There are many different meanings of the word "cheap". Time has a value. The $/h value of your time varies tremendously with whatever else is going on in your life. Piecing together a rear end and fabbing it up takes a lot of time. Also, parts bought on eBay are a crapshoot. If we are comparing costs, using a low price seen on eBay as the typical price for a part is the most optimistic scenario.

My point is simply that for comparable quality parts and convenience of installation, putting together a 12-bolt or 9" is not going to much more expensive than an 8.5" 10-bolt when the same assumptions are made about how much fab is going into it and how much scrounging for used parts you are willing to do. I admire the old "hot-rodding" mentality that is represented by scrounging up the stuff you need to do the job at hand. If you have the time, interest, and skills needed that's cool! Just pointing out that to some extent this discussion is "apples to oranges". The answer to the original question as I understood it is still the same - for someone to come up with a bolt-in 8.5" 10-bolt conversion wouldn't be significantly less expensive than a 12-bolt or 9". This is not to say that a skilled/motivated person couldn't do it on the cheap. But that isn't what most people mean by a "conversion".

Rich

 

i totally agree with everything DarkHorse has said. and to people who dont think the big rear ends rob power, a couple of my friends cars have lost two tenths in the quarter after swapping to a 9"

The 8.5" is what should have been in these cars from the factory. Theyre light axles that can hold a lot of torque and take a beating.

I guess what im not understanding is what is so difficult and expensive for a company to make a mold for an 8.5" housing with torque arm accomodations. Just seems to me like someone could easily turn a profit designing one, then mass producing and selling them for like $250. If someone does that... bingo: instant cheap conversion kit for someone who is inclined enough to fab the rest of his cheaply aquired 8.5" 10 bolt to fbody specifications.

Im no ASE mechanic by any means, but I would much rather attempt fabbing my own 8.5" ten bolt for ~$750. As hobbyists, we have a way of getting through the tough stuff to save money and get the job done. Im a college student with no money and less time, and id still rather spend the time when it comes to my car.

 

just because you get the housing done for a few $$$ doesn't mean you still don't have to buy new gears, bearings, posi, better axles, and pay someone to set it up for you. That is where all the cost is at.

 

I would use the gears and axles (that i would fab) from the "donor" 8.5" that i would be swapping the housing on. most 8.5" seem to have 3.42s /3.73s/4.10s already in them. I would also attempt to set it up myself. i figure everythings worth a try, if i dont succeed then i can pay somebody

 

No one has questioned that the 9" is less efficient than the stock 10-bolt... that's a well-known fact. But you will not see that kind of drop in efficiency with a 12-bolt or Dana 60.

All these rears are a little heavier than the stocker, so that will slow you down a tiny bit.

 

just adding here, my buddy had a 9" rear installed at extreme and they dyno'd it before and after. it lost 7RWHP. which equates to roughly 10-11HP from the flywheel. no track times but Im sure it would slow him a bit with the added weight and less RWHP but he upgraded the ring/pinion to 3:89's from 3:23's. so that wouldnt be an apple's to apple's comparo anyway. does anyone know if the dana 60 rear's are heavier then stock? lighter then 12bolt?

 

Weight is the biggest drawback to the Dana 60... According to http://www.tbyrnemotorsports.com/ the Dana 60 weighs 215lbs, compared to 189lbs for the 12-bolt, and around 200lbs for the 9". I can't remember what a stock 7 5/8 10-bolt weighs, but its definitely a lot less than 215.

 

at least its weight that is added to the best possible spot to help traction.