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I have A 68 oldsmobile 442 how do I know what kind of rear end I have in it?
It's all original and how hard is it to change it to posi?
If the seventh character of the VIN is the number "1" (indicating that the car was built in Canada), your original rear axle is a Chevy 12 bolt. If the seventh character is a letter (indicating that the car was built in the US), you original rear axle is a Type O. Parts for Chevy axles grow on trees. Parts for Type O axles are difficult to come by. Either way, setting up a rear axle requires attention to detail and some tools. There are lots of how-tos on line.
I can tell you that if it's not Canadian built it would have the Type O 12 bolt, which, to ward off JP, technically has 10 bolts where you can't see 'em and it does not matter. What you can see is the cover attaching which will be either 12 bolts, with two at the bottom in a line with each other, or 10 bolts, which pattern has one centered at the bottom.
The Type O diff has a smooth round cover; the Type C [Canadian, Chevy] diff cover has huge obvious Crinkles disturbing the smoothness of the cover, and also a crinkle or stiffening rib in the cover between each of the cover bolts.
Why do you think you need new axles?
You can ascertain the ratio by counting turns or remove the cover and find the numbers [tooth count] stamped into the OD of the ring gear, and divide one by the other. Example, if you find "41 10" stamped there, the ratio is 41/10 = 4.10. More likely you have the common 3.08, which is probably a 40/13 count. Note that one of the numbers is almost always a prime number.
Search the net for some photos of each.
How hard to change to posi?
Type C is probably a matter of making a phone call and spending money.
Type O- not sure, rumor has it some parts are now available, others will know more.
Last edited by Octania; February 11th, 2016 at 09:35 AM.
It's a type o rearend my car was built in fremont ca.
how do I figure out what gear ratio it is? I need new axle shafts If I don't go posi at least I need to do is new axles.
there is a two letter code on the axle tube that indicates what gears were originally installed when new. Scrub the tube & find the code roughly 4" from the center section on the passenger side tube. Spin the tires with it on jack stands to see if it is close to the code.
Finding the code of the axle tube can be challenging if the axle is crusty. Typically you have to scrape off a couple decades worth of dirt, grease, and rust in order to see the code. Pics below show what you're looking for:
Last edited by Fun71; February 11th, 2016 at 10:37 AM.
The reason I know I need new axles is because there a lot of play in the tire and I replaced the axle bearing and seals once and I just got a pipe and pressed them on myself and they went on pretty easy no press needed so I know there probably spinning on the shaft. Also the seals are leaking there was a lot of gear oil on my tire when I took it off. I could be wrong but I'd like to atleast replace the bearing and seals again before I put my new tires and rims on so I don't get gear oil all over my new tires and rims.
Is it worth putting rear discs on since I have front disc?
I had the bearing spin on the shaft of a '68 O-Type and it was very evident when the bearing was removed as there was a groove in the shaft where the inner bearing race sat.
Minor thread hijack...So does your Z code car have 344 on the cowl tag under the hood (not the VIN on the dash)?
Is it an AC car and is it an early build, Aug, Sept? I have an early build Z code AC car and just trying to do some documentation on it.
As far as changing to an anti spin; first you need to know what rear end assembly and series carrier you have. If its OEM to the car, its a O type, 10 bolt, 8.5" ring geared rear end. The cover will have 12 bolts but that means nothing. 10 Bolts hold the ring gear to the carrier not 12. Canadian cars received the Chevy C clip or C type rear). 1968 Canadian Chevy rears found under a 1968, 442s were a 12 bolt carriers not 10.
The carrier series can be determined by what ratio is in there (if OEM).
Once you determine that then you need to find a anti slip out of another 68-70 O style rear. Or call Auburn Gear and see what they have. Or install a complete O type rear already set up or a complete Chevy or Ford 9" style axle assemblies with the correct Olds mounts, (this will require a pinion side Ujoint conversion and drive shaft length alterations, both easy). Installing another O style or Auburn carrier in your existing housing is generally more cost effective but harder to find parts for vs a Chevy/Ford. The Ford or Chevy assemblies offer endless parts availability. Not so for 68 O types. The 68-70 O types share nearly noting in common with other makes.
My O type conversion cost me about $500-600. I wanted to retain the OEM housing as it was a Cali pit free housing. The cost was $100 for the bone yard complete axle assembly out of a 4 door CS. $60 for the spacer $100 for the crush sleeve, pinion seal and longer ARP fasteners and washers. $90 for a speed shop to set it up. $25 for Red Dot Synthetic lube. I also replaced all the bearings, races, seals and chassis bushings. Soft brake line too. I did all the work myself but the shimming(setting the gear lash).
As an example I put a anti-slip from a O style 2 series carrier (256:1) into a O style 3 series (308:1). We can use the 256 series anti slip carrier but you have to add a spacer between it and the 308 gear to get the pinion to ring gear mesh in spec. The 2 series gear is much thicker than the 3. A 4 series gear is much thinner than a 3 and so on. If you want to go that way you need to have the ring gear rear face cut down.
Sources:
Spacer= National Drive Train or Drive Train Direct.
Outer axle bearings, carrier bearings, pinion bearings, seals = BDI
Correct fasteners with correct thread count, style and right hand threads and mating washers = ARP
Crush sleeve = Help rack at NAPA
Shim Kit? the speed shop supplied that.
New axles, Speedy sleeves or spray welding and machining is the proper way to fix a spun axle...so long as its not spun so hard its blued. Then the axle is junk.
February 11th, 2016, 09:13 AM
