the VIN on the rear of the transmission case on the right side at the tail shaft extension housing mating surface.

VIN portion on the transmission: 28L189064

2 = Pontiac

8 = 1978

L = Van Nuys Ca.

189064 Production Sequence Number

My G80 Safe-T-Track "Posi-traction" Rear Differential

The Rear Axle is a 10 bolt axle with a 8.5" ring gear and the G80 Limited Slip option. Pontiac called the limited Slip option "Safe-T-Track". Another name for this option is posi-traction (clutch type).

The axle tube marking for my car

Decoding the axle code stamped on the front of the right axle tube gave me some bad news and some great news. 

The bad news is that this axle is from a 1976 Trans Am and mine is a 1978 (They were identical axles). Earlier I stated that this car had been in an accident on the left side of the car, the axle must have been also damaged and replaced. I did notice a bent left rear sway bar link when I first hoisted the car. I have straightened it since then.

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UPDATE MARCH 30, 2013:

Today my oldest son and I worked on the Trans Am removing all the brake parts and components in preparation for cleaning, painting, inspection, and replacement. While we were doing that I showed my son the axle marking (shown above) and told him of my disappointment with the axle being a 1976 model rather than the original axle. 

A better view of the axle tube marking for my car

My son took a look at the axle marking with his younger eyes and said "I think it is an 8 not a 6" He shined his flashlight on a better angle and I took a few more photos, HE WAS RIGHT! is is a 1978 Axle!, the original Axle with 3.23:1 gears (Part of the WS6 performance Package?)! See the photo above. 

It is great that this axle has 3.23:1 gears. This gives great acceleration and decent fuel economy in one gear ratio. My previous Trans Am had 2.41:1 gears which was good for fuel economy, but not for acceleration. I do not know yet if the speedometer drive and driven gear have been changed to compensate for the 3.23:1 axle gears. I also do not yet know what axle ratio my car originally came with. I am hoping to find a "Build Sheet" above the fuel tank on in one of the seat's frames.

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Rear axle code: 2 PX G81871 

2 = Pontiac

PX = 3.23 (RPO Code GU5) Limited Slip

G = Chevrolet Gear and Axle (Chevrolet Camaros and Pontiac Firebirds were made in the same assembly plant and used the same axles)

8 = 1978

187 = 187 Julian date (day of year built) July 6, 1978 (The day before my car left the Assembly plant)

1 = first shift

Additional Information:

Limited Slip (G80 RPO Code)

8.5" Ring Gear

42:13 gear teeth 

My Carburetor identification numbers

The carburetor is in great shape and is the exact part number for a California Emissions Oldsmobile 403 engine in a 1978 Trans Am.

An aftermarket EGR valve was on my engine

Someone had installed an aftermarket Exhaust Gas Recirculation (EGR) valve on the Olds 403. Luckily I found an online catalog of ACDelco (GM Replacement Parts) at ACDelco.com, found the correct part number for the factory EGR valve and actually found one on Amazon.com There is a guy selling ACDelco EGR valves on E-Bay, but his part number if for high altitude Oldsmobile 403s only, but his description does not tell you that (I almost bought the wrong one from him).

The correct factory EGR valve for my Olds 403 with California Emissions. There is another part number for high altitude emissions.

These EGR valves cannot be tested in the traditional manner of simply applying vacuum to the port and expecting the valve to open. These are back-pressure EGR valves; it requires a small amount of exhaust back-pressure to build and close a small port in the valve, and then the valve will open with vacuum applied. These valves were often mis-diagnosed as bad valves because of this odd operating feature. It was no surprise to see an aftermarket EGR on my engine.

Everyone who took off the factory single exhaust (specifically the crossover pipe) and "dueled out" the exhaust caused the exhaust back-pressure to decrease which prevented this EGR valve from working properly. The result was engine detonation and the only way to fix it was to buy higher octane fuel, or retard the ignition timing (and power), or put the factory exhaust system back on.

I am still researching other parts numbers, but it looks like my car has matching numbers on everything so far! After 35 years I find that amazing.