Buy a 12 bolt, or build the 10 bolt? Also, what vendors on here sell a 12 bolt?

[420]

I am getting to the point in my build where I need to start thinking about the rear axle. I plan on making some serious HP wiht this truck, and need a rear end set up that will hold FOR SURE. Not "It should stand up to the abuse for a while", but something I can count on, especially when there is money on the line. I searched this, and came up with a bunch of threads that turned into arguements, with no real answers.

So, my question is two fold:

A) Is it possible to build the 10 bolts in these trucks to a level that will let someone who beats the crap out of their truck sleep at night, or should I be looking to go to a 12 bolt? Before people start mentioning 9 inch or Dana rears, I need to keep the drive ratio the same front and rear, so if they don't make a 3.42 gear for it, I'm not interested

B) Are there any vendors on here that sell 12 bolt rear ends built to swap in easily?

Thanks!

- Matt

 

[warmpancakes]

Re: Buy a 12 bolt, or build the 10 bolt? Also, what vendors on here sell a 12 bolt?

dont bother with a 12 bolt unless you are going RWD only a 8.5 10 bolt PROPERLY built will take what you can throw at it

 

[420]

Re: Buy a 12 bolt, or build the 10 bolt? Also, what vendors on here sell a 12 bolt?

See, that's the problem though. One of the toys I have on the shelf is a switchable transfer case, so the truck will be RWD at least part time.

 

['JustDreamin']

Re: Buy a 12 bolt, or build the 10 bolt? Also, what vendors on here sell a 12 bolt?

Since you want to stay with the 3.42 ratio, that does limit your offerings....

Dana 60 is out, ratio isn't available. Same with the Dana 44, which is probably too light anyway. And I didn't look at a Dana 70 or 80, since the Dana 60 is huge / heavy, no sense going above that.

Ford 9" is available in 3.40 and 3.45 ratios, but not 3.42 (that I could find). Not sure if that's close enough. If it's close enough (in your opinion), that'd be something to look at. It is pretty stout (not bulletproof as everybody thinks) especially with the available aftermarket parts (big bearing pinion supports, nodular cases, etc). It also is less efficient than some other designs (like the 12 bolt) due to its pinion location (it "scrubs" a bit more than the 12-bolt). It's biggest benefit is the ability to swap gear ratios quickly, but in a 4wd application (without a 9" in the front too) that's of pretty much no use.


That pretty much leaves you with GM products.

The 10-bolt in the truck is a POS. It's a 7.5" / 7.625" 10-bolt and is weak weak weak. Don't waste any money on it. The biggest problem is that they're completely hit or miss. There are guys out there with stone stock LS1 camaros with autos that have broken them without trying. But there are also guys out there with modifed LS1 camaros with manuals running 10's & 11's on stock rears. I've busted a pinion in my LT1 / 6spd camaro (ripped 2 teeth right off) and it's a bolt on only car, (might turn high 13's).

You could run the 8.5" 10-bolt, which is significantly stronger and was available in S10's (after '95 only with V6 and 5 speed). That rear is available with 3.42's and either drums or discs and should basically be a bolt-in affair (except the driveshaft needs to be shorter by some amount, don't remember what the exact number is). Tough part is finding one, since alot of the salvage yards can't seem to tell the two 10-bolts apart, and they're only in V6 manual trucks (and you'd want a 4wd width one, not the ZR2 or 2wd widths). And the limited slip in those rears isn't all that good (Eaton Gov-Loc). Might be better to get an open diff and one of the insert-type lockers (there are a couple brands).

Or you can pony up to a 12-bolt. I'm sure there are some vendors out there who could supply you a 12-bolt built to your specs. I'm also sure that it won't be cheap, but it'll probably also have a warranty and all the parts you wanted (like fresh bearings, a good gearset, a decent limited slip or locker, brakes of your choice, etc).

Only other choices would be one of the other heavy GM rears, like the 10.5" 14-bolt, but that would probably be complete overkill (since those are usually found under 1-ton's).

'JustDreamin'

 

[420]

Re: Buy a 12 bolt, or build the 10 bolt? Also, what vendors on here sell a 12 bolt?

Good post. Thanks!

I am really leaning toward a 12 bolt, for pretty much the reason you mentioned. Everything else on the truck will be overkill, and I just can't see shortchanging the rear end only to have it remind me WHY everything is overkill. I'd rather pay $3.00 once, than $2.00 twice

My challenge at this point is finding someone who already has all the measurements and specs for 12 bolt fitment into a Sy. That is where I was hoping the board vendors would come in

 

['JustDreamin']

Re: Buy a 12 bolt, or build the 10 bolt? Also, what vendors on here sell a 12 bolt?

Spec'ing a 12-bolt to fit your Sy shouldn't be all that difficult.

There really aren't all that many dimensions required. You'll need overall width (wheel flange to wheel flange) and probably a dimension to locate the driveshaft relative to a wheel flange (so the builder can determine the lengths of the pass & drivers side tubes).

Need mounting method information, like stock leaf springs (would need center to center distance) or if you're running something else like a 4 bar what you need. Also need to provide what your desired pinion angle is.


I'd strongly suggest taking the measurements yourself. I'd hate to spend $2k to $3k on something and not be absolutely positive that it'll fit in my application. I'd worry about somebody else's truck being a little off and something stupid happening (like the axle ending up 1" out of center in the truck). Maybe that's just me.

You'll also need to decide on what bits / pieces / parts you want to use, especially differentials. There's lots of options, what to pick. Personally, I like the gear type limited slips (Zexel Torsen's or Detroit TrueTrac's) but you need to decide what will fit your application / needs best (ie, for mostly drag racing, a Detroit Locker or a spool may be a good choice). I personally think a spool is only suitable for a race only vehicle, but there are some folks who've driven vehicles with spools on the street.


Like I said before, the 8.5" 10-bolt is probably adequate, but by the time you put fresh bearings & gears in it, a decent limited slip, and maybe aftermarket axles, you've probably spent close to what a 12-bolt costs, but don't have the 12-bolt's strength (granted it's only got a 3/8" bigger ring gear and 2 more bolts).


The only other thing I'll suggest / ask is this: Do you want 3.42's? Or should you change both ends to 3.08's (which is the next available ratio down for the front axle)? Some fast trucks have gotten to the point where they need less gear because of wheelspin or other issues. Just a thought....

'JustDreamin'

 

[warmpancakes]

Re: Buy a 12 bolt, or build the 10 bolt? Also, what vendors on here sell a 12 bolt?

DTS drivetrain specialist has the specs and can build one, but Jesus works there going by their price sheet summit and jegs sell a housing thats the correct width, or just find a local shop to copy your rear diff, FYI you can run a 3:73 year you just have to run a taller tire in the rear than the front, I THINK its a 2 inches taller ask marty he knows the math

 

[420]

Re: Buy a 12 bolt, or build the 10 bolt? Also, what vendors on here sell a 12 bolt?

DTS drivetrain specialist has the specs and can build one, but Jesus works there going by their price sheet summit and jegs sell a housing thats the correct width, or just find a local shop to copy your rear diff, FYI you can run a 3:73 year you just have to run a taller tire in the rear than the front, I THINK its a 2 inches taller ask marty he knows the math

Well, current plans are for two sets of rims - 15" rims for racing, and 17" or 18" rims for daily driving. The different tire height issue would be a very simple fix on the drag rims, since there is every height / width combo under the sun available from summit (and more importantly that would let me run a 275/50 ET Street radial up front and a 275/60 ET street radial out back). BUT... once you get into the 17 and 18 inch terrority, the pickings get a lot slimmer.

I'm figuring I'm going to end up at the local drivetrain shop with this one. I just figured I'd ask on the board first, and try and throw some business toward the vendors who help keep this place running

 

[warmpancakes]

Re: Buy a 12 bolt, or build the 10 bolt? Also, what vendors on here sell a 12 bolt?

another thing to consider is narowing the rear axle to change the offset of the wheels, you could run a 2wd rear diff, iof you are getting a new set of wheels, the axles wont be as long so there is less chance of shearing the end off, Plus you can get the "fat lip" on the rims, Im planing on doing this, for a few reasons

 

[jbone]

Re: Buy a 12 bolt, or build the 10 bolt? Also, what vendors on here sell a 12 bolt?

go with a 14 bolt :tup:

 

[NOJIMMY]

Re: Buy a 12 bolt, or build the 10 bolt? Also, what vendors on here sell a 12 bolt?

I know Woz (aka Silly) with his Marlboro Ty has a 9" rear end in his vehicle that he has talked about selling.
You may want to PM him...(he`s running some awesome 15" skinnies/MT ET Streets).

There are several Rockford Racecraft Trucks that have "surprises" underneath.
Some 12- bolt Moser, some fab 9, and some ford 9". We just dont talk about it....<grin>

Larry Brown
(NoJimmy Ty)

 

[Silly]

Re: Buy a 12 bolt, or build the 10 bolt? Also, what vendors on here sell a 12 bolt?

I know Woz (aka Silly) with his Marlboro Ty has a 9" rear end in his vehicle that he has talked about selling.
You may want to PM him...(he`s running some awesome 15" skinnies/MT ET Streets).

There are several Rockford Racecraft Trucks that have "surprises" underneath.
Some 12- bolt Moser, some fab 9, and some ford 9". We just dont talk about it....<grin>

Larry Brown
(NoJimmy Ty)

Haha I have actually tried to sell that rear end to Matt a couple times.. I wanted a 12 bolt myself.

Moser has some pretty badass stuff out right now as well and not bad prices either.

Check out the M9 Series.

 

[420]

Re: Buy a 12 bolt, or build the 10 bolt? Also, what vendors on here sell a 12 bolt?

LOL, yeah, I talk to Mike on a regular basis (mostly cheap shots about his hot wife ). He's been trying to sell me that thing for a while. I wish it fit my needs, as I'd love to take it off his hands.

another thing to consider is narowing the rear axle to change the offset of the wheels, you could run a 2wd rear diff, iof you are getting a new set of wheels, the axles wont be as long so there is less chance of shearing the end off, Plus you can get the "fat lip" on the rims, Im planing on doing this, for a few reasons

I was unaware that there is a "2wd rear diff" vs a "4wd rear diff" ???

As for wheels, yeah, I'm 99% going custom anyway, so that would work well. I figure Bogarts for the track, and (if the wallet allows) HREs for the street

 

[Silly]

Re: Buy a 12 bolt, or build the 10 bolt? Also, what vendors on here sell a 12 bolt?

Matt, whats your thoughts on the information I emailed you a month or so ago.. that Moser stuff?

I think I scanned the build sheets and emailed them.. let me know if you need them again. That should fit your needs and still keep the weight pretty light.

Hell the cost of that will be about the same if not lower than my 9"

 

[420]

Re: Buy a 12 bolt, or build the 10 bolt? Also, what vendors on here sell a 12 bolt?

Honestly? I think I knew more about rear axles, so I had a better idea what I'm looking at. I'll take a look at it again, and see if it makes more sense this time around.

Here's a crazy question - Since I'm trying to be very weight concious with the truck, I know they make "fab" 9 inch rear ends, and the fabbed housing cuts a lot of weight out. Are there "fab" 12 bolts?

 

[warmpancakes]

Re: Buy a 12 bolt, or build the 10 bolt? Also, what vendors on here sell a 12 bolt?

yes but you dont need a 12 bolt plus it takes more power to spin a 12 bolt as opposed to a 8.5

 

[warmpancakes]

Re: Buy a 12 bolt, or build the 10 bolt? Also, what vendors on here sell a 12 bolt?

oh and a 4x4 rear diff is wider than a 2wd rear diff

 

['JustDreamin']

Re: Buy a 12 bolt, or build the 10 bolt? Also, what vendors on here sell a 12 bolt?

oh and a 4x4 rear diff is wider than a 2wd rear diff

And the ZR2 4x4 rear is wider still.

I don't have any data to back this up, but I would expect the 8.5" 10-bolt to be marginally more efficient than the 8.875" 12-bolt. But I'd bet the difference is pretty small. The 9" is know to have lower efficiency because of pinion placement (more sliding action like a worm gear than rolling like a bevel gear than the 12 bolt) which is why the Cup guys have to run rearend coolers (that and they're pushing 750+ hp for 4+ hours). Not sure how the 2 GM diffs compare. Could be that the 8.5" is less efficient due to design (again, I don't know for certain).

'JustDreamin'

 

[big gear head]

Re: Buy a 12 bolt, or build the 10 bolt? Also, what vendors on here sell a 12 bolt?

I have built several 12 bolt rear ends for these trucks, including the fastest and second fastest cars in Europe. The fastest is a Typhoon that I built about 2 years ago and the second fastest is the all wheel drive C3 Corvette, both from Poland. I also built Phillip Long's 12 bolt and one other for a Syclone. They are not too difficult to build, but you must know a few things to make them work in these trucks. The 12 bolt will have 3 inch axle tubes, which means that you will need new U bolts and you will have to modify the lower plates for the 3 inch u bolts. The rubber bumpers on the frame will not have anything to bump against because the new spring perches don't have the extra material for the bumpers to contact. I build these with the 3R yoke so that the original drive shaft will work, but they can also be built with a 1310 or 1350 yoke if you want to use a new drive shaft. I build them with 30 or 33 spline axles and Eaton posi or Detroit Locker, depending on how much abuse they will see. The price runs around $2000 to $2500, depending on options. Send me an email if you want more information.