• 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

All 93-96 7.625" (ring gear) housings are 1598mm wide (Chevy sedan only)

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.

8.5" axle shaft information - sedans only

 

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

All 93-96 7.625" (ring gear) housings are 1598mm wide (Chevy sedan only)

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.

8.5" axle shaft information - sedans only

I was able to measure the flange-to-flange width on two vehicles this past weekend

• - 1996 Buick Roadmaster Wagon with the 8.5" 10 bolt
• - 1996 Cadillac Commercial Chassis with the 9.5" 14 bolt

• The wagon width is 1645mm
• The commercial chassis width is 1567mm

Measurements were done with a flat plate bolted to each flange with a lug nut. The plate has a hole in it so the cone of the lug nut centers and locates the plate. I visually checked the plates for any bending once the lug nut was tightened and they were visually perfectly straight.

Wagon measurement below

I can also confirm the wagon LCA, Spring, Shock, Frame, etc mounts are all 2-3" wider than the commercial chassis.

 

Civie Disc (did those exist?)

Yes, in the WX3, but I think you meant the non-9C1, non-SS B-bodies, in which case, no. In fact of all the 91-96 B/D-bodies, only the 94-96 SS and 9C1 got rear discs.

 

Thanks! I was mostly curious but now its here and easily search-able again.

 

My 95 B4U in fact has the wider axles in it. I measured them when I switched it to discs from HD drums years ago. Turns out Im on the hunt for some myself. finally putting my gears in and found the axles just starting to wear.

 

The B4U does. You will need the longer ones. I bought Mosers for mine last year. Still have my stock ones just incase.

 

just wondering? What was the reason for the Narrow rear end in the 9C1's

 

To allow for the use of snow chains.

 

I've made the same statement a number of times--lost to the data crash--but more to the point, prior to the 1993 body change, all 91-92 sedan housings were the narrow (1566mm) variety, which was originally dictated by the shape of the rear wheel opening.

I'm not aware of any "official" statement from within GM regarding the housing width "spec" or choice based on intended use of the vehicle, but, when the difference in width first surfaced as a Forum topic back in the first or second year of the Forum, when the learning curve was pretty steep and there was a constant barrage of questions about many of the vehicle design basics of the B-body, I said then that the only reasonable explanation was that, as an emergency service vehicle, the expectations would include the ability to fit snow chains without any concern about body clearance.

If it's anything other than that, something even more fundamental, I don't think we'll be hearing from GM about it. If it IS in writing--such as buried in the GM 9C1 specs, or in the MSP (Michigan State Police) patrol vehicle evaluation program historical files, it would be nice to find out and be able to validate the assumption.

 

is there a way to put the fleetwood abs/ traction control system on a impala ss?

 

Not without a considerable commitment (financial - parts, labor, possible machine work, etc) and the determination to see it through.

You want to maintain rear disc, or will drums be OK? You want to keep the wider Impala axle, or will the narrower FW axle be acceptable to you?

The traction control system used on FW, called ASR (Acceleration Slip Regulation) was really quite crude compared to what is in use today--an electromechanical step motor arrangement that overrides the fuel foot feed and pulls back on the throttle opening based on a signal interface command from the 4-channel ABS.

I am not sure of it's reliability or actual effectiveness, so other than being able to say you've got something unique for (your) B-body, I wouldn't consider it worth the time, effort, or money involved.

Several articles that address "ASR" traction control--and there are plenty more out there if you go looking.

Stop to Match the Go - All About 1986 - 1996 C4 Corvette Antilock Brake and Traction Control Systems - Page 1 of 3

 

OK, slightly off topic but I did a search and didn't come up with anything. I'm guessing I'm just not plugging in the right terms but, anyway...

Friend has a wrecked early 90's 10 bolt half ton Chevy he converted to 3.73(he thinks) TruTrac and rear discs. Now I honestly considered taking the whole thing, cutting all the mounting hardware off the factory rear, welding it onto the truck rear and being done with it. But that sounds too much like work...

So how much of the rear can I simply pull out, intact, and stick into the car's? Perfection would be to slide the axles out, pull the entire pumpkins and swap them and call it a job well done but I assume this isn't going to happen...?

Point me towards the thread I undoubtedly missed and save yelling at me.

 

EDIT - nevermind. Thanks Bill. Added to the sticky.

 

Well I have a 96 9c1 caprice with disc brakes on the rear is it narrow or a wide one cuz mine shelled out and I want to just install a whole other one

 

Unless someone has changed the axle before you got the car, it has the narrow (1566mm) housing.

Find the code on the housing to confirm.

LT1: 2LW / 3.08 (GU4)/ disc / 1566mm (police) or 2LX w/G80

L99: 2LY / 3.23 (GU5)/ disc / 1566mm (police) or 2LZ w/G80

 

Thanks ill look can I get a Diff that has drums and put mydisc brakes on cuz my case kind of chewed up were the axle bearing goes.

 

Based on the published axle shaft lengths at Tom's Differentials, the 77-90 sedans had shafts that are 30-1/2", which is close enough to be "the same" as the narrow (1566mm) axle assembly used in 91-96 sedan applications. The Impala SS axle is wider and should work fine, based on the design of the boxy wheel opening--in fact, it will look better with the wider housing, in all likelihood. Just remember the later cars use a larger wheel stud pattern--your older car probably has 5 x 4.75" and the 91-96 cars are all 5 x 5".

There should not be any reason the late axle won't bolt into your boxy. Some of the bolts for the control arms, as well as the bushing sleeve IDs (on the housing upper ears), may be Metric instead of SAE, but they can be made to work.

If you're replacing a 7.5" axle assembly with an 8.5" unit, you may find it necessary to get a different (shorter) driveshaft or have yours shortened.

...can I get a Diff that has drums and put mydisc brakes on cuz my case kind of chewed up were the axle bearing goes.

Yes, you can put disc brakes on a SEDAN drum brake axle

 

Are the size for the 80-90 box chevy rear ends the same as the 91-96 sedans?

 

Are the 80-90 box caprice rear ends the same length as the 91-96 caprice's? Also how much trouble will it be to bolt up an impala ss rear end to a box? Sorry for the thread jack

 

help

Will a 94 wagon rear fit in a 94 sedan

 

Just as people have bolted a sedan axle into a wagon, it would be--theoretically--possible to do the same with a wagon axle into a sedan.

Sedan/Wagon rearend differences

 

wagon axles are meaningfully thicker and wider than sedan axles to better withstand the wagon's extra rear body work, and the wagon's significantly greater potential cargo payload.

I suppose if you limited your wagon's payload as if it were a sedan, thus protecting it, then you could get away with using a sedan axle assembly. I still can't recommend it, though.

Taxi companies did this very often (which is where people learned it was 'possible'); but when they did, they used 3.23, 3.42, or 3.73, and stiffer springs.

Using a wagon axle on a sedan is also possible, but it was rarely done with 91 & 92 sedans with skirted rear wheel wells [obviously].

Forgot to mention [,though it's probably obvious, and has already been mentioned by someone else,] that:

a) better to swap a wagon axle under a sedan, than to swap a sedan axle under a wagon

b) don't know if any bushings exist to deal with the unintended differences in rear lower control arm angles between the axles' and the frame's mounting points

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.

Question:
Are there [also] meaningful differences between the sedan's rear UPPER control arms mounting points [between the gearhouse and the frame crossmember,] and the wagon's?

 

I am going to be putting a 95 9c1 axle under my 77 coupe. Just got my axleshafts redrilled to 5x4.75" and am considering my brake options. I might stay disc if my stash of calipers has something useable, but with my current wheels, drums won't hurt appearances either.

I'll post fitment differences if I find anything. I don't expect anything, as the guy that bought my 77 coupe project is running a 95 9c1 chassis and suspension underneath with no issues.

 

If there a width difference in a 86 7.5 From the Flat part of the drum where the wheels go flush to to the other side, than a 95 9c1 Disk Brake Rear ? I'm just trying to weigh my Wheel situation out. Would It change the back spacing a bit ?

 

I have a 95 9c1 axle under my 79. No mounting issues, wheel fit was the same, or at least not enough to notice with the naked eye.

I converted it to 5x4.75 by having the stock axle flanges re-drilled, and ran 9" drums. Unless you are really hard up to have discs, it's a great way to go. The backing plates from the 79 7.5" fit the 8.5" axle with no issues. The only hang up was the OD of the feature that locates the wheel hub. The 79 was a smaller diameter so the 79 drums did not fit the 95 axle flanges. I ended up getting some drums from a 91-96 car (9") and re-drilled the bolt pattern. I used a transfer punch to mark them, and then drilled the new pattern on the drill press. Since the drum locates on the axle flange, the pattern does not have to be perfect and still be centered. This can be done with a hand drill if you really wanted to.

A little more homework might have yielded a drum with the right bolt pattern and hub ID that I needed, but I didn't have time to do that homework. I had a sat afternoon to swap the axle, and the drum fit issue came up while in the middle of the swap. In fact, it's possible that a later 80's car would have the 3.062" (IIRC) hub ID drum with a 4.75" bolt pattern.

A little hunting around may yield you a completely bolt on solution.

This winter, when I swap frames, I need to consider what I am ultimately going to do for an axle. I can do a full 9C1 disc brake rear, but I want to maintain the ability to run a 4.75" rear. I might do this with the same method of redrilling the rotors. All of this depends on how the 15" wheels I want to run actually fit.... if I stay with 15" wheels.

 

If there is, it would be "within the margin of error" in measuring.

Axle shaft length is essentially the same comparing 86 (30-7/16") & 95 (30-1/2"), as listed here.

 

so the 95 is actually 1/8 shorter ? but don't the disk brakes weigh it back out ?

 

Based on the numbers from the Tom's Differentials catalog, the 86 axle shaft is 1/16" shorter, meaning the overall track width of the 86 axle assembly is 1/8" less.

86 - 30.4375"

95 - 30.5"

The thickness of the drum brake flange and the rotor "hat" are not exactly the same--but the difference is not enough to impact any critical clearance (wheel/tire to body or frame).

 

Man Beertestr you did alot to keep the same wheels i guess i was lucky or lazy(depending how u look at it) and found a dual bolt pattern wheel

 

There are some options that start out with a 4.75 pattern.....

 

While I'm not 100% certain, it is possible to assume that an axle shaft from a 91-92 sedan with 7.5 or 7.625 axle (one & the same) would be the correct length and would have the 5x5 pattern and hub register for the 5x5 drum or disc to center on. The one thing I'm not clear on is whether the spline count is the same for 7.625" axles across all years.

Just understand this: the smaller (7.625) axle was narrow--same as boxy--only in 91-92. When the change was made in 1993 (opened up body for rear wheel), the 7.625 axle was only used in the wider housing version, same width as Impala SS.

From a lookup at Auburn Gear, the 7.5/7.625 axle went from 26 spline 1988 & prior to 28 spline beginning in 1988 on through 1996.

If your boxy is pre-88, you would need to replace the differential in your axle housing to provide a 28-spline side gear to work with the later axle shafts in order to use 91-92 shafts (from a 7.625 donor rear axle). That's a lot of added work & complexity--just find a complete 91-92 axle assembly and add the disc setup to it, if you really want to keep the 7.625 and narrower housing.

Why not just have the 5x5 pattern drilled on the axle in the car now? While this would not provide the center hub register support for the rotor, a centering ring could be made to press on each shaft for this purpose.

The other option would be to have axle shafts made "to order"--you can tell Moser, for example, that you need THIS axle, but instead of 30 splines, you need 26 or 28, to match your differential. The wheel bearing size is the same for both 7.5 & 8.5 housings, so nothing else would need to be changed.

The final option is just changing the entire axle assembly for a 91-96 8.5" axle (narrow version), which gives you the 5x5 pattern and matches the width of the 7.5 on your boxy now. Disc brakes just fall in place with this swap. It would be necessary to swap in a correct-length driveshaft with this option, too. If an 89-90 9C1 axle could be located, the same option would apply.

 

SOme good info in here. Anybody know where I could find out how wide a 71 impala rear is? Thanks