My 6 year quest for a CX coded THM400 just ended
 

Hi everyone,

Recently, I posted a topic here about the special Turbo400
transmissions used in the 396/375hp cars, COPO and other
super cars, etc.. These were CX coded. Over the weekend,
my 6 year quest for one of these babies ended successfully.
https://www.yenko.net/ubbthreads/imag...ns/naughty.gif https://www.yenko.net/ubbthreads/imag...ns/naughty.gif https://www.yenko.net/ubbthreads/imag...ns/naughty.gif

My original CX went bye-bye a long time ago (before I owned
the car). I had been looking for another one it seems forever. https://www.yenko.net/ubbthreads/imag...lins/dunno.gif https://www.yenko.net/ubbthreads/imag...lins/crazy.gif

A few weeks ago, there was an eBay auction for a complete,
untouched L/78 engine out of a 69 Nova. The seller also
mentioned it came with an M40 transmission. Seems it was
removed in 1974 due to the gas crisis - remember that?

So, I contacted the seller to get all the particulars. You
know, casting numbers, dates, and the code on the THM400.
To my shock, I was told that the code was a CX. When I
came to ( passed-out ), I knew what I had to do. Much to
my dismay, the seller would not break the THM400 away from
the L/78 auction.

Also, after he found all of the casting number & date codes,
he did not update his auction. The auction did not meet
the reserve price set, so it ended. I contacted the seller,
and ended up buying it all. Mostly, because he still would
not split up the items.

So, I have a complete "JL" coded L/78 engine and the CX
coded THM400. All I wanted was the CX, so the L/78 will go
up for auction. The main reason for this post is that I
found a slight date issue that I would like to resolve.
This engine has a assembly code of T02??JL. The ?? denote
two numbers that cannot be read. I have looked very close.
The heads are late January dates, the exhaust manifolds are
mid February dates, the intake is an early January date and
the distributor is a late December (68) date. Also, the
water pump is an early January date as well. The odd thing
is that the 3955272 block is an H-13-8 date. Almost six
months before the assembly date of the engine.

What do you guys think about that? I have every confidence
that this engine is the "real deal". Any thoughts? Images
below:

Steve

http://www.freewebs.com/nuch_ss396/MVC-001F.JPG
http://www.freewebs.com/nuch_ss396/MVC-003F.JPG
http://www.freewebs.com/nuch_ss396/MVC-004F.JPG
http://www.freewebs.com/nuch_ss396/MVC-002F1.JPG
http://www.freewebs.com/nuch_ss396/MVC-002F2.JPG

Re: My 6 year quest for a CX coded THM400 just ended
 

I don't think the block is too early for that build date. In talking with jeff of Dated Components, 6 months is well within the timeframe - he has seen as much a 1 year gap to as little as 2 days.

Re: My 6 year quest for a CX coded THM400 just ended
 

Steve,

I resized the 1st picture for you - will do the others in a few. Nice motor. Good luck!:






http://img.photobucket.com/albums/v6.../MVC-001F1.jpg

Re: My 6 year quest for a CX coded THM400 just ended
 

Looks like your pix are coming thru now. Were'nt the first time I looked at your listing.

Re: My 6 year quest for a CX coded THM400 just ended
 

Did you happen to get the converter? https://www.yenko.net/ubbthreads/imag...ns/naughty.gif

Re: My 6 year quest for a CX coded THM400 just ended
 

I could use one of those CX M40s. Hope I get as lucky as you.
You GO https://www.yenko.net/ubbthreads/imag...ns/burnout.gif

Re: My 6 year quest for a CX coded THM400 just ended
 

Steve, from the picture that looks like the real deal. The block has been lightly decked and the month date #'s were not as deep as the others that's why you cant read them. But just at a quick glance that's the original stamp. I also have seen a few block casting and build dates stretch out that long, although they are few and far between.

Re: My 6 year quest for a CX coded THM400 just ended
 

Six months is well the within acceptable range. A wider spread is always expected for a high performance big block.
Here you have a solid lifter automatic, not many made. That four bolt block may have just sat in inventory for a long time waiting for assembly.

Re: My 6 year quest for a CX coded THM400 just ended
 

Wow. Looks like enough of the partial VIN is present to figure out the VIN of the car it came in. What cars were made at the W factory? Looks like 19W42?366.

Lynn

Re: My 6 year quest for a CX coded THM400 just ended
 

[ QUOTE ]
Wow. Looks like enough of the partial VIN is present to figure out the VIN of the car it came in. What cars were made at the W factory? Looks like 19W42?366.

Lynn

[/ QUOTE ]

Willow Run, Michigan plant = Nova!

Re: My 6 year quest for a CX coded THM400 just ended
 

I'm interested. You have a PM.

Re: My 6 year quest for a CX coded THM400 just ended
 

The vin would also be on the trans

Re: My 6 year quest for a CX coded THM400 just ended
 

[ QUOTE ]
The vin would also be on the trans

[/ QUOTE ]

Where exactly would the VIN be on the THM400?

Steve

Re: My 6 year quest for a CX coded THM400 just ended
 

[ QUOTE ]
Did you happen to get the converter? https://www.yenko.net/ubbthreads/imag...ns/naughty.gif

[/ QUOTE ]

No 6-point converter! The seller told me he used it for
another project along the way. https://www.yenko.net/ubbthreads/images/graemlins/no.gif https://www.yenko.net/ubbthreads/imag...emlins/mad.gif

I have been told that they are still available from GM. Anybody know for sure?

And, while we are on the converter subject, other than the
six mounting points ( bolts ), is there anything special
about that converter? https://www.yenko.net/ubbthreads/imag...lins/dunno.gif

Steve

Re: My 6 year quest for a CX coded THM400 just ended
 

[ QUOTE ]
I could use one of those CX M40s. Hope I get as lucky as you.
You GO https://www.yenko.net/ubbthreads/imag...ns/burnout.gif

[/ QUOTE ]

Andy,

I ran across another one last year by accident. The seller
started with a $1,000.00 price, then up to $2,000.00, then
all the way up to $4,000.00 ! I bugged-out somewhere along
the way. Too much for a transmission. https://www.yenko.net/ubbthreads/imag...emlins/eek.gif

Steve

Re: My 6 year quest for a CX coded THM400 just ended
 

[ QUOTE ]
[ QUOTE ]
The vin would also be on the trans

[/ QUOTE ]

Where exactly would the VIN be on the THM400?

Steve

[/ QUOTE ]

Look on the drivers side of the trans just above where the pan bolts on

Re: My 6 year quest for a CX coded THM400 just ended
 

Thats not where its at on that trans Charley! Try looking on the passenger side of the bellhousing and it will be there. Close to the edge near one of the mounting holes. https://www.yenko.net/ubbthreads/imag...lins/beers.gif

Re: My 6 year quest for a CX coded THM400 just end
 

Could also be along the edge of the bell housing area, near the engine casting number

Re: My 6 year quest for a CX coded THM400 just ended
 

[ QUOTE ]
Six months is well the within acceptable range. A wider spread is always expected for a high performance big block.
Here you have a solid lifter automatic, not many made. That four bolt block may have just sat in inventory for a long time waiting for assembly.

[/ QUOTE ]

Tim,

Why would you expect a solid lifter automatic coded big
block to sit around longer? Were the blocks coded ahead
of time? That would defy logic - no? Can you explain?

Steve

Re: My 6 year quest for a CX coded THM400 just ended
 

Spacing out and thinking Camaro

Re: My 6 year quest for a CX coded THM400 just ended
 

Nice find,and good looking Original CX tag as well.
I wouldn't balk fo a minute on that engine timeline,it all seems acceptable.
Even that Trans. falls into perspective.
C=Chevrolet
X=Solid Lifter engine applications
69=Model year
2160=Serial No. My records show this falls into the right time line.
395=Assembly day starting with January 1st,1968 which decodes as Friday January 30th,1969.

Just curious..Have you thought about hunting for the Nova itself these came out of? https://www.yenko.net/ubbthreads/imag...ns/naughty.gif

Re: My 6 year quest for a CX coded THM400 just ended
 

[ QUOTE ]
Nice find,and good looking Original CX tag as well.
I wouldn't balk fo a minute on that engine timeline,it all seems acceptable.
Even that Trans. falls into perspective.
C=Chevrolet
X=Solid Lifter engine applications
69=Model year
2160=Serial No. My records show this falls into the right time line.
395=Assembly day starting with January 1st,1968 which decodes as Friday January 30th,1969.

Just curious..Have you thought about hunting for the Nova itself these came out of? https://www.yenko.net/ubbthreads/imag...ns/naughty.gif

[/ QUOTE ]

Rick,

The seller told me that the car was chopped up for racing
many years ago. No idea of where to find it. You know
how these stories usually end. https://www.yenko.net/ubbthreads/images/graemlins/no.gif

One question though. Can you tell me exactly what the
2160=Serial No. pertains to? How did you determine the
time line based on the number?

Steve

Re: My 6 year quest for a CX coded THM400 just ended
 

Chevrolet kept track of some of their Transmissions for service reasons through their serial numbers.
Yours was built at the Cleveland Plant.
They produced a spiral bound catalog.
I own that catalog.

Re: My 6 year quest for a CX coded THM400 just ended
 

Steve, figure that most people didn't know that you could order the L78 with an automatic in 69 so the engine could have been assembled way before it was ever ordered for a car. It also could have been a motor that was built and failed inspection due to some component being bad so it sat around before being fixed and placed back in the "rotation".

Re: My 6 year quest for a CX coded THM400 just ended
 

[ QUOTE ]
395=Assembly day starting with January 1st,1968 which decodes as Friday January 30th,1969.

[/ QUOTE ]

1968 was a leap year (366 days) so the assembly date should be Wednesday, January 29th, 1969 unless they stuck to the 365 days in a year as the standard rule. The 30th was a Thursday as well not Friday.

Rick H.

Re: My 6 year quest for a CX coded THM400 just ended
 

You're right,I was looking at my January 1970 calender. https://www.yenko.net/ubbthreads/imag...ins/tongue.gif

Re: My 6 year quest for a CX coded THM400 just ended
 

I want to thank everyone for the verification you've given
me on the L/78 & CX THM400. https://www.yenko.net/ubbthreads/imag...ns/worship.gif

OK, now that it appears that I have a true JL coded L/78,
my attention turns to rebuilding the CX THM400. It has
been sitting for almost 30 years and I want to have a good,
qualified shop rebuild it. I would be looking for a shop
that understands what the CX is and how to build it as it
came stock. Also, I will need the 6 mount point converter
for the CX. Are they still available from GM? https://www.yenko.net/ubbthreads/imag...lins/dunno.gif

Can anyone recommend a good person or shop to rebuild the
CX THM400? As they say, you only get one chance.......

Steve

Re: My 6 year quest for a CX coded THM400 just ended
 

Tranny rebuilding isnt brain surgery. The main problem doing it yourself is the clutch pack compressing tools. If you can rebuild an engine, you can do an automatic. Turbo 400's arent so complicated that with a good manual you cant do it yourself. I was always afraid of automatics but I couldnt run on the NHRA record with my stick car so I changed to a glide and ran about 3/10's under.

Built my first trans on the ramp of my race car trailer. When that one worked I wasn't skeered any more.
Give it a try ! https://www.yenko.net/ubbthreads/imag...ns/burnout.gif

Re: My 6 year quest for a CX coded THM400 just ended
 

Engine couldn't have sat around waiting for repair, it wasn't assembled until February something of 69 by the assembly code on the pad and most of the other components bolted to it are dated in early 69. The block was cast way back in mid 68, and it could have sat around somewhere at the foundry before it was assembled in the engine plant. But once the machining and assembly process started the engine was built and shipped off to the vehicle assembly plant.

The assembly plant (the car one, not the engine one) had some limited storage capacity for batch built components, like HP engines, but not alot.