[Navy Lifer]

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

 

[Beertestr]

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.

 

[Marky Dissod]

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?

 

[Beertestr]

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?

Nope, the center section appears to be the same casting, hence the ears are the same as well.

 

[Bonez305]

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 ?

 

[Navy Lifer]

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.

 

[Bonez305]

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 ?

 

[Navy Lifer]

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).

 

[Beertestr]

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.

 

[Bigdawg70]

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

 

[Bonez305]

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.

Why go back to Drums if I may ask ? I mean I've done the swap before just never actually measured to see what the difference between rear ends were, but now I'm curious due to Wheel Fitment

 

[Beertestr]

Why go back to Drums if I may ask ? I mean I've done the swap before just never actually measured to see what the difference between rear ends were, but now I'm curious due to Wheel Fitment

Basically, I didn't have a complete disc brake setup, and I wanted to have 5x4.75" bolt pattern. This winter, once I decide on bolt pattern (actually, I'm thinking of getting Moser axles with both patterns and screw in studs), I'll set up a disc brake axle with posi etc..

 

[Navy Lifer]

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

 

[newvanner]

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 in to your boxy. Some of the bolts for the control arms, as well as the bushing sleeve ID's (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.



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

so if i understand correctly that means i can take an axel shaft (the narrow )from a 91-96 b body to change the bolt pattern on my boxy with the 7.5 rearend ??

right

 

[Navy Lifer]

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.

 

[71impala]

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

 

[Navy Lifer]

If you have one already, you could try measuring it yourself. Don't know where the information might be, otherwise.

The wagon rear axle mounts it's sway bar (on lower control arms) at the same width as the 71-76 B-body, so I'm "guessing" the housing for the 71 sedan was very close to the 91-96 wagon (1642.5mm) - 64.665" wheel flange to wheel flange.

Unless you can find an original spec sheet or sales brochure, I don't think you're going to find the number published anywhere else.

Wish I could be more helpful....

 

[71impala]

Thanks for the info. I do have one but with Sandy hitting us now I was hoping I may be able to find it out on the net and then confirm on my car once it gets a little nicer out. Thanks again.

 

[burkey426]

Why not just buy some bolt on wheel adapters?

 

[Navy Lifer]

There is a minimum thickness for an adapter in order to have adequate strength. To do that, wheels need to be higher (positive) offset, so IF adapters are used, there's a likelihood that wheel offset will need to change in order to keep the wheel positioned laterally in relation to the frame and wheel opening on the body. And that may be an expense or change in appearance that isn't considered acceptable.