My car has come to the point of needing a different rear axle. My car has had 3 sets of gears with 58k miles, and I really don't feel like setting up another set.

After some research, 12b whines after a few fun days...so that axle is out.

Looked at the S60, and that is one bad *** axle for the money. If this was my Jeep, I would concider one with full float bearing hubs since weight isn't a concern. However, looking at some Dyno results I'm just not willing to give up to 3% of power and tq. I'm already at 6k feet of elevation...so that is working against me. Not looking for the weight either, handling is a big concern for me too.

So my last reasonable option is a 9" unless there is something else I haven't concidered? I have been in contact with Bob @ Brutespeed, Summit Racing, and left a message with MWC.

I have 3.73 gears now and may possibly go to 3.90s. 4.10s are a little low for a daily commuter, but do compliment the car nicely. Anyone have a M6 with 3.90 gears have any comments?

Thanks for any information and tech.

 

I also talked with Carl too, lots of great info from him as well.

No comments or suggestions?

 

In this section you need specific questions and you still need patience, if you're me anyway.

Most guys with m6 go 4.10. I started a thread a few days ago on mwc vs. Moser. That's all i can comment on.

 

Oh, I'm just looking for general stuff people have came across...not going to stop buying a rear axle.

I seen your thread..gave me some info I needed.

 

I beat the **** out of my car every time I drive it and I have not had a single issue with my 12 bolt. I also have 3 friends running the same rear, 2 of which are in strip cars who have also not had any issues yet. I did have a set mine up differently than moser had it though when I bought it. They had way too much backlash and carrier bearing pre-load was ****.

 

12 bolts don't whine. Improperly set up 12 bolts whine. That said, I would get a 9". They are the best design of the 3 and can handle a ton of power. I chose MWC for mine.

 

Here is my take on it.

The 12 bolt rears that are available for these cars is a step in the right direction. The 12 bolts are well known for being a stout rear that was a factory option back in the day in many performance cars. You can have a 12 bolt in an early Chevelle, Nova, Camaro, etc, and beat the snot out of it and not hurt anything. Put a 12 bolt into a late model f body that uses a torque arm, make a couple 4000 to 5000 rpm launches at the dragstrip, and I can just about guarantee you'll have a lot more gear noise on the way home. The torque arm seems to distort the housing on the 12 bolts, and it seems to happen to all the brands of 12 bolt rears. This does not happen to the 9 inch rears, and there is no price difference between the 12 bolt and nine inch rears. As the horsepower in our engines keep escalating, most people these days go straight to the nine inch rear. The 9-inch has an internal rear-pinion support that also supports the gear end of the pinion to limit gear deflection under high torque loads. This seems to be the major reason why the 9 inch doesn't start whining after high rpm clutch dumps, when the 12 bolt will pick up noise. The 9-inch locates its pinion gear lower on the ring gear to improve tooth contact, better the 12 bolt does. The 9-inch also has a 0.125-inch larger ring-gear diameter and internal pinion support than the 12 bolt. Bob

 

The 9" is a better rear end all around, the 3rd pinion bearing/pinion support alone makes it one of the best in my opinion haha. Not to mention there are more gearing options available for it than any other rear on the market lol. I have yet to hear of anyone around here complain about their 12 bolts and I myself have never had a problem with mine and I was launching at 4500(ish) at the strip.

 

I was ready to buy the 12b, so I could save a little coin on the driveshaft. After learning that the factory shaft isn't the best anyway...no contest.

 

I have always heard, because of the way the 9 inch has it's lower pinion, it takes more power to turn. = lower RWHP = higher ET.

 

It is only a 3 degree difference compared to the 12 bolt. Depending on the user's driving style and setup the strength benefits of a 9" housing would be un-needed, unless future upgrades call for it or the owner needs the ability to interchange planetaries.

12 bolts survived behind big blocks in the earlier years without problems but advances in transmissions, clutches, and ever increasing HP under the hood pushes the design differences of the 12 bolt and ford 9". The 12 bolt is not a bad choice for most builds but if you have a T-56 or launch hard at the track, weight cost versus time invested, and also consider future plans for your project, most will go with the 9" for piece of mind with proven reliability without added cost.

 

If youre gonna go 9 inch dont go 4.10 go 4.11. The 4.11 gear set will be a lil stronger because theres less teeth = thicker gears. 4.10=41 ring, 10 pinion. 4.11=37 ring, 9 pinion.

On the MWC vs Moser, https://ls1tech.com/forums/gears-axl...-new-pics.html

Why doesnt Moser have a post like that?

 

How do you like your MWC 9?

 

Very much, amost 10k on it & no complaints.

 

Good, thanks for the info. They look like solid rear axles.

 

12 bolts didn't use to have a torque arm mounted to them, which seems to be the reason why they have problems when used on the 3rd and 4th gen F Body. Bob

 

I'm running a Moser 9" bought from Brutespeed, but with a custom center section I assembled. Do NOT be afraid to run 4.11s with a M6 car. I daily drive mine and make several long trips a year..I love it. They are very streetable.

 

I agree, the overdrive ratio in these transmissions allows running 4.11 gears without that high of an rpm down the road. In town you can keep it in third almost all the time, it makes for a great combination. Thanks for the order! Bob

 

I will probably go with 4.10 gears. Been looking at several axles and axle manufactures. Love the 9", S60 has came back on the playing table after some more research.

Pricing has been all over the place on 9" axles. I have gotten quotes as low as 2700.00 and a "I ate a big bowl of dumbass for breakfast" quote of 4200.00(axle only). The Fab 9 has the best deal IMHO with everything you get and the price quote I got.

S60 is pretty much the same within 250.00, and has the best bang for the buck.

I will let you know what and who I go through to get the chickenhawk back on the road.

 

I went with a MWC Fab 9, but I haven't received it yet, but it is being built, hopefully it's done in a week or two

Now as far as price I was ALOT higher than the base price, but I got ALOT of upgrades and with a Strange 3" chromoly driveshaft with a forged yoke, and chromoly LCAs I came in just under $5K. It's a little more than what I wanted to spend, but now I won't have to worry about when it comes time to build my new power plant which will be in the 700 rwhp range.

And on top of it they were the only guys that were willing to do some custom things to my axle. Such as air bag mounts instead of coil spring mounts, shaved PHB mount, and I'm sure I'm forgetting something.

BTW my car is a street car and I went with 4.30 gears