71 differential AIM note. What does it mean?

[Mike E.]

Take a look at the red-circled note on the attached AIM sheet. I am having trouble interpreting and guessing what the alternative would be for an M22-equipped car. This note is also in the 72 AIM, not in the 70. Any ideas?

[Dennis C.]

Re: 71 differential AIM note. What does it mean?

Definitely, not clear, but to me the note is referring to the lube. Was a different lube or quantity used with the M22 transmission?

[Mike E.]

Re: 71 differential AIM note. What does it mean?

I thought it referred to the lubrication, too. But what effect does M20, 21, or 22 have to do with differential lube? Diffs were the same except for heavy duty caps vs. u-bolts for base motor vs. big block.
The note and its meaning is an enigma to me.

[Jeff B.]

Re: 71 differential AIM note. What does it mean?

Since one could order the rear end as positraction or non-positraction, I wonder if when the M22 trans was specified, then a posi rear end was mandatory? Because the AIM specifies the quantity of lube required, does this imply that quantity of lube is different depending on if a posi or non-posi?

[Joe L.]

Re: 71 differential AIM note. What does it mean?

Since one could order the rear end as positraction or non-positraction, I wonder if when the M22 trans was specified, then a posi rear end was mandatory? Because the AIM specifies the quantity of lube required, does this imply that quantity of lube is different depending on if a posi or non-posi?

Jeff------


Many engine/trans/rear end combinations required positraction. In fact, many more required positraction than didn't require positraction.

[Joe L.]

Re: 71 differential AIM note. What does it mean?

Take a look at the red-circled note on the attached AIM sheet. I am having trouble interpreting and guessing what the alternative would be for an M22-equipped car. This note is also in the 72 AIM, not in the 70. Any ideas?

Mike------


That instruction was added to the 1971 AIM very late in the model year. In fact, my copy of the 1971 AIM includes only revisions through #8.

In any event, it sure did not affect many cars at that point. By the time this instruction actually got to assembly line use, there were probably very few M-22 installations built. The instruction continued in the 1972 AIM but, of course, only affected 20 cars.

It certainly applied to the lubricant but I do not know what the difference was.

[Mike E.]

Re: 71 differential AIM note. What does it mean?

Since one could order the rear end as positraction or non-positraction, I wonder if when the M22 trans was specified, then a posi rear end was mandatory? Because the AIM specifies the quantity of lube required, does this imply that quantity of lube is different depending on if a posi or non-posi?

[Terry M.]

Re: 71 differential AIM note. What does it mean?

Jeff------


Many engine/trans/rear end combinations required positraction. In fact, many more required positraction than didn't require positraction.

By 1971 (the subject of this thread) Positraction was standard equipment on Corvette. Thus all Corvette production required Positraction.

[Mike E.]

Re: 71 differential AIM note. What does it mean?

Mike------


That instruction was added to the 1971 AIM very late in the model year. In fact, my copy of the 1971 AIM includes only revisions through #8.

In any event, it sure did not affect many cars at that point. By the time this instruction actually got to assembly line use, there were probably very few M-22 installations built. The instruction continued in the 1972 AIM but, of course, only affected 20 cars.

It certainly applied to the lubricant but I do not know what the difference was.

Just in time for the production of LS6, (began March 1) which was the only way to get an M22 from the factory.

[Joe L.]

Re: 71 differential AIM note. What does it mean?

By 1971 (the subject of this thread) Positraction was standard equipment on Corvette. Thus all Corvette production required Positraction.

Terry------


Yes, I was referring to more than just the 1971 model year. Positraction became standard on Corvette for the 1970 model year.

[Jeff B.]

Re: 71 differential AIM note. What does it mean?

Thanks for the clarification. I was not aware of that. Good information.

[Terry M.]

Re: 71 differential AIM note. What does it mean?

Actually 1970 was the first year Positraction was not optional, as Joe says above -- but that is another discussion.

The question of why different lube for the differential with M22 is a good one, and is still unanswered.

[Joe L.]

Re: 71 differential AIM note. What does it mean?

Just in time for the production of LS6, (began March 1) which was the only way to get an M22 from the factory.

Mike------


LS-6 was not the only way to get an M-22 for 1971. ZR-1 was the other way. In fact, for LS-6 one could order a special THM-400 or M-21. For ZR-1 the M-22 was mandatory.

[Mike E.]

Re: 71 differential AIM note. What does it mean?

Mike------


LS-6 was not the only way to get an M-22 for 1971. ZR-1 was the other way. In fact, for LS-6 one could order a special THM-400 or M-21. For ZR-1 the M-22 was mandatory.

[Bill B.]

Re: 71 differential AIM note. What does it mean?

I know that this post is a few years old, and perhaps the answer might appear in another post, however ... my theory was that because the "M22" Corvettes were ZR-1's, and that the ZR-1s were the "unofficial" factory competition race car, and the fact that I understand the ZR-1 rear differential plug came with a wire secured hand tag indicating a certain brand of hypoid gear oil be used, perhaps the reason for that may have been due to fact that brand of oil refenced on the tag may have been a sponsor of some leading race teams at the time ...

Of course, at that time, the AMA ban on factory sponsored racing activity was in full force (wink-wink), so there shouldn't have been any influence of outside forces within the walls of the great GM ... perhaps the reason for the cryptic note on the assembly manual without giving away the apparent real reason?

I'll see if I can find the source of the wire secured hang tag info and the exact info printed on it. The same tag may have also been applied to the M22 transmission fill plug as well ...