Ok, I have seen many discussions on this, and it seems usually people try to talk everyone out of ditching the 10 bolt, or a short recc on a 12 bolt for various small reasons.

So let me start off by saying, I am an abuser. I love feeling accelleration, in all directions, so I accellerate hard, corner hard, and get the police on my bad side without breaking the law (burning tires wastes valuable force, so I avoid it when possible). I have blown 4 10bolts, the 5th is no longer aligned properly, and bad enough that another 10 miles will almost surely kill it.

Further, I have an LT1 in the car, and really want to get the LT4 Hotcam or better, which stats show moving the power up over the 400HP recomendation from moroso and richmond.

The short spurts of info generally seem to try and say that a 12 bolt and 9" will be similar in strength, but something about the 9" having some kind of center section. I am guessing this means you can unbolt the center section from the axle tubes for a swap/repair without removing the whole axle?

Those questions answered, I want to know what most pros go for. The car isn't a race only car...yet But like I said, I abuse it, and am sick of blwong rears. (and no I just cant stop the abuse, I tried, I seem to go into a withdrawl of some sort and end up trying to catch back up) I also want an easy swap with a prebuilt axle. I am expecing to spend at least 2K and up to 4K for this, which is still less than what I put into that...10 bolt. I also can wait on this, as I have a new car now. (GTO, since there are no more new T/A's....why couldnt GM have just waited a little bit longer?!) So if its going to cost me, or something needs to be special ordered, etc, its not a big deal.

I also want to know names, advantages and disadvantages of various aftermarket axle makers. I know moroso, and currie, and I would like others, just to be able to comapre to. They are both on the low end of my price scale, so neither is necessarily a bad choice. I didnt see if currie makes the 9" so it bolts up to the F-Body, I did see on moroso's page they did. I have generally heard that most 12 bolt kits wont have a problem.

Finally, is there a clear "Best of the Best"? Thats what I'd prefer here.

Thanks
Corry

 

9" is the most common, and typically the best for strength/$'s.

12 bolt is as strong as the 9" but more efficient.

Dana 60 stronger than either, but more expensive.

Personally, I'd opt for the 12 bolt were I in the market.

 

I'm looking into a Currie stage-1 Ford 9" myself. I've also heard that a 12 bolt is more efficient, and I've also heard that the difference in efficiency is so small, it's a wash. And which is stronger?? Don't know that either. But I'm confident either rear will hold the power level I have.

You can call me old fashioned, but I tend not to go by what I've heard - but by actual data collected from extensive testing.

And BTW 5-7 - Not trying to bash your post at all. If you know of any data out there, I'd love too see it!! I know you're a highly competent gear head!

If you're serious about buying an aftermarket rear, PM me and maybe we can fanagle a package deal of some sort!

 

Most "Pro's" use fab nine housings since they are ALOT lighter than standard ford 9" housings. They use the Ford based rear end design since different tracks require different gearing and the Ford 9" design allows quick center section changes after testing to optimize their set-up for that weekend.

Most guys at the dragstrip also opt for the 9" since it is a proven design and typically parts amoung friends are easily attainible since many guys run them. I like my 9 and price wise they are about the same as a 12 bolt, but I still chose the 9" since. You've read the pro's cons for both and arguements for both. Cant say that I know anybody that has done any A-B-A testing swapping between a 12bolt and a 9" to make a real world comparison since 1. it would be a PITA
2. it would be an expensive proposition for the laymen.

I've personally seen 3 sets of Strange axles snap on the starting line. 2 snapped inside the spool, 1 snapped at the flange. Cant say I've seen a Moser or MW ever do that so I cannot speak on their behalf.

And, yes, either will hold up well to your power level, but it would be cheaper/easier if you were ever to switch you combination and want to try a new gear set using a 9" over a 12bolt.

 

A 12 bolt is just like any other GM diff. They have a different series for a selection of gear ratios so you need to buy the carrier to fit whatever gear ratio you choose.

A 9" has no series carrier. 2.50 gears fit the same carrier as 6.00 gears do.

Doing a quick swap with a 9" means you need another center section, carrier (posi), gears but it is all set up and ready to go built on a bench. Doing a swap with a 12 bolt takes longer because you usually install the gears on the same carrier providing it's the same series but you also need to change the pinion. Setting pinion depth takes a lot longer since it's done in the car.

For most people who decide on a gear ratio and plan on sticking with it for a long time, a 12 bolt is fine. Racers like the simplicity and better selection of parts of the 9".

Dana 60 is a monster strong diff but it's a nightmare to set up. Once it's set up you never want to change it.

I also know a few racers that use the Dodge 8-3/4" diff.

 

Sorry I've been away, my work had me doing enough computer stuff to keep me away from the things at home

Anyways, I'm unconcernec about "power level" ratings. By all those ratings I should never have killed 3 10 Bolts on a 305 TPI, but well, I did, like I said, I'm an abuser, and those Z rated tires from what I have read will cause some nasty case flexing when you accellerate hard....which I do waaaaaay too often (Ouch my wallet!)

So the little more research I did said something about 9" needing a "nodular" case/pinion bearing retainer, would an axle set up from one of the good aftermarket companies have this standard, or would I have to ask for it specifically/pay more, and if so, how much more?

Another question, I saw that Higher ration GM pinion gears tend to get progressivly smaller, but since ford gears dont have to be set to a carrier size, they can make their pinions bigger, so one would expect having read that that a 6.5 raito set would have the same size pinion as a 3.0 set, yet on the same page, you see a monster 3.0, and a 6.5 that looks to be as big as a chevy 4.10. Is it just that fords start out with bigger gears, and then can progress down through their sizes rather than a big jump like Chevy has?

This is more of an aftermarket ignorance question. Would most of these aftermarket axles have a supporting cover, axle tube braces, Nodular cases (where appropriate) C Clip elimination (where appropriate). Would the be offered? What about other mods.

Lastly, everyone seems to say the Dana 60 is well probably more than overkill. What are the aftermarket options on this? I'd like a drop in solution so I can do this on a weekend then drive the car down to where I am living in Virginia now, not a long drawn out building process.

I'd really like this to be the last axle I have to buy for the car. I'm sick of not having my TA around because of the rear end! Once I get that taken care of, a Painless harness for the LT1, some interior components, and the dreaded bodywork, I wont be so embarassed of taking the car places, but for me, having a solid powertrain comes first.

 

First of all you're not going to find a direct bolt in Dana 60. Even finding a junkyard one is going to take a lot of modifications to make it fit. The majority of them are on 3/4 and 1 ton pickup trucks with full floating axles. I doubt you'll find one narrow enough to fit under a third gen. By the time you're done modifying to make it work, it would probably be cheaper to buy an aftermarket 12 bolt or 9".

There's nothing special about my 9". I use a housing from a 1970 F100. Only downside is that the pinion is offset to the passenger side so both axles are now the same length. I guess it's not too bad since I can swap axles left to right every year so they don't keep twisting the same direction. Normal car diffs have the pinion directly in the center so the passenger side axle is longer (not including GM diffs). I use 31 spline Strange axles in a factory production C7AW-E housing. I welded the axle tubes but that's about it for modifications. I use ladder bars so I didn't have to worry about mounting a torque arm.

http://www.kevinstang.com/Ninecase.htm
http://www.ridgecrest.ca.us/~biesiade/Fordrears.html
http://www.enjenjo.com/9inch.html
http://www.gearheadracing.com/Refere...FordDiffer.htm
http://www.maliburacing.com/ford_9_i..._nine_inch.htm

It's a lot easier to find and swap in a junkyard 9" than it is a 12 bolt. Those pages repeat a lot of stuff but that's about everything you need to know about 9" diffs. Finding a car 12 bolt is getting very hard and I never recommend a truck 12 bolt. It's not the same diff as a car.

You can buy a torque arm bracket from Currie for $150 to weld onto a junkyard 9". All the other mounts for the shocks, springs, panhard, LCA can just be cut off the 10 bolt and welded onto the 9" housing.

http://www.currieenterprises.com/ces...e.aspx?id=1037

 

thanks for the link for the tq arm bracket from currie. I have been wondering what it would take to make a 9 inch work with my car(short of dropping $2000 for a complete unit)

 

Thanks for the info on the Dana 60.

I am not going to go junk yard searching though. I am looking to buy a complete fully set up rear axle, and built stronger than the original.

I think based on what I have seen I'll probably look for a 9" setup. It just seems like the 9" gears are beefier, and like I said, I'm sick of killing rears

 

Corry -- please update regarding what you've done with getting a bullet-proof rear. I just had to change a complete rear in our '92 Z28 'cause it was cheaper than the estimated $700-1,000 here in Hawaii to rebuild it. I, like you, need to invest is something unbreakable out here in the middle of nowhere.

I've been strongly considering the 9-inch, but am concerned about vibration caused by the geometry offset pinion angle.

Any truth to this, anyone with the F-9-inch installed?

 

Nothing I'd consider unusual, think I get more vibration through the solid motor mounts than anything else. Regardless, no matter what there will ALWAYS be a trade of somewhere when bullet proofing something.

 

I have a Dana 60 in my car, and it has given me absolutely no troubles whatsoever since I set it up and installed it over 10 years ago. It has Moser 35 spline axles, Richmond 4.10 street gears, and a Strange spool. This is in a 3500# back-halved car with 32x14 slicks that gets into the 1.2's for 60' times. I personally think it's ideal for my application, but it would be overkill for a non-tubbed, stock-style rear suspension car.
The D60's got a 9 3/4" ring gear!! Like the others have said; get a 12 bolt or a 9".

 

I would hope the trade-off to installing a 9-inch would only be the additional expense of the product itself. Investing $1-2,000 into a 10-bolt seems senseless when the driver has to "hold his breath" everytime the horses are unleased.

So, the peace of mind that comes with knowing the rear end won't fold like a deck of cards is worth the cost of admission to the "big boys club" of 12-bolts, 9-inches and Danas. In particular, the option with the 9-inch to swap the pumpkin with another one already setup is attractive, even if it's only used a couple times a year.

However, most of these "big" rears seem to be used for drag applications -- some feedback from drivers using using these rears for extended periods of highspeed interstate driving at 80-100 mph would be really useful to determine if they're quiet and vibration-free to be worthwhile.

I'd really hate to spend several thousand $$$ on a rear that is only suitable for drag racing where my cruising speeds of 80-90 mph are moments long in a 10-sec car topping out at 130 or so.

A few of the archive posts here refer to vibration problems possibly caused by the offset driveshaft geometry of the 9-inch, but I've found nothing conclusive yet.

 

I drive mine quite a bit on the hwy getting to the places I need to get, unfortunately with no OD I'm limited to about 65mph at 3200 or so, I dont feel comfortable cruising for long periods over 3500 if I dont have to. I cant say I feel any vibration of sorts coming from the rear end, I do feel the vibration of the motor through the steering wheel though as everything is solid mounted and has a more mechanical feel I guess you'd say.

One draw back to most drag racers is the gears we have to use have a different heat treat process and regardless of how you set it up there is gear noise. If drag racing and low 60's are not priority you could opt for some "softer" gear sets and made it just like a factory car as far as quiteness is concerned. I've never run this new rear end with poly or rubber mounts so I cannot give accurate first hand info on how it really reacts, hopefully there's some drivers on here that have stepped up to the 9" and have some useful information for you.

 

All of the afforementioned rear ends have been used in production applications, and when properly set-up with a good gearset, noise and/or vibration should not be a concern.

If the proper gear ratio for your combination is selected, this also shouldn't be a concern. If you're happy with the gear ratio that you currently have, just get something similar in the new "big" rear.

I'm not sure exactly what you mean by "offset driveshaft geometry". The pinion centerline on a F-9" does sit lower in relation to the axle centerline compared to other rears, but is usually compensated for when the rear is fabbed up in a jig, so the rear u-joint angle remains the same as the original rear. If pinion angle needs to be fine tuned, it can easily be adjusted with an aftermarket torque arm. As long as pinion offset (take the measurement from the left axle flange to the pinion and the right axle flange to the pinion, and find the difference) on your stock rear is the same on any "big" replacement rear end (which it should be), you shouldn't have any problems. If memory serves me, pinion/drivetrain offset is close to 1" to the right on our cars.

 

Thanks MCM,

This is the thread that is the source of my concerns about 9-inch vibrations at highway speeds -- https://www.thirdgen.org/techbb2/sho...hreadid=280143

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Confuzed1
Senior Member

Registered: Oct 1999
Location: GO PACK GO
Posts: 1556
Car: 83Z28 HO
Engine: 409
Transmission: G Force 5 speed, Moser 9"

"...and it looks like i have a problem, or maybe it isn't. But the driveshaft is offset towards the pass. side in the rear. I don't even have the driveshaft in and I can tell it won't be aligned..

"In other words, the pinion yoke is offset to the pass side on this rear, so the driveshaft is at a weird angle. I'm about ready to give Moser a call and ask. The U-joint in the rear is almost touching my exhaust pipe. Don't look right at all.

"Is that normal??

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Confuzed1
Senior Member

Registered: Oct 1999
Location: GO PACK GO
Posts: 1556
Car: 83Z28 HO
Engine: 409
Transmission: G Force 5 speed, Moser 9"

"Thanks EvilCartman - Then I definately have a problem. I was waiting for someone to look at theirs before I call Moser.


quote:
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"Mine was offset to the passenger side a little too. I called DTS about this and was told it was the way of the 9". I've seen several threads on here about the offset issue. After I put the 9" in my car, I noticed some vibrations around 60 - 80 MPH. I again called DTS, they told me the vibrations was the culprit from the Pinion being offset. They also told me the only way to get rid of the offset, is to totally fab-up (from scratch) a 9" specifically designed for our cars.
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"That's exactly what I'm afraid will happen with mine. If I wanted vibrations, I would've kept the 10 bolt in and not spent a dime. What's worse is the fact that Moser advertises this rear as a "Bolt-in" made for 82-92 F-bodys.

"I'll start another thread and post a pic of the offset if I can. I know I don't like it at all. Before I even run one mile on this thing, I need some assurance that this is the way it supposed to be and it won't cause any problems....including vibration."