Broke half shaft! Need opinions on what to buy so this don't happen again!

[tt335ci03cobra]

You've done great. Only things I'd look into other than you've deduced:

-main caps
-deeper wheel studs for slicks/simple mod to do while the assembly is out
-stainless brake lines for the rear
-possibly a line lock if you drag race a lot
-definitely the ftbr fuel filter relocation kit, and checking the fuel filter for sure irregardless if you relocate it or not. It's a bitch to get to...
-rear brake system may need pads rotors et al, easy to do off the car.

Anyways you've done awesome man, 3.73's, ftbr, ford racing cover, jeez. I literally have the same stuff, and mine did phenomenal at 920wtq. The t56 blew apart to bits though haha.

 

[03slaminator]

Mr. b_98gt I've already got the complete bushing kit installed. I should have took pics for a how to but wasn't thinking about it at the time. I also made all my own bushing removal tools. And don't be afraid to do it your self. The irs came out so easy. I was really surprised on how easy it actually was. The hard part is rebuilding the diff and putting the irs back in. Lol

You've done great. Only things I'd look into other than you've deduced:

-main caps
-deeper wheel studs for slicks/simple mod to do while the assembly is out
-stainless brake lines for the rear
-possibly a line lock if you drag race a lot
-definitely the ftbr fuel filter relocation kit, and checking the fuel filter for sure irregardless if you relocate it or not. It's a bitch to get to...
-rear brake system may need pads rotors et al, easy to do off the car.

Anyways you've done awesome man, 3.73's, ftbr, ford racing cover, jeez. I literally have the same stuff, and mine did phenomenal at 920wtq. The t56 blew apart to bits though haha.

Ya I was gonna buy longer wheels studs. But wasn't sure if my lugs would stick out on my 18s if I don't have a spacer. And where could I buy main caps at?

920wtq! Wish I could be at least 700. Haha. Ya I feel my car should hook and go.. 473/526 is my power level. I bought some qa1 adjustable rear shocks. Do you have those on your car? If you do then can you tell me how you have yours set up on the street? Thanks for the replies guys

 

[tt335ci03cobra]

Mr. b_98gt I've already got the complete bushing kit installed. I should have took pics for a how to but wasn't thinking about it at the time. I also made all my own bushing removal tools. And don't be afraid to do it your self. The irs came out so easy. I was really surprised on how easy it actually was. The hard part is rebuilding the diff and putting the irs back in. Lol

Ya I was gonna buy longer wheels studs. But wasn't sure if my lugs would stick out on my 18s if I don't have a spacer. And where could I buy main caps at?

920wtq! Wish I could be at least 700. Haha. Ya I feel my car should hook and go.. 473/526 is my power level. I bought some qa1 adjustable rear shocks. Do you have those on your car? If you do then can you tell me how you have yours set up on the street? Thanks for the replies guys

You'll be hooking and moving out man, it'll rip. I had mm poly bushings, coil overs, flsc and so on, stock pumkin, stock shafts, and could beat awd sti's to 60mph when I was bolt on mods at 470whp/490wtq. I had 17" nt555r's. If I had that combo with nt05r's or something as sticky, I could see it pulling easy 1.70-1.65 60fts. For an idea, sti's and evo's are right about 1.75-1.85 driver/launch dependant from what I've seen. Basically, you'll be rippn out if you can launch it well. I've also seen built irs cobra guys struggle to run 1.8's on slicks so it's definitely driver mod required. The right clutch helps a ton though. I had a spec stage 3+ back when I was bolt ons.

Shocks wise, I have tired and worn stockers. The bilsteins are a good all around setup, but I'm looking to get the sport valved ones mm sells with specced springs based on my cars proportions/specs. I haven't pulled the trigger yet because I want to research if anyone makes a great alternative like a mag shock or nice electronically adjustable shock kinda like tein et al do for the import scene.

Ive heard the qa1's are very adjustable, and from what I've read, about 6-8 clicks does a great area to play in for various driving. It depends on your areas road conditions etc. I'd imagine for drag racing, 3-5 clicks in is good depending on front settings, and for bumpier/uneven circuit events, 7-8, for smooth tracks maybe 9-10, and for parking lot/totally flat cone challenges and auto-x, maybe 11-12 but you'd need it like paper smooth id imagine, all of that is just guestimation, I can't say that it'd hold any water, but if I was tuning and adjusting with those shocks I'd start in those ranges, and look up what others are running.

Oh, you mentioned your differential was pretty toast, if it's in your budget, upgrade to a Detroit tru trac, auburn, or torsen. The truetrac is strongest but handles the tightest, the auburn is great, but they aren't as strong, the torsens can handle 500wtq but don't really like it, gt500 guys have blown em apart often enough with 6-700wtq... I went truetrac. It's a huge improvement over stock, and the ford racing cover fits it when specced correctly. If your mechanically inclined, you could try building a diff cooler for the rear as well, the ford racing cover has provisions for one. It's like $5-600 in parts, then your time. It's worth it though if you drive spiritedly.

Also, that paint job is clean and impressive as hell man, makes me want to paint my car haha, it's about the only thing still stock on mine

 

[xtreme_exploder]

Ok guys, I went ahead and ordered the install kit and ford racing 373 gears. I hope the 373's was the right decision. Does anyone have a write up on how to rebuild the diff? I'll be doing this myself along with a friend that has done his own gear install. He is sra and I'm irs. A how to would be a huge help. Thanks again guys!!

An IRS diff rebuild is exactly the same as a solid 8.8. The only extra parts are the axle output bearings and seals.

I run 3.73s in my car, I think they're perfect. I have all the FTBR bushings in the IRS, except I have Maximum Motorsports poly diff bushings, and have FTBR toe endlinks. I have MM coilovers with Sport series shocks and 600lbs springs. I got MM full length subframe connectors. Running the stock axles; never had a problem with them. With my Nitto NT01s or Mickey Thompson ET drag radials, I have never been able to get any wheel hop on any road or track surface at any time with this setup. I'm super happy with it, and I'm at 650rwhp.

 

[xtreme_exploder]

Also saw you had 75w90 gear oil. You'll want the 75w140, that's the Ford spec and even says "75w140 only" on the diff tag if I remember correctly. The friction modifier shouldn't be needed, as the Royal Purple fluid has friction modifiers already in it. Keep it to the side and only add if the rear end chatters real bad in turns.

 

[SYMach1]

Dont run drag radials lol, thats the worse thing for the irs, i had over 50 passes on my stock half shafts, ive broken two this year so i put the pros in, no one has broke pros as of yet, there is 1200hp turbo car that runs 9.30s with a six speed/irs with pros level halfshafts

 

[03slaminator]

Tt335ci03cobra, thanks for the advice!! And thanks for the compliment on my paint. I got a lot of time in this car. From the time I stuck a piece of sand paper to it, tore it all apart. And shot it in my favorite green it took me 8 months to finish. Having to take care of my newborn son while trying to rebuild the cobra was a major pain in the a$$. Lol

Extreme_exploder, so what's so bad about using the gear oil I got? I seen a post on here awhile back saying it was better to go with the 90 over the 140. I'll see if I can dig it up.

SYMach1, pro's are defiantly out of my price range now. Plus I already picked up 2 used shafts 300.00 for the pair. That's a good deal considering they sell for 250 a piece used. Also why not use DR's? Iv been using them since 2012 and have had no problems until now. Almost every bushing was shot, no flsfc's, 1 blown out shock. And taking the weight out of my trunk, is what caused this to happen. All brand new stuff, I don't think I should have any problems what so ever. If I do then I have an extra half shaft laying around now. Lol

 

[MBoyle1]

I run 3:73 also! On26" tire I'm at 6500 RPM in 4th @ 134 MPH in 1/4 mile.

 

[tt335ci03cobra]

The drag radial concern is because the radial construction doesn't twist and absorb torque load like a wrinkle wall slick does, but the compound is so sticky that it grips very hard almost like a slick. The torque generated has no where to unload because the tire doesn't wrinkle, and grip is very good.

This mitigates all of the torque force into the mechanical parts.

If the IRS is built, tight, and basically free of deflection and unwanted movement, there isn't a huge problem.

If the IRS is tired, deflects a lot, and basically loose, the drag radial tires will grip hard, the sidewall won't flex, and all that torque will be channeled to the weak links of the IRS. It will chatter and hop like a jack hammer. Parts will sheer and break.

Now if the IRS is built and tight, the issue can't develop nearly as much as there won't be any chatter or hopping. The torque force is still very strong though and will be channeled to all the mechanical parts.

A wrinkle wall slick absorbs much of the torque, much like a soft nerd rubber ball (football, basket ball et al) absorbs and deflects upon impact with a wall, vs a hard rubber ball. The soft ball won't bounce far off a wall. In stop motion, it's compressing very hard on impact. A hard ball bounces much better because the force isn't absorbed, it's temporarily transferred to the wall, and right back off, as it maintains most of its speed.

Full tilt boogie facing has nice go pro videos on YouTube of the IRS under wheel hop and once fortified, and it puts it all into context. Elsewhwhere on other channels, there are lots of good videos on tire deflection too, and why irs and drag radial can be a terrible idea.

I have level 5 s2's axle wise, and with a tight irs, I don't have any hop, so my drag radials haven't been a terrible issue. It sees more street time than track time, and I like to hook so I run drag radials. You also want to use a softer launch technique as well. I use 3500 on 4-6psi and roll into power. It's a 1.60-1.70 approach. If I tried 4500 and 10psi+, it'd be gripping it on a hot prepped surface, but literally twice the torque load, and lead to wear and tear related damage much faster.

 

[mr. b_98GT]

Mr. b_98gt I've already got the complete bushing kit installed. I should have took pics for a how to but wasn't thinking about it at the time. I also made all my own bushing removal tools. And don't be afraid to do it your self. The irs came out so easy. I was really surprised on how easy it actually was. The hard part is rebuilding the diff and putting the irs back in. Lol





Ya I was gonna buy longer wheels studs. But wasn't sure if my lugs would stick out on my 18s if I don't have a spacer. And where could I buy main caps at?

920wtq! Wish I could be at least 700. Haha. Ya I feel my car should hook and go.. 473/526 is my power level. I bought some qa1 adjustable rear shocks. Do you have those on your car? If you do then can you tell me how you have yours set up on the street? Thanks for the replies guys

Ah, I didn't catch that the FTBR kit was already installed. It does seem pretty straight forward, so I'm confident that with all the threads and videos out there for the FTBR install, I'll be okay. I do agree about the differential being the hardest part of an IRS rebuild. When the time comes, I was going to most likely take the differential with new gears and parts to a reputable shop and have them do it for me while I do the FTBR kit at home, but if there is a thread that shows how to do it, then I might tackle the differential as well. Good Luck with it all!

 

[03slaminator]

Does anyone know of a nice write up on rebuilding/changing gears and setting it up right with the correct tools? Any help would be greatly appreciated!!

 

[xtreme_exploder]

http://www.mustangandfords.com/how-...-mustang-cobra-gears-upgrade/photo-gallery/#1

Go through the photo gallery, there's some nice info specific for our cars. Look up Ford Racing gear install instructions somewhere on the interwebs, they're probably the best for helping you set the clearances and patterns.

I wouldn't recommend 90w oil because our IRS centersections get much hotter then an SRA under abuse. Whether or not you'll see a problem with the 90w depends on how hard you run the car. Normal street driving it'll be fine, but if you did a track day or something, there's a chance you'd roach the rear.

 

[03slaminator]

No track days, I dd my car and it's not driven hard. I street race sometimes. And plan to take car to the drags just a couple times a year.

 

[03slaminator]

Well I still haven't got everything in the car. I'm just now getting around to rebuilding my diff. And for some reason I thought I ordered 75w90. But I checked my box of parts and I did in fact order 75w140. So that's good.