Gregs' is a 3.07 12 bolt Posi.

QN 12-bolt 4.88 ~ Positraction w/4 wheel disc
QS 12-bolt 2.56 ~ Positraction w/4 wheel disc
QT 10-bolt 2.73 ~ Positraction w/4 wheel disc
QU 12-bolt 3.07 ~ Positraction w/4 wheel disc
QV 12-bolt 3.31 ~ Positraction w/4 wheel disc
QW 12-bolt 3.55 ~ Positraction w/4 wheel disc
QX 12-bolt 3.73 ~ Positraction w/4 wheel disc
QY 12-bolt 4.10 ~ Positraction w/4 wheel disc
QZ 12-bolt 4.56 ~ Positraction w/4 wheel disc

When the Ebay ad for the car was up I was contacted by a guy who claimed he knew my car and it was the last JL8 produced. According to the NCRS report it was produced on June 6th. Is there any way to verify such a claim?

William,

So the ECL's you spoke of were for the QX and the QY rear ends. Is there any way to find the ECL for the QU rear? I believe I remember Kurt saying that is what his car originally came with and that is what my car has.

There are a pair JL8 Z/28s sold by Schukei Chev Waterloo IA, built approximately the same time. Cars were not built in exact VIN order so it is difficult to say. But typically, they weren't all that far off. N651702 [BDY 342866] N652055 [BDY 342865]. N652055 was owned by the late Warren Malkin, Jr. and was displayed at MCACN a few years ago. W/S is in Jerry's book.

The latest known JL8 car, a Z/28, was about 1,200 units after yours. There were just over 1,000 cars built last week of June at Van Nuys after the strike, possible there was a JL8 in that group.

We need factory paperwork or engineering records to learn the ECLs for the other ratios.

QU Rear
 

CRG shows the QU rear as a 3.07 posi with 4 WHL disc brakes. Under trends report G80 option, there is only 1 3.07 rear axle listed with and ECL of TA, no?

Paul

The Trends report as of September 1969 shows G80TA production 5,595 units.

G80 ECLs are the same for JL8 and J52. ECLs for JL8 with ratios other than 3.73 and 4.10 are needed.

Since the JL8 option was to homologate for TA racing kind of surprised in a way that there were no Firebirds fitted with it. I know the rules were sometimes adjusted on the fly like how Firebirds were raced with Chevy 302's. Maybe the same thing happened wit the brakes. Sorry if this is perceived as a thread hijack.

Probably because Chevy did all the R & D [$$] on the system and Firebird was viewed as a competitor. In production, Firebird used Pontiac-built rear axles.

The Van Valkenburg book Chevy=Racing? has valuable insight on the braking problems the T/A cars experienced. What they thought was severe brake fade turned out to be insufficient master cylinder fluid capacity under racing conditions. JL8 did not initially solve the problem. And, as it was designed for a lighter car, wasn't all that much better.

How were the ECL's for the 373 and 410 rears discovered? Can't the ECL for the 307 be found out the same way? Was it on the build sheet?

Factory paperwork. Window sticker, dealer invoice, shippers' copy. Don't have that info for other ratios.