They aren't a 9" but I blew up my 10-bolt but my 9 has worked perfectly behind my big engine. The definalty hold more then a 10 bolt.
Common sense tells you 4 spiders are much better then 2. Plus some other things. Overall a very good rear for the price.
They're cheap from the junkyard

 

You must be one of the lucky ones who can pick them up cheap out of a junkyard. When i broke mine I always went looking and they were wanting like $250 for a 2.77 rear, and around $400+ for the 3.27 and 3.45 rears. I ended up just paying for it and I still needed to replace bearings. The brake mounting is also different on those rears compared to the newer ones as well.

 

If you want a cheap rear end that'll do what your asking just go buy a Moser 9 inch housing and 31 spline axle setup. They run about 9-950 shipped from many vendors. Then either go to ebay and buy a used 9 inch 31 spline 3.50+ posi center section out of a pick up. I've seen them as cheap as 150 buy it now on ebay. So with shipping its probably 250. You can either bolt it in and go or get the posi rebuilt. So for probably 12-1300 you can have a 9 inch that'll do what you want. For another 50-100 you can build your own 3 channel abs setup for it and go.

 

Again, let's assume for a second here that we're talking about some guy that puts down 250rwhp - why should he sacrifice soaking up all of that HP that a 9" is going to rob him of? Put yourself in the shoes of the guys that put down between stock and say 450 - these guys don't necessarily NEED a 9" or 12bolt. In fact, it's going to hurt them more than anything (Speaking on the lower end of those numbers at least).

 

Well you're too picky you can't have everything. You want a cheap but good rear that doesn't eat up power. Its kind of like having a cammed car. You want a big cam to make power but you don't want to give up drivability and gas mileage. You must make some concessions sometimes with your car unless you have the ability to make it on your own. I also think you overrate the amount of power lost. You mention droping approx. 50 rwhp by adding a 12 bolt. I think at most a person would lose would be 20 and thats pushing it. Also what you tend to lose in hp you gain in ET because you are able to hook so much better and have it survive.

 

How am I being too picky? $1500 for a rearend is cheap? I guess everyones perception of "cheap" is different as well.

EDIT: I must say that I am grossly mistaken here with the following comments. After searching for our dyno results - it was the switch from the T56 to the A4 that had the drop in HP for Grease. I'm leaving my post here - to show that I can eat crow with the best.

I'll talk to him tomorrow and find out what the drop was with the 12 bolt install as obviously - I can't remember.

You "think" and I know - we put GREASE's car on the dyno after installing his 12bolt dropped from the 412 listed on AI's website to 360ish - after tweaking we got it back up to 390 I believe. Had we played with PCMforless's mail order tune before we installed the 12bolt we would have seen a pretty big increase in power but we didn't - so the drop is relative. Does every car lose that much? No, probably not but that's what I personally saw on the dyno so that's what I'm going with.

 

Also, I agree that you can launch harder but that doesn't mean you're going to hook any better - a rearend is not a traction device. A stronger rearend will survive a harder launch but that doesn't mean squat if you can't get it to hook with proper suspension and traction pieces.

Bottom line is this - there is a genuine desire for people that don't plan on flogging their cars at the track all the time to have a relatively inexpensive (or cheap) replacement rearend that is stronger than the crappy 7.5" that comes stock in our cars. I would think that these same people would like to install said rearend without fear of losing any of the little power that they may currently have - whether that be 20, 30, 50, 100 - whatever.

I'm just surprised that no company has stepped up and addressed this - the market would be there I think.

 

My first post, just recently bought a '94 a4 Z28 I remember these cars when they were new in HS, when I worked at the dealer. Anyway.....I have alot of experience with the GM 8.5,12 bolt, 7.5.Also Ford 8.8 in friends and brothers stangs. Did all the rear work on a friends Buick regal with a 400 P, also my old 80 bird went 9.50's w/an 8.5 w/GM posi. I also have 2 Chevelle 12 bolts in my old GTO's and an old 8.2 10 bolt from my old Chevelle. I know how crappy those 7.5 rears are, the original "vega" rear. We tried to be on the cheap with my friends buick and used a jy s-10 3.73 non posi, ended up blowing the pin out. Then an 89 TA posi and jy 28 spline axles and 4.10's from a s10 4wd, ended up breaking the side gears. The car only ran high 12's low 13's. I am afraid to run the Z28 hard for fear of the rear. Why did GM use those crap rears??? What is considered junk the 8.2 would be better! I even thought about that since it is just laying there, of course 'cept for the ta mnt. BTW: the 8.8, 8.5 and 12 bolt are real close internally 'cept for ring gear size,the 12 has an 8.875 ring gear.The 9 in uses the most power. Sorry about the long post for my first one.

 

Thanks for the post, and welcome to the board.

Who knows why GM would put a piece of garbage at one of the most abused and vulnerable parts of the car. Let's give the car rods that will withstand almost twice the power, but give a rear that isn't good enough for stock. Yeah, that sounds like the ticket!

 

Why would it be any cheaper than a 12-bolt or 9"?

Rich

 

I'm getting ready to start my 8.5 inch ten bolt project. I think with a eaton posi and what ever gear set I would be able to get the rear end out the door using stock brakes and rear girdle for around 1600-1700 no problem. Now that would be for a 4 channel and I would have to work on a 3 channel but I dont see that being too much of an issue. Of course the torque arm mount is the biggest issue but I wont weld it too the cast iron. The tubes would be welded thou too the diff itself. I'll keep the board notified as too the progress and let you know how it turns out. I will take my time with it thou so that I get it done right. will post photos when done.

 

I'm with Rich... I don't see if any of the major companies offered a drop-in 8.5" for the F-bodies how it could be any cheaper than a 9" or 12-bolt. Just adding up the cost of gearsets, gear install kits, axles, differentials, etc., etc.... the $2000-$2500 cost of brand new, ready-to-run 9", 12-bolt, and now Dana 60 rears really doesn't seem that expensive to me. Heck, people are paying $1000 for a set of headers - looking at the huge difference in materials, machine costs, etc. a $2000 rear seems like a lot better deal.

The 8.5" 10-bolt truly is the rear end that GM should have put in the car at the factory, but it doesn't seem like a logical upgrade path to me. Tbyrne is running a GP on the new Strange F-body Dana 60 rear... $2049. This rear is the closest thing to indestructable for our cars, and is theoretically more efficient than the stock 10-bolt due to the pinion shaft / axle centerline relationship.

All this talk of losing big HP with a 12-bolt just doesn't make sense. The 12-bolt and 10-bolt have very similar geometry... and similar efficiency. Now, a 9" is less efficient, but the new Dana 60 is actually more efficient.

 

just added up all the parts for the conversion and the most expensive part or it is the posi. All the other stuff can be had for under 250 bucks. And thats including the backing plates for the axles. all said and done the conversion can be done for around 1200-1300 dollars depending on gear set and extras that some might want. and for that you have a rearend that is damn strong and will handle just about all the abuse you can throw at it. now for those cars that are running in the low tens and faster then ya start looking for the dana 60 and the 9inch fords.

 

Don't forget that you need to fab the housing with proper mounts for the LCA's, shocks, PHR, anti-roll bar. And don't underestimate how difficult it will be to fab a TA mount that won't end up breaking. Time is money, and Strange already has all that stuff done for you with their Dana 60.

The 8.5" 10-bolt is a good rear... that's what's in my Blazer, and I like it. The idea of a strong F-body rear for under $1500 is certainly appealing, but if/when my 10-bolt breaks, I'm going overkill with the Dana 60.

 

For what it's worth, there are a number of 2-ton 10-second B-bodies running 8.5" 10 bolts. http://dan.esteban.com/impalass/Retu...SelectedClass=