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Positraction In A '62 340HP

Old 12-05-2018, 02:36 AM
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6T2Vette
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Default Positraction In A '62 340HP

I'm curious to know if the rear end in a '62 C1 with 340HP engine and a 4sp was always a 4.11 with Positaction?
Bob
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Old 12-05-2018, 07:18 AM
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Simple answer is no. I think that the default ratio for that engine was 3.70 but various ratios could be ordered. The 4.11 would have to be specified in the order.
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Old 12-05-2018, 11:35 AM
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The standard axle ratio for '62 340/360 HP engines with the base three-speed manual trans was 3.36 with an open differential. Positraction was optional, but there were no other available axle ratios with the three-speed manual trans.

If ordered with a four-speed the standard axle was 3.70, open diff., but Positraction was an option. In addition, five other ratios were available: 3.08, 3.36, 3.55, 4.11, and 4.56, and they were only available with Positraction.

Positraction was ordered on all but about 300 '62 jobs, and 4.11/Positraction was probably the most popular axle ratio with SHP/FI engines, but I'm not aware that the axle ratio count was ever published... just the number of Positraction options.

Duke

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Old 12-05-2018, 02:31 PM
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The rear end is definitely not Positracton, but I have a slight suspicion it may be a 4.11. It's getting cleaned up now so they can read the tab attached to the diff.
A couple of years ago I bought a C1 third member with the large "P" on it. It had frozen 4.56 gears so I had it cleaned up and changed to 3.55 gears and put it in my '56 Chevy. Should I think of swapping third members? Would it retain "numbers correct" status?
Bob
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Old 12-05-2018, 09:14 PM
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Well, from what I've read, my case pictured here is for Positraction gears. I've read the large "P" indicates it is Positraction. I am posting a pic of the case, and a pic of the VIN tag on the steering column. How can this be deciphered?
I am also posting a couple of pics of some brackets that were welded onto the frame and axle housing. For traction bars?
Bob






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Old 12-05-2018, 10:43 PM
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This post caught my eye because the poster who put a pic from another board put up the pic of my 62 frame the day I pulled the body off.

here is what I see .....your car was assembled May 21, 1962, your third member cat number 812 is a posi unit and the aluminum tag on says 411 gears.. what I don't know without looking inside at the ring and assembly would be is it a real 411 posi? The other data point is the cast date is d182 which is April 18, 1962....that is good , now remove grime and rust on the opposite side and look for a stamping that will confirm Corvette and date code
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Old 12-05-2018, 11:13 PM
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Originally Posted by 6T2Vette View Post
Well, from what I've read, my case pictured here is for Positraction gears. I've read the large "P" indicates it is Positraction. I am posting a pic of the case, and a pic of the VIN tag on the steering column. How can this be deciphered?
I am also posting a couple of pics of some brackets that were welded onto the frame and axle housing. For traction bars?
Bob





Without exception, ALLLLLLLLLLLLLLLLLLL 59-62 Corvettes had factory traction bars or radius rods (above the axle housing). And ALLLLLLLLLLLLLLLL 60-62 Corvettes had a rear sway bar. Those welded-on brackets were most likely added by a previous owner for more traction.

That casting date on the rearend case is for sure a good date for a 62 Vette (D 18 2 translates to Apr 18, 1962). That tag under the nut at the 2 o:clock position indicates a 4.11 ratio. With the big P on the case, it was for sure (originally) a posi rear. If both axles do not pull together now, then very possibly the clutches are worn out causing it to pull (on one side only) like a non-posi rear.

The VIN's for 1962 were 100001 to 114531. Yours is 111521, indicating your car was the 11,521 Corvette built in 62, meaning yours was about 3,000 cars from the end of 1962 production. Thus, the Apr casting date on that rear is just right for your car (very possibly the original rear).


I have added a 1960 axle housing to my 56 as well as a 60-62 rear sway bar. Also, I have installed aftermarket (Traction Master) traction bars. You can see below what the FACTORY brackets/traction bars look like on 59-62 Vettes as well as the rear sway bar.
To install the NON FACTORY aftermarket traction bars on my 56 (below the leaf springs), longer U-bolts were required.






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Old 12-06-2018, 12:03 AM
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Great news! Thanks guys. Everything so far is jibing with what the previous owner told me. He did tell me it was a Positraction rear end, and that he thought it was a 4.11 gear ratio because of the high RPM at 60mph (which was 5mph over the speed limit when he was driving it back in the 60's).
I was disappointed when the fab guy doing the restoring underneath told me it was not Positraction, but he was basing it on only one wheel spinning forward. This car has not been run since 1978, and not moved since about '94 so it's very possible the clutch plates are messed up. Should I be considering a complete rear end overhaul, or just flush it and add fresh Posi lube?
I've instructed the fab guy to remove the brackets. What ever they were meant for, I hope I won't need them.
Bob
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Old 12-06-2018, 02:17 PM
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Originally Posted by 6T2Vette View Post
I was disappointed when the fab guy doing the restoring underneath told me it was not Positraction, but he was basing it on only one wheel spinning forward. T
Bob

You left out the important part. What was the other wheel doing while one went forward and was the car in gear or out?

Last edited by MikeM; 12-06-2018 at 02:18 PM.
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Old 12-06-2018, 03:46 PM
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Originally Posted by MikeM View Post
You left out the important part. What was the other wheel doing while one went forward and was the car in gear or out?
Good questions but I don't have an answer for both as I wasn't there. They are removing the transmission and drive shaft as we speak to clean and repaint. Haven't decided as to how to address the differential problem. I'd rather not have them take it apart, but they may have to. I'm thinking perhaps I should just give it a couple of good flushings and fill it back up with a good Posi lube and drve it a while and see how it works. Should I just pull it and have the whole rear end overhauled?
Incidentally, my fab guy is asking me what color of black he should use. Same with the engine bay?
Bob
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Old 12-06-2018, 04:10 PM
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If you're not going to be spinning the tires, I wouldn't worry too much about the posi traction whether ir worked or not or even if it was there and not working. If the clutches are worn totally worn out, it'll act just like a standard differential.

Seems like your major concern is that big P on the carrier casting?
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Old 12-06-2018, 04:17 PM
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Originally Posted by 6T2Vette View Post
Good questions but I don't have an answer for both as I wasn't there. They are removing the transmission and drive shaft as we speak to clean and repaint. Haven't decided as to how to address the differential problem. I'd rather not have them take it apart, but they may have to. I'm thinking perhaps I should just give it a couple of good flushings and fill it back up with a good Posi lube and drve it a while and see how it works. Should I just pull it and have the whole rear end overhauled?
Incidentally, my fab guy is asking me what color of black he should use. Same with the engine bay?
Bob
Your car, but if I had the center section out, and it was as you describe, I would put new clutches in it at a minimum... PS- the bolts that hold the case halves together are left handed.

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Old 12-06-2018, 05:00 PM
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I'm not spending $4,000 to have the 327 rebuilt and do a half assed job on the rest of the drive train, please excuse my "French". If I can't get the diff to work as it should, I'm pulling it out and sending to a rear end specialist. Those near me in the South Bay may know of Rear End Specialties. They did a great job on the 'vette Posi I put in my '56 Bel Air.
I didn't mean to emphasize on the large "P". I just remembered reading when I bought one for the Bel Air that the large "P" identified it as a corvette Posi 3rd member. It had frozen 4.56 gears which Specialties removed and replaced with 3.55's. Axles had to be modified to fit.
I am posting another thread with pictures of the under carriage. Looking for much appreciated help on that as well.
Thanks,
Bob
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Old 12-06-2018, 05:16 PM
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Originally Posted by 6T2Vette View Post
I'm not spending $4,000 to have the 327 rebuilt and do a half assed job on the rest of the drive train,

They did a great job on the 'vette Posi I put in my '56 Bel Air.
I didn't mean to emphasize on the large "P". I just remembered reading when I bought one for the Bel Air that the large "P" identified it as a corvette Posi 3rd member]]

hanks,
Bob

You asked for advice but you didn't specifiy whether you wanted half assed advice or expensive advice. My advice was based on your perception of what seemed to be important to you.

$4000 to rebuild that 327 is a lot of money for what?

I don't understand why you think that big "P" means it's a Corvette rear end. It also means it could be a passenger car third member.


Some here have to have the finest and best. Others don't need to spend the big bucks to have a nice car. Please specify in the future. High dollar answers are readiiy found on your copy of the service invoice you just paid for on in books you can buy and read up on. Half assed answers usually come from people that have been around awhile and know what you can do and what you can't. How much you have to spend and how much you can save.

Last edited by MikeM; 12-06-2018 at 05:20 PM.
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Old 12-06-2018, 05:18 PM
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Bob,
If you should have any more questions, I would STRONGLY suggest that you ask them BEFORE throwing a bunch of money into a bottomless hole.

IF, IF, IF, you should decide that you want to have a higher gear ratio in your rearend (for lower rpm and better fuel economy on the hiway), you CANNOT, CANNOT, CANNOT put any 3-series gear set onto the 4-series posi unit in your car (I'm not talking the outer case, I'm talking about the internal posi unit). To switch to a higher gear ratio, such as a 3.55, 3.36, 3.08, it would be necessary to go with a 3-series (internal) posi unit. It's too bad that you are so far away. If you were near Okla City, and had the center section removed from the axle housing, I could take a look at it and go from there.

Oh ya--------------your transmission will be (or should be) a Borg-Warner ALUMINUM case T-10-----------------------THEY WERE NOT PAINTED FROM THE FACTORY, THEY WERE BARE ALUM!!! I would recommend telling them NOT to paint it----------------not even silver!
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Old 12-06-2018, 06:16 PM
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Originally Posted by MikeM View Post
You asked for advice but you didn't specifiy whether you wanted half assed advice or expensive advice. My advice was based on your perception of what seemed to be important to you.

$4000 to rebuild that 327 is a lot of money for what?

I don't understand why you think that big "P" means it's a Corvette rear end. It also means it could be a passenger car third member.


Some here have to have the finest and best. Others don't need to spend the big bucks to have a nice car. Please specify in the future. High dollar answers are readiiy found on your copy of the service invoice you just paid for on in books you can buy and read up on. Half assed answers usually come from people that have been around awhile and know what you can do and what you can't. How much you have to spend and how much you can save.
Please don't misunderstand me, or misquote me. I never insinuated any help or advice I've received here has been half assed. I'll never use that term again. I meant I did not want my efforts to be half assed. $4,000 is not even half of what this little venture is going to cost me. I just gave the machinist $1,500 to begin ordering parts. The Voodoo roller cam kit will probably cost me over $1,000. The machine work on the heads to improve airflow and add hardened seats will not be cheap. I may need to order special parts to fit under the original Corvette valve covers. I don't have all the parts for the diff shield and I will be polishing air cleaner and diff shield and valve covers, I haven't decided on a carb yet or whether to rebuild the Carter AFB. I'd like to keep the carb if it will work.
The machinist gave me an initial quote of $3K-$3.5K for a normal rebuild. It seemed to be in line to me. I've just spent $70K-$80K in restoring a '55 Nomad and it's almost done I don't want to do it again anytime soon.
Bob


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Old 12-06-2018, 06:26 PM
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Originally Posted by MikeM View Post
You asked for advice but you didn't specifiy whether you wanted half assed advice or expensive advice. My advice was based on your perception of what seemed to be important to you.

$4000 to rebuild that 327 is a lot of money for what?

I don't understand why you think that big "P" means it's a Corvette rear end. It also means it could be a passenger car third member.


Some here have to have the finest and best. Others don't need to spend the big bucks to have a nice car. Please specify in the future. High dollar answers are readiiy found on your copy of the service invoice you just paid for on in books you can buy and read up on. Half assed answers usually come from people that have been around awhile and know what you can do and what you can't. How much you have to spend and how much you can save.
No No No Mike, I never implied any help or advice I've received here has been 'half assed". I stated I didn't want MY efforts to be half assed. I only want to go through this rebuild once. It becomes expensive when the job wasn't done right in the first place. That's why I place a lot of value on the advice from those who know.
Don't take offense my friend. I sincerely appreciate your inputs.
Bob
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Old 12-06-2018, 06:57 PM
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Originally Posted by DZAUTO View Post
Bob,
If you should have any more questions, I would STRONGLY suggest that you ask them BEFORE throwing a bunch of money into a bottomless hole.

IF, IF, IF, you should decide that you want to have a higher gear ratio in your rearend (for lower rpm and better fuel economy on the hiway), you CANNOT, CANNOT, CANNOT put any 3-series gear set onto the 4-series posi unit in your car (I'm not talking the outer case, I'm talking about the internal posi unit). To switch to a higher gear ratio, such as a 3.55, 3.36, 3.08, it would be necessary to go with a 3-series (internal) posi unit. It's too bad that you are so far away. If you were near Okla City, and had the center section removed from the axle housing, I could take a look at it and go from there.

Oh ya--------------your transmission will be (or should be) a Borg-Warner ALUMINUM case T-10-----------------------THEY WERE NOT PAINTED FROM THE FACTORY, THEY WERE BARE ALUM!!! I would recommend telling them NOT to paint it----------------not even silver!
Thanks DZ. I will continue to ask for help with the restoration of this car. I have reached out for help with the engine. In the end have to digest the information I receive and come up with my own solution...sometimes in contrast with the help I received. If wrong, I'll have to live with it, but so far I've been doing OK.
Your advice has been very helpful. The engine is now on it's way to being rebuilt. I'm hoping it will be done by mid January. Now I've got the rest of the drivetrain, suspension, brakes and steering.
Also, how much should I do to the cosmetics of the under carriage of a car I want to look like a survivor on the surface but a well built car as a driver.
Here are some pics of the Under Carriage. I was going to create another thread but I messed it up. Here's some pics.
What color for rear end? Engine bay? Was frame painted?
Bob








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Old 12-06-2018, 07:18 PM
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Originally Posted by DZAUTO View Post
Bob,
If you should have any more questions, I would STRONGLY suggest that you ask them BEFORE throwing a bunch of money into a bottomless hole.

IF, IF, IF, you should decide that you want to have a higher gear ratio in your rearend (for lower rpm and better fuel economy on the hiway), you CANNOT, CANNOT, CANNOT put any 3-series gear set onto the 4-series posi unit in your car (I'm not talking the outer case, I'm talking about the internal posi unit). To switch to a higher gear ratio, such as a 3.55, 3.36, 3.08, it would be necessary to go with a 3-series (internal) posi unit. It's too bad that you are so far away. If you were near Okla City, and had the center section removed from the axle housing, I could take a look at it and go from there.

Oh ya--------------your transmission will be (or should be) a Borg-Warner ALUMINUM case T-10-----------------------THEY WERE NOT PAINTED FROM THE FACTORY, THEY WERE BARE ALUM!!! I would recommend telling them NOT to paint it

Fresh pics from Fab guy before it goes into degrease.




----------------not even silver!
My fab guy just sent me some pics of the tranny. I like the date codes if I read them correctly. Do you agree? I've instructed them not to paint.Bob

Last edited by 6T2Vette; 12-06-2018 at 07:36 PM.
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Old 12-06-2018, 07:42 PM
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Originally Posted by 6T2Vette View Post
No No No Mike, I never implied any help or advice I've received here has been 'half assed". I stated I didn't want MY efforts to be half assed.
Bob
Believe me when I say that I am probably the last one on this forum that will be offended by anything printed here!

PS. The price you were given for a stock rebuild sounded okay if someone else did all the work. Don't know why a guy would need all that hot rod stuff.
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