hey guys just wanted to shed some light on my vibration issue i've been chasing down. at first i had thought i had a driveshaft issue due to the violent vibrations above 65 mph.. well after inspecting the shaft/ujoints etc. i decided to pull the cover off the 12 bolt to peak inside. which i then noticed the large chip in the ring gear tooth, probably 1" by 1/2" piece chipped out of the tooth. and after "sloshing" around in the diff, it has scraped up the carrier housing pretty bad. I then called moser, and asked why this would happen, i've had under 1000 street miles on this thing, followed the proper break in, and its whined from day one. they said that they coudlnt warranty it due to being a "race" product and that i had launched the car. so all in all.. 200 bucks later i have a new ring and pinion being shipped to the house.

ill post some pics later on.

has anyone experienced this problem w/ their moser 12 bolt? the car is a 6 speed, and hasnt seen better than a 1.60 60' yet. im worried that i could possibly do this again? any suggestions, i really dont feel like dumpin more money into my already expensive "bulletproof" 12 bolt.

thanks,
Nick

 

12bolts are for automatics, get a 9", that is all....

 

I can chime in here. Moser 12 bolt, less than 4000 miles and a few launches. Leaked from day one (pinion seal). Had to replace both axle bearings, and pinion bearing and seal(#2). oh ya it still howls like a wolf, always has! Great product!

 

Just wait 'till the posi blows up and destroys EVERYTHING inside. It's FAR from 'bullet proof' trust me!

 

spool

 

9"... w/spool

 

yea i noticed the leaky pinion seal from day one also.. not to mention my tq arm bolts keep coming loose! wtf, well i cant see buying a 9" now, just cuz my 12 bolt is nearly brand new, and well yea maybe a spool is in order.. eh?

 

May not be related to Moser.

My truck spit a ring gear tooth one day just rolling down the highway (8.75 ten bolt).

 

Strange with a spool. that is all
Fuq four bolts for the torque arm. Strange uses the two big *** stock ones.

 

Man, Im afraid I'm gonna start sounding like a broken record around here.

First of all, Moser's 'break in procedure' is the weakest attempt I think I have ever seen for gearset break in for a street driven chassis. Now as for a 1320 or other race car, it might work just fine, but not for a consumer passenger car, thats for sure.

Their 'break in' procedures should read something more like this:

~All new and reinstalled used gear sets require a break-in period to prevent damage from overheating. We find the best method is drive for 15 to 20 miles for average heat saturation and then let the differential cool all the way down to ambient temperature (cool to touch). This is considered "one heat cycle". It is advised that you take the time and complete five to six complete heat cycles before any towing, high speed or performance driving which would consist of any impact loading. After the recommended number of cycles, basically drive like Grandma during the first 500 miles.~

My recommendation...... if you have enough distance (15-20 miles) and can keep the speed closer to 55-60 for that distance (like going to work in the morning and for the drive home) you could get two heat cycles done in one day. Do that for a week or so and you'll be ready for the weekend to get the remainder of the other 500 or so miles in before you go and play.

Unfortunately, Moser and other builders that offer a "bolt in" differential, can not even do a test drive on the initial product without the car being present. So how do they even know, if how they set up the diff even had a chance at being quite from the get-go or if it had any other problem before it was shipped to the end user ??? They dont and that is another loop hole for them to say that you didnt do the specified and supposed correct break in.

What I have been noticing as of late, is a lot of people talking about gear set up and its better (or they advise) to keep the lash tighter than the standard engineering method of 0.001" for every inch of ring gear diameter as a MINIMUM. Lets just sum it up with this: The less lash, the more heat. If you run tight lash, step up in gear oil viscosity. If you dont, you will never get a gearset with the proper work hardening that gives the gearset its first chance to live to the abuse you are going to dish out.

For those who might not grasp the idea of work hardening, I will throw this in. Work hardening is similar to forging in the way that it compresses the metal molecules into a very compact and hard formation. This can only be accomplished if the metal surfaces are lubricated and the gear temperature stays cool enough that the molecular structure does not change. If the temperature of the metal gets hot enough to change the molecular structure, it will soften the surface instead of hardening it. This may seen like a balancing act but it all happens easily & passively as long as the oil keeps the gear cool while it is breaking in. Most all differentials taht I build (depending on size of course) leave with 0.008 to 0.010" and straight 140 weight gear lubricant. Because, I know what your gonna do to it.......

Because I do it myself.

Thats why it is so important to take your time and follow a more complete and through process, to protect your investment. Because if you dont, you just get to spend the money twice.

And a 9" isnt the solution, nor is a spool. Well, lets see....... My 12 bolt has been in the car now.... for..... 39 years. It has had at least four engines that I have put into it. The last two were of the 585 and 630 hp variety and it still has the OE (circa 1966) 3.55 ring and pinion in it and also uses a factory EATON limited slip. It has run middle to late 10 second times (and yes, with that ratio), been on quite a few road course's and I think I have personally put over 240000 miles on the chassis itself since I purchased the chassis back in the 80's.

But I guess a 9" with a spool would IDIOT proof it.....

 

Must be a quality control issue. The "12-bolt" has a 8.875 ring gear, pretty stout stuff. Everything breaks, but there are some really old, heavy high powered cars running factory rears and they aren't falling apart like the aftermarket F-body products

This sucks to be sure, but how many are happy vs sad...hmmm

 

I've sold a boatload of Moser 12 bolts, and for the most part I have not encountered any problems with them. My own '99 Z28 has had a Moser 12 bolt for three years, and I have launched it anywhere from 4000 rpm to 6200 rpm, without any problems.
As with any high performance part, someone somewhere is going to have a problem with a part. With the internet, everyone finds out about it. The torque arms on our cars act like stethoscopes, and any gear noise is transmitted to the passenger compartment much easier than in many other vehicles.
I do wish that Moser would design their rear-ends with just two long bolts for the location of the torque arm, but we have not had too many torque arm bolt loosening problems since we started loctiting the bolts. Bob

 

The bolts Moser sends for the torque arm are to short for an aftermarket torque arm.
A slightly longer bolt and some red locktight will work wonders on the lossening issue.