01ssreda4

iTrader: (96)

Converter surge is soft. You cannot get a manual to run half worth a **** without hammering down out of the hole. Its proven they are far more destructive on drivetrain parts. Anyone who argues that either has no experience or has no experience actually going fast.

MidwestChassis2

iTrader: (1)

The Company is Powertrax.

You are not going to notice any difference in performance between any rear end. This has been proven over and over and over again.

The advantage however is overall weight, we can build one of our fabricated nine inches lighter than a factory 10-bolt. Then add in the fact you do not have to run a torque arm that requires a separate rear end mounting bracket and you just saved weight with the torque arm as well.

weedburner

I disagree, and believe i can show how that's not necessarily the case.

Here's how the typical manual trans drag launch goes...as soon as the clutch is dumped, you can hear engine rpm drop. That's the sound of inertia energy exiting the rotating assy, creating a torque spike that smashes the rear tires into the track. As that quick torque spike dissipates and the engine starts gaining rpm again, the rear tires bounce back up and your front end drops a bit. Now you are accelerating on engine power alone, without any boost from the torque spike. But you are not accelerating with as much power as you could, as some engine power is being fed back into the rotating assy as it gains rpm. Basically there was a temporary torque boost as rpm dropped, but that boost was paid back in full before the engine reached it's original launch rpm. If the clutch had slipped just enough to carry the same rpm out until the car was going fast enough to match engine speed, there would have been no loss of rpm (no inertia energy discharge), launch would been smoother overall and slightly quicker with less wasted motion, less sensitive to shock settings, and that parts killing torque spike would be completely gone. You don't have to have a SoftLoc to achieve that.

weedburner

It's pretty well documented in the Mustang world that an 8.8 is about 3% more efficient than a 9", meaning the 8.8 has about a 15hp advantage at the 500hp level. This is mainly due to the difference in hypoid offset. The 9" pinion comes in at a lower point on the ring gear, which means it acts more like a worm gear with added rubbing along the face of the gear teeth.

The reason i bring up the 8.8 is that it is a practical clone of the 12 bolt. Same hypoid offset, even takes most of the exact same bearings.

I have no personal experience with the S60, but i believe the hypoid offset is less than the 12 bolt so the gear design should be more efficient. That advantage may be offset if the S60's components are larger/heavier than the 12 bolt and that extra strength isn't required.

Pharcyde50

iTrader: (11)

Running a Moser 9" here. I setup a set of Ford SAP 4.30 Gears in a strange center section. Gears are very quiet. I've got all rod end suspension so it does transmit some road noise.

dailydriver

Isn't this just a slightly different version of a Detroit Locker??

01ssreda4

iTrader: (96)

Weedburner, in a perfect world on a perfect launch I definitely agree with you. I think though the practical application of the torque spike vs the torque multiplication of the torque converter yields the spike to be more harsh 99.9% of the time when leaving equally fast.

And yes the above info posted about the gear offsets and differences is on point.

MidwestChassis2

iTrader: (1)

No it is nothing like a Detroit Locker and more similar to a Trutrac. We won't offer Detroit lockers or anything that works similar to a locker. They are extreme nuisance to drive especially with a manual vehicle.

dailydriver

OK, thanks.

Is it a higher biasing diff than the Truetrac, and stock T-2 Torsens?

Do they bother to make one for the 7.5 10 bolts, or only the larger axles??

MidwestChassis2

iTrader: (1)

I don't have a full list of available rear ends at this time or full details on the Truetrac or T2 to give a comparison. They have been one of our most popular selling differential units and the feedback has been amazing.

http://www.powertrax.com/index.php/products/grip-pro

01ssreda4

iTrader: (96)

Just glancing it looks similar in appearance to a wavetrack.

dailydriver

OK thanks. I will call them for more info.

This is a fairly new product for them, as I was thinking you meant/were talking about their old, locker type diff, the "Lock Right".

weedburner

It's only that way because the average stick racer does not really understand what's actually going on. Most believe the "harder" you leave the faster the pass, not true if that leave was unnecessarily violent due to a flywheel induced torque spike. A flywheel spike is something that can make a car seem to launch harder initially, but that quick initial surge of torque as the engine lost rpm is paid back as less net torque produced by the engine as it recovers the lost rpm. No net gain in the end, that's just basic flywheel physics.
Bottom line- if engine rpm goes down after just after launch, you have a flywheel induced torque spike that's unnecessarily punishing the drivetrain and tires.

An automatic's torque spike comes from the converter's ability to provide initial torque multiplication, which quickly diminishes. A typical automatic's 1st gear might start out with an added multiplication factor of around 2.5, but by around .2 seconds in that multiplication has dropped down to around 2. By .4 sec, the multiplication factor is down around 1.6. A car equipped with an automatic must choose a drivetrain and tires based on the torque available in the first few tenths of a second, making the car less efficient than it could be for the rest of the run.

A manual can be launched without any torque spike at all (no rpm loss), basically a nearly constant amount of torque applied to the input shaft for the entire duration of 1st gear. With the launch spike gone, you can get away with running smaller tires and lighter drivetrain components than the automatic, making the car more efficient.

Everyone seems to think that you cannot run radials with a manual, but if you eliminate the manual's flywheel induced torque spike on launch, it becomes even easier to run radials with a manual than it is to run them with an automatic.

While it is possible to achieve the level of clutch control required with your foot, consistency is typically a big problem. I installed a small hydraulic cylinder on my clutch pedal to control clutch release, effectively eliminating the torque spike on launch with repeatable results. There are other ways to do basically the same thing, but the cylinder has proven to be much more convenient to dial in.

You might think this is all theory, so I'll add some personal experience with the concept...
2550lbs 700whp
17lb steel flywheel
2800lb diaphragm PP
900 series Ram sintered iron disc
Faceplated Toploader 4 spd w/ 1-1/16" input, 28 spl output
2-1/2" x .065" driveshaft w/ 1310 yokes, off the shelf Spicer cast slip yoke.
Chev 10 bolt rear w/ TruTrac diff and 28 spline axles
275/60 M/T radials
5.73 1/8th
1.308 60'

No way this car would survive if it had the typical flywheel induced torque spike. An automatic would twist that driveshaft in two almost instantly.

01ssreda4

iTrader: (96)

Looking at the specs on your drivetrain id say youre due for a failure any time now. Having fun is the name of the game but so is being safe, especially when you can plow into someone in the next lane when your flimsy driveshaft lets go. I'm sure youll swear your car is bulletproof so we are gonna have to agree to disagree.

weedburner

I have a customer in the UK with a 1200hp awd Subaru Impreza Time Attack car. He was running 8.20's @ 173 at the drags having problems launching and breaking parts. He had me send a cylinder to control the clutch pedal, a month later he's running 7.74 @ 179.

When racers find an advantage, they rarely broadcast it to the world.

98cherrySS

iTrader: (2)

Update: I placed the order for the MWC Fab 9" on 11/27. I was told that the rear would take 3-4 weeks to produce. I am hopeful that it will deliver by Christmas. So far MWC has been excellent to deal with. They've been very informative over the phone and the guys I've spoken with are friendly and professional. I went with their 4 channel ABS config with the Powertrax Grip Pro differential. It'll be a bare metal finish and will include the back brace. This is pretty much their entry level fab 9". Their base package appears to be above and beyond my needs so we didn't think the upgraded differential or case was necessary. I'll post pictures once it delivers and will document my installation experience for others to see.

MidwestChassis2

iTrader: (1)

We appreciate your order and if you have any questions please feel free to ask.

Won-Ton

The 9inch rear end is the most buildable axle on the planet. Your limiting factor is money here. You can make a 12 bolt live, you can make a 9" thrive. Your 9" rear end has the same tooth area contact between the pinion and ring gear no matter the ratio you have. The numerically higher ratio you have on nearly every other axle the weaker the combination becomes. The other holy grail of the 9 inch is the pinion support, which the deflection of the pinion under torque causes your ring gear failures. The third member is another huge benefit, easy to setup gears when compared to a 60/12. The axles themselves are very light, yet with the proper trussing they are unbelievably strong. You can buy complete third members ready to go, you can upgrade to 40 spline axle shafts, you can make them full float. There is a reason its the most used axle in Baja, Ultra4 etc. You can always upgrade the setup as you go too. Plus you can buy a whole fabricated 9 inch housing for cheap that is light years stronger than the chunk of steel 12 bolt. Plus, you can weld anywhere to a 9" housing. A 12 bolt to survive with a torque arm you need to weld the tubes to the housing which if not properly done can warp your housing (Never mind the gear setup). Then you need to attach the torque arm, but your differential section is cast which if not done properly again, ugly failure. And say anything you want, I would sleep better at night knowing that the arm is welded to a steel housing versus a cast housing.

JOHNNY59

iTrader: (398)

Love my MWC fab 9" as its the last thing I have to worry about at the track.

01ssreda4

iTrader: (96)

I love people who go on and on and it's mostly bullshit but they say it with such dedication the average reader takes it as gospel. Nobody welds torque arms mounts to 12 bolts. Moser and strange cast brand new housings with torque arm mounts. These arent some 1970 GM centers with welded brackets on them. Thats foolish to imply such a thing. Weight? Well not as light as a fab9 but about the same as a 10 bolt and id bet the same or maybe lighter then a cast 9. But your right there are some fancy parts for a 9 inch. The part you left out is most people dont need them. Your average racer wants to have a quicker then average car thats reliable. That's it, no more no less. 40 splined axles? You are now talking about a teeny tiny portion of the population. Quick gear changes? How many times does the average person change ratios? Once, twice maybe? Makes that argument fairly useless. There is nothing wrong with buying a 9 inch, but most people dont benefit from all the "advantages", and there are other rears that can fit the bill.