'61 positraction carrier

[Richard P.]

The rear end of my 1961 was making a roaring noise. I thought it might be the axle bearings so I took both axles and the rear differential to a machine shop. They are telling me the the positraction carrier is bad, along with a few other things. I don't think it even came with positraction, but I got one now. The shop is having difficulty finding a positraction carrier. Any suggestions? Does it have to be for a Corvette or will a pssenger car work as well.

[Domenic T.]

Re: '61 positraction carrier

The passenger will work in a corvette 1955 to 1962.
The carrier housing rarely go's bad and there are kits available to put inside if needed.
Save the case (carrier housing) if original and load it with good parts.

DOM

[Richard P.]

Re: '61 positraction carrier

Thanks for the reply. I relayed it to the repair shop and he said what he meant instead of the big carrier housing, was the piece that holds the ring gear. Any idea where I could find one?

[Domenic T.]

Re: '61 positraction carrier

That's good news,
they are available after market or in wrecking yards.
My son wants me to install an aftermarket in my chevelle. He swears by the aftermarket one's but old fasion me would want the original in a vette.

DOM

[Richard P.]

Re: '61 positraction carrier

If I were asking a parts hound for it, what specifically do I ask for?

[Domenic T.]

Re: '61 positraction carrier

I would ask for " the posi unit".
The ring gear bolts to the posi unit which has the 4 spider gears and clutch pacs inside of it.
The clutch pacs can be tested by your mechanic and replaced if necessary on a used posi.
Setting up your ring & pinion is easier than the newer ones because the ring gear movement to the pinion is adjustable (threded) rather than having to add or subtract shims.
But if the shop does not specialize in differentials I would find one that did. They look easy but will sing you a song if not spaced right.

DOM

[Richard P.]

Re: '61 positraction carrier

Does anyone have a source for a 1961 posi-unit?

[Donald L.]

Re: '61 positraction carrier

I believe Eaton is now making posi units for 58-64 chevys. They suppose to be a beefier unit than the original Dana unit.

[Richard T.]

Re: '61 positraction carrier

The C-1 Corvettes used 2 differant "carriers" in the positraction assembly. There is a 3 series and a 4 series used depending on the ring and pinion ratio. If your going to use a 4:11, 4:56 or deeper then the 4 series is needed. A 3:70, 3:56 or higher uses the 3 series. One of the main differances between the two is the number of clutches used in the posi carrier. Good Luck

[Terry D.]

Re: '61 positraction carrier

I think I would find a new mechanic. Those units are rebuildable. Have you checked the archives? Google chevrolet posi units.
Terry

[Tom P.]

Re: '61 positraction carrier

The C-1 Corvettes used 2 differant "carriers" in the positraction assembly. There is a 3 series and a 4 series used depending on the ring and pinion ratio. If your going to use a 4:11, 4:56 or deeper then the 4 series is needed. A 3:70, 3:56 or higher uses the 3 series. One of the main differances between the two is the number of clutches used in the posi carrier. Good Luck

ACTUALLY, there were 4. There is a 3 and 4 series EARLY posi (57-59) and a LATE 3 and 4 series posi. The late posi was used in 60-62 Vettes and 60-64 pass cars.
Here is some additional information that I put together in the past (I am CONTINUALLY amazed at just how little knowledge NCRS members have about these early cars!).
http://www.chevytalk.org/fusionbb/sh...hp?tid/223802/

[Domenic T.]

Re: '61 positraction carrier

Tom,
I know you probably remember that changing the rear ratio in those days (as you being the same age as I) was a comon thing , not to mention all the one's that were changed because they blew.

I would bet that there are very few original units in those C1 cars today
because in my area those vettes and cars were active in the sport of drag racing.

I know that I personally had every ratio from 3:08 to 4:56 in my car then and both ratios of the borg warner 4 speed. In the TRI State area we put gears in for the winter and then changed them in the spring. I remember borrowing a gear in the winter just for a street race and switching gears with another car just for the heck of it. With a good axel puller and a fresh gasket it took 20 min once it was on the rack.

Very seldom did we rebuild them in those days (not to say that we didn't). I cleaned the junk yards out and remember them all fiting. Also looking for the 3:70 in the panel trucks.

I would be amazed to see one that was still in the same car it was born in.

As you will remember all that changed in 1965 for pass cars with the new design rear end and the ring & pinion had to be changed in the car along with the vettes new pumpkin design in 1963.

JUST MEANT TO BE A WALK DOWN MEMORY LANE

DOM

[Joe L.]

Re: '61 positraction carrier

Does anyone have a source for a 1961 posi-unit?

Richard------


Tom's Differentials (www.tomsdifferentials.com) can fix you up with a complete new unit or parts to rebuild the old one. However, I'd be very leery about using an original case unless I had it completely and carefully magnaflux inspected. These things develop cracks, especially after long and/or hard use. If it were me in a case like this, I'd replace the whole unit with a factory NEW piece.

[Tom P.]

Re: '61 positraction carrier

Dom and Joe,
Oh yes, I clearly remember the days.
Today, I take my time in my temp controlled 6car garage, but at one time, from rolling the jack under the car, to setting it back down on the ground (and that was with a lug wrench, NOT an impact gun), I could change out a center section in 45min (and I can still do it today, but maybe faster with the impact gun). But I'm not gonna try-------------there's no need to rush today--------------my drag racing days are over. If I need to change out a rear, I MAY roll the jack under the car tonight, and finish up on Sunday afternoon.
Right now, I'm replacing the bushings in the lower A-frames of the 70 Chevelle. I started Sat afternoon (today is Wed) and so far, I've only got bushings in one A-frame. Last night all I did was stick the A-frame under the front cross member and install the bolts/nuts. I just don't have the ants in my pants to get things done in 30sec like I did 30-40yrs ago.

Joe,
Brand new rears may still be out there, but they are NOT commonly available.
One of my most desireable sources for rears is from more or less plain jane 62-64 4dr sedans that had a 6cyl or 283 2bl and PG tranny. Usually, those kinds of cars in the junk yards didn't have much abuse on the rears. I've pulled out some beautiful (insides) rears from those kinds of cars. Posi rears are almost non-existant in those care, but now that Eaton makes a posi unit for those early rears, it's just toooooooooooooo easy to build up a posi rear for the early cars. NO, you don't get the big P, but what the heck, it is a good posi rear!

[Joe L.]

Re: '61 positraction carrier

Dom and Joe,
Oh yes, I clearly remember the days.
Today, I take my time in my temp controlled 6car garage, but at one time, from rolling the jack under the car, to setting it back down on the ground (and that was with a lug wrench, NOT an impact gun), I could change out a center section in 45min (and I can still do it today, but maybe faster with the impact gun). But I'm not gonna try-------------there's no need to rush today--------------my drag racing days are over. If I need to change out a rear, I MAY roll the jack under the car tonight, and finish up on Sunday afternoon.
Right now, I'm replacing the bushings in the lower A-frames of the 70 Chevelle. I started Sat afternoon (today is Wed) and so far, I've only got bushings in one A-frame. Last night all I did was stick the A-frame under the front cross member and install the bolts/nuts. I just don't have the ants in my pants to get things done in 30sec like I did 30-40yrs ago.

Joe,
Brand new rears may still be out there, but they are NOT commonly available.
One of my most desireable sources for rears is from more or less plain jane 62-64 4dr sedans that had a 6cyl or 283 2bl and PG tranny. Usually, those kinds of cars in the junk yards didn't have much abuse on the rears. I've pulled out some beautiful (insides) rears from those kinds of cars. Posi rears are almost non-existant in those care, but now that Eaton makes a posi unit for those early rears, it's just toooooooooooooo easy to build up a posi rear for the early cars. NO, you don't get the big P, but what the heck, it is a good posi rear!

Tom------


I was not referring to a complete rear gear assembly. I don't think those are available in the aftermarket. I was referring only to the positraction case and contents.