TH-400 Tag decoding

[Petter T.]

Hi all, I just became a member of NCRS and this is my first post.

I bought a 1974 Coupe L-82 / TH-400 a month ago, and have already started a light restoration. I find the history of the car as interesting as the restoration it self, so I'm currently trying to determine whether I have a "matching #" car or not.

To start with, the car looked used and in need of tlc, but the general impression is that the car is mostly complete without after-market parts. So far I have determined that VIN and Engine Identification Number matches. The engine and transmission was pulled last week and the transmission tag was available. This is where I'm a bit puzzled - The picture shows the TH-400 Tag, and at first glance it looks fine CZ for L-82 / TH-400 combo and 74 for the Year. However the Julian date 227 is strange, because it suggests that the transmission was built August 15 1974. Now if you combine this with the fact that the car has a vin-serial number of 401339 it suggest that if the transmission is the original, the car was produced some time after August 15.

This is my first Corvette, and I may be missing something, or simply that the transmission has been replaced at some point...
Hope that someone can help enlighten me.

Best regards
Petter

2015-11-18 20.07.32.jpg

[Terry M.]

Re: TH-400 Tag decoding

Hi all, I just became a member of NCRS and this is my first post.

I bought a 1974 Coupe L-82 / TH-400 a month ago, and have already started a light restoration. I find the history of the car as interesting as the restoration it self, so I'm currently trying to determine whether I have a "matching #" car or not.

To start with, the car looked used and in need of tlc, but the general impression is that the car is mostly complete without after-market parts. So far I have determined that VIN and Engine Identification Number matches. The engine and transmission was pulled last week and the transmission tag was available. This is where I'm a bit puzzled - The picture shows the TH-400 Tag, and at first glance it looks fine CZ for L-82 / TH-400 combo and 74 for the Year. However the Julian date 227 is strange, because it suggests that the transmission was built August 15 1974. Now if you combine this with the fact that the car has a vin-serial number of 401339 it suggest that if the transmission is the original, the car was produced some time after August 15.

This is my first Corvette, and I may be missing something, or simply that the transmission has been replaced at some point...
Hope that someone can help enlighten me.

Best regards
Petter

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The Julian date of 227 is two hundred and twenty seven days from the start of 1974 TH400 production. When was the start of TH400 production? Excellent question, but my guess would be some time in July of 1973 if 1974 Corvette production began in August of 1973 as was true in most years.

[Petter T.]

Re: TH-400 Tag decoding

The Julian date of 227 is two hundred and twenty seven days from the start of 1974 TH400 production. When was the start of TH400 production? Excellent question, but my guess would be some time in July of 1973 if 1974 Corvette production began in August of 1973 as was true in most years.

Hi Terry.
227 days from the start of production - and the start of production is unknown...
It makes sense if I combine your information with the casting date on the engine block that says H 73 (August 73).
If I understand correctly, determining a matching # corvette requires in depth knowledge and interpretation.

But in my case I guess, that given the history of the car and the state of the car (my subjective view), the transmission is correct for the vehicle.

Br
Petter

[Terry M.]

Re: TH-400 Tag decoding

Hi Terry.
227 days from the start of production - and the start of production is unknown...
It makes sense if I combine your information with the casting date on the engine block that says H 73 (August 73).
If I understand correctly, determining a matching # corvette requires in depth knowledge and interpretation.

But in my case I guess, that given the history of the car and the state of the car (my subjective view), the transmission is correct for the vehicle.

Br
Petter

Peter

In the earlier C3 years the VIN derivative of the car was stamped on the automatic transmissions on the driver's side near the transmission gear selector lever, right above the transmission pan. This would have been the same number that is stamped on the engine block pad. Check for that as verification of the originality of your transmission.

[Petter T.]

Re: TH-400 Tag decoding

Peter

In the earlier C3 years the VIN derivative of the car was stamped on the automatic transmissions on the driver's side near the transmission gear selector lever, right above the transmission pan. This would have been the same number that is stamped on the engine block pad. Check for that as verification of the originality of your transmission.

Thanks Terry for your help - Rushed of to the garage and found the missing piece of information. The stamped number is derived from the VIN. This confirms that the car is fairly untouched and complete.

Br
Petter

2015-11-21 08.41.37.jpg

[Terry M.]

Re: TH-400 Tag decoding

Thanks Terry for your help - Rushed of to the garage and found the missing piece of information. The stamped number is derived from the VIN. This confirms that the car is fairly untouched and complete.

Br
Petter

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Congratulations