C2 Differential Vent

[T P.]

Is the vent a judged item?

[Edward J.]

I know that the 63 vent was all metal and and all the others were plastic.I don’t think a judge has time to inspect every item on a corvette and if he saw something wrong he likely would only make a note of that item as it really has no point value.

[Gary R.]

64 had the metal vent and machine thread fill plug as well.

[Duke W.]

It's actually an axle vent. The differential is the gears (and Positraction clutches if so equipped) inside the differential case that also holds the ring gear, which is mounted in the differential carrier.

Install the rear cover and you have a complete axle.

Duke

[T P.]

Gary, is the vent for a 65 also metal?
I have only found plastic. Are metal ones still available somewhere?

[Harry S.]

64 had the metal vent and machine thread fill plug as well.

Gary, please take a peek. Is this the same as used in 63?

https://www.zip-corvette.com/53-62-rear-differential-metal-vent.html

[Gary R.]

Gary, is the vent for a 65 also metal?
I have only found plastic. Are metal ones still available somewhere?

All the 65's I have built had plastic vents. Many were original, untouched diff's. 65 was a transition year for the ring and pinion, with an early revision. Also the first year for the Eaton posi & 3/4" npt fill plug. The first design Eaton wasn't too good but better than the 63-4 Dana posi.

[Gary R.]

Looks like it.

[Mark M.]

A very early 65 I restored 229* Nov. build, has it's original rear end and cover which is probably remaining castings from 63-64s that has the 303 last # opposed to 375 last #s seen in 65 and up. Even though this 65 has 303 # cover, the vent is the plastic vent and the plug is pipe thread with red posi tag of 65 and up. It also has the better Eaton posi. All the 63-64 rear ends I have, 303s, have the steel vents and fine thread plug with metal posi tag. Just as Gary replied.

[Gary R.]

A very early 65 I restored 229* Nov. build, has it's original rear end and cover which is probably remaining castings from 63-64s that has the 303 last # opposed to 375 last #s seen in 65 and up. Even though this 65 has 303 # cover, the vent is the plastic vent and the plug is pipe thread with red posi tag of 65 and up. It also has the better Eaton posi. All the 63-64 rear ends I have, 303s, have the steel vents and fine thread plug with metal posi tag. Just as Gary replied.

Hi Mark,
One thing, the 65-68 Eaton posi's were not too good. They were very prone to cracking and had 10-18 spiders. The 69-late 71 were a little better, the very late 71-79 were the best and had the best spiders,10-17's. They still cracked buy not as bad as the earlier ones. Of course the clutches were junk and ring gear bolts backed out a lot.

[Mark M.]

Hey Gary, I totally agree on the part strong and weaknesses through the years. I started doing stingray rear ends with GMs chevrolet power book from 1980 which pointed be in the right direction. Back then good cores were plentiful and cheap. I do avoid the postage stamp window 65-69e posi carrier if for a higher horse car. I lean toward the stronger gears and discs for a car that will see harder use or higher horse power. You too must have seen many carriers with cracks in the windows or spider pin holes which means it's scrape even if it didn't let loose yet. When they do let go, it is ugly. I had a 3:55 lock right up on an easy turn which left me stuck in an intersection back in the 80s. First time I needed a flatbed. New eaton carriers are getting pricey. If I remember right, I thought I saw you mention somewhere the use of a pinion spacer opposed to a crush sleeve. I like em better. You definitely seem to be a number of cuts above the rest on rebuilding these. Enjoy your posts.

[Gary R.]

Hey Gary, I totally agree on the part strong and weaknesses through the years. I started doing stingray rear ends with GMs chevrolet power book from 1980 which pointed be in the right direction. Back then good cores were plentiful and cheap. I do avoid the postage stamp window 65-69e posi carrier if for a higher horse car. I lean toward the stronger gears and discs for a car that will see harder use or higher horse power. You too must have seen many carriers with cracks in the windows or spider pin holes which means it's scrape even if it didn't let loose yet. When they do let go, it is ugly. I had a 3:55 lock right up on an easy turn which left me stuck in an intersection back in the 80s. First time I needed a flatbed. New eaton carriers are getting pricey. If I remember right, I thought I saw you mention somewhere the use of a pinion spacer opposed to a crush sleeve. I like em better. You definitely seem to be a number of cuts above the rest on rebuilding these. Enjoy your posts.

Hi Mark.
Yes those 65-68 postage stamps cases were bad, the 69-71 not much better. The BB cases were said to be shot peened, but it really didn't help, I have seen plenty of BB cases broken. You're correct, once a crack forms that case should be replaced. However, that hasn't been the case for some.

About 12 years ago I was asked to inspect a rebuilt diff from a place in Tx. The customer bought and put it in his garage for a few months. He brought it to me while picking up a steering box I just blueprinted for him. Once I removed the cover, I saw a 2" crack in the posi case. The diff was never installed in the car.

The owner fought with the vette shop and was told after a lengthy discussion, it was a 40-year-old part, what did he expect? I correctly built the diff and surprisingly he got his money back from a place that is about as corrupt as they come.

The new Eaton cases are much better machined than any original case, CNC's do some nice work. They are made in China and assembled in Mexico. Summit sells them for about $830 now. They have been on back order for months. I never use them as is, out of the box. I rebuild new posi's. I don't use the fiber clutches and you can't tune a posi using them.

I use both crush sleeves and solid sleeves, depending on the application. I build diff's to about 6 levels. The solid sleeve is good but takes time to dial in correctly. The crush sleeve works as well and for a street car is fine. I use the solid sleeves in high power builds.

Stay safe