kmspruill242

I know not as many of you guys road race your cars but there is a lot of knowledge on rears in this forum.

I'm finishing up a NASA American Iron build. The 10 bolt has lived well behind the stock power. I've now moved onto a Carb'd LS6 and Tick built T56, so the rear is the weak point on this car now.

What do you guys recommend? I've looked through the S60s and 12 bolts and most of the bolt in packages are drag race oriented. If I where to find a 9inch housing in the junkyard, is there a sponsor here that can fab it up to be bolt in? Or should I just get a bolt in package built?

Thanks guys

MrDude_1

iTrader: (4)

well, the nice thing about all the 12 bolts and 9" rears is they are truly custom. they're usually built without a single OEM part in them.

as far as the housing goes, they all will bolt in... with minor issues i'll mention below
as far as the axles are, the aftermarket ones are stronger, and eliminate C-clips.. a very good safety feature. If you're willing to pay more, they can even be lighter, and remain stronger.

I think what you're worried about would be weight, handling changes, diff setup, longevity and possibly price.... oh, and rules... i do not know your rulebook on this stuff.


that said, if it was my race car, I would go with a 9".. I would buy the axles and housing as a kit, and the center section separately.

you can easily get the housing and axles as a kit from several vendors... I personally prefer Moser, and several sponsors will carry Moser... they all drop ship direct from them.
this kit will give you everything except the center section.
There are other vendors that make housings, but this is the one I like. there are fabricated aluminum housings that are lighter, but I have never seen one under a road race car. I dont know if theres really a reason why. I dont have experience with aluminum housings. if you have the cash, you can get the axles gun drilled or even star flanged.. saves rotating weight. before you order this kit, you need to decide on your centersection, as the number of splines on the diff determines the number of splines on the axles. btw 28 is the OEM ford car size and should not be used. 30, 31, 35, and 40 are the sizes, but 35 is the most common "aftermarket" size. given your application, the 30 and 31 size will work for you as well.. as long as your center matches.
40 is huge and only the pro-level drag guys need it. you will never break a quality aftermarket 31 spline axle on a NASA road course... 31 is the count most ford trucks used, so theres alot available in that size.

For your centersection, I would have a shop build it. You can easily bolt the center to the housing yourself, then slide the axles in. (you only need a couple wrenches to do it all.)

A thru-bolt aluminum case would be my choice for the lighter weight, but if you're not worried about weight, an iron (really, its steel) case would be more durable. the aluminum one will last, but you should inspect it between each season.
I know you want a limited slip, but this is where your only real hard choice is.
I like the Truetrac diff... with its all gear design, theres no friction material to wear. its always engaged, so its smooth, with no chatter or slip... on the larger 9" rear, the gears in the diff are physically larger, and therefore stronger... so you wont blow it apart like you can on a 10bolt. (same design).... I feel im in the minority on this, as the other diffs are more popular... primarily because of cost, and how long they've been around.
I would also run a daytona pinion support... thats about it for the "custom" stuff... you can get a billet yolk if you want, but if you do, dont get a cheapie off ebay. some of them arnt square and can cause an inbalance at high speed eventually leading to U-joint failure. a normal cast one is fine.. billet just looks cooler.



ok, so heres the catches to a 9"

first the axle tubes are physically larger. the spring sits on the axle tubes.. so your car will be raised slightly.
next, the torque arm will be offset to the side some. this may cause a slight clearance issue. nothing a tap with a hammer cant fix.. or if you're running a aftermarket arm, you can use a second set of bolt holes. this offset is due to the design of the case and torque arm mount. also the top bolt of the mount may contact the chassis under full compression. check for clearance.

you may need an adjustable panhard rod.. while the rear is made to match OEM specs, theres enough variables between cars, ride heights, tire clearances, etc to add up to you needing to move the rear a bit from one side to another. If its legal in your rules, and you road race, a bolt in Watts link may be even better then the panhard.

also, the rear itself will weigh more.. you may find this effects your damper settings.

MidwestChassis

iTrader: (5)

kmspruill242 we possibly have what you are looking for. We have a built in watts link for our fabricated housing. I would also recommend a long arm as far as the torque arm.



With our housing based off the axle tube diameter you will see a slight increase in rear ride height, how ever our torque arm design does not have body to floor pan issues. Now if you are just doing road racing and building on a budget you could use a posi style diff unit. For a case I would stick with an iron case as it will do fine for what you are using it for because an aluminum case (non thru-bolt) will have to much flex and a thru-bolt could be possible over kill and yes it is lighter than an iron case not by enough to make a difference unless you are trying to subtract every pound possible but that needs to extend out past the rear end build to start adding up to account for something.

As for axles do just standard axles in what ever spline you may need depending on the diff unit. I would not recommend how ever doing star flanged ends to cut weight as they are not designed for a side load application. Gun drilled axles and lightened flanges work well for those guys trying to cut every bit of weight out of their car they possible can in a drag race application.

Bob@BruteSpeed

iTrader: (16)

http://shop.brutespeed.com/Moser-M9-...y-Complete.htm

Take a look at the Moser fabricated rear in the above link. The fabricated rears basically weigh the same amount as the factory 10 bolt, yet with the backbrace are very strong. The rear here ships just two days after the order is placed. Bob

kmspruill242

Thanks for the responses guys. I wasn't expecting to see so many fabricated rears for these cars.

Any real benefits to the fabricated setups versus a standard bodied 9" made to fit under an F-body?

Bob@BruteSpeed

iTrader: (16)

I can tell you the Moser fabricated M9's torque arm fits much better under the car, when compared to a standard Moser 9 inch. The fabricated M9 allows a car to be lowered without having to worry about the torque arm rubbing anywhere, plus the torque arm is an excellent design. Bob

MidwestChassis

iTrader: (5)

One of the benefits of the MWC rear end is the fact it comes with a drain plug, brake line tabs, e-brake brackets(98-02), torque arm and cross member for not much more than the cost of everyone elses stamped style housing. Our rear end is like bolting back in the 10 bolt as it mimics it as much as possible.

roy

kmspruill242,
Ensure that you request tapered roller axle bearings instead of the standard ball bearing axle bearings that usually come as standard. The ball bearing axle bearings donot stand up to the rigors of roadcourse track duty so well.

garygnu

go HD on all of your suspension parts.no spool!

MidwestChassis

iTrader: (5)

With our rear end builds we set all them up this way unless it is a track only vehicle. It is a good point you brought that up how ever as many do not know the difference.