View Single Post
Old 12-13-2018, 06:25 PM   #1
IROCZman15
10 Second Club / Meet Coordinator
 
IROCZman15's Avatar
 
Join Date: Dec 2004
Location: Roxbury, NJ
Posts: 2,100
iTrader: (8)
Seeking some advice before ordering a Moser 12 Bolt

SHORT VERSION:
I am buying a 12 bolt rear for the iroc and had a few questions that I was looking for some community input on before ordering it within the next few weeks. the plan currently is 12 bolt rear with new big ford ends. 1350 yoke, 33 spline (or 35 spline) TrueTrack, 33 spline axles, (full details below) and link is http://www.moserengineering.com/12-b...d-package.item
Questions:
- sealed ball bearings or a tapered roller bearing ?
- will these adaptor plates work for mounting my 12" rotor 2piston PBR caliper brake setup onto the rear axle? http://flynbye.com/catalog/i11.html and this is the brake kit I have now on my 10 bolt that I want to move to the new 12 bolt. http://flynbye.com/catalog/i11.html
- 3.55 or 3.73 gear ratio ? (it will be behind a highly beefed up 700R4)



LONG VERSION WITH DETAILS:
I apologize if this post is long, but I wanted to lay out all my thoughts and tech info as much as possible to give a clear picture of what my plan is....

As some of you may know, and for those that don't, my major winter upgrade to the car this year is a new rear axle and a driveshaft capable of handling 800 horsepower. I have anther thread going where I have information about the transmission (done), fuel system(done), suspension (done), engine (next winter) and chassis mods (next winter?). here is that link: http://www.njfboa.org/forums/showthread.php?t=68229 This car is and always will be a street car. I have autocrossed it, road track raced it, and done some drag racing. I plan on doing way more drag racing with the car's next engine but will also not shy away from autocross and a short road track event either. Yet, the car will remain a street car and will put down several thousand miles a year.
The engine will make around 525 hp NA and then I plan on spraying it with a 200 wet shot. I hope to run mid/low 11's NA and hopefully mid/low 10's with the nitrous. The car will need a cage, and currently weighs 3,400 pounds without me in it. If I only bolt on a set of rear slicks, and keep the rest of the car in street trim, I would love to run 10's so I need a rear end that can handle that task for years to come

I have been doing reading and research online for the better part of this past year and I am of the opinion that a new 12 bolt setup is what I want. Nothing against the 9", 8.8", or 60 rears, I just don't think that it is what I want. I know the 60 is the most severe duty use but also heavy, more expensive, and more for pure drag racing. the 9" and 8.8 were options, but I honestly don't think I'll ever be that super intensely competitive with drag racing or any racing (for this specific car) where I'll want to be changing out 3rd members based on what event I'm doing. They do eat a good amount of power too and are also heavier. I also don't want to deal with the extra bracket that would be needed to mount my S&W racing adjustable torque arm either.. and I have read that it is common for the torque arm/bracket assembly to bang into the transmission tunnel and cause interference while driving down the road. No thanks . Also, i don't like the way it looks from underneath the backside of the car.

Therefore, the 12 bolt is the answer. I am not going to spend a single penny beefing up my 10 bolt, as I know it will fail with the amount of power the next engine will be bringing. It has 3.73's and stock 26 spline axles. the posi unit has been on its last legs for several thousand miles, and one of the 5 fasteners that hold the diff case together is sheared off!

I have looked at Moser, Currie, Strange, Quick Performance, Mark Williams, Drivetrain Specialties and so forth. A moser seems like the best bet. Their website is simple and straightforward, unlike some of the others. I called Moser tech support today on the phone and went over basically everything that I am discussing here. They are also of the opinion that a 12 bolt will suit my intentions very well.

here is a link to the part of their website where I can piece together the rear:
http://www.moserengineering.com/12-b...d-package.item


and here is the rundown of my selections in each category:
- Diff fluid : Motul 75-90
- Truck Freight: Residential liftgate required
- Axle type: Bolt in
- Year/Make/Model: 1982-92 camaro/firebird * can-NOT use stock brakes
- Custom width and pinion offset: none needed ??
- Axle spline count: 33 spline (bolt in axles)
- Differential: 33 spline TrueTrac
- Gear Ratio: 3.55 or 3.73 (still undecided now but will be one of those)
- Pinion Yoke: 1350 series
- Rear cover: aluminum girdle
- Bolt pattern: 5 on 4 3/4"
- Bearing type: Tapered roller bearing (see my comments below though)
- Stud type: 12mm x 2.5" (I actually have to check my measurements and make sure I get long enough studs to be legal at the track and probably get longer lug nuts to work with them accordingly)
- ABS: None
- BRAKE OPTIONS: OTHER (I will need to write a detailed description of the 12" PBR setup and probably describe to them the brackets I plan to use; maybe I'll send them a link or photo ?)??
- Additional Brake options: None
- Additional Options: 1982-02 Fbody sway bar mounts, 1982-02 Fbody lower control arm mounts, and flange access holes
- Powdercoat options: semi-gloss black powdercoat




I currently have a 12"PBR brake package (from when I converted my old drum brake 10 bolt to a disc brake setup) from Ed Miller at FlyNBye performance ( http://flynbye.com/catalog/i11.html ). Since I already own the 12" rotor and PBR kit, I wouldn't want/need to buy a rear axle from Moser that has a brake package pre-installed on it.. I would want to use what I have since they work great and I already have it here.

My major questions are:

1. what would be the best way possible to mount the kit to the new Moser 12 bolt rear end, which will have the NEW style Big ford ends. I found this bracket on Ed's website, Item #BFNew12 ( http://flynbye.com/catalog/i73.html ) and unless I am missing something, it looks like that would be all I need ?? .... I just got off the phone with Moser technical assistance and they looked at the bracket and agree that it should work and be able to slide on later/after they press on their bearings etc. they did request that I ask Ed about two things though:
- I sent Ed an email as well and hope to hear his thoughts on this, but also figured I would ask you guys too
a: on his website it says that those caliper brackets work but give the 2.75" offset...however Moser says that they typically build their ends to be spec'd to the 2.5" offset. they recommend a 2.5" offset, but if needed they would possibly make adjustments for a 2.75" offset? thoughts/input?
b. should I go with a 'sealed ball bearing" or "tapered roller bearing" setup ? they have a note on their website that the tapered roller will not work with 93-97 fbody brakes, but I do not believe that the 12" PBR disc setup is similar to the LT1 fbody brakes?? if it is, or if the tapered roller bearing setup will not work, please let me know so I do not make a mistake when ordering. Moser suggested tapered roller bearing because the car is mostly a street car that sees about 3,000 miles a year and will later see 8-10 drag-strip days as well as some autocross and aggressive street driving.


Anyways, sorry for the extra long post. I want to make sure that I order this rear axle once and have it done and only need fluid changes every so often for many many years to come.

Once the rear is here and in the car, I will have to measure for a driveshaft and order one. It should be exactly the same measurements as a stock length 3rd gen auto-trans driveshaft, but just in case something is a small amount of difference, I am going to hold off on ordering the driveshaft until the rear is actually in the car and set.

Thanks for the advice and any positive/negative feedback will be listened to.
__________________
1987 IROC-Z - modified


Last edited by IROCZman15; 12-14-2018 at 11:31 AM.
IROCZman15 is offline   Reply With Quote