[longnlow66]

Hello,

I have been toying with an idea and wanted to see if anyone has tried it. I was looking into the feasibility of putting a 78-96 B-body wagon 8.5 rear axle in my 66 Grand Prix. The width is close to the same and the bolt pattern is right. What got me thinking about this was the fact the rear sway bars from most mid 70's b body sedans and '78 and later wagons will fit on the 65-70. I would have to assume the lower control arms run in a similar plane across the various model years. Anybody have any info they could share?
Thanks

[mechanic17]

I'd be interested in hearing from anyone who has successfully used one, as I have one from a '94 caprice wagon with 3.23 posi. It is something like 4" wider than the standard b-body axle, if I remember right.

[Ragtop Man]

I like this line of thinking... all it takes is a measuring tape and a little trigonometry. Would have to assume that axle is pretty stout, too.

There is a guy in Smoke Signals with an original 3.42 Posi axle drum to drum for an outrageous price. Love the idea... but pass.

Good parts of this swap would be the axle still has 11" drums; a disc swap from an SS or a V57 trailer package car would be a no-brainer. The Imp SS guys are all up in it on durability mods for drag versions, and there are zillions in the fleet of ex-cop and taxi models. It'd be the shizznit to find this axle swap would also accomodate the 9C1 rear bar, but if I keep thinking about this, hair will grow on my palms

[mechanic17]

Yes, I have a 9c1 sedan w/rear disks and the stock braking feels significantly better in it than even the 11" rear drums in the standard b-body (which is fine).

Looking at my complete wide unit (out of the wagon and on the floor), it seems as if the perches are the same as the standard b-body, but the axle tubes are simply longer and extended out of the housing further. In other words, if they were pulled out, cut 2", and reinserted and welded straight, it'd go right up into a sedan like factory.

I'll try to upload pics in a few days, if this thread lives. Unfortunately, I do not have another rear end at the same location to put next to it for comparison.

longnlow66, is the 5x5 bolt pattern correct for your car? I know certain b-bodies through the years used it, including my buddy's '77 Delta 88.

I'd sell my 3.23 posi drum-drum for say $500 to anyone who cares to pick it up about 10 miles north of Providence RI. I think even the e-brake cables are intact. Remember it's the wide station wagon one.

[longnlow66]

I have been thinking about this swap for a while. I have a spare 8.2 out of a 68 Pontiac full size. I can take some measurements on this housing and we can compare it against the measurements from a newer wagon housing.

mechanic17, the 5x5 pattern is correct for my car.

Here is some info I pulled from the Impala SS forums about the B-body GM corporate 8.5 axles

Chevy
91-92 sedan
1566mm - narrow (all)

93-96 sedan
1566mm - narrow (9C1 - disc & drum & some other drum applications)
1598mm - wide (Impala SS - disc & B4U - drum)

Buick 91-96 & Fleetwood 93-96 sedans
1566mm - narrow (all)
NOTE: Fleetwood housing is unique to the application - 4-channel ABS provisions

91-96 wagon, all
1642.5mm

Sedan housings, in both widths, have the same lower control arm bracket location/spread distance, and will fit any other sedan frame. Wagons have a wider spread distance (approx. 2") between lower control arm brackets on housing, and corresponding wider frame lower control arm mounts.

I did some reading on the Impala SS forum about swapping disc brakes to the wagon rear axle. The wagon rear axle has larger diameter axle tubes as well as thicker hub flanges. These differences prevent the disc brakes from being a direct bolt on.

Does anybody have a flange to flange width for the 65-70 factory axle? I had written down 65.5 in my parts book for my 66, but I can't remember if I actually measured the housing, or got this off the net.

[Rapdron]

I have a 3.42 posi rear out of my 66 Bonneville at my shop.
I will be there later this morning, and will take smoe measurements
Ron

[Ragtop Man]

Wasn't J65 part of the Buick, ahem, "Trailering Package?"

A former client of mine was at Buick when that was being cooked up. Turns out more than one engineer in Flint needed a new RWD tow car for a race car... and a better way to get the kids to soccer than the dustbuster minivan.

So, they basically stuffed the entire 9C1 Police Car into a Roadmonster, and had a car of supreme quiet and refinement that would scare holy hell out of anything south of a Corvette... in particular, the Marauder.

Of course, Buick being the fuddy duddys they tend to be, would have nothing to do with a "performance" Roadmaster, and rather than kill all the good work, hid it in plain sight in the order guide under "V57 Trailering Suspension" or something similar.

Back to the first part, though: I was 99% sure the stawag came with 4-wheel discs and the better brake linings. Or is my memory permanently toasted

[FullHawgPoncho]

Originally Posted by Rapdron

I have a 3.42 posi rear out of my 66 Bonneville at my shop.
I will be there later this morning, and will take smoe measurements
Ron

Do you have any rear ends for sale? Looking for one like that for my 66 gp.

[longnlow66]

I am still looking into this swap. I have located wagon axle with 2.93 gears for sale. I need to go take a look at it. If I can get it cheap I will post some side by side pics of it and the 68 axle with measurements.

[rustyrelic]

Interesting thread. Seems no one has hit upon a cheap alternative to the old pontiac factory stuff. Going to kick myself if late model stuff is easy and cheap.

Myself, I have pursued "the great white whale" and have scored a used 66 3-series posi carrier with 3:42. So far I have 300 in the carrier and gears, and another 350 in bearing and rebuild kits. Been quoted around 500 to put it all together in my 68. I really like the idea of not having to worry about control arm locations, alignment, etc. Hope this will really pick the stop light performance over the open 2:73.

Anyone know of a good shop in or around Nashville to do the differential install?

[Engine-Ear]

This is a great thread!

I am really looking forward to both the elegance of anything that comes out of FabCraft for the '65-'70 P/8 cars AND the establishment of reliable alterations and deployment of the '90s Impala/Roadmaster rearend hardware into the '65-'70 P/8 cars.

[Ragtop Man]

Rustyrelic: sure wish I could repeat that score, am hoping something comes of the search for a good alternative for our old war wagons.

[AROWHED]

The 65-70 B body rear end is 65.50" drum to drum. Frame rails near the rear tires are about 51.50" at widest point. Wide Track Pontiac! Sure does make it difficult to find wider than stock wheels, because the backspacing\offsets are usually not deep enough. I am currently looking to stuff a pair of 20 x 9.5" wheels I got a killer deal on, but of course their 5" backspacing puts them 2" from the frame rail and zero inches from wheelwell lip, and thats even with it rolled up...not good. Only solution is a narrowed rearend.

[Ragtop Man]

Just did some math on the axle width: a '66 will be about 1664 mm so the b car axles will be too narrow or need spacers to get to the orig track

[mechanic17]

Finally got around to shooting some pix with my phone--sorry for the poor quality (dark garage). This one came out of a '92 or '93 Caprice wagon with 3.23 or 3.42 (I forget) posi. Hopefully this will confirm some of the measurements others have posted.

I am the owner of several b-bodies, so I'm probably gonna strip the internals out of this housing for use in the standard sedan--unless somebody offers to buy it first.

['ol Pinion head]

The axle housing dimensions are the same on all '77-'96 Chevrolet B-bodies (Chevrolet Caprice's and impala's) I've measured. Don't have any 90's era Hollander books to double ck, but are the '90"s B series wagon rears any wider than 90's B series sedan rears?
I've pulled quite a few 8.5 B series rears of this vintage & torn apart quite a few 8 7/8 in mid 80'sBuicks & Caddys & don't believe they are any wider, I in fact believe they are the same width rear. That would make them all too narrow to fit in a '65-70 B series Pontiac.

Once one starts comparing the below rears, they are basically the same axle flange to axle flange & as far as the geometry goes with the upper control arm perches. There are different styles of housing ends, 28 spline or 30 spline axles, different looking spring mounting tabs, Spicer 1310 & 3R pinion flanges & theyre were two different factory rear disc brake set-ups (the '77-78 LeSabre Sports Coupe version & the '90 Caprice version).

GM rears:

'73-77 A-body 8.5 c-clip
'73-77 A-body 8.5 bolt-in axle (one of my favorites)
'77-78? B-body 8.5 bolt-in axle (same as next above)
'77-78? B-body 8.5 c-clip (Palla cop cars of these years will have usually have 8.5's)
'77-mid 80's 7.5 c-clip B series (weak junk)
'77-84 B series 8 7/8" MP series c-clip
mid 80's- 96 B-Body 8.5 c-clip (30 spline '88 & later)

Another style of GM rear that is wider than the '73-77 A-body/'77-96 B-body rear AND the upper control arm perchs may be very close in geometry to the 65-70 B series PONTIAC is the '71-76 GM B series rears. Know these are not a direct bolt-in to '65-66 B series Pontiacs, as I've built them all, but could be something to ck out to see if upper control arm perchs have the same spread & same geometry. If they do, its as simple as removing lower control arm/shock perchs & correctly positioning & welding the the early Pontiac style on.

Of these GM 71-76 B series rears:
-'71+ 2 door & 4 door Chevy Impallas & Caprices typically had the 8.5 C-clip axle rear. Also were used in some low horse '71- (maybe) '72 Pontiac Catalina's
- 455 equipped '71- Pontiac B series & often Olds Delta 98's of these years had the 8 7/8 MP series rear (some manuals may refer to it as a 8.75).
-Biggest '71-73 Buicks with 455's typically had a 9 3/8 which is also very hard to find good ratio posi & gears for. 3.42's in this style are real tough!

Good luck, as I'm out yarding I will try & get some detailed pics. I have nothing anymore for '65-70 B series Pontiac rears in my racks. Just sold the last of my '65-70 P series axles (with new axle bearings installed).

[mechanic17]

Yes, the 90s wagons are wider than the sedans by about 4" I believe. If you were to cut two inches off each axle tube, push it in and re-weld it to the center section, you could use sedan axles and it would bolt in a sedan with the same geometry, is my theory. I will be testing it this summer.

As for compatability with earlier sedans, I have no idea about that.

[monzaz]

Well one thing you have to remember here is that your all looking at width and forgetting about the shock mounts and how wide all the other lower control arm geometry will be off too. I guess if your car will only be tooling around the streets at no more that 40 MPH and never hit a corner at over those speeds you will be fine... lol.

All these components need to be in the same locations for Pinion angles to be correct and rear end suspension and articulation work correctly.

The 1965-1970 Pontiac rear is a very good alternative with the Fab Craft gears 3.55 installed. That rear will handle all your power up to 11 sec range...beyond that you will have to watch for the posi unit to start spitting spider gears out.

I have worked with Brad at Fabcraft on other rear end projects and his gears are top notch quality USA gears. Here is a rear that we have that is the 10 bolt cover 12 bolt ring 8.875 1965-1970. Fabcraft 3.55 gears installed.

The upper control arms are ALWAYS the hurdle in the GM rears as they aRE cast IN and require a spherical rod end and adjust control arms - we sell these to help install and swap GM rear into other year GM rears...
IE We do G-body swaps with 73-77 8.5 centers and change over all the rest of the lower and spring perches and narrow them to the same width with the Custom upper controls arms... We do this with 8.8 LTD centers and 12 bolt chevy rears too. It WORKS great.

We just never had as much interest from anyone coming at us for FULL SIZE cars. It seems to always come down to the money... One way or another you will have to spend some money to get a stronger rear with more selection of parts.

We are working on a GM 14 Bolt 9.5 3/4 ton truck housing to solve the super power needs of the 800+HP cars. It is Slow going as we have to fit it in between all the regular BILL PAYING orders and parts. Jim JD

[AROWHED]

Is Fabcraft looking at producing tougher spider and axle gears to compliment their new 3.55s for the 65-70 fullsize rear? I would be interested...currently running Brad's 3.55s on a 1972 2-series posi...I'm turning up the heat to 650 HP soon, and the spiders worry me.

[monzaz]

As far as I know that is it for the 65-70 Pontiac rear. It will not get anymore attention.
This is why I am trying to come up with a complete NEW rear.

10 bolt 8.5 is ok if your going to drive the car around on the street and do burn outs...BUT if you put the power to the geround at the track...FORGET IT the 8.5 in that big car will blow the small spider gears right out.
If you do not use a FULL SPOOL with that weight your doomed.

This is why I am working on the 14 bolt GM custom rear. This GM rear is the same size as a DANA 60. BUT ALL GM.


We do camaro rears and 55-57 chevy rears from these. BUT they are easy because they are all LEAF SPRING set-ups. Jim