coltsneckbob

What is my rear axle
I have a 1970 442 w-30. The original window sticker says it has an "anti-spin" rear axle with an MSRP of $42.13.

It has an aluminium diff cover (W-27) installed by dealer (as specified on the sales document I have). The housing is cast.

I find the numbers 402227 on the housing (driver side, shaft side) and CFD 7 on the housing right under shaft. There is also an "SE" stamped on the passenger side axle tube on rear facing side of tube.

Are there ususally numbers somewhere else? Where?

I know there is a technique to raise the entire rear end and while spinning the shaft to count how many turns it take to rotate a tire 1 time, but that is somewhat difficult and not 100% accurate. Oh, and I don't want to pull the cover off and count gear teeth!!!!

Any other suggestions/help would be much appreciated.

Oh, one other thing.....at 50mph the tach reads 3500. I don't quarantee the tach is 100%, but still it seems high and that leads me to believe it is a rather high gear ratio.

rcorrigan5

I'm wondering if someone has changed the entire rear axle assembly in your car before you bought it. The "SE" code indicates that it is a 3.23:1 open rear end and that rear end did not come with the W-30 model, according to my book. W-30s came with anit-spin rear ends in either a 3.42:1 (code TM) or a 3.91:1 (code TO) ratio.

wmachine

X2

Bluevista

3500 rpm at 50 miles per hour?

I don't think that's a 3.23:1 gear ratio. It must have been changed if the tach isn't way off?
Works out to about a 5.56:1 ratio in my book.

Try plugging the numbers into the rear end calculator, just need your loaded tire diameter, should be about 26-27 inches with 14's I think? The Tire Mart site has the diameters if you know the tire size.

http://www.angelfire.com/fl/procrastination/rear.html

Allan R

I had a problem like this with my car's tach once before. It was out of calibration by about 25%. (on the high side) After the bench fix and test it also ran in perfect coordination with the tune up tach. I'd check that first.

As with any gear ratio, the obvious thing to do is jack up the rear of the car (both sides if it is posi) and turn the tires 10 full revs. Mark the tire so you know where 10 revs starts and finishes. Have a buddy put a white pen mark on the driveshaft and then count the number of revs it does with 10 wheel turns. Don't spin the tire too fast. That will give you the gear ratio. total driveshaft revs divided by 10.

If you turn one wheel and the opposite wheel turns the same direction, you've got posi.

It sounds a lot like someone did a rear end switch with your car before you got it.

BTW, when you're at 50 doing 3500 RPM, does it sound like the motor is working? Or is it just a normal run? Also, if you do a hole shot and you've got really tall gears, you should be able to light your rear tires up for quiite a distance.

coltsneckbob

OK, I looked at the window sticker and see that the axle option is G-80. After much Googling I see that that axle was a 3.91:1 ratio.

I can't say that the engine was working hard at 50mph, but it did sound slightly pushed. Hard to tell with the wind and the thrumm of dual exhaust.

I know for a fact I don't have posi. Will the car leave rubber.....yes. I have not really tried to smoke the tires, but have left one or 2 marks on road about 10-15 feet long. It is an automatic, but if I stay on it then it will also leave a small mark going from 1st to 2nd.

Still there should be codes stamped somewhere else on the axle, but where?

wmachine

G80 is the code for posi, and nothing to do with the ratio. The code SE you found on the axle tube *is* ratio code 3.23, but like Randy said, it is not correct for a W30. Apparently the axle housing is not original to the cars, so any numbers you find on it are rather meaningless.

scrappie

How many bolts are holding the rear differential cover on?

coltsneckbob

There are 12 bolts

coltsneckbob

Wmachine,

If it is posi would it also be anti-spin. I thought the 2 were mutually exclusive. The sticker says anti spin.

Jamesbo

Posi=anti spin
peg leg= open carrier [non posi]

coltsneckbob

OK thanks! Learn something new everyday

coltsneckbob

OK, I know that this will be like finding a needle in ten story haystack, but does anyone know where I can find an original (or even reproduced) G80 axle that is correct for the car?

joe_padavano

Anti spin is the brand name Oldsmobile used for the clutch-based differential assembly that other automakers called positraction or limited slip. They all function basically the same way, which is to use friction, either through spring-loaded clutch plates or cones. This is different from a locker or torque-sensing differential.

wmachine

Okay, let's start this over.
Basically, there is the axle housing, and there is the carrier and gears (and axles & bearings) inside.
The same axle housing can contain various different gears (thus differnent gear ratios) and either an standard carrier or a posi carrier.
Your housing is fine, it only has the wrong numbers on it to be the original one. You need a posi carrier (if yours isn't) and a 3.42 or 3.90 (or whatever gears you decide) gearset.
G80 is just the designation for a posi carrier, nothing to do with the housing or gears.

coltsneckbob

I think I understand that. But, with my vehicle everything is matching except for I guess now the rear. I would like to put in the same "exact" rear that the Window Sticker and the sales sheet list for the car.

If that means finding a correctly stamped axle with the right gears, then I think that is what I want to do.

wmachine

If I understand you correctly, you don't have anything that determines what gear ratio you had originally. So you will have to decide what you want. Makes sense to go with what would have been standard, either the G92 3.42, or the G88, depending on how your car is equipped (auto? air?)
You *may* have a posi that has shot clutches, and you still haven't even established what gear ratio you have. You may have what you need, short of the stamping on the tube.
May be best just to open it up and be sure, then go from there.

88 coupe

"Posi" = Short for "Positraction" = Used by Chevrolet only.

"Limited slip" = "Generic" for all differentials that transfer power to both wheels as needed.

Norm

coltsneckbob

My car's window sticker said it should have the G80. It has auto and air. So, that is why I wanted the G80 axle (stamping too) and of course the right gears.

88 Coupe, your explanation of limited-slip is more if what I thought. I always thought Posi was pwr to both wheels all the time (with slight slip on turns). With posi if u spin tires both will leave rubber. I interpreted anti-slip as power to the one wheel with traction.

wmachine

I'll try one more time: Anti-Spin, Posi, Positraction, Limited-slip, Sure-Grip, Traction Loc, Anti-Slip, etc. are all names for the *same* thing! All will (when working properly) "lay 2 strips of rubber"
There is no stamping for G80. G80 is for the Anti-Spin (Oldsmobile's name for the the above carrier), and applies to *any* gear ratio, so there is no code stamped anywhere for it.

coltsneckbob

OK, I guess it is my multitasking (working and doing this - LOL) and I am not being clear. The axle I have is stamped "SE". Wmachine said that would indicate it is a 3.23:1 ratio open end, but he also said that was not correct for my car.

So, what I am saying is that I would like to get the correct stamp on the axle (TM or TO)....plus of course....the correct gearing. Which if I understand these notes should be 3.42:1 or 3.91:1 anti-spin or posi rear.

The value of the car to me is that it match exactly the original Sticker and sales receipt. Now except for the axle here everything else does.....right down to the little map light and electric seat. All other numbers and date codes conform....so being a bit OCD as I am I wanted the rear to be conforming too!

I do understand the terms now...thanks!! Obviously marketing terms are part of the confusion. But, I also own a GL450 and I think that when they use the term limited slip they don't mean posi, but instead a form of traction where the power goes the wheel with grip. In traditional (non-posi) rear ends if you go one wheel on something slipperly it would spin and not the wheel with grip.......hence my confusion. THANKS though for your explanations.

scrappie

You can always put out a parts wanted add for the TM or TO. I would think TM would be the better fit. You might get lucky. Although I did hear parts for those may be harder to get. I would give Supercars Unlimited a call. Maybe they have a lead or some info.

coltsneckbob

OK thanks for the tip scrappie!

wmachine

You're doing much better. But your limited slip *is* posi. When both wheels slip (like when you burn rubber), the axles are both engaged.
But the object is good traction, not burning rubber!

wmachine

Whoa!!! Hold the show a minute, coltsneckbob! You may indeed have the original rear end.
I checked to be sure, and with an auto trans *and* AC, a 3.23 gear ratio *is* optional! But the stamped code should be SF, not SE.
Please take another *very* close look and tell us it is stamped SF.

coltsneckbob

LOL. Yes I actually do think I understand. Problem is I've been away from good old (and I mean old) American cars too long. And yes I do get the idea is traction, but leaving that long black (double) strip on the road is still fun.....even though I should have gotten that out of my system 30 years ago.

Does anyone know what the 1970 option codes for a 442 were? And what they included? Is there a site that lists them?

I am on a quest now to find the correct rear end for my vehicle. From the info you folks have provided I should have a posi rear with the 3;42:1 or 3.91:1 gearing.

I don't know why my vehicle has the rear it does, but I do know that the springs were replaced sometime in the last 40 years of its existence. Perhaps some thing happened. I had the car inspected by a mechanic I trust for any an all signs of accident repair and nothing was found or even suspicious.

I checked the tachometer in the car against my external tach and find that at idle there is 150 rpm difference (the car tach is higher). My mechanic confirms it too. I don't know if that difference is constant, linear, or something greater as engine rpm increases. If it is is constant or even linear I might suspect that the gear ratio was changed (regardless of what is stamped in axle tube) to a higher ratio given the extremely high rpm reading at 50 mph.

I purchased this car only last month, but have already received an offer of nearly (not quite) double what I paid and they know about the axle. However, I intend to hold on to it for a few years.

Again, you folks have been very helpful.....thanks again!!!!

jensenracing77

i don't think that this is a must but all the A/C W-30s i know of do not have 3.91 in them. i would think you could get a TM (3.42) and probably be correct. is this car a 4 speed? you may have said but i missed it. if you run a 4 speed with 3.91 it will have to have a ratio adapter for the speedometer to be correct. these are hard to find. i know where a 3.42 TM is at but the mounts have ben cut off and leaf spring pads were welded on it. it needs rebuilt. he wants $450 plus shipping. i am sure you could find a better one out there but wanted to offer it to you. i was going to get it but figured it would be to much work for me.

coltsneckbob

Jensen

Mine is an auto. Interestingly enough though that u bough up the speedo. I measured mine against the local cops radar and the speedo's is very exact. Like right on the money after multiple runs. SO, now that makes me think that whatever is on the axle the gearing is whatever the trans was set for.

I appreciate the offer, but I don't want a modified rear and then have to re-modify it.

But, if I do get a reference to the right axle I would gladly come up with a nice "finders fee"!

monzaz

Does any one KNOW hat a T3 code 'O' type 12 bolt is?

I was told it was a hurst olds code only 3.91 this rear has 31 spline axles and anti spin unit 672 casting. Let me know. I t may help the W-30 guy out. I have this rear diff all reconditioned and ready to go minus brakes. I do know 31 spline axle rear is rare and optional in 1967 1968. Jim

wmachine

T3 is a 1969 O type 3.91 with power disc brakes. That could be from a '69 Hurst, but it is not exclusive to the Hurst.

wmachine

coltsneckbob, you (and others, I guess) not paying attention again here. I'm telling you that you already may the correct original rear. 1970 W30 with Auto with AC has a 3.42 standard and a 3.23 optional. But the stamped code should SF, not SE if it is Anti-Spin.
Please take another *very* close look at your stamping!

And yes, I have the option codes for 1970.

MN71W30

I certainly caught it,
If it were mine I'd be scratching on that axle tube looking for the "SF" Great work Kurt.

coltsneckbob

wmachine....I missed ur post. Yes, I will look at the stamp very carefully to be certain it is an E or an F. Thanks

joe_padavano

Your interpretation is incorrect. Posi(traction) is one brand name for a limited slip unit.

coltsneckbob

Joe, isn't that what I said I understood earlier in the thread?? That being that posi is a marketing (not actually a brand is it?) term.

Years ago....like late 60's and early 70's we (kids at the time) used the term "posi" to mean power to both wheels all the time. In fact I remember feeling a sort of skipping (on inside wheel) when my friend's Mustang made tight turns. That to me was another sign of "posi" (or positive traction). What I don't think we ever called it was "limited slip"....probably because that was a marketing term and none of us were old enough at the time to buy a new car......so posi was all we knew. Among the cars I've owned recently are some foreign/German cars where the brochure speaks of "limited slip", but I know that these manufacturers means something entirely different. Coupled sometime with 4 wheel drive they are trying to simply decribe the cars ability (usually electronically or computer controlled) to change the wheel receiving more power to the one that "has" traction. In the older cars if you jacked up a rear wheel on a non-posi car that wheel would receive most if not all the power because it could rotate the easiest. This was great at solving the "chatter" or skipping while making a tight turn because it meant the outside wheel would power through the greater distance of the turn's arc.

So I think my initial confusion was about application of the correct term to the techology. And of course nowadays the technology involves much more then simply a set of gears and clutches.

wmachine

I guess there is no convincing you that limited slip and posi are the same thing. Maybe one day you'll understand how they work.
For now, I'll be happy if you find a "SF" on your tube!

Jamesbo

Look at it this way

Kleenex is a brand name but has become generic meaning tissues.

Although Positraction [according to Norm] was used by Chebby. It has become the standard "generic name" for limited slip, and anti spin.

Get it?
Got it?
Good.

coltsneckbob

Wmachin. I agree posi and limited slip are exactly the same. All I am saying is that due to the marketing of these products over many years and many manufacturers the definition has become fuzzy.....well at least for me.

Nevertheless within the context of this forum I recognize what when u say limited slip it is posi. Were I on a Mercedes Benz forum I might have to apply a slightly different meaning to the terms.

Today I am gonna grab a brush, a jack, some stands and possibly a camera and search for all the codes on that damn thing!

Anyway guys I really appreciate all your help!!! Thanks!

coltsneckbob

Well, I looked very carefully is it SE. See pic. Apparently this is not the correct axle for the car. Somewhere some time it must have been changed. The SE is on the passenger side and faces back of vehicle

coltsneckbob

Incidentally, I also checked the tach in car against my hand held unit. Apparently the car's tach is way off. At idle it reads 950, but it is really 650. When I rev the motor up to 3000 according to the car tach the hand held unit tells me the rpm is really about 1700. So this kinda makes sense to me.

Unfortunately just another blasted thing to try and fix !!!