I need to get a new rear end and there are so many options I'm a bit lost here and curious about options and opinions.
1978 Caprice with 2004 Avalanche 5.3 and 4l60e. The most I'll ever has is maybe at some point 400 crank hp. Right now it's stock. This is a daily driver. I would like to get a new bolt in unit that would have Limited Slip, disk brakes and a gear ratio of choice.

I've spec'd out new rear ends from the typical new companies like Moser and Currie and they all seem to run around $3,500.00. I like to do a burnout, donut or get sideways when it's raining sometimes, but that's about it. Maybe I'm overspecing these things.

Does anyone have any other companies or suggestions. I suppose I could find some kind of stock housing and replace the 3rd member and disc brakes, but I figure by the time I do that I could have a brand new unit.

 

You have to pay that kind of money if you can't fab it up yourself. If you have the time and skill, grab a 8.8 Ford posi disc break rear from a suitable width junkyard donor ( Exploder or F150), get the weld on bracket kit from A&A Manufacturing and start grinding, measuring and welding. By the end of that process, you will likely wish you just spent the money with Currie or Moser. If you already have the GM 8.5 in that Impala, a new gear set and Auburn or similiar posi unit and a disc conversion kit are all you really need until you put too much boost, nitrous or slicks on that thing.

 

A 94-96 Impala rear end gets you 3.08, Limited slip and disc. You most likely will have to replace the POSI unless you get lucky and find a low mileage unit. The POSI is not rebuildable.

94-96 Caprice, Roadmaster, Fleetwood. 2.56 or 2.93 Can also have limited slip as an option, not standard. These are drum brake rear ends.

94-96 Fleetwood with V4P towing option - 3.42, Limited slip, drum brakes - (Very rare, would be almost impossible to find)

Stay away from police and Station wagon rear ends from the 94-96 years. They don't fit exactly. Some have bolted them in but the track and mounting points are slightly different.

These rear end uses a metric fitting for the brake lines. Either get an adaptor or get some metric tube nuts and make a new line.

You also can bolt in rear ends from the 77-93 range but I don't know the specifics.

The most bang for the buck is probably the Caprice, Roadmaster, Fleetwood read end with 2.93 and POSI. Impala rear ends usually go for big bucks compared to the others.

 

With the disc rears, you will need wheels w 5x5"pattern. No more 4.75" after 1990.

And you could swap the front knuckles, rotors and calipers so the vehicle had one pattern, with bigger brakes.

Getting everything at once from a donor Imp makes a lot of sense. But a 3.42 sure sounds nice.

 

That car should have a 8.5" 10 bolt, just upgrade to a posi carrier and change the gears while you're at it.

 

Is there something wrong with the rearend it has now? Could it not be rebuilt with new bearings seals, gears and a posi?

 

The 10 bolt should be plenty strong. New posi, 3:73 gears and new moser or currie axles and let her buck. You can get the axles in 4.75 or 5" bolt circle. Also if you are doing a disc brake conversion the axle company can turn the register on the axle down to match the disc brake rotor.

 

This.

 

As already stated just keep the 10 bolt you already have and drop in a nice posi unit, gears and disc brake kit of your choice.

 

You all are assuming the car has a rearend and that's rebuildable. If it does and is, then I agree just rebuilding it is the best option. But if not or if he's starting from scratch, maybe a good option would be finding a stock replacement from a junkyard and rebuilding that instead of going all new.

 

You must have missed his 947 other threads.

 

Maybe. Was his present rear axle mentioned in any of them? Help us out here....

 

Good call on the 5 on 5 bolt pattern. I have a 77 Cadillac with 5 on 5 and forgot that the Impala was a 4-3/4 bolt pattern. As to rebuilding these rear ends, at least on the Cadillac there is no aftermarket support, no ring gears or POSI unit. Other than axel replacement there is not much you can do. The factory gears are 2.28 48 state, 2.56 California, I have heard of a 2.73 for towing, but have never seen one. Maybe the Impala gets more aftermarket support.

 

That's good news. If I can use the original rear end housing and rebuild it that seems like it would be the way to go. As I stated, the most the car will ever see is maybe 400hp at the crank and I might take it to the local 1/8 mile track once just to see. Just normal daily drivings donuts and horsing around.

The car has 2:41 gears in it now according to the build sheet. I had thought it was a 7.5 rear end, but according to what I've been looking up it appears to be an 8.5 10 bolt (see pic below).

I know about as little beyond nothing as you can get about rear ends. If I rebuild this (assuming I'm correct and this is an 8.5, and I'll have a reputible shop install it) I can put a new limited-slip differential with gearset of choice and new axles and convert to disc brakes. I'm sure they make a kits to do all of this, but so far I've found there's about a million different types and options for types of differentials and axles. What are opinions on retaining the c-clips or eliminating them?

 

That is an 8.5". For 400 HP you don't need new axles or C-clip eliminators.

Many years ago I had a rat motored 72 Camaro that ran 10.90's consistently with stock axles, they're plenty strong for what you're doing.

 

If your car has a bunch of miles inspect where the axle bearings ride on the axle. Sometimes they get pretty worn. You can do "axle" saving bearings but I would just replace them.

 

In his main build thread he has shown pictures of the rear end a couple of times, including the same pic that has been posted in this thread, so the type of rear end could've been determined in that thread just as easily as here. And he's driven the car, which addresses -TheBandit-'s concern about whether he even has a rear end or not.

 

So then instead of being a smartass, just refer to those aforementioned pics and help HIM out. Not everyone goes over the few involved threads. It's not that big a deal.

 

Thanks guys for all the good info. I'm glad you mentioned the 5x5 pattern. Until I started my build here I had always thought my car was a 5x5 pattern. I had once again forgotten it was a 5x4.75. I would have absolutely ordered the wrong thing. Man I'm really glad to hear that about the 10 bolts. So if I understand correctly I can basically order new guts for the diff housing, new axles and bearings and I'll be good to go. I suspect I'll order new axles as well as this car's body, and so rear end, probably has near 200K miles on it now. I realize this question may be like asking if "Ford or Chevy is better," but what type or brand of differential should I consider. Are there any generally agreed upon types that I definitely wouldn't want on daily driver? For example, I know enough to know I wouldn't want to buy a locker. Do some have better longevity than others? For the 400 crank hp max level, do 28-32 splines make a difference?


I wouldn't worry about that AAII guy too much . I've already tried to explain to him the purpose of an organized information library setup in an easily indexed manner that for the sake of the posterity of the site and hobby can be used to quickly answer very specific questions which may be applicable to more than just the type of car I'm building by breaking down the individual questions into separate threads and then also compiling all of those answers into a single thread that can be hyperlinked. This topic proves my point that when searching for information a person may want to find the specific issue in a dedicated thread rather than read an entire thread of 6 months of unrelated progress just to find that their question may or may not have been addressed. As an example, sometimes I'm in the garage and have a simple question, like a torque setting for example, and I appreciate not having to read through an entire 13 page build thread to find it hidden on a random page. He continues to feel the need to make sarcastic comments about his approval, or lack thereof, my questions.

 

Yeah, I get your reasoning. I think I even commented on the multiple threads once, but once you explained it, I saw the reason. Carry on...