I just got off the phone with IWE and the guy there was telling me a few interesting things. One was not to even consider the 9" because is whines like a biatch. Second was that the 12 bolt housing is hard to come by. So he recommended a 8.5" 10 bolt rear. He says that it will be able to handle the power like the 8.8" 12 bolt rear. They use all the same parts. The only difference is the 2/10" ring gear difference. Even the bolts even out, so to speak. The 12 bolt just uses smaller bolts while the 10 bolt are larger bolts. That didn't make much sense to me but whatever.

Anyway, I need some feed back from the rear end experts here. Do you think the 8.5" rear is actually as strong as the 8.8" 12 bolt?

Thanks
-Ken

 

Well a couple of things
I am not sure why the 9-inch gets a bad rap for noise. It has been running around under Fords since the fifties. Possibly there are numerous aftermarket gears sets or pumpkins that aren’t quite up to snuff.
Be prepared to spend some cash as most nine inches are 28 spline axles with substandard or no posi.

Although there are few 12 bolts laying around there are at least aftermarket housings that have torque arms mounts cast in.
Factory, they are at least 30 spline axles.

The actual gear sets in the corporate 8.5 10 bolts are plenty strong.
Other than the 90'ish and up "B" body the 8.5 used "fair" 28 spline axles.
30-spline Eaton posi's are readily available but use some goofy low angle bearings to fit them in the 8.5 side housings.
You still have the issue of trying to mount the torque arm.

As for strength, the 8.5 with 30 spline axles seem to stand up to a number of very heavy Impalas and Caprices.

As for shear size the 9 inch may go under an "F" body but it leaves little room for anything else.

No matter what you do under there are going to be custom work or parts. But to answer your original question, I believe a correctly built 8.5 would be up to the task.
Gerry

 

Once the car is finally dialed in it should be pushing out ~400 rwhp then adding 200 shot of n2o in a year or two. Do you think the 8.5" 10 bolt will hold up to it.

In other words... will the 3/10" diferance from that 10 bolt to a 12 bolt really make that much of a diferance in strength?

 

IWE is right about the 8.5" its a great rearend too. i got one and ill be running on in my combo (see sig) ill be running it into the 9's and pulling the tires on it, it will get the job done. its a good cost effective rearend.

 

Number one issue is to be honest with yourself about the aplication you plan to use it for. For example, if you want to try some open track or auto cross events, you won't want to use a locker and 35-spline axles.

But also, I was told "better to over build it, than under build it."

Andy

 

Shut up Andy. I know one 95 TA with a 8.5" and I've seen 8.5's and 12 bolts side by side, they look the same, except the aftermarket 12 bolts look like beef!

Also, I have over 400RWHP and I've dead hooked tons of time and beat on my 10 bolt 7.625" with 4.10's with not a single wine or any problems, I think a lot of it has to do with how well built this stuff is.

 

oooookkay Matt

 

and a 8.5" is that much better then a 7.5". alot of it is to do with the housing strength itself also. its pretty similar to a ford 8.8, and they are strong rearends, lots of them going 8's. i beat on my stock 8.5" with gears for 4 years and when it came apart it had no signs of wear, and thats with many years of slick launch and burnouts and street racing etc. and that was bone stock. if you get the diff support cover, weld axle tubes and put a good posi in there or a spool, with some good axles, you will never have to worry

 

LOL

 

It's only a matter of time Matt, trust me on that one.

Ken, I have heard the 8.5" 10-bolt is almost equal to a 12-bolt. But the costs to weld one up to fit into your car? I don't know if that's worth it really. I'd also think twice about IWE, I have had some bad luck with them in the past.

 

I spoke directly with the guy that does all their custom work and he says that most of the parts are the same for the 8.5 and the 8.8 rears.

Cost wise he said it would be about the same price. The only diferance would be that the 10 bolt housing is cheaper than the 12 bolt. There would be some custome fabing for either rear so the cost of making it a bolt in app. is the same.

 

Well Moser & Strange make bolt-in 12-bolts for your car, I think Moser even makes a bolt-in Ford 9-inch for your car as well.

I don't think there are any bolt-in 10-bolts for F-bodies

How come youre leaning away from a bolt-in unit?

 

I'm just leaning towards whatever will cost me less without sacrificing the durability or strength.

I'm looking to get one in Feb. so I'm still shopping around to see what I can get. So far it looks like whatever I choose its gonna cost around 3 g's to get it to my house ready to bolt in.

 

It can be done cheaper just takes a llittle time to look for the right parts. I built my 9 inch for under 2000 3 years ago. The Housing and axles from moser were around 900. All the rest of the parts were picked up locally minus the gears for 250Cdn. Gears were just ordered from summit racing. All in all it costed me less then 2000 cdn for my bolt in Moser 9 inch with a detroit locker ,35 spline axles and Nodular case.



Happy shopping

 

Did you build it yourself?