1969w3155

What's the going rate for a decent set of O type 3:91 ring and pinion? How much with the posi unit? (no carrier).

jensenracing77

I am terrible with the terminology of rear end parts... When you say "with the posi unit" no carrier, What does that mean? I sold a 3.91 setup with the posi unit in 2012 for $600. The gears were very nice. I would bet they would go for a little more now but not sure.

66-3X2 442

The carrier is the posi unit or the open unit.

1969w3155

Eric, here's a pic of the posi unit with the ring gear. I also have the pinion gear. I want 3:91's for my '69 (ring and pinion only), but I would consider selling this set with the posi to someone restoring a '68-70 W30/W31. I need to get a good look at the splines to get a count to see whether it is the '67-68 31 spline, or '69-70 28 spline. I was told that it was a '69 31 spline, but in '69 they went to the 28 spline axles with better metallurgy.

Fun71

I read on the old Chebucto e-mail list nearly 20 years ago that the metallurgy change occurred in 1970 along with the different bearing design.

Ancient Iron

What is a whole 3.91 rear end assembly worth???

jensenracing77

An SJ with a nice housing should bring at least $850+ unrebuilt but working, A TO with a nice housing would likely be in the $1200+ range.

1969w3155

Somewhere, in one of my books is where I read it. I agree with the bearing change in 1970, that is mentioned in Supercars Unlimited "442 by the Numbers" booklet, which also indicates that the '70 was a higher strength unit.

Fun71

Cool, I didn't know that info was actually published. I learned it from first hand experience - I currently have one of each version of the O-Type 12 bolt: a 1968 standard 28 spline, a 1968 Heavy Duty 31 spline, and a 1970 28 spline. I have a spreadsheet with all of the data I could gather, such as bearing part numbers and dimensions, seal part numbers, bolt sizes, carrier casting numbers, etc.

1969w3155

What does your spreadsheet have for this unit? I am trying to confirm what Monzaz (Jim), told me, that it is a '69 31 spline, but it may be my lack of correct info as I was sure that '69 & 70 was the 28 spline.

joesw31

That posi is 31 splines for years 67 and 68 application. In 1969 they went to a 28 spline axle shaft and the casting number for that posi is "588". Further, in 1969 they used two different axle shafts a heavy duty axle shaft, and a non-heavy duty application. Each axle shaft has a different casting number. In general, the heavy duty axles have white paint on them. The same also applies to 1970. However, 1970 used a different axle shaft bearing. Also, for 1969, the ring gear bolts were changed from right hand thread to left hand thread. Hope this helps.

1969w3155

So, this "672" posi is for 1967-'68 Olds rears with 31 spline axles? Therefore the ring and pinion will not directly swap into a '69 due to the '69-70 having a larger ring gear? (My '69 has a TY rear under it, currently housing 3:42's). I ordered a RH 7/16-20 bolt from Rock Auto just so I could check to see what threads it had RH or LH. Oddly enough, I pulled this posi from a '69 LeMans about 35 years ago when I had a '66 GTO with 3:08's not knowing back then what it took to put more aggressive gears into a car, nor the fact that this wasn't even a Pontiac gear set, as pointed out by Jim. Thanks everyone for their help. Now to figure out a value for a '67-68 posi rear!

11971four4two

I would think a 1967- 68 31 spline axle would be stronger. Just not as common or as easy to find parts for

11971four4two

HERE ARE A FEW PICS 672 vs 588 carriers 301 vs 342 ratios



THE gears should be 8.5 10 bolt with 12 bolt cover IE the same fitment. The carriers and left hand / right hand bolts etc... will be different for 69 - 70 and other mobiles

value???

I was told my 31 spline TO axle was worth $xxxx
not sure if that is realistic for a quick sale
but that is as low as i will go on mine

joesw31

Your ring and pinion will work fine in your 69 W31 "588' posi with no problem. You just need the correct bolts. Ever thought of 4.33's? I learned the hard way about ring gear bolts years ago...

joesw31

Those bearing caps are installed reverse on this diff. The arrows on the caps should be facing outward.

1969w3155

I have a set, sometime in the future, if I ever get his thing on the road again, I may try them for one summer. My car was factory 4:33 equipped, owner number 2 had them removed by an Olds dealership back in the 70's when he was commuting to Junior College, hence the 3:42's in there now.

joesw31

I ran a set of 4.33's for while in my W31. The 308 cam liked the 4.33's. Not the best street gear. You should be fine with those 3.91's.

Mr Shifty Sidney

Thanks to all for the good info.

​​​​​​​Don W

1969w3155

The ring gear is stamped: 11A43 GM LH, which is telling me the tooth count on the gears, General Motors, and is LH for left hand threads? Pinion also has 11A43 GM plus DT and 394705 243 332 if it helps I.D. which set that it is.

joesw31

The 68 ring gear should be right hand thread if it wasn't changed. The posi should have a Julian date, the ring gear Julian date, and the pinion as well. 243 or 332 can be the Julian date.

Fun71

As joesw31 said, it's a 31 spline O-Type posi carrier.

Unfortunately, I do not have one of those - my 31 spline O-Type is a TL code 3.42 rear with an open carrier, casting number 359.

1969w3155

Anybody have one 7/16-20 right hand bolt that they can sell me? The one That I ordered from Rock Auto was a left hand bolt, so I still want to make sure of what I have before ordering a set. Thanks.

66-3X2 442

If you're just checking bolt size and thread count,the hardware store has that size. Just sayin.

1969w3155

No longer have any local hardware stores, and Home Depot didn't have any.