GM 8.5 10 bolt swap from a 96 impala ss

Is there a page that breaks down the axle length and spline count as well as gear ratios? Maybe this should be a sticky like on other forums. I belong to several B-Body forums as most are not organized and information is spotty at best.
I have a 1987 Caprice Classic Brougham. I am replacing the 305/700R4 with a LS1/4L60E. Id like to upgrade the Rear as well with the SS disc brake assembly. Can you just swap parts rear to rear or do you have to swap the whole assembly?

The older 8.5 10 bolts were 28 spline axles that's one reason they had rather a poor rep for years and everyone wanted a 12 bolt.

The later 30 spline (Like the SS) are stronger when they switched I am not sure but I  know it was the late 80s or after    yours

is probably a 28 I think they  went to 30 spline because of the LT1's and the heavier B-Body  which was the 90s.In the 90s they

even beefed up the 7.5 to a 7.625. Most of the late 70s and80s rearends are pitiful from GM or even Chrysler at least Ford had

some sense using the 8.8 in the 80s Mustang.(Not a fan though)

 
   In the 80s I am pretty sure even the Iroc didn't have them(They did have the odd 9 bolt though). . To answer your question an

assembly swap is definitely the best bet unless you plan to rebuild a rearend. I am doing a swap myself and at this  point I'm

leaning towards a RoadMaster or Impala 8.5 assembly with disc brakes. It's easier to swap rearends then rebuild them unless you

are just adding new  axles. The write up here is good, there are plenty of them in yards still  and it can be done in your driveway

in a day. And most yards do list the gear ratio even on car part the RoadMaster varies even in Posi from 2.56 and up the SS I

know are higher but I am not 100 perecent I know may are 3.08 and some RM Posi are 2.93 as well.

Motor City Impala wrote:Is there a page that breaks down the axle length and spline count as well as gear ratios? Maybe this should be a sticky like on other forums. I belong to several B-Body forums as most are not organized and information is spotty at best.
I have a 1987 Caprice Classic Brougham. I am replacing the 305/700R4 with a LS1/4L60E. Id like to upgrade the Rear as well with the SS disc brake assembly. Can you just swap parts rear to rear or do you have to swap the whole assembly?

Welcome to the forum!
It's easiest to swap out the whole assembly.

Here's the gear ratios available.

Impala And Caprice Available Rear Gear Ratios
Axle Ratio RPO Code Ring/Pinion Teeth Application
2.56 GM8 41/16 Std. Roadmaster LT1
2.73 GU2 41/15 Std. Caprice L99 (exc. 9C1)
2.93 GW9/GU3 41/14 Std. Caprice LT1 (exc. 9C1), Opt. Roadmaster LT1
3.08 GU4 40/13 Std. Caprice 9C1/LT1 (Police), Std. Impala SS
3.23 GU5 42/13 Opt. Caprice L99, Std. Caprice 9C1/L99 (Police)
3.42 GU6 41/12 Std. 91-93 Caprice 9C1/L05, Std. 94+ Fleetwood w/V4P
3.73 GT4 41/11 Std. 91-92 Fleetwood Brougham w/V4P

*V4P = 7,000 lb. trailer towing package... look for a hitch.

I hope this helps

Driveshaft length you said yours needed to be shortened 1" what transmission do you have th350 or?

It's slightly off topic, but most people don't know that Paulsons Motorsports will make certain wheels with both 5x5 and 5x4.75 bolt patterns drilled.
They actually make the wheels there. You can get Chevy Rally style wheels all the way up to 17x9. Any offset or backspacing you want. They're fairly inexpensive too.

Here's their address: http://www.petepaulsen.com/home.html

Oh cool I might need a pair! Yeah I'm trying to see if he has th350 like me which is the shortest transmission other than the 200r4

the rest are a bit longer. That's why I find the 1" odd the th350 is 27 11\16 with 6" tail and the 700r4/4le60 is 30/3/4"? Even if the 8.5

comes towards the front more where'd the other 2" go? Is the positioning of the rear and the powertrain that much different in a later

B-Body ? Unless that Caprice Classic here has different Transmission ?

I know I'm bumping a 2 month old thread, but here's some thoughts on the 8.5 94-96 rear swap. I did this twice on my 79, once right after I bought it and found the stock 7.5 to be a leaking pile. The first time was with a stock 3.08 10 bolt that didn't have any brakes.

If you get a drum brake axle and want to stay drums, you can move your backing plates over from the 77-79 7.5", they bolt right up. The trick is the "hub" on the 94-96 axle shafts is larger so your original drums will not fit over the pilot/hub. My car had the 9" drums, and I got some drums from a 91-96 car, they actually made 9" drums for that era, but with the larger pilot hole, and are 5x5.

If you want to convert to 5x4.75, you can find a machine shop to re-drill your axles to 5x4.75. A local guy did mine for $60. You can easily re-drill the pattern by using your freshly drilled 5x4.75 axle as a template (do this before installing the studs). I just transfer punched the pattern and drilled the holes slightly oversize. The drum locates on the pilot/hub so accuracy is not as critical.

My car currently is running 5x5 since I swapped over to the 94 frame,and I did axle #2 in the process. This one was a 3.08 axe out of a 9c1 that got an Eaton Posi, 4.10 gears, and Moser axles. Since I am never 100% sure on what bolt pattern the car will end up at, I had Moser make the axles with both patterns and screw in wheel studs. I can change the rear from 5x4.75 to 5x5 in about 20 minutes. I also drilled my rotors to accommodate the swap too.  

If you guys have any axle or interchange Q's ask away, I've been messing with 77-96 BBodies for 15 years now.

Hope this helps!!

Great information when I did this swap I intended to get new axles that are 4.75 and a diff in the spring. The 5x5

are much harder to find wheels for. I talked to Moser about axles I didn't get the screw in stud info what did

the axles run you?

I didn't get any deals on the axles, I think they were about $300, plus another $30 or $40 for the screw in studs and second bolt pattern. It was a very reasonable up-cost considering what I paid to have stock axles redrilled and I supplied the studs. I did the axle upgrade 2 or 3 years ago, I am not sure what Moser's pricing was.

GM B-Body Forum wrote:UPDATE 3-30-14

Got the rear end sandblasted, primed and painted. All new seals, calipers, rotors, brake pads, brake hoses and outer pinion cone bearing on the way. I think im going to paint it gray or silver, i like black, but we'll see. Im hoping to have it in possibly late next month or some time in may. Everythings going smooth and i cant wait!

Random question but my is ther a dent in the diff cover 
The 95 impala ss rear end. Picked up has the same dent same size and same location on the diff cover

Thats where the magnet is located, to pick up any small metal particles to keep them from getting circulated in the gear oil. When i took my cover off the magnet was covered in metal particles and gunk. Im sure yours will be the exact same, the posi units wore out quick and all the shavings on the magnet are from the posi unit.

I like my new cover it's thick aluminum and has a drain with a magnet right on the end. The drain is nice for yearly

fluid swaps. I still say old diff fluid is the smelliest gunk under the sun.

Myloth wrote:I like my new cover it's thick aluminum and has a drain with a magnet right on the end. The drain is nice for yearly

fluid swaps. I still say old diff fluid is the smelliest gunk under the sun.

The drain plug bung is a great place for the pick-up for a diff cooler.

Myloth wrote:I still say old diff fluid is the smelliest gunk under the sun.

OHH yes i agree, that is some funky stuff, ill never forget that smell lol

Hey admin I wanna know if the impala master bolted right up to the caprice brake lines and what size is the flare nut wrench for the master cyl. And the rear axle lines ..sae or metric so I can buy the set .
Also is the caliper line bolt..banjo bolt?...for the 95 impala (12" rotor) and the 77 caprice (11" rotor) the same ? I have my eye on stainless brake lines for he rear left/center/right lines and front also, hoping they fit.
 Thanks for any info.

I havent switched the master cylinder or the proportioning valve yet, so its all original up front, im gonna change it sometime next year when i upgrade to the stronger 5/8" ball joints and spindles, with the 12" rotors, im considering putting a brake kit on from wilwood but that might be over kill. Anyway i had an issue with the center rear brake line, i assumed since the rearend came from a 96 ss that the line would be metric, but only where it connects to the body line is metric, where the line tee's off to go to the calipers stayed the same standard size as the old one. So what i did was bought a rear center brake hose for a 96, and it didnt fit, so i bought a new one for my 79 and it fit. I do recommend changing the master cylinder along with the proportioning valve, because my pedal goes to the floor, it stops good, better than the drums but the pedal is spongey. I bet with an adjustable proportioning valve and a master cylinder for the 94 to 96 ss or 9c1 with the 1-1/4" bore would firm the braking right up. But to answer your question, no they are not the same they are def metric, if you buy one of those kits with the 5 piece stainless braided lines, youll have to get an adapter for the rear center line, or run new lines altogether, the other 4 braided lines should be good, since they use banjo bolts, and you can go to your local parts store and check the dorman aisle for banjo bolts for the calipers if you dont have them.

Wow deja VU that was my experience as well with the center rubber hose and the brake pedal the Master is

fairly new and my pedal is spongy and goes down and I bled it 4x lol all the way around. My next step is the

proportioning valve as well.

HeavyChevy77 wrote:Hey admin I wanna know if the impala master bolted right up to the caprice brake lines and what size is the flare nut wrench for the master cyl. And the rear axle lines ..sae or metric so I can buy the set .
Also is the caliper line bolt..banjo bolt?...for the 95 impala (12" rotor) and the 77 caprice (11" rotor) the same ? I have my eye on stainless brake lines for he rear left/center/right lines and front also, hoping they fit.
 Thanks for any info.

The newer plastic style MC bolts right on.  Make sure to use the plunger rod from the plastic one because it's a different length than the old style one.  I had to replace both lines going from the MC to the old style Combo-valve.  Metric threads w/bubble flares on the MC end, and SAE threads w/double-flair on Combo-valve end.  That's using the standard C-V.  If you switch to the newer aluminum C-V, you'll have to re-do all the lines with metric/bubble-flaired lines or you'll get serious leakage.

Myloth wrote:Wow deja VU that was my experience as well with the center rubber hose and the brake pedal the Master is

fairly new and my pedal is spongy and goes down and I bled it 4x lol all the way around. My next step is the

proportioning valve as well.

Idk what the previous owner did to the car while it was in his possession, but the combo-valve was replaced when I had the front hard and soft lines replaced.  The master cylinder is almost brand new, but it was a re-manufactured one to replace the other NEW re-manufactured one that was NG.  It may have an internal leak like the 1st one did, idk.  If you got all the paperwork I sent with the car when I sold it, you should have the receipt.  Advance Auto might warranty it, if it's the problem.  
Bleeding brakes can be a real PITA to get all the air out.  If you want, swing by here and I'll use my pressure bleeder on it to get any lingering air out of the system.  My neighbors would love to see the car again!  You bring the fluid.

I was wondering if that valve was new it looked it. Yeah the bleeding is pain but I not only gravity bled it x3 I

bled with a borrowed foot x3 as well it feels the same from the 1st time to the last time. Maybe it is the MC

as there isn't anything else that it could be. I do have the paperwork as well so Advance will be hearing from me

shortly thanks we will see how that work out first. I will have to stop down sometime soon with your old girl.

Sweet Seventy9 wrote:

The newer plastic style MC bolts right on.  Make sure to use the plunger rod from the plastic one because it's a different length than the old style one.  I had to replace both lines going from the MC to the old style Combo-valve.  Metric threads w/bubble flares on the MC end, and SAE threads w/double-flair on Combo-valve end.  That's using the standard C-V.  If you switch to the newer aluminum C-V, you'll have to re-do all the lines with metric/bubble-flaired lines or you'll get serious leakage.[Quote]

I bought a new combo valve for the drum brakes they have 4 wheel disk ones for my car same thread pitch and all
Do you think this should prevent me from having to re hard line from the master to the combo valve? But from your post u say the master cyl has a different tread pitch from the original master.
As for the rear center line, ill go buy a center rear brake line for a 77

HeavyChevy77 wrote:I bought a new combo valve for the drum brakes they have 4 wheel disk ones for my car same thread pitch and all
Do you think this should prevent me from having to re hard line from the master to the combo valve? But from your post u say the master cyl has a different tread pitch from the original master.
As for the rear center line, ill go buy a center rear brake line for a 77

If you go with the newer style MC, yes you'll have to at least change the ends at the MC.  The newer style MC has metric threads and bubble flares vs SAE threads and double flares.

bogote="Sweet Seventy9"]

HeavyChevy77 wrote:I bought a new combo valve for the drum brakes they have 4 wheel disk ones for my car same thread pitch and all
Do you think this should prevent me from having to re hard line from the master to the combo valve? But from your post u say the master cyl has a different tread pitch from the original master.
As for the rear center line, ill go buy a center rear brake line for a 77

If you go with the newer style MC, yes you'll have to at least change the ends at the MC.  The newer style MC has metric threads and bubble flares vs SAE threads and double flares.

[/quote]

I plan to get this master cyl. From rockauto
It's a centric brand
Do they have adapters for the line fitting or the master

Maybe? I never thought about using adapters so I've never checked into it. I imagine they do though.

Does anyone kno the size and thread pitch of the 95 impala ss master cylinder and also of the 77 caprice brake tubing fitting
There's a handful of adapters but no way to sort it out without the info thanks guys
Trying to get everything ready to make the swap and want it to go smooth since I'm gonna do it alone (friends don't kno about cars the ones who do are working) and want it to go plug and play....I hope

the 77's fittings should be 3/8-24? that's what the wheel cylinders are and the tee hose fitting.

I think the problem Sweet is Cardone no reflection on you but they are JUNK. I have had way too many

Cardone remans fail out of the box. I am going to buy the Vette style for drum that are brand new no

Remans.