8 3/4 rebuild? or upgrade?

[SBDave]

My car is a 1973 Barracuda, 318 904 and I'll assume it's an 8 3/4 rear end.  I haven't actually identified it but assume it's stock.  Don't know what the gear ratio is either, but also assume it's stock.  I just brought the car to an alignment shop after rebuilding the whole front end.  The guy took my car for a test drive after alignment and said the bearings in the axle were most likely shot (he said they were howling).  This makes sense since I have always thought the rear end sounded loud, and when I rebuilt the front end the wheel bearings needed to be replaced because of pitting.

So, now I'm trying to decide what to do.  Do I just replace the bearings and seals?  Do I change the gearing, go with a sure grip and stronger axles? Does it make sense to upgrade to disk brakes in the rear now while I'm doing all this other work?... and is that a direct swap (drum to disk)?  What is worth keeping from what I have?

I know that's a lot of questions but I'm having a hard time finding good information about this.  The car will be 99% street driven.  I'm making it a corner carving car that I might take to a road track once or twice a year.  I don't know what I'm going to do for an engine, but it will most likely be a small block.  I would eventually like to change the tranny to a manual, either an 833, 833 over drive or a 5 speed w/overdrive.

Are there any special tools I need to be aware of when working on the rear end?  I have access to presses, bearing splitters and lots of tools, just not much mopar specific.

thanks,
Dave 

[Moparal]

Doc diff has a timken A7 bearing kit for both sides he sells for 100 bucks. Comes with the seals inner and outer. This is for an 8 3/4   a little labor goes a long ways.  he has new powerloks for 395 I think  add 38 bucks for the carrier bears and races

[Chryco Psycho]

I would try to repair what you have , typically the gear will whine so you may have to replace those as well as the bearings

[Tonefiend]

My 70 Challenger with a 318 and 904 trans came with the smaller rear end.  The previous owner put in an 8-3/4 which I had to rebuild.

I had never done it before and managed to replace the center section, pull the axles, replace the seals and bearings and install a disc brake setup.

Check out what you have, you may want to find an 8-3/4 rear end if you dont already have one and have a diff shop rebuild it with a fresh sure grip and the gears you want.  They might as well throw bearings in there while it's apart.  While you are at it replace your leaf springs they are probably shot.  I am going to have to do mine.  My left side rear end is sagging.

[SBDave]

I just assumed the 8 3/4 was standard on the V8 equipped cars and that the Dana 60 was the upgrade.  I'll have to find out what I have.  I would like to just replace the bearings/seals if they are shot and go with a sure grip diff and better gearing.  I guess my question is, while I'm working on the rear end what other things should I consider? 

I was trying to describe what I will use my car for so that I could get some suggestions for specific mods I might be interested in.  For example if one diff is better than another (lighter weight, stronger, etc.). 

I have brand new leaf springs, shackles, front hangers and shocks already installed.  Still waiting to install my sway bars.

thanks,
Dave

[moper]

Welcome 

It's more a question of do you like what you have for performance now? Aside from the axle bearings have you noticed anything else like leaks or clunks? The original bearings were designed to be servoced... they neede to be greased every once in a while and they never have it done. My own feeling is if there is no other problems and your happy with the way it drives, it doesnt make sense to get way into it. Pop the axles, replace the bearings and seals, and go cruising. If there is a reason to get into it, then do it right. Which for me means new everything except castings and then you never have to worry about it again.

[Road_Runner]

I just assumed the 8 3/4 was standard on the V8 equipped cars and that the Dana 60 was the upgrade.  I'll have to find out what I have.  I would like to just replace the bearings/seals if they are shot and go with a sure grip diff and better gearing.  I guess my question is, while I'm working on the rear end what other things should I consider? 

I was trying to describe what I will use my car for so that I could get some suggestions for specific mods I might be interested in.  For example if one diff is better than another (lighter weight, stronger, etc.). 

I have brand new leaf springs, shackles, front hangers and shocks already installed.  Still waiting to install my sway bars.

thanks,
Dave

It could be either rear end.  My 73 318 auto Barracuda has an 8 3/4 but I've read that it could have come with the smaller 8 1/4.  Does yours have a smooth pumpkin (center section) in back or does it have a bolt-on cover?  If its smooth its the 8 3/4, bolt on is likely 8 1/4 but Dana's also have a similar cover but are MUCH larger...

And one thing I would highly recommend checking is the U-joints.  If these are worn and fail it can get real ugly fast, especially if its the front joint.  Chrysler rear ends are not necessarily the easiest to work on.  Changing axle seals & bearings aren't terrible and you can pull them and put them back in yourself.  If you don't have a press you'll have to get a shop to press off the old bearings and install the new ones.  Although I haven't installed them yet, I'm definitely going with the Chrysler "Green" axle bearings (or something similar) that don't require that you adjust the end play of the axles.  Do this incorrectly you'll be pulling the axles and replacing the seals again (Trust me, I know).  Unless you are very mechanical I would recommend leaving the rear end work to someone who does this everyday, and do your best to find someone who regularly works with Mopar differentials, because those who work with Chevys & Fords won't necessarily know the right way to work on yours.  Good luck.

Later, Jim

[Tonefiend]

http://www.usaimports.co.uk/Mopar_Tech_Pages/mopar_rear_ends.htm

[Road_Runner]

http://www.usaimports.co.uk/Mopar_Tech_Pages/mopar_rear_ends.htm

Great article, but definitely dated.  $350 for a new Sure-Grip?  I wish!!

[Moparal]

doc diff is sellin new sure grips for 375

[SBDave]

Great link.  Well, I'm sure I have an 8 3/4 now but still don't know what center section (think it's a 3.23 ring gear though).  I would like to do this rebuild myself as I should have all the tools and if I can't figure it out I have plenty of people I can ask for help.  I would like to get a new pinion and ring gear for the car to make it a little more snappy.  I played around with the program and looks like I want something around a 3.55 to 3.90.  I want it to be faster off the line but still be able to cruise the freeway (is that too much to ask?).  Any recommendations on gear ratios?  Again I have a stock 904 trans right now but am considering a 4speed, 4speed OD or 5 speed down the road.

I assume checking the U-joints is as simple as seeing if there is any play in it?  I haven't done that yet, but will.  Most likely they will need a rebuild since everything else on this car has, oh well.

thanks,
Dave