I just snapped my 10 bolt, it had richmond 3.42 ring and pinion, i ran it on slicks a few times. I knew it would eventually snap. Im running nitrous, headers, lid, ec. My mods are in my sig.



im about to order a Moser 12 bolt... Im getting 3.42s unless im more likely to shave ANY time off my 1/4th and 1/8th if i go with 3.73s. i dont care if i only shave a tenth off. Im paying 2,000 for the rear end and i can get any ratio i want and im not gettign anything other then 3.42s and 3.73s.

What rpm were you shifting at and what rpm were you crossing the finish line at? If you ran out of track before running out of rpm then get some deeper gears. If it was set up almost perfect then keep the same ratio you had.

Order it with 31 spline axles. 28's will work but 31's are better. 35 spline is overkill unless you're pushing well over 700 hp.

what exactly do the splin axles do? I saw that option, but i dont know alot about rear ends.... I dont rememebr what rpm i was crossing dureing the finish line. i never looked at that stuff.... i could give some track times if it helps...?

The number of splines relates to the size of the axles. 28 spline 9" axles are huge compared to GM axles. I doubt you would come close to breaking a ford 28 spline axle. Ford produced 28 and 31 spline axles over many years. Parts are plentiful for both. Once you get into the larger axles, 35 and 40 splline, parts like bearings and carrier get expensive because they're not considered factory replacement parts but more a specialty part. The larger axles start to get heavy. They get around this by gun drilling the axles. That's where the center of the axle is bored out to make it lighter. Also costs $$$.

Getting 28 spline axles is good for a factory replacement type car with mild performance. Going to 31 spline is added strength plus it will take you a long time before you excede the limts of the axles.

I only use 31 spline axles in my car.

The nice thing about using a 9" and deciding what gear ratio to use is that if you decide to change the ratio, you only need to change the gears. The carrier (posi) is the same for all the 9" ratios.

Uh Stephan he said Moser 12 bolt!!!

oops. Ok then the standard axle size is 30 spline which is more than enough for anyone. I think the next step up for 12 bolt axles is 33 spline.

Stick with 3.43's.

Ok, im 100% sure im going to buy the Moser 12 bolt 33 splin axle on monday. Im most likely going to stick with 3.42s since i cant get much advice on 3.73s...

Also, would 33splin be over kill for my car? Would it hurt performance at all? My current times are.

60ft 1.7
7.4@94
11.5@118

You're running mid 11's now. 33 spline axles should have no problems running 8's or 9's.

The only downside is that they're a little bit heavier than the 30 spline axles. Also you'll need a 33 spline carrier for the ring gear. Since 33 spline isn't a factory size, only an aftermarket carrier can be used. Since you're buying the complete assembly already put together, there's nothing to worry about unless you choose to change gear sizes and need a different series carrier. The price difference between a 30 and 33 spline carrier should be little to none but you'de have to check first.

I can't offer any advice as to 3.73 gears since you can't give any referance to shift points, finish line rpm, tire size etc. Since there's no way to tell if the 3.42's are the best, there's no way to guess if 3.73 are better.

If your finish rpm is lower than your shift points then you need more gear. If you go to a taller tire, you need more gear. To many variables to say what's best.

I originally started with a 26" tall tire and 3.27 gears which was a poor combination unless I shifted at less than 5000 rpm. I'm now at 29" tall tires and 4.56 gears. I shift at 6800 and cross the finish line at 6800. I'd love to squeeze a 30" tall tire into the wheel wells and drop the gears to 4.30's

ok, so you recommend 33s?

Not really. An aftermarket 30 spline is much stronger than a factory 30 spline so it would be more than enough for your application plus parts would be more plentiful if needed. A 33 spline 12 bolt axle is an extremely large axle the same as the 35 spline Ford axle.

Moser has a calculator to determine the size of the axle required.

http://www.moserengineering.com/mose...r/axletech.htm

As stated on their site.
"To achieve maximum performance you should use the smallest axle available that will safely handle the torque your car produces"

i would go with 373 if i were u