Considered IRS but going to just build my 8.8...do they offer drop in 8.8 with 9" ends?

killer5.0

killer5.0

5 Year Member
Oct 8, 2009
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#1
So i currently have MM PH bar installed and the HD TA waiting to go in. Didnt have time this year to do it so planning on tearing the car down end of season and slapping it on the rotisserie to tackle the undercarriage the way i want and then install all my new parts (mm k member, TA etc). At that time i will upgrading the fuel system and exhaust and i want to build the 8.8. Are you guys finding local shops or does someone offer drop in setups? My car is street and show only...currently at 500rwhp but plan to hit 750-800rwhp in the future when i build the dart. Considered the IRS and still considering it, but for what im building i think the solid axle will be just fine and stronger for the higher HP. And since i want to run as wide a wheel as i can and the IRS pushes the wheel out an additional 1.5" per side i believe which would limit my wheel size even more.

Thoughts?
 
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#2
I like the irs, but it's fairly expensive to begin with, then you need $1600 axles and a bunch of other supporting parts, it just adds up too quickly and even worse the extra width.

I'd probably build the 8.8 as is. New bearings, 31 spline axles, carrier, gears etc. Since you aren't drag racing it at the track and with all those mm parts it shouldn't wheel hop, I really doubt you would break it.
 
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#4
Oh they make them alright. Companies like Moser, Strange, Currie, all make a 8.8 or 9" rear to "drop right in" to your car. It's 3350.00 for a 31 splined 10" drum brake equipped new housing w/ your choice of ratios.
http://www.moserengineering.com/Moser-M88-MUSCLEPAK.item
An 8.8 can be made to handle a lot of power, but there's a fair amount of money involved to do that as well. Considering that most JY 8.8's have seen a fair amount of abuse already, you may have to consider having the axle tubes straightened (They pull forward) so you'll have that expense too. I'd think that if you're considering that route, you'd ditch the 8.8, and just upgrade across the board, and get a full 9" and be done with it.
 
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#5
To answer your original question , no . Everyone I know of has had it sent out to someone who has a jig to do it . They straighten tubes at the same time and then do the ends as well as weld the tubes up .
 
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#6
I overbuild everything lol. Im OCD like that. I have a tendancy to make everything more detailed and cause myself more work lol. That being said im building this car to handle whatever at throw at it if the need arises. From what ive seen 8.8 with 9" ends is a very common practice. I assume people dont go full 9" because of added weight? Money is a concern but i dont mind forking out some extra for a superior product. I like to do it right the first time or at least the best i can afford to do, if that means waiting a little longer to save up some more than so be it. For instance if i can build a decent one for 2800 but a really good one is 3800 then ill opt for the 3800 setup.
 
#8
A 9 inch is stronger, but your suspensions may not work with it if it is 8.8 specific. Find a junkyard rear end and a local guy who cam do it, or send it off. As already stated, 31 spines will probably serve you well, especially with 9" ends. I wouldn't be afraid of taking a traclok and 31 spines to 500hp or a little better, especially with the 9" ends and no race time.

Joe
 
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#9
I want this built to hold 800rwhp which is what i plan to hit when i build my dart. Good call on the suspension parts never thought about that. MM panhard bar and HD torque arm...most likely their rear sway bar as well and coilovers.

And i have no one around here who does anything like that. I guess ill have to search for somewhere to send it. Does strange and moser work on supplied 8.8s? Or just there own stuff?
 
#14
RangerJoe said:
A 9 inch is stronger, but your suspensions may not work with it if it is 8.8 specific. Find a junkyard rear end and a local guy who cam do it, or send it off. As already stated, 31 spines will probably serve you well, especially with 9" ends. I wouldn't be afraid of taking a traclok and 31 spines to 500hp or a little better, especially with the 9" ends and no race time.

Joe
Click to expand...
My frpp has seen way more then 500 at the tire with 31 spline mosers with no issue . We all know I’m not the easiest on my stuff either

6A135F70-A5DC-4410-93CF-BC5F271D9995.png
F75C83E4-C612-408E-B105-7D6CD91429CC.jpeg
 
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#15
TOOLOW91 said:
My frpp has seen way more then 500 at the tire with 31 spline mosers with no issue . We all know I’m not the easiest on my stuff either

6A135F70-A5DC-4410-93CF-BC5F271D9995.png
F75C83E4-C612-408E-B105-7D6CD91429CC.jpeg
Click to expand...
You make just a little more power than I do, lol, but my rebuilt, 100k+ mile explorer traklock has been holding up well for me too. And they are easy to rebuild.

Joe
 
#17
Im upstate ny right in the middle of nothing lol...and trust me ive been into cars my whole life and there are no performance shops within hrs of me let alone any that id trust to build me something like this. I have no good welders, performance shops, chassis shops etc. I figured between $2-3k for a built and powdercoated rear. If its a touch more and ready to drop in then so be it. Each winter i work on stages so i can afford to build the car i want.
 
#18
How many of you are using 31 spline? I haven’t begun my rear brake setup as of yet but planning on ordering it here soon, I was told from the company I could upgrade to 31 spline for an extra 75 bucks added to the kit. I know if need a trak lock which I’m not sure which one I’d need or how much they are. What else would I need to change if I decided to go this route. So I’m guessing my power to be around 4-500 hopefully once I get my motor all done with the stock block. I am considering going 347 dart instead but that’s not sure. Not a track or road race car by any means just want to make it fast and for the weekends. Is it worth the effort to swap or should I just stick with 28s? Thanks
 
#19
Reddevil91 said:
How many of you are using 31 spline? I haven’t begun my rear brake setup as of yet but planning on ordering it here soon, I was told from the company I could upgrade to 31 spline for an extra 75 bucks added to the kit. I know if need a trak lock which I’m not sure which one I’d need or how much they are. What else would I need to change if I decided to go this route. So I’m guessing my power to be around 4-500 hopefully once I get my motor all done with the stock block. I am considering going 347 dart instead but that’s not sure. Not a track or road race car by any means just want to make it fast and for the weekends. Is it worth the effort to swap or should I just stick with 28s? Thanks
Click to expand...
It’s worth the peace of mind .

I run moser 31 spline Fox length axles with 94-04 flange for the disc brakes .
FRPP cobra 31 spline posi unit
94-04 gt rear brakes .
North race cars caliper backing plates to retain stock fox track width
 
#20
Are you planning on running drag radials and launching it? Since you said your vehicle is only street and show, I would assume you are going to be running street tires and not going after 60' times, which is what puts the most stress on a driveline. How is your traction with 500whp? I would assume almost non-existent full throttle in 1st-3rd and just starting to really hook in 4th (a TA will really help with that). Reason I bring that up is that increasing your HP is not going to effect the force on your driveline (except maybe in 4th and 5th, which doesn't give you the torque multiplication that the lower gears do) much unless you do a lot to increase your traction. Quality 31 spline axles can hold up to a lot in street/strip machines. It's when you dump the clutch at 4K+ in 1st gear and actually hook all the power to the ground you really start stressing components.

The only reason I would count out the IRS in your situation would be because of the width. You will have to run a different offset wheel to take advantage of the wheel opening, or go wide body like I am with custom wheels. Other than that, all the other issues can be taken care of. The main reason people break the IRS is because of wheel hop. You fix the wheel hop issue (and a couple other things) and the stock 31 spline axles (on the newer units and especially the 03-04 cobra units) handle quite a bit. I know of one local 03' cobra guy with 800+whp launching on the drag strip with an IRS that has no issues (and he is at full weight). He has all the full tilt-boogie parts on his IRS but is running the stock axles and differential. The whole reason people think the stock IRS is so week is because of all the compliance the factory built into the unit and the wheel hop/rear steer issues it created. Plus the rear cover was a weak design, but all those issues have aftermarket parts to fix them. Also, you have to take into consideration most of the failures are also on cars that weight a good 600-800 lbs more then our foxes do. I finally got to ride in an IRS fox a couple weeks ago, it was a night and day difference in the ride quality.

My end goal is about the same as yours, 800+whp when turned the full way up. I already have the IRS and aftermarket parts. I also did a hard tail conversion on mine and will be re-enforcing the IRS subframe to eliminate deflection, but I'm planning on cornering the crap out of this car which is something I don't believe you will be doing.

800whp would be my personal "limit" for 31 spline axles in either setup with no plans for drag racing, though.

Just my 2cents.
 
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