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98_shortbed
01-25-2011, 05:45 PM
I am bagging and bodydropping my 98 fullsize truck. I know that a impala ss rearend is narrower than a fullsize truck rear but someone told me that a caprice rear is even narrower than a impala ss rear??? Is this true or B/S??? :argue:

someotherguy
01-25-2011, 06:11 PM
They're BS'ing you. Impala and Caprice are the same car, just trim level differences. Same width rear.

Richard

fastlt1
01-26-2011, 04:54 AM
I think the impala ss had the truck bolt pattern and the impala had the camaro s-10 bolt pattern.

mudbuddy
01-26-2011, 08:02 AM
I think the impala ss had the truck bolt pattern and the impala had the camaro s-10 bolt pattern.

As in axle to wheel bolt pattern? I highly doubt that it would be a 6 lug not to mention it would take a lot of cutting and welding to remove the mounts from both and weld them back onto the new rear end, since it isn't a bolt in swap.

fastlt1
01-26-2011, 08:22 AM
As in axle to wheel bolt pattern? I highly doubt that it would be a 6 lug not to mention it would take a lot of cutting and welding to remove the mounts from both and weld them back onto the new rear end, since it isn't a bolt in swap.

I figured by the pic he was bagging a OBS 5 lug 2wd truck.

fastlt1
01-26-2011, 08:52 AM
I had a awd astro van that was a truck 5 lug but I don't know how wide. I think a OOBS 2wd axle is a couple inches shorter then a OBS axle.

BlackBlazer92
01-26-2011, 09:41 AM
if you have the tools to cut off the old brackets off a shorter axle and weld on yours you should have the tools to shorten your stock axle. i never did it but the jeep guys do it to dana 60s all the time. they even do it with steer axles. it will probably be cheaper than buying an impala ss rear and you can cut it to the exact length you want. the most expensive part will be getting your shafts cut and resplined. a machine shop can do that and i dont think its to bad

someotherguy
01-26-2011, 12:57 PM
I think the impala ss had the truck bolt pattern and the impala had the camaro s-10 bolt pattern.
Nope...Caprice or Impala SS, 5x5 pattern, both of 'em. There were some B-body cars in the early/mid 80's, and also in the 60's-up that had 5x4.75, but it was fairly common to see 5x5. Example; my '71 Impala convertible had 5x5; my '65 Impala SS had 5x4.75. All the later model Caprices I've owned were 5x5 - and that's 4 or 5 of them.


As in axle to wheel bolt pattern? I highly doubt that it would be a 6 lug not to mention it would take a lot of cutting and welding to remove the mounts from both and weld them back onto the new rear end, since it isn't a bolt in swap.
When fastlt1 said "truck" pattern he meant 5x5, since the original poster is talking about a '98 fullsize truck. But yes, would require spring pad and shock mount modification and relocation. The Impala SS rear is coil sprung with trailing arms, instead of leaf sprung like the truck.


I had a awd astro van that was a truck 5 lug but I don't know how wide. I think a OOBS 2wd axle is a couple inches shorter then a OBS axle.
Another mixed example - some Astros were 5x4.75, some were 5x5, and of course the later ones are 6 lug. Dunno about whether squarebody axles are narrower than GMT400 but they might be; could explain why the stock backspacing on the wheels was less than the GMT400 stuff.

Richard

98_shortbed
01-26-2011, 05:46 PM
Well thanks for the help gus, yeah i kinda figured it was the same rearend. I just hope its narrow enough to run my rims, i really dont want to get them narrowed.

454cid
01-26-2011, 06:04 PM
Are you guys sure the rear axle is the same between the SS and the Caprice? The SS (and police package Caprice) used rear discs, but the regular Caprice used drums. While it may be possible the different brakes bolt onto the same axle it's just as possible that they don't.

someotherguy
01-26-2011, 07:39 PM
Yep, Impala SS/Caprice 9C1 have the JL9 disc/disc RPO; regular Caprice has JM4 disc/drum - but if you look at how the exact same wheels fill the gap (check a Caprice Classic with Impala SS wheels) I'd say the rears are the same width, within an inch or less. As tight as those rear wheelwells are, I'd say no significant difference.

You do bring up a valid point though, since all the late model Caprice's I've owned have been 9C1's. :D

Richard

98_shortbed
01-27-2011, 12:28 AM
One more thing, can somebody tell me what the stock gear ratio would be in a impala ss rear?

Badass69
01-27-2011, 07:16 AM
You guys are actually all wrong. And yes to the Op, you were not being BS'd. There are 2 rear diff widths in the 94-96 B body disc brake cars. The Impala SS rear end is not a direct swap for a 9C1 width wise. The 9C1 axles are shorter and the housing is in fact narrower than an Impala SS.


GM PART # 26038684
GM LIST: $328.83
DEALER COST: $194.93
DESCRIPTION: SHAFT,R/A - Caprice 9C1 w/rear disc (8.5/30 narrow)

GM PART # 26018080
GM LIST: $249.19
DEALER COST: $147.72
DESCRIPTION: SHAFT,R/A - Caprice sedan, Buick Roadmaster sedan w/rear drum (8.5/30 narrow)

GM PART # 26043164
GM LIST: $353.88
DEALER COST: $209.78
DESCRIPTION: SHAFT,R/A - Impala SS - rear disc (8.5/30 wide)
NOTE can be used in place of 26033203 on B4U Caprice applications (26033203 discontinued)



The overall width between the "narrow" and the "wide" housings is approximately 1.25". So a narrow axle shaft is 30.5" and a wide is 31.125 approximately. The drum brake cars are a direct swap for the rear disc setup as well if you find a narrow rearend to steal. All 91-96 B bodies used the 5X5" bolt pattern as well. Older square bodies( 1977-1990) are 5X4.75" bolt pattern unless they are a station wagon or a 9C1 package car and then they are 5X5". Furthermore the old 77-90 Caprices had 7.5" 10 bolts if they were not a wagon or a cop car. So.... all the 5X4.75" cars have a garbage rear diff.


Caprice w/Disc Brakes 91-96, Cadillac RWD 91-92, Buick 91-96 Also includes 91-92 Caprice with drum brakes and some 93-96 (ie. taxi) with drum brakes (does NOT include 93-96 B4U Caprice which uses wide housing)

Those use the narrow rear end housing, and "narrow" axle.

The factory gear ratio in an LT1 powered 94-96 Impala SS or 9C1 is 3.08, or RPO GU4. The L99 ( 4.3) powered 9C1's have 3.23 gears ( RPO GU5). The LT1 powered Caprice's otherwise from 94-96 ran 2.93's. Buicks and Caddies I don't know all of for sure. The TBI powered 9C1's ran 3.42's.

3.42 is a nice driving ratio in an LT1 b body and is what I put in when I rebuilt my 96 9C1's rear diff a few months ago. If you want more info on this stuff you can go to the site I pulled the quotes from, being www.impalassforum.com

someotherguy
01-27-2011, 08:14 AM
You guys are actually all wrong. And yes to the Op, you were not being BS'd. There are 2 rear diff widths in the 94-96 B body disc brake cars. The Impala SS rear end is not a direct swap for a 9C1 width wise. The 9C1 axles are shorter and the housing is in fact narrower than an Impala SS.

The overall width between the "narrow" and the "wide" housings is approximately 1.25".


if you look at how the exact same wheels fill the gap (check a Caprice Classic with Impala SS wheels) I'd say the rears are the same width, within an inch or less. As tight as those rear wheelwells are, I'd say no significant difference.

So sue me for being off 0.25" :D

Richard

Badass69
01-27-2011, 08:33 AM
They're BS'ing you. Impala and Caprice are the same car, just trim level differences. Same width rear.

Richard

More what I was in reference too, and no I was not talking directly to one individual in the thread. It's not much, but GM did it for whatever reason.

No I am not picking on anyone either:punch:

someotherguy
01-28-2011, 08:25 AM
No sweat, that's why I gave it the :D - there's no way we can all know everything about a particular model, or why GM did it that way. When I did the GMT400 salvage parts I learned something new (sometimes more than 1 thing) a day, just when I thought I knew everything! :D

All I can do is be thankful that while GM is kind of bad about changing things up, they're way, way better - miles better - compared to Ford - who seemed to change something significantly depending on variables ranging as far as which engineer was on design duty that day, which supplier was making the parts that week, what mood the lineworker woke up in that morning...

Richard