1969 L36 with Code AZ Axle

[Floyd B.]

😊IMG_5583.jpg IMG_5032.jpg

[Joe L.]

Re: 1969 L36 with Code AZ Axle

I’m attempting to determine if the car has a M-20 or M-21 without dropping the tranny to inspect the input shaft. Based on condition and date codes, I do believe all the major driveline components are original to the car.

The car appears to have been reasonably well maintained but shows no signs of restoration. It has surface rust throughout the chassis, as would be expected of a vehicle that spent the majority of its 52 years and 57,000 miles in Michigan.

Build date: C02 - 10/2/68 (Trim Tag), 10/4/68 (Shipping Data Report)
Engine Stamp: T0926LM

Various numbers from the transmission housing:
Casting # 3925660 1" Countershaft Bore, Lg Input Bearing
Tail Housing 3857584 Passenger-Side-Mounted Speedometer, 27 Spline Output
Side Cover 3950306 No TCS Switch
Date Stamp P9P23 Muncie Plant, 1969, Sept 23

This was an early ’69 model year build so the date code stamp does not include the gear ratio suffix code. That would have made it easy! 

The car has a performance axle (3.55), code AZ, that I believe is original to car. The reason I assume it is the original axle; the condition is consistent with the remainder of the of the chassis and the date code is consistent with the dates on the other driveline components. See the pic. Even if the axle had been replaced, it is highly unlikely that any previous owner would have put any effort into selecting an axle with a matching date code. No such effort was made when someone replaced the intake manifold and carb. Nor was any concern shown for originality when the interior was painted/dyed from its original bright blue to black.

It is my understanding that unless the axle was special ordered, 3.55 (AZ) performance axles were only mated to M-21 transmissions. I’m not sure of 3.55 with M-22 transmissions but I think it’s safe to assume that it is highly unlikely that a L36 received one of the 101 M-22’s installed at the factory in the 1969 model year. It is also my understanding that M-21 was only available w/o C60 and this is a non-air car.

Based on this information, is it safe to conclude the transmission is a close-ratio M-21? Are there other clues I should look for?

Thanx

-Floyd-

[ATTACH=CONFIG]100330[/ATTACH] [ATTACH=CONFIG]100331[/ATTACH]

Floyd------


As far as 1969 L-36 goes, a 3.55:1 rear axle was only available with M-21 transmission.

No 1969 L-36 was available with M-22. For 1969 the M-22 was limited to L-88/ZL-1.

[Larry M.]

Re: 1969 L36 with Code AZ Axle

Use your speedometer and tachometer to determine the first gear ratio. Pick a speed around 30 MPH in fourth gear and read the RPM. Then do the same in first gear.

The ratio of the two RPM will provide the first gear ratio.

Fourth gear is 1 to 1 for both transmissions, but the first gear is obviously different.........and the test I outlined will provide you the first gear ratio and the answer you seek.

Larry

[Duke W.]

Re: 1969 L36 with Code AZ Axle

It's easy to tell just SOTP. The difference is the 3/4 intergear ratio. With a CR the rev drop shifting to fourth is about the same as 1/2 and 2/3. With the wide ratio the 3/4 rev drop is much greater.

If you can't "feel" the difference, take it to 3000 RPM in third and shift to fourth noting where revs pick up. If a CR it will be in the 2300-2400 range, and 2000-2100 if a WR.

Duke