Pulled from a 66 442 with a SF axle code, (3.23). But I didn't trust
that since it had silicone on the pan, but it may be right?
The #'s read 42 13 GM 5 66 TM. Anyone know for sure?

 

Yes that is 3.23

 

Thanks Don. I was trying to do a search on the #'s with no luck.
How were you able to decipher them?

 

What is 42 divided by 13 ??????????????


Answer 3.23.


Not sure why you need help deciphering this but there you go.

 

OK Dave. That was what I didn't know, to divide these two #'s.
Maybe this thread can help some more guys out that didn't know as well.

 

I have to agree with Dave on this one - this is why you wanted to stay awake in math class.

42 is the number of teeth on the ring gear. 13 is the number of teeth on the pinion. The ratio of these two numbers is the definition of "gear ratio".

42:13

Divide both sides by the same number (13) - which doesn't change the ratio - and you get

42/13 : 13/13

Which divides out to

3.23 : 1

 

The point is guys, I Didn't know this is how it was done, that's all.

 

That is a good all a round ratio. I'll bet you remember that "lesson." Nice find.

 

It will go under the 70 442 to replace the SF unit under it that needs a good going through, also a 3.23 type O. GAF if it's a 66 cone type 8.2 or whatever. It's for fun.

 

Here is more help if you like....
The 5 means month so that will be MAY
The 66 is the year so that is 1966

This helps to determine IF you have the correct gear in the correct housing also, for those guys into date code parts.

Next - the posi unit is aftermarket Auburn NOT original GM product...Which may or may not be a good thing depending on the importance to you.

That unit will be Auburn part number 542099 PRO UNIT or 5420114 High Performance unit the round part bodt of the posi unit will have the last 3 digits stamped in...IE 114 or 099

Hope this helps more. Jim
J D RAce

 

Jim,
I did not know about the date code part, thanks for that info. Always good to learn!

Adam,
These numbers will also be found on the pinion gear. The ring gear & pinion are machined as a matching set & you can not swap these two parts around with other ring gears & pinions or bad things will happen.

 

Sweet! Thanks for the break down Jim. And thanks to you too Scott.
I always try to learn something new daily. Shoot, back in the dime a dozen
days we just unbolted and bolted another back in. Go through them, heck no.

The 70 project is going slow, but I have slowed some too. Here is the rear today. I am less than 6K on payoff on the vert and when that's done, I will be able to get a little more done hopefully. My GMC will be paid for about that time too.

There is that one little glitch...Momma is going to want a replacement for her Trailblazer I'm thinking. I have been hearing about it since '14. Dad-gum Honey, It's only got 123 on it...

 

123K ain't bad. I didn't give up my '02 S10 until it had 197K on it! Tell her to wait awhile longer!

Randy C.

 

My 66 442 3X2 car came with a 3.23 rear axle and a M20 wide ratio Muncie trans. I've had a lot of early cars and have driven a lot of others. I've never had a better combo in a car. If you got a 3.23 rear axle in 66,a M20 wide ratio was mandatory. I've said it before and I'll say it again,if we took all of the close ratio Muncies and dumped them in the ocean,the world would be a better place.

 

It may be to late Randy. I may have popped off and said something like "When the truck and the red car are paid off, then we'll look at it again." (You have to CYA). At least for a year or two, ha.

 

Funny you should mention that Mike. The 68 455 F-2 block I have for the '69 has the drilled crank and the wide ratio 4 speed is under the bench out in the shop. That bastid is the one I have really spent the $ on buying parts for over the years. All 3 of my 442's will now have 3.23 limited slip units under them. I, like you, feel they are overall great rears. If I keep and am able to do the 69, I want to have my 87 200 4R GN trans built for it and see how that would work for an automatic. Getting older sucks, never enough time or $$...

 

Didn't you know basic date codes Oldsmobile Dave??? Did you not learn to answer a question properly ? Basic communication? I suppose they just taught you basic math in your elementary/high/home school

 

Hey 76olds not sure where your attack is coming from or why but the post graduate degree hanging on my office wall suggests that my schooling was just fine, thanks for asking.


You must be having a slow day to worry yourself about this.


Also, did you notice that Joe posted that he agreed with me on the naivety of the question? I don't see you climbing up his *** for piling on.

 

Joe P agreed jokingly, you initiated the incompetence smart-*** like. WTF???

 

I have to agree. When driving an M21 or 22, you can always afford to skip a gear, and it doesn't seem to matter.

Before the wise guys start cracking wise, notice I said "driving" and not "racing."

Ideally, a five speed with an OD ratio and a 3:23 should give you a similar spread, but vastly improve mileage.

- Eric