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I've been reading this thread about the different transmissions, different manufacturers, etc. My, (what I'm assuming is the build sheet), says M20 but in box 5 & 27 the broadcast code is UH. Can anyone tell me what that code means? I will introduce myself once I have possession of the car!
Can you scan and post an image of the document? The box 5 and 27 are the transmission boxes so I'm curious what you're looking at. And of course, we are assuming you're looking at a 1978 document.
Are you trying to find out what tranny is actually in your car ?
Yes Sir. Well curious anyway.
Originally Posted by hunt4cleanair
Can you scan and post an image of the document? The box 5 and 27 are the transmission boxes so I'm curious what you're looking at. And of course, we are assuming you're looking at a 1978 document.
Yes those boxes say 'Tran'. I saw your post stating the box would read, in the fella's particular circumstances, SR. I looked at the build sheet for mine and they read UH. What is left of the sheet! Here is a copy...
It is the sheet for the car as everything matches what the car has.
Yes those boxes say 'Tran'. I saw your post stating the box would read, in the fella's particular circumstances, SR. S6. I looked at the build sheet for mine and they read UH. What is left of the sheet! Here is a copy...
It is the sheet for the car as everything matches what the car has.
Had to think through this but in 79, the Saginaw was eventually replaced by the Borg Warner M20 and I suspect if you looked at the tranny, its aluminum. The UH would be the code for a 79 L48 M20, of which there were two. You estimated build date shows February 7th so I suspect you'll find the B/W four-speed.
You could count the number of bolts on the side cover and that would further confirm which four-speed is equipped in your 79. You could also check the assembly code but those are difficult to see and/or photograph. I forget now when that article was published (above link) but I may not have had the 79 broadcast codes. The table shows the 78 codes.
Your buildsheet is in great shape, Can you scan and send me the entire buildsheet. Send to hunt4cleanair@earthlink.net and much appreciated.
Last edited by hunt4cleanair; 12-27-2018 at 08:50 AM.
Just as the engine has a code on the build sheet or what ever , so does the transmission . It allowed the line worker to visually find the transmission , reach and grab it fast from the block onthe build sheet.. Alot of times those transmissions had that build sheet code inked stamped on the housing in huge letters Like 2-3 inches height .. Allowed for,fast picking and easily identified two letter codes . They did not have to think much . Goal was easy , fast and accurate line work.
Totally understand. I spent 17 years with the company I still work for in our OEM automotive business unit and have spend more time at assembly plants than I care to remember. It's a wonder I still love cars!
Originally Posted by hunt4cleanair
Had to think through this but in 79, the Saginaw was eventually replaced by the Borg Warner M20 and I suspect if you looked at the tranny, its aluminum. The UH would be the code for a 79 L48 M20, of which there were two. You estimated build date shows February 7th so I suspect you'll find the B/W four-speed.
You could count the number of bolts on the side cover and that would further confirm which four-speed is equipped in your 79. You could also check the assembly code but those are difficult to see and/or photograph. I forget now when that article was published (above link) but I may not have had the 79 broadcast codes. The table shows the 78 codes.
Your buildsheet is in great shape, Can you scan and send me the entire buildsheet. Send to hunt4cleanair@earthlink.net and much appreciated.
I spoke with the fella that has the car. He said it is an aluminum case. Mystery solved, thank you.
The guy laminated a copy of the build sheet for me. He was able to lighten it up on the printer so it is more legible. As soon as I get the car and paper work I'll certainly email you a picture of it. Are you like a curator of all things Corvette?
The three speed manual was an opel unit if I remember correctly and that was a rail shifted unit. Its been a long time, my first car was a vega 3spd manual.
The 71 - 72 Vegas used the Opel manual boxes for both the 3 and 4 speeds.
GM switched to the Saginaw boxes in 73 as the Opel boxes were weak and would grenade quite easily.
I got real good at swapping Opels for Saginaws back then as I trashed many an Opel box....
Had to think through this but in 79, the Saginaw was eventually replaced by the Borg Warner M20 and I suspect if you looked at the tranny, its aluminum. The UH would be the code for a 79 L48 M20, of which there were two. You estimated build date shows February 7th so I suspect you'll find the B/W four-speed.
You could count the number of bolts on the side cover and that would further confirm which four-speed is equipped in your 79. You could also check the assembly code but those are difficult to see and/or photograph. I forget now when that article was published (above link) but I may not have had the 79 broadcast codes. The table shows the 78 codes.
Your buildsheet is in great shape, Can you scan and send me the entire buildsheet. Send to hunt4cleanair@earthlink.net and much appreciated.
I replied yesterday but I got a notice saying once a moderator approved the message it would be posted, odd.
Anyway the casing is aluminum so a Borge-Warner it is.
As soon as I get the car and paperwork I'll certainly send you a copy. Are you like a curator of Corvette information?
I replied yesterday but I got a notice saying once a moderator approved the message it would be posted, odd.
Anyway the casing is aluminum so a Borge-Warner it is.
As soon as I get the car and paperwork I'll certainly send you a copy. Are you like a curator of Corvette information?
That would be too generous of a description but a nice compliment. Over the years, owners have shared their buildsheets with me which has allowed me to interpret and give meaning to the many codes by production year. Thus, I'm able to help owners, such as yourself, understand what options and configurations are installed on a given Corvette. I publish the Corvette Buildsheet Book that helps owners understand the link between their build records (buildsheet) and installed equipment via the broadcast codes printed on the sheet. It specifically targets 1973-82 Corvettes.
As an example, recently, we used buildsheet information to tease out, understand and confirm the installation of fan clutches on 1974 Corvettes for the 1973-74 NCRS Judging Manual revision. We looked at codes on the owner's buildsheet versus what was installed on the car to better understand how cars were equipped.
We spoke on the phone years ago. I just read this thread and I have a hunch about the 1979 L48+M20 and L82+M20 codes. I'm basing this hunch on your work and the Corvette Parts and Illustration Catalog (effective December 1983).
It is posted above that a 1979 L48 Corvette with 'UH' on the build sheet (box 27) indicates the L48 has the M20 4-speed manual. The P&I Catalog confirms (front engine section, page 15). Further, the 1979 M21 identification code is 'UK'.
The P&I Catalog indicates only the UH identification code for the 1979 M20 and in parentheses indicates "(Warner)".
Question #1: Upon review of your collection of 1979 build sheets, will 'UH' be used on both 1979 M20 transmissions, the early Muncie/Saginaw and the Borg Warner which replaced the Muncie early in 1979 production? (The P&I Catalog seems to indicate this, as it does not list another M20 identification code.)
Now, to continue, the build sheet in the above post indicates an engine stamping of ZAF (box 26). That translates to an L48 with manual. Ok, good.
The ZAF stamping is not indicated in the P&I Catalog, but we know that ZAF was used after the start of 1979 production. The early production stamping code for the L48 with manual was ZAA.
Question #2: Again using your 1979 build sheets, is it possible that early 1979 M20 manuals with the Muncie had engine blocks stamped ZAA and then when the M20 manual changed over to Borg Warner, is it possible that the blocks were stamped ZAF?
I understand that Flint engine would not know which transmission was matched at the factory, but perhaps there was communication from St Louis to Flint or through some other type of communication channel (HQ, Warren, etc) and, once the Muncie had run out of stock, word was passed on to Flint to begin the use of ZAF for the BW M20.
These became much more interesting questions after I delved back into my archives of buildsheets but answers came up short...see below!
Originally Posted by GoGo87U
Question #1: Upon review of your collection of 1979 build sheets, will 'UH' be used on both 1979 M20 transmissions, the early Muncie/Saginaw and the Borg Warner which replaced the Muncie early in 1979 production? (The P&I Catalog seems to indicate this, as it does not list another M20 identification code.)
Great question...and I don't have an answer. I only have three 79 buildsheets, two of which are L82 M21...no L48s. So have no insights whatsoever. However, I suspect, just as GM did in 78, each will carry a unique broadcast code/RPO as a different part number. I figured out the Saginaw broadcast code when I saw the yellow S6 stamped on the cast iron case.
Question #2: Again using your 1979 build sheets, is it possible that early 1979 M20 manuals with the Muncie had engine blocks stamped ZAA and then when the M20 manual changed over to Borg Warner, is it possible that the blocks were stamped ZAF?
Buildsheets would not cough up any insights into this question. You're assuming transmission was driving the engine configuration and we do not have enough information to conclude that.
Now having said that, we could speculate and assume that transmission gearing changed from one transmission to the other and that change affected emission control monitoring, thus requiring a different carb/block configuration and engine suffix block stamp. See how complicated federal law gets with a rather minor change?
I understand that Flint engine would not know which transmission was matched at the factory, but perhaps there was communication from St Louis to Flint or through some other type of communication channel (HQ, Warren, etc) and, once the Muncie had run out of stock, word was passed on to Flint to begin the use of ZAF for the BW M20.
These changes would have been engineering changes with production changes to follow.
Muncies were long gone by 1979. They stopped producing them in 1974.
M-20, M-21, M-22 are Regular Production Codes (RPO) that only tell you "wide ratio, close ratio or HD close ratio. It does not indicate it was Muncie.
Example - A '69 Camaro with a 307 base V8 would have an RPO M-20 wide ratio specified and a Saginaw wide ratio transmission would be installed. The same car optioned with the more powerful 396 engine and an RPO M-20 transmission would come with a Muncie.wide ratio installed. Same M20 RPO code but different assembly line broadcast code and different transmission. If the application did not need the stronger, more expensive Muncie transmission to satisfy the requirement, they did not install it.
Muncies were long gone by 1979. They stopped producing them in 1974.
M-20, M-21, M-22 are Regular Production Codes (RPO) that only tell you "wide ratio, close ratio or HD close ratio. It does not indicate it was Muncie.
Example - A '69 Camaro with a 307 base V8 would have an RPO M-20 wide ratio specified and a Saginaw wide ratio transmission would be installed. The same car optioned with the more powerful 396 engine and an RPO M-20 transmission would come with a Muncie.wide ratio installed. Same M20 RPO code but different assembly line broadcast code and different transmission. If the application did not need the stronger, more expensive Muncie transmission to satisfy the requirement, they did not install it.
I think everyone should read your work on the 1978-79 transmissions, as those few pages and photos clear up so much about the subject, especially the Muncie/Saginaw M20 of 1978-79. This is the link:
I have this nagging idea that the specific combination (L82 + M20) was never made in 1978-79 except if it had the RPO G95 Highway Gear (3.36 ratio).
I know this idea sounds absurd, but I'm throwin' it out there because I've never seen that combination on a 1978-79 L82.
Lots of L82 M20s and I have several with the 3.70 rear axle. It appears that 3.55 was the base axle. I have only one illustration of the G95 3.36 highway gear. Why is that significant?
Below is the information from the 78 owners manual on this topic. The L-82's only came with a Borg Warner Super T-10, either close ratio (2.43 first gear) or wide ratio (2.64 first gear)...no other 4 speed transmissions in 78/79 for the L-82. If you had an L-82, you had a BW tranny. MOST L-82's that I have every seen have had the close ratio 2.43 BW AND 3.70 gears. The wide ratio 2.64 BW tranny is very rare coupled especially with the 3.36 rear gears.......very few were made and fewer probably exist today. I have never come across an L-82 with the wide ratio 2.64 BW and 3.36 gears.
If you had/have an L-48, you DO NOT or should not have a BW transmission with that engine since only the L-82's were slated for this transmission. The L-48's in 78/79 all were suppose to have a saginaw wide ratio 4 speed with 3.36 gears....no other options.
If you had/have an L-48, you DO NOT or should not have a BW transmission with that engine since only the L-82's were slated for this transmission. The L-48's in 78/79 all were suppose to have a saginaw wide ratio 4 speed with 3.36 gears....no other options.
And L48's weren't supposed to have 4 bolt mains either but do. I guess some of us are just lucky
And L48's weren't supposed to have 4 bolt mains either but do. I guess some of us are just lucky
Yes, that is true but 4 bolt L-48's and L-48's with a BW tranny is going to VERY RARE. When i rebuilt my 78 L-82 close ratio BW 4 speed with 3.70 gears in 2014, I must admit that I was mildly concerned that it may not be a 4 bolt main BUT IT WAS, thank the Lord.
No significance, it’s just that I had never seen a 1978 L82+M20+GS4.
For 1978, I’ve only seen L82+M21+GS4.
In 1978, there were only 382 units built of L82+M20+GV4 (that’s the G95) so they are going to be super rare. (Post #42 above is an L48+M20+GV4, which is not the G95)
TRANSMISSION CODES
I also had been reviewing the Corvette Parts and Illustration Catalog (see attached photo above):
M38 will be coded 5WB or 5TL
L48 with M38+GU4 = coded either 5WB or 5TL, not sure which
L82 with M38+GV7 = coded either 5WB or 5TL, not sure which
M21 will be coded ZW
L82 with M21+GS4 = ZW code
M20 will be coded ZU or S6
L48 with M20+GV4 = S6 code (determined from your paper)
L82 with M20+ ?? = ZU code (determined from your paper)
Would the ZU include both the GV4 application and the GS4 application?
Perhaps the answer is found within the M38 transmission codes. It seems that the L48 would have one code and the L82 would have the other, meaning that the L48 has one transmission code whether it has the GU4 or the GV7 (CA & Hi-Altitude).
What bracket for a Hurst competition Plus with the Saginaw
I have a Hurst competition Plus 391 - 7992.. and Jegs told me the bracket I need is part number 117 - 4208.. can anybody confirm this before I spend the money?
What bracket for a Hurst competition Plus with the Saginaw
I have a Hurst competition Plus 391 - 7992.. and Jegs told me the bracket I need is part number 117 - 4208.. can anybody confirm this before I spend the money?
12-27-2018, 04:08 AM
