12 bolt ID

m_kulsziski
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12 bolt ID

Postby m_kulsziski » Thu Jul 06, 2006 9:14 pm

I just purchased a 71 chevelle with a 12 bolt rear. Where can I find the numbers to ID the rear and what they mean

:D

mr.smartboard

Re:12 Bolt ID

Postby mr.smartboard » Fri Jul 07, 2006 12:32 am

Hi, Welcome to JD Race and Restoration m_kulsziski!!! :)

Soon we will have an id chart posted on the site. I will talk with Jim (the owner) about how soon and I will have him answer you asap.

Thanks again. Enjoy the site ;)
Cheers:)

monzaz

Id the 12 bolt

Postby monzaz » Fri Jul 07, 2006 12:58 am

Ok, Glad you can join us.

first the most important numbers are stamped into the passenger side axle tube, parrellel with the ground facing front of the car - between the spring perch and the housing center section.

The code will start with 2 to 3 letters then followed by 4 numbers and then another letter.

example CW 0409 B

CODES OUT TO : CW - 3.31 ratio, 04 - MONTH APRIL, 09 - Day 9TH Day, B - Assembly plant Buffalo

Under these number there maybe another letter too. this would tell you if the rear was an original posi car and what posi was installed

E- Eaton posi
D- Dana posi
W- Warner posi

On to the date code... In the webbing of the center section casting you will find casting numbers and date codes.

Date code example is D209 decodes to april (D), 20th day (20), 1969 (9)

Casting number example is 3894939 (NF) could have the letters N or NF for nodgular forged after the numbers too.

If you get me your numbers I will run them for you. Hope to have some numbers up soon for everyone.

Just remember the only true way to tell what you have in the rear is removing the cover and physically inspecting it. Ok? Take care and hope to hear from you soon. Jim

m_kulsziski
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Postby m_kulsziski » Sat Jul 08, 2006 9:36 pm

I just purchased A 71 chevelle and am told that the car is all original drive train. I have pulled some numbers off the motor and rear.
vin 136371r117117

on front pass motor block pad I found t0916ckh7 and 117r411869

on the rear
driverside front embossed 3969278nf
driverside rear web con2
passenger side front kdc 2571 and gm51 on the web
passenger side rear h280 and 12345

Whit out pulling the motor are there other numbers I can get to. Also on the tranny wehre can I find them.

last is there a web site that I can use to determine what is really what

Thanks very much for any help or direction.
Mikek

monzaz

Id numbers for the Chevelle

Postby monzaz » Sun Jul 09, 2006 8:34 pm

13637 in the vin is for 2 door Sport Coupe Malibu 8 cyl.

next is the 1 which is the year 1971

next the R it is the plant where it was built (ARLINGTON, TX)

117117 IS PLAIN AND SIMPLE... 17117th car off the line The number for malubu/chelle starts with 100001. Ok.

On to the motor- T0916CKH7

First the 'T' this is the ASSEMBLY plant the motor was built (TONAWANDA, NY)
Next two numbers are the month it was built (09 - september)
Next two numbers are the day it was built (16th of september)
Next letter is the motor division (C - chevrolet passenger car)
last two letters are the suffix code for the car it was used in. ( KH - is a 307 powerglide transed 130 horsepower motor ) 1972 motor.

Might want to double check those letter suffixs to be sure that is what it is. Jim

Ok on to the rear-
will start with the easy stuff first.
H280 is casting of the housing -- 'H' being month of August '28' being 28th day of August and 0 meaning the year 1970.
12345 are simple test digits and mean nothing more. Youll probably find 67890 some where else too.
KDC 2571 ok this is what the ratio is and the date the housing was assembled 'KD' is the ratio - this rear has /had 2.73:1 ratio , freeway gears we consider that. 'C' IS THE BUFFALO PLANT and the 257 is the day of the year 257th day out of 365 and the 1 is the first shift You did not find any othe letters so we can assume NO posi (D, E or W)

You stated it was a 12 bolt correct? So I assume the cover has 12 bolts on it? Cause the Casting Id Number seems to point to a 10 bolt rear...??? 396927nf. Correct?

Casting on rear housing can be unreliable and best to phyically check the rear out. Like if you see 12 bolts on a Chevy rear (c-clip retained axles) it is a 12 bolt ring gear on the inside carrier. Same with the chevy 10 bolt cover ...it will have a 10 bolt carrier also.

Gm51 some other coding and con2 more unworthing coding to the factory needs. Like foundries etc.

You can buy a book at any book store called Chevrolet by the numbers

Robert Bentley Publishers by Alan l. Colvin they have about 3 different books 1970-1975 1965-1969 and I think 1960-1965 check them out. Jim

m_kulsziski
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Thaks for the info

Postby m_kulsziski » Mon Jul 17, 2006 6:27 pm

I appreciate the insight into the numbers on the car. I have double checked the engine code and the only thing that might be different is the 16 which might be 15.

Any way is there a way to tell if this is actually a 307 (another place for the codes) and also is this the original motor

monzaz

engine numbers

Postby monzaz » Tue Jul 18, 2006 12:41 am

Ok well the casting would be its own on the driver side engine to transmission bell housing area.

It would be a 7 digit number like this 3970020

A 350 WOULD BE 3970010 A VERY POPULAR CASTING NUMBER


i WOULD SAY IT VERY WELL COULD BE THE ORIGINAL BLOCK... Malibus did come with 307 in 1969 1970 71 72 and 1973 too. I doubt if the seller could tell whether it was a 307 350 or 327 for that matter. All small block chevy motor look identical. Very small tell tail signs are present but only someone very familiar with them could tell. Heads are all interchangable balancer are too. except for the 400 small block externally balanced.

So if you have a mirror you should not have any trouble checking th ecasting number which will give you your answer. Ok? Jim

m_kulsziski
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Postby m_kulsziski » Wed Jul 19, 2006 7:55 pm

Ok
So the casting number off the drivers side rear of the motor is 3970010 which I guess mean 350. But the stamp say t0916ckh. The trany is a th350

Is there any other info that I can get with out taking the engine apart that would tell

monzaz

engine casting

Postby monzaz » Thu Jul 20, 2006 11:44 am

Well if the casting is what you say it is ...It should be a 350. Maybe the stamping is wrong could it be a ckd? That is a 350 engine with a 350 TH trans combo... Alot of stuff from back then and all the time and people tinkering around really is tuff to get all the info straight. I would say the casting is correct if it is that number. the stamps on the pad are put in manually and could be wrong. That is my opition on the deal. the serial number of the car last 5-6 digits should also be on the stamoed pad for number matching car...transmission also. Check that out too.

If someone decked the block they could have restamped it too. Alot of bad people that are sneeky out there too. Not saying that this happened ...just heard people doing it. Muscle cars are big money so that pushes people to do some things not so honest. Jim

m_kulsziski
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more on the rear

Postby m_kulsziski » Wed Jul 26, 2006 8:25 pm

:?:
OK
SO it is a 12 bolt. The Casting code is what I have presented.

I would like to put a posi unit in the car. The gearing currently has some to be desired off the line but is great for highway. I would liek to get to 3.31 or maybe as far as 3.73. not sure
Can you give me you opinion on those gears.
ALso how do I tell what posi unit (Carrier) I need to get. You show a number of different ones both new and used. I am on tight budget
What do you recommend?

Thanks again for all the help up to this point.
Sharing the knowledge is a wonderful thing :lol:

monzaz

12 bolt stuff

Postby monzaz » Wed Jul 26, 2006 9:55 pm

Ok Mike, Well that is great. 3.31 is a GM only gear ratio and there are NO aftermarket 3.31 ratios reproduced for the 12 bolt chevy. I do have 3.42, 3.55, 3.73.

You need to figure out your own driving needs. How much freeway where you cruise at what you do with the car...Drag race, burn outs, just cruise, long trips short trips etc. I think either the 3.55 or the 3.42 are good choices for cruising and power. 3.73 might be a little on the high cruising RPM side. depending on the diameter of your tires. More rpm comes more engine noise can you handle that or do you want to handle that...????

Posis Again if your just gonna cruise a rebuild unit will be fine. But if you like to hammer it alittle or alot a new unit is always the way to go.

Definete needs: your going to use some sort of mid 3 series gear , So you will NEED a 3 SERIES POSI CARRIER. Or a 2 series posi carrier with a spacer will work nicely too.

3.42 3.55 3.73 gear ratio needs to be picked 3.42- 165.00, 3.55 - 179.00, 3.73 - 169.00. Used 3.31 gears 165.00 excellent used SS gears.

Are you going to do it with all new bearings??? I think this is the time , spending all that money and then using 30 year old bearing just sounds like a bad idea. 79.00 for new bearing and everything to set up a rear all in one kit. marking compound new ring gear bolts crush sleeve gasket seal pinion nut and washer bearings all new. 12 bolt chevy.

Please take your time and or if you have more questions , keep asking or you can call me too. I will give you my number if you need. I want you to feel comfortable about your choice. This way you'll be happy in your decision and feel your money was well spent. Ok? Jim

m_kulsziski
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Postby m_kulsziski » Fri Jul 28, 2006 7:33 am

:D

OK
So I am into most times cruising around town. There is or should not be a ton of highway. I do like to jump on it a little, but I am putting this together more for my wife to drive. SO I am guessing 3.55 sounds like the right gear.
do I need to worry about which Eaton posi, Dana posi, Warner posi we are working with.
And yes I will be putting all new bearing in, but guess that a used carrier is ok.
Are the carriers you have typically rebuilt or they can be. how does this compare to new.
Just trying to understand what I need, and what is the best bang for the Dollar. I am usually the guy who buys A and finds he need B C and D to complete the job.
I really appreciate the help. :P

monzaz

12 bolt questions

Postby monzaz » Wed Nov 22, 2006 1:54 am

WOW very sorry been gone for a while. Just got high speed broad band and am ready to work on this site guys.

Ok all my reconditioned rebuilt and or new are top quality. I know how it was when i was young and got ripped of many times...Hated that feeling BIG TIME . Will not do it I stand behind my products if it is my fault or htere fault. We will work out a 'happy place' for everyone involved. lol. Really.

Ok now on with the question

Best bang for the dollar is ALWAYS a new posi unit hands down. I make the least amount of money on them. PLus they usually come with a factory guarentee. If you are installing a new unit and gears Bearing should be a must too. Old will work but if just one of those bearing surfaces is nick or worn... it could cuase a whirl hum any kind of noise after the install of the new gears. Think about it they are probably 30 years + old... That would be like a 100,000 mile motor and you put new bearings and rings in and did nothing else??? It will work BUT for how long . Best to buckle down now and have a well built rear you will not need to go into for hopefully another 30 years. Jim

bparke11
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Re: 12 bolt ID

Postby bparke11 » Tue Feb 25, 2014 3:00 pm

Hi guys, new to the forum. Got a tip from a friend that this site knows rears. I also have a 12 bolt that I've had trouble identifying. It has serial #3917124N and code "LJ1116K" stamped on the tube. Can't seem to find the date code casting?? According to one source online the serial # indicates a late 67-69 Chevelle and another source says the "LJ" means 70 Pontiac with 2.56:1 ratio. Since this info is conflicting, I was hoping you had some knowledge or a source for more info. I haven't opened the cover yet but plan on putting it under a 71 Buick Skylark eventually, hoping it will fit. Thanks,

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monzaz
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Re: 12 bolt ID

Postby monzaz » Fri Feb 28, 2014 7:06 am

h=oK WELL IT SI A 68 OR 69 tHAT WILL BE HARD TO FIND IN THE CASTING AS 8 AND 9 ARE HARD TO MAKE OUT. iT CAN BE AT THE BOTTOM OF THE CASTING UNDER THE COVER BACK SIDE OF THE CASTING COVER LIP FACING THE FRONT OF THE CAR. CHECK THERE.
LJ IS THE CODE FOR THE RATIO WHICH I THINK IS 3.31 OPEN IT WILL HAVE A PONTIAC GRAND PRIX SO THAT WOULD MAKE IT A 1969, YOKE 1 1/8 CUP U-JOINT CUP AND WILL HAVE U BOLTS TO HOLD IN THE -JOINT.... SO IT WILL FIT ALL bop WITH OUT ANY MODS TO ANYTHING FROM 67-72 A- BODY

PROBABLY WAS A CANADIAN BUILT CAR AS THEY USED 12 BOLT CHEVY REARS AS STANDARD EQUIPMENT STOCK REARS IN THE BUICK OLDS AND PONTIAC CARS BUILT IN CANADA.
J D Race


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