C1 Ring and pinion change (3.70 to 3.73)

[William V.]

Thanks

BV

[Pierre J.]

Re: C1 Ring and pinion change (3.70 to 3.73)

Bill,
I installed a 3.73 Richmond gear #49-0099-1 in my '57 without the problems you're referring to. The difference is that I had a (non original) 3:36 gear in it to start with.
Pierre

[William V.]

Re: C1 Ring and pinion change (3.70 to 3.73)

Pierre

49-0099-1 is the part number I am installing. The carrier should be the same for 3.08 thru 3.70.

Thanks

Bill.

[Tom P.]

Re: C1 Ring and pinion change (3.70 to 3.73)

Just out of curiosity, what year is the differential that you have?

[Pierre J.]

Re: C1 Ring and pinion change (3.70 to 3.73)

Bill, shouldn't ask this but you're sure you don't have the axles mixed up?

Pierre

[William V.]

Re: C1 Ring and pinion change (3.70 to 3.73)

Pierre

I'm sure they are not mixed. The left side axle is missing three flange studs which are replaced with bolts. It's the short axle, left side, that's too long. The other, longer right side fits ok.
Thanks

BV

[Tom P.]

Re: C1 Ring and pinion change (3.70 to 3.73)

Again, what year model is the differential unit?

[John N.]

Re: C1 Ring and pinion change (3.70 to 3.73)

Thanks

BV

Answer Toms question first and consider his answer. The left side has this problem quite often on 56-62 Corvettes. I will measure the space between the axle end and the cross shaft. I will have the axle faced in a lathe to give a .100 end clearence. Most people don't realize they have a problem and they may get by without damage.
Regards

[William V.]

Re: C1 Ring and pinion change (3.70 to 3.73)

Tom



Thanks

Bill

[Gary C.]

Re: C1 Ring and pinion change (3.70 to 3.73)

Bill, Tom and John are trying to help you determine if it's the original non-posi casting # 3707306, or a 57 up cast # 3725899 or a positraction cast #3743833. If the axles are original John has experience with cutting to proper length. 57 axle lengths non-posi 28 9/16" left, 30 1/16" right, posi 28 7/16" left and 29 15/16" right. Gary....

[William V.]

Re: C1 Ring and pinion change (3.70 to 3.73)

Thanks for the input. When I get over to the owners house, I'll see what casting number is on the case.

Thanks

Bill

[Tom P.]

Re: C1 Ring and pinion change (3.70 to 3.73)

OK!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Now we're finally getting somewhere!!!!!!!!!!!!!!!
If in fact the differential is a 56 unit--------------THAT IS YOUR PROBLEM!!!!!!!!!! Short and sweet!
The 55-56 pass car and 56 Vette rears--------------AND axles are the same and are interchangeable.
IF, IF, IF you put a later gear set and/or a gear set (SPECIFICALLY the ring gear) for a 57-64 rearend, into a 56 ring gear carrier, that is the source of your problem. PERIOD!
WHY?
Because the 55-56 ring gear carrier was different from the 57-64 ring gear carrier (the carrier is the differential unit INSIDE the case).

Also, 55-56 ring gears are thinner (consequently weaker) than 57-64 ring gears. So, if you bolt a thicker 57-64 ring gear onto a 55-56 ring gear carrier (differential), which by the way won't fit correctly, it is necessary to move the carrier to the extreme left. This also moves EVERYTHING inside the differential over, including the pin for the spider gears. Thus, when the left axle is inserted into the left axle gear, it bumps up against the pin for the spider gears. Addidionally, the RIGHT axle splines are not fully engaged into the right axle gear.

Here is a comparrison of a 3.70 57-64 ring gear (left) and a 55-56 3.70 ring gear (right). As can be seen, the 55-56 ring gear is thinner.


The next three pictures are comparrisons between the thinner, weaker 55-56 ring gear carrier and the 57-64 carrier. No confusion which is which.






The next two pictures are a comparrison of the 55-56 case (top, with a posi unit). I have outlined the areas which are the major structural differences between 55-6 and 57-64 cases. You can clearly see that the 57-64 is beefier, thus stronger.




The easiest way to resolve this problem is to locate a 3-series non-posi (assuming you are not interested in having a posi) differential unit from any 57-64 rear and replace the 3.73 ring gear on the later 57-64 carrier. These things are fairly easy to locate ant the price should be somewhere between FREE and $20 max.
I absolutely would discourage you from cutting off the end of an axle!!!

[William V.]

Re: C1 Ring and pinion change (3.70 to 3.73)

Tom

Thanks for the information. We have the early light duty ring gear carrier and are in the process of locating a non-posi 57 and up unit.

Thanks

Bill