New Axle Help

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67BBCuda

67BBCuda

'67 Barracuda Fastback
Joined
Mar 24, 2022
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Hey FABO,

Officially got the front end done on the '67 Barracuda. Here are some pictures to quench that thirst.

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We're ready to get started on the rear end.

Right now it has an 8 3/4" axle housing. The differential casing is stamped 2881489 with a large 9 and a star above it.

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It has rear drum brakes with a small bolt pattern. Once again, the plan wayyy down the road is to put a big block 440 in it. We will probably end up putting disk brakes on the rear at some point as well, but that is not a priority. Right now the goal is to get a new axle with the large bolt pattern to get the matching rear wheels.

Apparently, Doctor Diff is the place to go for the new rear axles with the large 4.5" bolt pattern. When it comes to ordering them, it asks a few questions.

1. Just confirming that the rear housing width is 52 5/8" per this thread?
An accurate 8 3/4" rear axle width list

2. How do I know if I need 30 or 35 spline axles without taking them out?

3. Opinions on the bearing options provided by Doctor Diff?

4. Will the current drum brakes work on the new axle, or will I need to modify or purchase new ones?

5. Obviously the axles are ordered with studs installed for drum or disk brakes. Will I be able to modify down the road for disk brakes, or will I need to buy new axles again?

6. Will the 8 3/4" be sufficient for the 440, or should I be looking to upgrade to the Dana 60?

Sorry for the wall of questions, thanks for all the help in advance!

-Marc
 
I cant answer all of your questions but I can start with some of them while others fill in the rest.

1) We can't measure your rear end for you. If you can confirm with 1000% certainty that the rear end originally came out of an A-body then those should be your measurements. (The fact that they are SBP is a good sign that they are) If you can't confirm then you will have to do your best to measure it yourself.

2)To my knowledge although I may be wrong, all stock axles were 30 spline, and the 35 spline axles were aftermarket heavy duty upgrade stuff. Someone will chime in to correct me or confirm.

3) There are 100s of debates of modern green bearings vs timken, it has been beaten to death. On a mild street cruiser you would probably never notice the difference between the 2 but for race applications look up the pros/cons people have posted about them (I personally recently bought axles from Dr. Diff and went with the green bearings because I believe they'll be enough for MY application)

4) BBP axles have different offsets, so they will require new brakes. Dr. Diff sells what you will need, If you plan on going to disk brakes, It would make sense to do that swap now

5) The axles I ordered from him had 10 holes, 5 for press in studs (installed) and 5 for screw in studs. Swapping out studs for different lengths is just a matter of pulling the axle and swapping what you need, I am a big fan of that feature.

6) Also debatable, what kind of power do you plan to run? Transmission? street use or heavy drag use? In theory your 8.75 should handle just about anything your 440 can do on the street with a reasonable tire (not crazy wide or sticky) Many people upgrade do Dana 60 if they plan on racing on big blocks and for peace of mind. A 8.75 can survive longer behind an automatic trans based on how power is sent to the back but manual transmissions can be brutal on drive trains and sometimes require more beef.
All that being said Mopar teams raced with 8.75s behind Hemi's for years before they decided to put Dana 60s in their cars
This issue, again, has been beaten to death in 100s of threads on this site
 
Projectile Dart said:
I cant answer all of your questions but I can start with some of them while others fill in the rest.

1) We can't measure your rear end for you. If you can confirm with 1000% certainty that the rear end originally came out of an A-body then those should be your measurements. (The fact that they are SBP is a good sign that they are) If you can't confirm then you will have to do your best to measure it yourself.

2)To my knowledge although I may be wrong, all stock axles were 30 spline, and the 35 spline axles were aftermarket heavy duty upgrade stuff. Someone will chime in to correct me or confirm.

3) There are 100s of debates of modern green bearings vs timken, it has been beaten to death. On a mild street cruiser you would probably never notice the difference between the 2 but for race applications look up the pros/cons people have posted about them (I personally recently bought axles from Dr. Diff and went with the green bearings because I believe they'll be enough for MY application)

4) BBP axles have different offsets, so they will require new brakes. Dr. Diff sells what you will need, If you plan on going to disk brakes, It would make sense to do that swap now

5) The axles I ordered from him had 10 holes, 5 for press in studs (installed) and 5 for screw in studs. Swapping out studs for different lengths is just a matter of pulling the axle and swapping what you need, I am a big fan of that feature.

6) Also debatable, what kind of power do you plan to run? Transmission? street use or heavy drag use? In theory your 8.75 should handle just about anything your 440 can do on the street with a reasonable tire (not crazy wide or sticky) Many people upgrade do Dana 60 if they plan on racing on big blocks and for peace of mind. A 8.75 can survive longer behind an automatic trans based on how power is sent to the back but manual transmissions can be brutal on drive trains and sometimes require more beef.
All that being said Mopar teams raced with 8.75s behind Hemi's for years before they decided to put Dana 60s in their cars
This issue, again, has been beaten to death in 100s of threads on this site
Click to expand...

Thanks Projectile Dart! All of that information is very helpful. Guess I have to look at new brakes now! Oh darn...
 
1. Are you SURE that it is a A-body 8 3/4 (with the small bolt pattern, it probably is.
You 489 case is a later piece I think. (May be original in a 69)
2. ALL 8 3/4 are 30 spline, except for aftermarket spools, and possibly Detroit lockers. (HIGHLY unlikely in your case.
3. I prefer the original style bearings, but Dr.Diffs "green bearings" are much better than the old ones that have a bad reputation. If you plan on going to disc's later, you will NEED the green bearings.
4. Ask Dr Diff (Cass).
5. Small bolt pattern use 7/16 studs, big pattern use 1/2. Do yourself a favor, have Dr put in 1/2x3 studs.
6. Depends a great deal on power of the 440, stick or auto, slicks drag radials or street tires. Without more info how you plan to use it, I won't try to answer.
I will say: 500 hp, slicks, and a four speed, I wouldn't spend a dime on a 8 3/4.
450hp, a 727, 3000 converter, and STREET tires, a 8 3/4 should last just fine.
Edit: Projectile Dart posted as I was typing (slowly). Treed again. Looks like we agree.
 
How do people feel about the redrilling of the axle and the drums for the large bolt pattern? That wouldn't be the permanent solution, but would that work until we intend to convert to disk brakes? I've seen a few threads of people doing so.
 
67BBCuda said:
How do people feel about the redrilling of the axle and the drums for the large bolt pattern? That wouldn't be the permanent solution, but would that work until we intend to convert to disk brakes? I've seen a few threads of people doing so.
Click to expand...
It's been done a lotta times for a lotta years. Success depends on the quality of the work (like most anything).
I'm gonna stick with the sbp on my 67 barracuda, I've got a set of sbp wheels that I like.
 
440 and 8 3/4 poor choice. 9 1/4 out of a pickup is the way to go unless you have to coin to pay for the dana 60 which is heavier than the 9 1/4.
 
There is a reason why ma mopar put a dana behind hemi and 440 6 pack cars.
 
33IMP said:
3. I prefer the original style bearings, but Dr.Diffs "green bearings" are much better than the old ones that have a bad reputation. If you plan on going to disc's later, you will NEED the green bearings.
Click to expand...

Dr Diffs rear disk kit allows the use of the factory tapered bearings. I've been using that setup for years with no issues.
 
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