65Delta88

I am looking for gears and possibly a posi for my car (1965 Delta 88 w/ 425), but I can't seem a) to figure out exactly what rear the car has (was told a 8.2, then a 8 7/8) b)can't find anybody that sells gears and stuff for the rear. From what I have gathered so far is that it has a pontiac rear in it............so please help..........



Thanks

J-(Chicago)

Send a PM to https://classicoldsmobile.com/forums...rs/monzaz.html

Very nice guy, and helpful builder.

65Delta88

Thaknks

aliensatemybuick

The rear in your car is shared (inner parts anyway. i.e., carrier, ring and pinion gears, etc...not sure the housing is quite the same) with Big Pontiacs of the same era (1965-70 I think). I beleive it is known as a "p type" rear. I think (going from memory here) the ring gear is 8 7/8 in diameter. Its a 12 bolt (12 bolts hold the ring gear on the carrier), but the diff. cover has 10 bolts.

This one would work:

http://cgi.ebay.com/ebaymotors/Posi-...spagenameZWDVW

So would this one:

http://cgi.ebay.com/ebaymotors/PONTI...spagenameZWDVW

Only problem is the ratio on both of these (2.56) may not be desirable to you (it wouldn't be to me!). The higher (numeric ratios) are generally more desirable, much harder to find, and you can expect those to go for in excess of $400 just for the gears.

This site (see bottom table):

http://www.teufert.net/fullsize/rearends.htm

shows the ratios and under "notes" the number of teeth on the ring and pinion gears, respectively. So a 2.56 rear for example has 41 teeth on the ring gear and 16 teeth on the pinion gear. Generally, the higher the ratio (numerically), the fewer teeth on the pinion gear. This causes an issue: the more teeth needed on the pinion gear, the bigger (wider) the gear, and thus the ring gear has to ride out further from the centerline (i.e. further out towards the passenger wheel) to mesh properly. As a result,there are different carrier "series" (i.e, 2, 3, etc.) which are designed so that the flange the ring gear bolts to is either further or closer away from the car's centerline. It can get quite confusing. And you can't just swap a ring gear from a higher (numeric) gear ratio on a lower series carrier. There are specific cutoffs (I think 3.23 and 3.42 for example, two of the most desirable ratios, are interchangeable, but if you go up or down, no longer). When I say desireable, I am thinking what I would want in terms of a nice balance between off the line acceleration and keeping engine RPM within reason at highway speeds. A 3.42 rear would be sweet, but should you see one come up for sale, count on it going for $500 or more.

Bottom line (in my opinon) is the best way to proceed is the find the entire set of "guts" you want and swap them into your differential housing. Or if you know your ratio, you could try to find a posi setup with the same ratio and just swap out the carrier and ring gear (retaining your original pinion gear). There are "shim" issues involved, reagardless, which USUALLY preclude your doing this job yourself.

I mentioned the Pontiacs because posi rears were more common in those cars. Though you might have success finding them in 65-66 Olds Starfires, which often had 3.23 ratios (a nice ratio in my opinon). Best bet is to keep an eye on Ebay.

There is a table at this link:

http://www.442.com/oldsfaq/ofdif.htm...ential%20Codes

which will tell you the code for your differential as well as the gear ratio and number of teeth on the ring and pinion gears (matches up well to the table I linked to above). The code can generally be found on the bottom of the axle housing on the pass side, closer to the diff than not. You may not be able to read it, however, after 40 years.

J-(Chicago)

Personally, I like the old clunky gears. Some may think it's the placebo effect, but I believe the cars running their motors at lower rpms their whole lives got better gas mileage, and more miles on the odometer.
If you're not going to race the thing for faster times, there's no need for lower gearing in my opinion.

65Delta88

Thanks for the info guys, I'll try and see if I can find the code to see what ratio I have. I haven't technically really even driven the car yet aside from rides around the block because I am still in the process of putting it together. Will it say anywhere on the axle housing if it is a B or P type axle?

aliensatemybuick

Assuming your car has the original rear in it, pretty sure it will have to be the Pontiac type. I think Olds went over to a Buick rear in later years (around '68 or so), but a '65 WILL have the Pontiac unit as stock.

65Delta88

yes the car is all original, so for sure it has the pontiac diff in it ( which is what I figured ) So in theory I could find a full size Pontiac and use the diff?

aliensatemybuick

Yes, but likely only the internals; I think there may be some differences in the axle housings between Pontiac and Olds (possibly where the control arms mount..I'm just not 100% sure on that). And you would want to limit your search to 65-70 big Ponchos.

Check out this auction:

http://cgi.ebay.com/ebaymotors/1965-...spagenameZWD1V

I know its expensive, but I hear good things about this vendor. And it is (to my mind) a nice ratio, though based on the auction description I was wrong about the series cutoff above (3.23 ratio does not use the same carrier).

I'd be willing to bet your car's rear may share this carrier series (if its a 2.73-3.08 rear it will), and if so, you could swap your ring gear onto this carrier and walla, no more peg-leg! Even if not, it might be worth calling the guy, he may be able to hook you up.

65Delta88

thanks I'll definatley check that out......

65Delta88

What type and how much oil should I put in my rear end? Also where can I get a gasket for the inspection cover can I get it at a parts store?

65Delta88

Any input on what oil to use?

aliensatemybuick

Victor Reinz makes the right gasket (part number P27943) and you can order it from your local NAPA store if they don't already have it in stock:

http://www.dmauto.com/web/dmauto/Cat...fg/NGA/P27943/

As for oil, I think you can use 80W-90 weight gear oil. If you do upgrade to posi, you will nead to put in a bottle of GM Limited Slip ("Posi") additive FIRST. As for how much oil to add, there is a plugged hole on the side of the housing you add the oil through which basically limits how much you can put in. You will likely need to buy 2 bottles of gear oil.

65Delta88

Do you think it will hurt if I run synthetic? I have 2 bottles of Mobil 1 gear lube laying around from a previous project.

aliensatemybuick

I have no personal experience with using synthetic gear oil in my classic cars. Probably OK, but perhaps an unknown...and then consider that the original stuff may have lasted as long as 40 years and 2 bottles of it is not going to break the bank!

aliensatemybuick

I have a 2.73 posi carrier and ring gear from a 1965 Dynamic 88 that I would be willing to sell for $200 plus shipping. If your car is already a 2.73, 2.93 or 3.08 ratio open rear, you can just swap your ring gear onto the carrier. If you have a 3.23 or higher open rear, I believe you can use a 12 bolt chevy Mr. Gasket ring gear spacer and still swap your ring gear onto it (though I have no experience with this and thus cannot say for certain). It would be ideal for someone with a 2.73-3.08 open rear who wanted to convert their car to posi-traction. I'll throw in the correct paper gasket (Victor Reinz part I mentioned earlier in this thread).

Should work for all 65-67 big cars, excluding Jetstar 88s.

if interested, E-mail me at scottfettner@hotmail.com

65Delta88

Hmmm.....I think I figured out that I have a 3.08 gear ratio in my car. What kind of posi is it? is it a gear or clutch type posi? Is it ready to use?

thanks

aliensatemybuick

Not sure what "type" it is (gear?); doesn't seem to have the plates/springs you often see in posi units. Its unquestionably a posi carrier, though. I've added a link to a pic. I bought this a few years back with the intention of using a ring gear spacer to fit my car's originally 3.23 open rear, but decided to go another route. The unit was pulled along with the bearings, races and factory shims, and a wire run through it all to keep it all together. I'm sure it will work fine for your application (that is assuming yours is a 2.73, 2.93 or 3.08). For the record, the ring gear has 41 teeth. A 3.08 ring gear will have 40 teeth.

monzaz

The posi is manufactured by Eaton corp. for GM . It takes clutches and the clutches are sold in the aftermarket. All you need are the spider gears, cross pin and the case to be in good condition and your good. Clutches are the same as 12 bolt chevy c-clip (chevelle camaro type) and the spring cages are the same also all sold in the aftermarket.

This is a Pontiac 10 bolt 12 bolt ring gear rear.

Does your cover resemble the one under that posi unit? Cause if it has 12 bolts this unit WILL NOT FIT. If it does look like theat one with 10 bolts and 9 and 3 o'clock cut outs you should be good to go. Then all you need to check is spline count on the axle shafts. Yours should be 31 the But I would double check to be sure.

Good luck on the sales guys. I have all the bearing info on that rear on www.jdrace.com if you need to know the bearings and seals. etc. Plus you can ask diff questions on the forum also. Jim

I will check back here to from time time. Take care. Jim

65Delta88

Thanks for the input, I know for a fact that it is a Pontiac diff with a 10 bolt cover with a 12 bolt ring.

65Delta88

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