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Re: '57 Differential Question...
Thanks Tom, that is such a relief to hear that from you! I was really starting to get worried about getting into a pissing contest with the Vendor. There was no way I could count the teeth on the pinion gear. You can see that in the picture below.
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Re: '57 Differential Question...
One last question...my Gear head buddy told me that all the '56-'64 Chevrolet's used two different length axles in the same car. One right and one left. Then the positraction length was one right, one left for a total of four different axle lengths.The original rear end that came with this car was a single traction rear. Is this in fact the case? Thanks for any information on this. Patrick
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Re: '57 Differential Question...
Patrick,
Here are the axle lengths as from my 1960 Chev P & A catalog.
All are 17 spline.
1957 - 58 Corvette & Chev pass car ( except positraction )
Left 28 & 9/16" overall length: Right 30 & 1/16" overall length
1957 - 58 Corvette ( with positraction ) and 1959 Corvette ( with or without positraction )
Left 28 & 7/16" overall length Right 29 & 15/16" overall length
1960 Corvette ( w & w/o P.T. )
Left 28 & 7/16" O. L Right 30 & 3/16" O. L.
Later versions of the Chev P A catalogs list the following:
1957 - 62 Corvette
Left axle - 28 & 13/16" O. L. part #3775689
Right axle - 30 & 5/16" O. L. part #3775690
RayComment
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Re: '57 Differential Question...
Let me clarify this axle length confusion and misunderstanding. I DO NOT care what the book says, this is present day real world!!!!
The 55-56 pass cars and 56 Vettes used the same axles. And it is true, ALLLLLLLLLLLLLLL 55-64 axles are two different lengths, the left is shorter than the right. The 55-6 axles WILL NOT, WILL NOT, WILL NOT fit anything except a 55 or 56 axle housing ---------------- including 56 Vette housings. PERIOD!
The 57-58 pass cars and 57-62 Vettes shared the SAME axles.
POSITRACTION AXLES
Positraction axles were ONE YEAR ONLY axles. PERIOD!!!
Positraction was a mid-year option in 57. Thus, ALLLLLLLLLLLLLLLLLLLLLLLLLLL 57 pass cars and 57 Corvettes used the same axles. When positraction was introduced (late Dec 56), it was discovered that the splined ends of the axles would make contact with the cross shafts inside the posi unit. At the least, this could effect the action of the posi unit and at the worst, the cross shaft(s) could be broken.
Below is a picture of a cross shaft where the end of an axle has made contact (round shiny area).
And this is a broken cross shaft as a result of severe side loading from an axle shaft.
Consequently, the fix was shorter axles for 1957 ONLY cars (BOTH pass cars and Vettes). ALLLLLLLLLLLLLLLLL other factory built NON-posi cars received the regular length axles in 1957------------------AGAIN, THIS ONLY APPLIES TO 1957 CARS!
The 1958 pass cars, and ALLLLLLLLLLLLLLLLLLLLL 1958-62 Corvettes received the regular length axles (REGARDLESS of posi or non-posi). Rather than make shorter axles for 58-later cars with posi, Chevrolet simply went to a 1/8in wider rear axle bearing. TOOOOOOOOO SIMPLE! The Corvettes got a spacer installed between the axle tube and the axle bearing. BUT, when ordering a new bearing for a 58-62 Corvette, ONLY THE WIDER BEARING IS CALLED OUT IN THE PARTS BOOKS! Thus, the original factory spacer is discarded when replacing an axle bearing in a 58-62 Vette (this DID NOT apply to 58-64 pass cars, they just went to the wider bearing in 58).
SOOOOOOOOOOOOOO, if any of you independently wealthy Corvette owners who like to spend money should need a new axle for your 57-62 Corvette, there is no need to pay hiway robbery prices for a Corvette axle. Simply search and surf for an axle(s) for a 58 pass car. And if you need an axle specifically for a 57 Vette------------------and it has a posi rear, also acquire an axle from a 58 pass car--------------and cut off 1/8in from the splines (this is clearly spelled out in the 1957 Chevy posi shop manual).
Now, with all of that said, why not use a 59-64 pass car axle? Because in the 59-64 pass cars, the axles were longer than the 57-58 axles. The added length of 59-64 pass car axles was from the bearing seat out to the wheel flange. Would a 59-64 pass car axle fit in a 57-62 Corvette axle housing? Yes, it would, but the wheel base would then be wider because of the extra outboard of the 59-64 axles. And I suppose if a person liked the idea of a little wider wheel base in the rear, then the 59-64 pass car axles would be fine.Comment
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Re: '57 Differential Question...
Tom, thanks again for the great information. I guess I'll know the final outcome when I get the 4:11 pulled out and have the rebuilt 3:55 installed this week. I was going to install it myself lying on my back like I did 20 years ago but for some reason 75 pounds seems a lot heavier now!
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Re: '57 Differential Question...
Don't feel bad.
I used to lay on my back with a Muncie lying beside me, reach over, pick up the Muncie and lift it up and stab it straight in (without first taking a brake to lay it on my chest before lifting and stabbing it!!!). I did the same thing with these rearends. I got to where I could put a floor jack under the rearend housing, jack it up and change out the center section in 45min. In almost the past 50yrs, I was so good at changing out a rearend that many people didn't believe I could swap one out that quick. Now, I'm lucky to get it done in 2hrs (mainly because I'm no longer under pressure to get it done).Comment
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Re: '57 Differential Question...
Patrick,
As I referenced yesterday 1957 -58 Corvette and 1957-58 pass car ( non-positraction ) used the same axles.
However, I doubt that you need to procure different axles, but it would behoove you to check the axle shafts for length. As Tom pointed out an axle that is too long will cause interference with the pinion shaft which usually results in breakage.
From my 1956 - 60 Corvette Chassis service operations guide I found the following information regarding the installation of axle shafts with positraction:
NOTE: Make sure the spline end of the axle shaft does not interfere with the pinion mate shafts. This is best determined by measurement. Use a steel tape, and with the aid of a flashlight, measure from the bottom of the axle shaft bearing bore to the pinion mate shafts. Then measure the axle shafts from the corresponding point of the bearing to the end of the spline. The minimum clearance is 1/8 " of an inch. Grind off the spline end of the axle shaft if it is too long. Check the other axle shaft in the same manner.
Regarding bearings. There are some differences, again as Tom pointed out. I do not have dimensions or old samples to reference.
As a suggestion, before you install the differential assembly in to the car, I would take an axle shaft and insert it into the axle side gear to make sure that the splines on the gear and the side gear ring are in alignment. Do this on both sides. Much easier to correct now rather than when the unit is installed.
Hope this helps.
RayComment
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Re: '57 Differential Question...
Many thanks for the information Ray. For what it's worth, I bought the 4:11 from Chicago Corvette 23 years ago, installed it and the axles went right in with no problems to this day. This 3:55 I bought was also purchased from Chicago Corvette and they guarantee it will work, for what that's worth.
I'm getting this rebuilt 3:55 installed at a Corvette shop up the street on Friday. I will go up there tomorrow and see if they have an old '57 Chevy axle. If they do, when I bring the new rear end in, we can check it then to see if it fits before pulling the 4:11 out. I can see the splines in the new rear end with a flashlight but they are way inside and there is no way I can count them. They should hopefully fit like the 17 spline '57 Corvette axle shown below. Man, is this getting complicated! I know it's a tossup but I hope the odds are in my favor.
Patrick
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Re: '57 Differential Question...
Patrick,
TRUST ME, ALLLLLLLLLLLLLLLLLLLLLLLLL 55-64 pass car rears and ALLLLLLLLLLLLLLLLLLLLL 56-62 Corvette rears have the SAME 17spline axle gears and axle splines. There were none, nada, zip, zero differences in the splines of the above rearends.
Also, furthermore, the 62-63 ChevyII rears had the same bolt pattern for installing the rearend center section into the axle housing and the same splines. But, NOTHING, NOTHING, NOTHING from the 62-3 ChevyII rears is the same as the pass car or Vette rears. NOTHING! The ChevyII rears are thinner, lighter, weaker. NEVER touch one with the thought of putting it into a Corvette or pass car rear!Comment
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Re: '57 Differential Question...
Patrick
All the axles are 17 spline. With a positraction there are two sets of splines that must be aligned, the side gear ring and axle side gear. Sometimes the inner axle side gear gets rotated out of position and the axle will not go all the way in. You can then use the axle shaft engaged in the splines of the ring gear to rotate it slightly until it aligns with splines of the axle gear and gives you engagement with both parts. If both components are aligned the axle will bottom against the pinion shaft. If the builder who assembled this unit did the assembly correctly this should not be an issue, as he will have already checked this.
RayComment
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Re: '57 Differential Question...
Here is an illustration of the two internal splined components of a posi as mentioned by Ray.
The splines of two parts must be in alignment before an axle can be installed all the way.
During assembly of the posi unit, this alignment is accomplished by inserting an axle in each end of the posi unit BEFORE the bolts are tightened to pull the two halves of the posi unit together.
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Re: '57 Differential Question...
Thanks Guys, I'll let you know how it goes. PatrickComment
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Re: '57 Differential Question...
Tom
Thanks for the backup with the photo's.Comment
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