The Mustang Forum for Track Enthusiasts

Track Mustangs Online was built specifically for those who track their Mustangs!

Open diff on v6 sn95 for budget racing series?

johnjamesmiller

TMO Beginner
4
2
Omaha
Building a 2001 V6 automatic for a 24 hour race. I've never tracked an open diff car. What's it like? Should I trade 50 penalty laps to get an LSD?

The plan for my setup so far is:
  • Stock v6. Hopefully up to the 190 hp stock rating.
  • 17x8 inch wheels with 225 Hankook R-S4s all the way around.
  • Full roll cage 1.75 x .120 DOM tied to both front and rear shock towers should stiffen things up
  • SR Performance 1.5 inch Lowering Springs. 460 lb/in - Front; 280 lb/in - Rear.
  • Steeda X2 ball joints and outer tie rod bumpsteer kit
  • DIY panhard bar. Trying to avoid penalty laps. I should probably give up and get the MM unit.
  • Front Cobra calipers and 13 inch rotors, stock rear calipers and rotors with Carbotech RP2 on front and back.
My priorities are:
  1. Stay Safe. Facing the wrong direction in a corner does not sound safe.
  2. Have fun. Babying it through the corners does not sound like fun.
  3. As many hours of seat time as possible. Spin = Black flag = Hour off the track.
  4. Avoid unnecessary time away from family doing upgrades that won't impact priorities 1 - 3. Can 190 hp through an auto transmission really break loose a 225 R-S4?
  5. Somewhere at the end of the list: Getting more laps than everybody else at the race.
Any other thoughts on my setup welcome!
 

JDee

Ancient Racer
842
703
halfway between Mosport and Shannonville
W2W Racing
20+ Years
Welcome and nice first post! Like the humour, that's always good. Your priorities make a lot of sense as well, though the first two might be in conflict with each other a bit.
I ran an open diff in endurance racing but it was a FWD car so I think my experience may not be helpful. For me though I would say it was very doable. I ran a 225 tire with 175 hp and it was easy to induce wheelspin though back in those days we had nowhere near the grip modern track tires have. We just needed to manage weight transfer and throttle very carefully, that much will transfer over to any platform I think.
 

TMSBOSS

Epic Contributor
5,194
2,164
Illinois
HPDE
5-10 Years
You can break a tire loose without power.

If you can gain an advantage with a modified stock PHB. Borrow an adjustable unit, set it up, get your measurements and modify.

Have you looked at transmission cooling requirements?

Welcome to the site!!
 

johnjamesmiller

TMO Beginner
4
2
Omaha
JDee and TMSBOSS Thanks you for the replies!

JDee good to hear its not a deal breaker. Thinking through this more I see your point TMSBOSS. If I carry a bunch of speed through the corner I may be able to only put down 1hp on the one wheel before I break loose. The HP is just one part of a big equation. At the end of the day I just need to get it out on the track for a test day and see if the setup is fun for me and the (low) amount of talent and skill I have.

Great idea on the modified stock PHB. I think I will pursue that.

For transmission cooling the popular thing to do in this series is splice the AC condenser into the stock transmission cooler return line. Some discussion about possible loss of pressure and the transmission possibly not functioning well but as far as I can tell everybody that has tried it or does it runs fine.
 

blacksheep-1

TMO Addict
2,357
1,865
really no future in an open diff on a roadracer, if you need start packing shims into the spider gears to force them to engage. There is a product out there called Phantom Grip, that takes this to an extreme. They are basically a cigarette sized pieces that are spring loaded and fit between the spider gears, they work awesome, and are relatively cheap, but I don't know if they are available for the small Ford diff, although they do sometime make some custom units, they are really stupid simple in their methodology. Barring that, there are plenty of them available on Ebay and came in most foxbody 7.5 diffs.



 

blacksheep-1

TMO Addict
2,357
1,865
While I'm at it, the PHB on the stock "triangulated 4 link POS" is a complete no no. The suspension arrangement is already in a bind, the PHB just adds another binding arc that is so horrible that you can actually jack up one side of the car by adjusting it. A lot of this is covered in the "Junkyard Dog build" which you really need to look at. You would be much better doing the poor man's 3 link, or by using stiffer bshings in the bottom trailing arms and using extremely soft ones in the top arms. with no PHB.
These cars are very prone to snap oversteer as the car goes on corner exit as the seriously really crappy triangulated 4 link desperately tries to find the center. Adding a PHB to that just make sit worse.
 

steeda5

TMO Race
215
113
Moving to a 8.8 rear end will give you lots of options as to configurations with it. Im running MM torque arm/PHB set up in my SN95 racer(might be overkill in your car). A IRS out of a 1999 or 2001 cobra (28 spline) might be something to think about as well if your budget allows.They bolt right in to your sn95. There a lot cheaper than the 2003/2004 Cobra (31 spline) ones. Blacksheep-1 can give you feed back on what a IRS can do in a sn95. Believe he had one in his Sn95 autocross/ track car he just sold.
 

blacksheep-1

TMO Addict
2,357
1,865
you can find the IRS units for the 99-02 cars but you will have the 3.08 (or something like that) for around 600 bucks. the 03/04 units with the 3.55 and 31 spline axels are going for about $1K. for that much money you can source an 8.8 (I've seen them for under 100 bucks around here) and then build the limited slip unit and get a set of gears that you need for way under $1K. The 8.8 is pretty much a fire and forget unit for your car...BUT...there are plenty of left over 7.5s from the early mustangs, the thing is, once you have the 8.8, you can pretty much put any engine in front of it without worry.
IMO..build an 8.8 if you are going to spend more than $200 bucks on the 7.5.
 

blacksheep-1

TMO Addict
2,357
1,865
there are so many gems in here that are applicable to your car that you really need to read it.

 

johnjamesmiller

TMO Beginner
4
2
Omaha
Blacksheep-1 Thank you very much! The Junkyard Dog build is awesome. Read it cover to cover.

The redneck 3 link is right up my alley. Grabbing a QA1 PCMR8-10 rod end with 19300 lb rating from speedway. Think it will suffice? I'm not sure if I will be able to find the spherical bushings for the axel side in the right size/price range. Time to do some measuring and ebaying and track testing. Maybe on the UCA body side new rod end and worn rubber on axel side? Maybe try 1 UCA and try 2 UCA? I think this is a dumb question but will I know when the rear end is binding? I'm assuming I wont feel the rear end respond to the track as it should followed by a loss of rear end traction? Hitting some of the curb at apex a good way to test?

Steeda5, I agree IRS is the way to go. Even in best case scenario It won't fit in the "$500 budget". That has thrown some interesting decisions my way! Brakes/safety/wheels/tires/driver comfort except from budget. I've thought about trying to convince the bs judges IRS swap is necessary for driver comfort but not sure that will pass! One day I go buy a new front cobra brake setup in a few minutes and not worry about it - next day im stressing over a $50 AC delete pulley and spend a few days of spare time figuring out how I can use an $8 junkyard pulley and an interesting belt routing configuration to "save" $42 on my "budget"
1594134117620.png


Best bet right now for LSD is getting a $150 u pull it 8.8 from a GT. Probably going to tackle that next season if this experiment lasts that long.
 

blacksheep-1

TMO Addict
2,357
1,865
You can also do this, depending on the rules, if you MUST run the stock suspension then the rules will probably let you run any kind of bushing material you want. So in one side, run a poly material, and on the other side use roll bar padding (thus negating the roll bar padding side) and install a PHB. IT's basically, the redneck 3 link that gets around the rules.
 

captdistraction

GrumpyRacer
1,650
1,121
Phoenix, Az
You can also do this, depending on the rules, if you MUST run the stock suspension then the rules will probably let you run any kind of bushing material you want. So in one side, run a poly material, and on the other side use roll bar padding (thus negating the roll bar padding side) and install a PHB. IT's basically, the redneck 3 link that gets around the rules.
This I like a lot. I ran the PM3L for a bit on a SN95 and it mostly works very well (compared to quadrabind); but I like the idea of a dead bushing to pass rules
 

blacksheep-1

TMO Addict
2,357
1,865
it's your lucky day, PM me your address and I'll get these out today. I no longer have any SN95 stuff but I found this in my pile of misc crap.
The bushing has a chunk taken out of it, but the forces are linear so don't think it will be an issue.

BmJFemBl.jpg
 

johnjamesmiller

TMO Beginner
4
2
Omaha
Sorry for the silence! Thanks for checking in on me!
PatientZero really appreciate the offer. I've got a new (to me) 8.8 with trac loc so I'm good! Can't say enough good things about all the people on this forum helping me out!

Mid July I spent 3 fulllll days working on it. 12 to 16 hour a days.
  • Stripped the interior.
  • After a few tries it started up again. It had been sitting outside for a year. Shocked the battery was still holding a charge after the winter.
  • Removed the poorly hacked in security system.
  • Tacked in the cage and fully welded a few spots like top of the main hoop.
    IMG_2280.JPGIMG_2282.JPGIMG_2284.JPGIMG_2289.JPG
  • Test fit the seat - ordered the seat brackets too late so wasn't able to install. check out my awesome wood seat brackets.
    IMG_2308.JPG
  • Dropped the fuel tank and installed a new fuel pump. realized the evaporator sensor plug was wrong. reinstalled the previous but pretty new looking pump. new fuel filter. Ran a lot better with new gas!
  • After tripping over the rear sway bar 4 times I just installed it to get it out of the way.
  • I think i have the kill switch figured out drew a diagram but didnt start wiring.
  • Realized both rear axles are bent. Previous owner hydro planned it into a ditch pretty bad I guess. 2 of the rims were cracked pretty good!
    IMG_2265.JPG
  • Radiator support pulled out and put the bumper back on.
    IMG_2268.JPG
  • Last week the car got sent down the street to the professional welder for complete welding
  • On Thursday after spending weeks on craigslist, fb market place, and the local u pull its I finally found an 8.8 rear end from a 99-04 mustang in the u pull it an hour away in Lincoln! I know I have been spending too much time looking when my wife is excited I found one. Hopefully get some new bearings in it and cleaned up tomorrow
    IMG_2335.JPGIMG_2336.JPGIMG_2339.JPGIMG_2356.JPGIMG_2359.JPGIMG_2360.JPGIMG_2362.JPG
In about 10 days Ill spend another 2 full days on it. Planning for track test day Aug 22nd and race weekend September 12/13

On my really needs to get done to pass tech list:
  1. Seat mounted, harness bar welded, seat belts installed
  2. Kill switch
  3. Roll cage padding
  4. Fire system
  5. Wiring secured and buttoned up
  6. Securely mount battery and cover hot posts covered
  7. Take a look at that oil drip and decide how bad I need to do something about it.
  8. Drain and clean radiator
On the I really want to get done list but probably won't get to it.
  1. Splice AC condenser into transmission cooling return line
  2. Install rear end with junkyard dog 3 link (with some sweet stickers!!) and torque box re-enforcement
  3. bypass inertia switch
  4. replace fluids
  5. big rear view mirror
  6. cool shirt
  7. install radio
  8. box in the radiator and cut some cooling vents in the hood
  9. window net
  10. steering wheel quick release
  11. grip tape on drivers side floor
On the I really want to but no way I'm getting to it
  1. lower and stiffer springs. Ebay SR performance $61.
  2. adjustable shocks. founds some tokico spec d ones at u pull it. $40.
  3. steering rack bushings, inner tie rods, outer tie rods / bump steer kit, ball joints, hubs & bearings
  4. 13 inch cobra brake upgrade in the front, new rotors and pads in the back
  5. front brake cooler ducts
  6. strip out unnecessary junk from wiring harness
  7. Remove AC compressor
  8. new hoses and double clamp them all
  9. u joints
  10. MM pan hard bar - gave up on diy.
  11. box in lower control arms
  12. remove smog stuff and tune
 

TMO Supporting Vendors

Buy TMO Apparel

Buy TMO Apparel
Top