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73-77 A vs 77-96 B suspension swaps

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Post by texan01 Thu Feb 23, 2012 8:11 pm

There was a question posed on Facebook earlier by Mark, that I think needs further discussion in a place where it is more likely to be preserved and used.

His question of; Question for those with knowledge. I understand that a bolt in upgrade for the rear suspension is that from a late 90's or early 2K Caprice, specifically the SS. Has anyone tried or heard about this modification?

got me to respond as I had been doing research on suspension swaps and trickery on our cars to make them handle better than they already do.

I have known for a long time that 77-96 B cars share a lot of suspension and chassis parts, despite being a full 6 inches longer overall. In my case, the 4 door A cars have nearly the same chassis at 116" WB vs. 115.9 for the B cars and that may be to GM not rounding up our cars. The two doors have a 112" and the Montes/Special cars also have a 116" WB.

73-77 A vs 77-96 B suspension swaps Photo-10

My car has a 95 Caprice 9c1 (cop car) rear sway bar, with 77 Fleetwood trailing arms because I didn't want to drill holes in my original arms. The later trailing arms are identical, the only changes is in the bushings. the 77 up B cars have a larger bolt that holds the trailing arms to the car and axle. The OE rear bar for our cars is a V shape.

The biggest hurdle is making sure you have the correct bolt pattern. Bs can be had with a large 5" or small 4 3/4" which is what our cars have.

On the front, you can use 77-96 front sway bars, but you have to get longer end links to correct the change in bar geometry to make the endlinks work in a vertical rather than at an angle.

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Post by thatfnthing Fri Feb 24, 2012 11:03 am

FWIW, the 91-96 B spindles use the exact same ball joints and tie rod ends as our cars, so the nearly identical front spindles can be swapped in as well, which at the very least yield bigger brakes (12" versus our 11"). If you want to go further, this also opens up the door to swapping in the stand-alone ABS system as well:

73-77 A vs 77-96 B suspension swaps Rwheelfrontview
Front view: 92 B spindle on 73 Monte. 12" drilled and slotted B rotor; black ABS cable runs from top to sensor in center of photo. 17" wheel.

73-77 A vs 77-96 B suspension swaps Rwheelrearview
Rear view: Same D52 caliper as our cars, but with metric banjo bolt. ABS cable routes along frame just as with B car.


And for anyone who wants to try the ABS swap, here's a much easier arrangement for the rear sensor than swapping the B rearend and changing reluctor band on the pinion gear:

73-77 A vs 77-96 B suspension swaps Absrearsens1
73-77 A vs 77-96 B suspension swaps Absrearsens2

Caveats:
o B spindle sits 1/4" inboard from A spindle
o Bearings are also larger on B spindle
o B rotor uses 5x5 bolt pattern
o 15" wheel will probably be too small for 12" rotor setup
o Used D52 caliper, don't know how 9C1 caliper will differ (if at all)

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Post by texan01 Fri Feb 24, 2012 11:34 am

the 12" B-rotor is a 5x5, the 11" is the small bolt pattern. I was hazy on when they changed to larger wheel bearings on the B/C/D cars. I think the bearing size changed sometime in the mid 80s.

!5" wheels barely clear the 12" rotors, as that was a factory option on the 71-76 B-cars and they had 15" wheels as well. Heck the 9c1 car I pulled the rear bar off, had 4 wheel disc brakes and 12" rotors up front with 15" wheels. that extra 1/2" could allow people to run wider wheels up front.

Calipers from what I've read and seen (4 years as a auto parts counterman) 11 and 12" rotors use the same pads and calipers. I walked into the parts department once to get factory pads for my 76 and they said they didn't have any. I asked them for front pads for a 96 SS and lo there they were. In the Raybestos/Wagner catalog, they are the same part number.

The ABS thing is interesting.

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Post by ant7377 Fri Feb 24, 2012 6:07 pm

Just so you know if you have a Monte the steering stabilizer (all 73-77 Monte are equipped) is the same as the B-body commercial Chassis (Hearse,Limo) from 93-96,now that I am writing this I wonder if the center link is also the same? It isMonte specific and obviously a wear part.
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Post by 73CopperMonte Thu Apr 12, 2012 9:24 pm

I swapped in 91 Astro Van lower control arms with the larger 5/8" ball joint and matching spindles with 12" rotors on my 73 Monte. They are the same as the 96 Caprice, and my original calipers bolted right back on. I also swapped a complete 96 Caprice 3.23 disc rearend, they measured the same backing plate to backing plate, may be 1/4" wider due to the rotors. All wheels are now 5x5 pattern. The Caprice gas tank was also fits perfect, just the Caprice straps need to be modified, they are too long.

The Monte also has a 2001 LS1/4l60e swapped in it with moog 5664 front spring (IROC),95 Caprice front swaybar and 96 Roadmaster wagon rear springs. Should handle/stop good when I get it running.

*also I used a Malibu/Cutlass centerlink to get rid of the steering stabilizer.

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Post by Jim_Rockford Tue May 29, 2012 9:43 pm

91 was the change to 5x5 for civi b cars, 90 and below 5x5 was only on wagons and police cars. Where did you find a 3.23 factory rear disc unit in 8.5? lowest factory offered gear from 94-96 was 3.08. police, civi tow package and impala ss all only got 3.08's .
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Post by alleyball4 Wed May 30, 2012 4:11 am

I bought a 91 Caprice Classic Police rear end, with the idea of doing the rear end swap. I had some new Weld Draglite rims that were 5 x 4 3/4 that fit on my original 73-77 rear end.
When I went to do the swap, the bolt pattern of the 91 was 5 x 5, so my new rims wouldn't have fit without modification.
Also, the axle and posi unit are a 30 spline, not the 28 spline on the 73-77.
Everything does line up however, but to make it easy on you, I would just buy 5 x 5 rims, rather than redrill the axle plates, or run an adapter.
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Post by 73CopperMonte Wed May 30, 2012 9:23 am

Jim_Rockford wrote:91 was the change to 5x5 for civi b cars, 90 and below 5x5 was only on wagons and police cars. Where did you find a 3.23 factory rear disc unit in 8.5? lowest factory offered gear from 94-96 was 3.08. police, civi tow package and impala ss all only got 3.08's .

I found it in a Phoenix pick a part for $150, RPO code GU5 3.23 gear,GU4 is a 3.08. GU6 I think is the RPO for a 3.42 gear in a Caprice.

Google the RPO codes and you can find the list for a Caprice to confirm.


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Post by texan01 Thu Feb 14, 2013 12:09 pm

73CopperMonte wrote:
Jim_Rockford wrote:91 was the change to 5x5 for civi b cars, 90 and below 5x5 was only on wagons and police cars. Where did you find a 3.23 factory rear disc unit in 8.5? lowest factory offered gear from 94-96 was 3.08. police, civi tow package and impala ss all only got 3.08's .

I found it in a Phoenix pick a part for $150, RPO code GU5 3.23 gear,GU4 is a 3.08. GU6 I think is the RPO for a 3.42 gear in a Caprice.

Google the RPO codes and you can find the list for a Caprice to confirm.


Good info to know!

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Post by 73CopperMonte Sun Feb 17, 2013 11:33 am

The Caprice rear housing is not exactly the same as the 73-77 A body rearend, the lower control arm mounts are made for the larger full size control arm and bushing. Wider spacing were the control arm sits and larger holes for the bolts. Instead of using spacers and bushings to take up the slop, I am swapping all the Caprice parts (30 spline axles, disc brakes) to my 73 rear housing.


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Post by texan01 Sun Feb 17, 2013 2:15 pm

73CopperMonte wrote: The Caprice rear housing is not exactly the same as the 73-77 A body rearend, the lower control arm mounts are made for the larger full size control arm and bushing. Wider spacing were the control arm sits and larger holes for the bolts. Instead of using spacers and bushings to take up the slop, I am swapping all the Caprice parts (30 spline axles, disc brakes) to my 73 rear housing.


Why not build hybrid trailing arm and put the B-body bushing in the rear hole and the A-body bushing in the front?

Which reminds me.... I need to rebush my trailing arms..... They are B-body arms that I ground down the bushing inserts to fit the car.

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Post by brownbomber77 Thu Jun 06, 2013 1:15 am

The center brake line is the same in case anyone was wondering....only thing to change is to redrill the bolt pattern, which I did with an aftermarket brake hub to get the holes, and then change the parking brake cables which I'll post up in a little.

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Post by DoctorLarry Thu Jun 06, 2013 10:19 am

I just used the rear brakes and re-drilled the rotors on my 76.
73-77 A vs 77-96 B suspension swaps S7301018

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Post by Olds98 Sun Feb 02, 2020 12:50 am

Curious if anyone knows if a caprice rear end also fits into a olds 98? I know it's a bit off topic, but curious how much crossed over with gm. Thanks

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Post by 76 Malibu Tue Feb 04, 2020 2:50 pm

Bringing back this old topic, what suspension parts directly swap from 73-77 A-bodies to B-bodies? I notice in the Rock Auto Catalog the control arms are available for the 77-90 cars but they say they won't fit a 73-77. I am assuming there are only minor differences? Anyone know for sure?

Olds 98, it would help if you told us what year your car is.
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Post by fasrnur Tue Feb 04, 2020 9:15 pm

From what I've heard the B bodies bushings and bolts that hold them in the car is bigger than the A bodies. Only small modification to make the B body control arms fit the A body. not sure about the A into the B body though.
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Post by brownbomber77 Thu Feb 06, 2020 1:11 am

B-Body stuff IS a hair larger and also metric in the 80s switch. So the 1/2” control arms bolts are actually M14 1.00. I remember having to drill out my frame bolt holes for the rear. Otherwise all the suspension is shared between the two cars. Front upper and lower control arms are all the same dimension. Might have to wallow out some frame holes but otherwise the bushings are beefier.

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