1965 Delta 88 Diff.......

[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 http://classicoldsmobile.com/forums/members/monzaz.html

Very nice guy, and helpful builder.

[65Delta88]

Originally Posted by J-(Chicago)

Send a PM to http://classicoldsmobile.com/forums/members/monzaz.html

Very nice guy, and helpful builder.

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 2.93, 3.08 and 3.23 for example, the most desirable ratios, are all 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]

Originally Posted by 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?

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......