LocostUSA.com

I got a complete MN12 rear assembly last weekend, I will need to rethink my frame a little but I am really exited. I have been wanting to use this setup from the start and now I've got all the parts, disk brakes and all. I can also now measure out the A arms for less guesswork on the suspension, the diff is a 3L27 so it should be good for all around driving.

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Custom +4 IRS Chassis
2.3L Ford Turbo

"The ultimate skill is to take up a position where you are formless." Sun Tzu

After spending the day working on the MN12 parts I found two things to be true, the diff has a 1" offset that really screws up my plan, however the knuckles and hubs fit my merkur axles.
My delema, the 3L27 diff is rumored to weigh 150lbs but its posi, the Merkur diff weighs less than 100lbs but its not posi. So I put it to you guys, what would you do?

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Custom +4 IRS Chassis
2.3L Ford Turbo

"The ultimate skill is to take up a position where you are formless." Sun Tzu

Posi, if you plan on putting down some power. If you just want to cruise, use the lighter open diff. What's 50 lbs. anyway?

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He is a wise man who does not grieve for the things which he has not, but rejoices for those which he has.

I agree with chet...
50 lbs is not that much when thinking about your total project! If it were a matter of 50 lbs here and 50 lbs there and here another XXX lbs there it might be an issue. Review your build and WEIGHT budget and see what you can AFFORD (weight wise).

Depends on your goals....(as stated preiously).

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I'll keep an eye out for you!

To err is human...
I am more human than most.

Ok, posi it is. does anyone know what it takes to modify axles? I dont wanna go cutting apart my frame to move the rear of the tunnel over an inch, if I dont have to. The MN12 is fairly wide, losing an inch on 1 axle would actually help bring it in to a good track width, and allow me to still put the input down the centerline. What does Deman do, they use this diff.

http://www.deman-motorsport.com/build/image4.jpg

I also learned that the $450 aluminum case only saves 15lbs over the iron case, not worth it. But if a guy wanted the posi and the aluminum, all the Mark VIII's had non posi with aluminum cases, a good jy dig might get you both and you could do some Frankendiffing.

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Custom +4 IRS Chassis
2.3L Ford Turbo

"The ultimate skill is to take up a position where you are formless." Sun Tzu

I would use one custom Moser axle. They cost about $150 each with all the grooves. Each groove has a price.

I use 90's 3.8L Ford Taurus outer boots for the cvs and stock tbird for the inner. The taurus boots are more compact (which is an issue on a miata). Note that the boot retaining groove to axle end distance is different depending on whether it is the inner or outer end. The splines and snap ring grooves are the same on both ends.


The entire rear subframe probably weighs 150# with those massive iron lcas. The iron diff with traction loc should be about 80#, 5# over an open carrier.

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Miata UBJ: ES-2074R('70s maz pickup)
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An 00 Cobra R rear with it's heavy carrier weighed 68 lb with packaging minus rear cover, which is light. I paid 100 for a complete diff out of a MK VIII. DSS, IIRC, wants 99 for a replacement shaft (reuse your CVs) for any length.

If you are looking for a Torsen T2 most of the lowcost ones are the T2(OEM) which is not machined for the IRS but I believe by moving the C clip it should work fine, just havn't gotten to that point yet.

Thanks for the info guys, it might cost me a few more $ but I think having posi will be worth the extra $. The info I got about the diff weight came from MN12 performance.com, it seems that it was incorrect info. It makes sense to me that the reason the assy. is so heavy is the huge LCA's. Can you imagine the fuel savings if all car manufacturers focused on weight reduction like we do. HMMM, Lotus 7 inspired family sedan.

_________________
Custom +4 IRS Chassis
2.3L Ford Turbo

"The ultimate skill is to take up a position where you are formless." Sun Tzu

I can get Explorer diff complete with aluminum housing, rear cover, 3.73s, and 31 spline Lsd for less than 200 if you are interested.

That would have been tempting before I purchased the MN12 setup, way it looks now I have a Murker rearend to get rid of myself, since I've decided to make the changes to frame and axles and use the 8.8 3L27 out of the MN12. Thanks anyway.

_________________
Custom +4 IRS Chassis
2.3L Ford Turbo

"The ultimate skill is to take up a position where you are formless." Sun Tzu

Just thinking outloud,
I wonder what the effects of running a full driveline designed for a 3000# car in a 1500# car will be?

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Custom +4 IRS Chassis
2.3L Ford Turbo

"The ultimate skill is to take up a position where you are formless." Sun Tzu

Quick and less likely to break.

Yep.. will be a lot faster.

I'm basically doing the same thing with my build. The entire Nissan 240sx drivetrain is in mine except for the rear suspension. I reason that it was relatively quick in the donor car, so it should be scary in the locost. And with such a light car, I wont be breaking anything, at least anything that came out of the donor car.

Should be very durable that way. I am going the way of the solid axel 7.5 inch rear from a 88 tbrid and lsd. I am keeping the 3.08 gears for now and as it is 1st gear will be optional as its quite low but with those gears I should be able to hit 60 mph in second which should make a good 0-60 time. I have the 2.3 lima turbo refreshed, just using the e6 manifold and the stock t3- need to do a bearing rebuild on the turbo. (Unless I can find a holset for cheap). Doller per hp its hard to beat this engine. I figure I am running about a dollar per hp right know.
Dale