Just to make sure I'm not looking down the wrong alley here. To find a posi axle for my centurion I can look at: 71-73 centurions, since it was an option, right? What else, did any electras come with this option? How about the wagons? was there like a tow package that included posi? Any other GM that had the 9 3/8's I know, I know, we've seen this topic 10 times by now. :boring: Sorry, just had to ask.
71-73 Riviera too. The 71-73 wagons have a different rear suspension but the gears would be the same. Electras had the option too. Later models would fit too but many of them had the Pontiac 8 7/8". Olds models probably have the same gears. I think that the 9 3/8" axles found on the 71 and newer Buicks were manufactured by Olds... http://www.oldsmobility.com/newsarticle.htm
Kimson, Easiest to find it on is a boattail Riv GS. Frequently on big Olds cars, too. It's a hunting game, for sure. I haven't changed, because my hunt is more specific. I just want the locking set... I want to keep the 2.93 gears (I like the power at the higher speeds, rather than off the line), but change the internals to posi. I almost had it, but got outbid. All it really takes is time dedicated to looking. I always tell the GS people with their high ratios... "OK, the quarter mile is yours, but give me a five mile dash and you're history...."
I'm not too good on the gears at the moment it feels like. Sitting on the freeway and listening to the engine roaring cause it doesn't have enogh gear is getting a little bit annoying. I changed my axle to one that came out of an electra, and the gear ratio became more off the line type. Now I've also put on the smaller tires, so for every turn of the wheel the car travels a shorter distance, so the gear ratio changed again. I don't really see the need for the off the line ratio, but a posi wold be sweet just so you can really floor it. I think your solution is in the right direction. I see a lot of electras at the yards around here, but I've never seen a riv at the pick a part yards. The only place that has them is memory lane, and they want some money or their stuff. I'll just have to keep on looking, I've been unlucky with two cars going in the crusher bfore I got to take parts of em that I needed, but maybe some day. I'm in need of the driver's side exhaust manifold, and I came across one of a 76 electra. The problem was that there was some kind of valve at the bottom, and I could just picture myself spending a day at trying to get that thing apart, so I left it. Patience seems to be a big part of this yard scavenging business. But as they say, they don't make any more of em.......
Yeah, I still need the posi unit for traction. Even with 2.93 gearing, the 455 has so much torque, the wheel will easily cut loose with even modest acceleration. Also helps me get up to 14mpg on the highway
I can't speak from complete knowledge there, but I THINK '74 and later went to the GM corporate rear.
In 1974, most had the smaller Pontiac 8"7/8, some cars continued to use the larger gears in 74 and 75 but by 1976, they all had the Pontiac unit. The 1976 Electra manifold would probably work without problems on your Centurion (as long as it has a 455), the valve at the bottom is the heat riser valve, it uses a vacuum diaphragm instead of a weight and spring like the older models. You just have to use your heat riser instead of this one.
what size of rear end and what size ring gear do 71-73 rivs have because i would also like to get a posi unit for my car
9 3/8" ring gears in those cars. Big, strong, and NO aftermarket parts (because they don't break) Lots of these in yards with open carriers, posi's are hard to find.
typical ratios were 2.73, 2.93, 3.23 and 3.42... all were available with posi option, but most posi's are 3.23 and 3.42. I believe 2.73 and 3.23 were '71 and '73 and 2.93 and 3.42 were '72. Most boneyard have been stripped. Probably some out there, but a lot of work to find. Easiest way is usually to do what Adam did. Find a cheap boattail Riv GS for sale, verify the rear end code, buy it, swap the rear, then sell the Riv. Some other full-size Buicks and Oldmobiles with towing had them, but less often than Riv GS.
That's right, Adam. I'd forgotten. They upped the ratio slightly going into '71 to help somewhat in offsetting the power drop (except I think Electra stuck with the 2.70-something). Then went back down in '73 to help gas mileage.
To get a 2.93 posi for my highway LeSabre, I had to buy a 2.73 posi and a 2.93 open rear, then combine them. For the 71-75 9 3/8", 2.73-3.23 all take the same carrier. Take it from me, the 71-75, 9 3/8" 3.42 carrier is hard to find. I've found one in my life, and it's under my other LeSabre. Both LeSabres are 76, and both had the 8.5" corporate rear, not the Pontiac 8 7/8"- although I have several of those too. Anyway, I saved one of the corporate rears in case I need to be able to build one from aftermarket sources.
I've occasionally seen the internals on eBay. Really fuming over the last time. I fogot to up my bid at the last second and got outbid by a buck. I had $70 and it went for $71. Of course, I don't know how to do the swap myself, so that's probably another $350, or so. But well worth it.
I found mine under a Pontiac Grandville convert, and thats where my next one is coming from too. Open up your search to include any BOP full size 71-76. They are out there.
