Differential ID stamp decode help?
Thread Starter
Le Mans Master
Joined: May 2005
Posts: 7,362
Likes: 2,281
From: Central Maryland
Differential ID stamp decode help?
Hi, all.
Curious about the diff that's in my '63. The stamp is not easy to read, but best I can tell it is as follows:
LR W 127 E 1
I'm betting the brain trust here knows what that suggests it is -- or at least what it was when it started its life. All I know about it so far is that I'm told it has 3.70 R&P, and that seems about right, given what the tach indicates in 4th gear.
TIA for any insights.
Live well,
SJW
Curious about the diff that's in my '63. The stamp is not easy to read, but best I can tell it is as follows:
LR W 127 E 1
I'm betting the brain trust here knows what that suggests it is -- or at least what it was when it started its life. All I know about it so far is that I'm told it has 3.70 R&P, and that seems about right, given what the tach indicates in 4th gear.
TIA for any insights.
Live well,
SJW
Last edited by SJW; Oct 20, 2020 at 06:38 PM.
Thread Starter
Le Mans Master
Joined: May 2005
Posts: 7,362
Likes: 2,281
From: Central Maryland
Thanks a bunch, Wayne. Greatly appreciated.
So it's likely this came out of a '74 Corvette, it seems. No surprise there, given that much of what's on this car is not its born-with components. This does square with one other data point that the previous owner told me, which is that he had the ratio changed from 3.36 to 3.70, although he didn't seem to know (or perhaps just didn't remember) whether it had been a swap of the R&P, or of the entire case. Looks as though the entire unit may have been swapped in first, then the R&P changed, given that the case is not original to the car, and the R&P is not original to the case (not that that level of detail is of any importance to me). I was mostly curious to see what year this unit likely came from, as I understand the later units are stronger.
Thanks again!
Live well,
SJW
So it's likely this came out of a '74 Corvette, it seems. No surprise there, given that much of what's on this car is not its born-with components. This does square with one other data point that the previous owner told me, which is that he had the ratio changed from 3.36 to 3.70, although he didn't seem to know (or perhaps just didn't remember) whether it had been a swap of the R&P, or of the entire case. Looks as though the entire unit may have been swapped in first, then the R&P changed, given that the case is not original to the car, and the R&P is not original to the case (not that that level of detail is of any importance to me). I was mostly curious to see what year this unit likely came from, as I understand the later units are stronger.
Thanks again!
Live well,
SJW
Tech Contributor
Joined: Aug 1999
Posts: 15,176
Likes: 3,990
From: Connecticut, USA
later units are better then the 63-4 but not without their own issue. 74 for instance had soft axles and weak clutches. So depending on what was done way back when will determine what you really have inside.
Thread Starter
Le Mans Master
Joined: May 2005
Posts: 7,362
Likes: 2,281
From: Central Maryland
Thanks so much, Gary. I always appreciate your expertise and informative posts. All of this is good to know.
I presume "soft axles" refers to inadequate hardening of the surfaces at the inner ends of the stub axles, which leads to rapid wear -- and that I should therefore keep an eye out for excessive end-play in case these are the soft ones?
What's the scoop on the clutches?
Live well,
SJW
I presume "soft axles" refers to inadequate hardening of the surfaces at the inner ends of the stub axles, which leads to rapid wear -- and that I should therefore keep an eye out for excessive end-play in case these are the soft ones?
What's the scoop on the clutches?
Live well,
SJW
Last edited by SJW; Oct 20, 2020 at 07:45 PM.
Tech Contributor
Joined: Aug 1999
Posts: 15,176
Likes: 3,990
From: Connecticut, USA
The Eaton limited slip case was first used in corvettes in 1965, it had solid steel clutches which are the best. The spring pack keeps constant pressure on the clutches and depending on how tight the spider lash was set up during assembly of the unit they may chatter in turns, even with posi additive. The solid steels locked up good and did not break. By 72 they switched to the type of clutch I coined as the snowflakes years ago. They were weaker and did not resolve the chatter issue. When the car was abused hard enough the clutches broke. These were run in the posi's till the end of the run in 79 and than were available as a service part for years. Then about 10-15 years ago they went to carbon fiber over solid steels and that does resolve the chatter issue but the material is sacrificial.
Thread Starter
Le Mans Master
Joined: May 2005
Posts: 7,362
Likes: 2,281
From: Central Maryland
The Eaton limited slip case was first used in corvettes in 1965, it had solid steel clutches which are the best. The spring pack keeps constant pressure on the clutches and depending on how tight the spider lash was set up during assembly of the unit they may chatter in turns, even with posi additive. The solid steels locked up good and did not break. By 72 they switched to the type of clutch I coined as the snowflakes years ago. They were weaker and did not resolve the chatter issue. When the car was abused hard enough the clutches broke. These were run in the posi's till the end of the run in 79 and than were available as a service part for years. Then about 10-15 years ago they went to carbon fiber over solid steels and that does resolve the chatter issue but the material is sacrificial.
Here's hoping I never need to find out what components make up the guts of the mutt that's in my car, but at least I'd know what to look for now.
Thanks again, Gary.
Live well,
SJW
