When to upgrade diff. and rear 11-14?

Discussion in 'Mustang Chit Chat' started by skaarlaj, Jan 31, 2018.

  1. skaarlaj

    skaarlaj Probie Former Pink Bus Rider

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    I'm wondering when auto coyote cars start seeing broken parts at the drag-strip with their stock differentials, and axles. On one hand, the shock to the rear in an auto car is probably next to nothing compared to a stick car, and the S197's all at least had 31 spline stuff from the factory instead of the 28 spline stuff from earlier generation Stangs. On the other hand it's always cheaper to upgrade instead of fixing broken parts and upgrading at the same time.

    I'm of the uneducated opinion that I'd be good with the stock rear axle internals until a trans-brake shows up in the picture, or single digit ET's start becoming a true possibility? When/if that day comes I know I liked the Trutrac diff that I had in my 04 Cobra, and would staying with 31 spline axles, but using aftermarket replacements be good enough? Thanks all.
     
  2. Juice

    Juice forum member

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    The 8.8 is a pretty tough rear. Run it till it breaks, then its time for a 9" rear swap.
     
  3. redfirepearlgt

    redfirepearlgt forum member

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    running 10.8's to low 11 teens and have never had an issue. 60 ft 1.6-1.7 so it's not really hitting the tires hard. The stall converter upgrade should bring that down hopefully. Most guys I know running 2005 up (same 8.8 for the most part) don't worry much until getting into the 1.4 60 ft range. For safety sake, I did weld up my axle tubes, but that was a preventative measure for ease of mind. at my level most don't even do that until much deeper into their 60 ft and lower 1/4 et's.
     
  4. Pentalab

    Pentalab forum member

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    This is what I used on my 2010 auto. 31 spline eaton tru-trac. http://www.vmpperformance.com/Eaton-31-Spline-TrueTrac-Differential-for-05-14-8-p/dts-913a561.htm 3 pinions per side. Zero issues, works superb, maintenance free. 3.5:1 bias ratio. In normal operation, it's totally transparent. The eaton is 1/2 the price of the 13/14 GT-500 LSD.

    This version uses FOUR pinion gears on each side and a stronger box, and is the beefed up 33 spline version.... which requires new 33 spline axles from Strange engineering or Moser. http://www.vmpperformance.com/Eaton-33-Spline-TrueTrac-Differential-for-05-14-8-p/dts-913a701.htm

    I did however, use a bob's auto sports catch can on the rear axle. http://shop.bobsautosports.com/Mustang-2005-14-axle-reservoir-KR-style-axle-reservoir.htm Built like a tank. Plenty of hose included, to allow for full suspension droop, when car is up on a 2 post lift.

    Don't even mess with rebuilding the oem LSD, with either oem clutch plates, or the GT-500 carbon fiber clutch plates. Both are junk, and the CF will just eventually melt. You will just end up with a repeat failure over and over.

    If you plan on a rear gear swap, then do both items at the same time.
     
    raredesign likes this.
  5. Wes06

    Wes06 forum member

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    Ive heard of the 31 spline diff breaking at drag strips, granted its probably better to use lockers or such at the strip than a gear diff, i dont believe ive heard of the 33 spline diff breaking in the same manor
     
  6. Pentalab

    Pentalab forum member

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    VMP sez they have the 33 spline version of the tru trac on their 2011 auto, which runs in the 9's and cuts a low 1.3 for a 60' time.

    I read someplace that the Strange engineering axles were stronger than the moser version. The strange eng version was slightly less expensive.
     
  7. raredesign

    raredesign forum member

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    Nice. Does that Bob’s Auto Sports catch can replace the vent that sometimes get’s clogged in the rear? If I understand what it says on that page, rather than vent to ground, it vents upward to the can. That is a great design!

    Do you think the Eaton 33 spline truetrack is a good option compared to the Detroit Locker? The DL is just an enhanced version right? This Eaton looks great since it has normal operation, but without discs...impressive.
    I really should pick one of these up as I hope to have my 1000hp build done this summer, and was only planning on replacing carbon fiber discs every time they burned out lol.


    Sent from my iPad using Tapatalk Pro
     
    Last edited: Feb 4, 2018
  8. Pentalab

    Pentalab forum member

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    This shows how the eaton tru trac works. It applies tq to the wheel that has the most traction. The max tq that can be applied to one side is 3.5 times the opposite end. Dunno if the 33 spline version would be suitable for a 1000 rwhp setup.
    With a 1000 hp eng, A 9" rear end would be the ticket and probably a conventional locker. VMP is running some crazy high rwhp on their setups with the 33 spline versions..which of course also require the mating 33 spline axles....and the oem 8.8" rear end.

    For run of the mill street use, auto X, road course, and strip use, the tru trac works superb. Dino oil used, no synthetics and no friction modifier additives used. It requires friction to operate.

    The axle catch can hose..attaches to the oem vent. Vent is on pass side on the 05-10 cars....and on the driver's side on the 11-14 cars. Without the catch can, u end up puking gear oil all over the axle, then to the ground. There is hardly any gear oil in there to begin with, something like 3 qts..and that has to also lube both axles and LSD differential..and crown + pinion rear gears.

    With either the Torsen LSD, or the eaton tru-trac LSD, you don't require a differential cooler either.
     
  9. RED09GT

    RED09GT Senior Member

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    The stock diff usually dies due to a dead hook. Spider gears or an axle tube are usually the first to go. The axles themselves are pretty tough.

    I
    damaged my gearset when my spider gears died. I went with the Yukon Grizzly locker, it is an updated version of the detroit locker. It is not for the faint of heart, it is noisy, kinda klunky, not easy to use in a parking lot, but is tough as nails and makes launches consistent.
     
  10. raredesign

    raredesign forum member

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    Thank you Pentalab and RED09GT for the great info. Much appreciated.
     
  11. Sky Render

    Sky Render Stig's Retarded Cousin

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    Here's a whole article on the Eaton TrueTrac:
    http://www.motoiq.com/MagazineArtic...art-5--Putting-the-Power-Down-with-Eaton.aspx

    You don't want a locker on anything driven on the street, in my opinion. A locker works by "locking" both rear wheels together when power is applied. Great for perfect launches at the drag strip, not so much for turning into a parking spot.

    The OEM "TracLock" differential (on GTs, '11+ V6s, and most GT500s) uses clutches to distribute torque to both wheels. The advantage of the clutch-type diff is low NVH, but the problem is that clutches wear out and have a low bias ratio. Theoretically, if you use that TracLock once, it has a reduced bias ratio because the clutches have already started to wear out.

    The BOSS 302s and older FR500s come with Torsen diffs, which distribute power using worm gears. The T-2R has the highest bias ratio of 4:1. However, it is rather spendy at around $1,000 for the unit and has known longevity issues when used for anything other than corner carving (such as launching on slicks at a drag strip).

    The Eaton TrueTrac has a high bias ratio of 3.5:1, is half the cost of a Torsen T-2R, and is pretty dang sturdy and low-maintenance. Only disadvantage is increased NVH during deceleration.
     
  12. Pentalab

    Pentalab forum member

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    Your 4 page article was superb. And for folks that want to run crazy power, the 33 spline version is not much more $, albeit requires 33 spline axles. At that point, the axle tubes should def be welded.
     
  13. skaarlaj

    skaarlaj Probie Former Pink Bus Rider

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    I actually had the Tru-Trac in my SRA 04 Cobra, and it worked great. If there was an increase in noise or vibration, I didn't notice it at all on that vehicle. Definitely a thumbs up on that diff, and not having to find, or run that stinky friction modifier is also a benefit as apposed to the clutch style diffs as well.
     
  14. Sky Render

    Sky Render Stig's Retarded Cousin

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    You're even supposed to use standard (not synthetic) oil in the diff, too.
     
  15. Juice

    Juice forum member

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    Clutched diffs are not bad. My 91 has over 170,000 miles on the factory original diff. Still works great, no "one leggers". I did get several fluid changes due to gear changes over the years finding the right gear ratio for WGI.
     
  16. Sky Render

    Sky Render Stig's Retarded Cousin

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    Go spend a season autocrossing or doing track days and then come back and report. Clutch-type diffs wear out VERY fast when accelerating out of corners.

    Having a lower-torque motor, an automatic transmission, or using higher gears can prolong the life of the factory TracLock, but even the carbon fiber clutches found in the later GT500s can lose a substantial percentage of their bias ratio after a single track day.

    Guys in SCCA who are limited to using factory parts actually replace their clutch packs after every single autocross.
     
  17. Juice

    Juice forum member

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    Been open tracking that car since 2000. Diff works just fine. You actually want more of an "open" diff when going around corners.
    I've been open tracking that car since 2000. Thousands of track miles on the fox. For turning you actually want an Open diff. (Turn in, and mid corner maintainance throttle).

    Even a brand new clutch type diff will do one leggers under certain conditions. (one wheel on slick surface like ice or oily pavement) This is why the torsen is the ideal diff. Behaves like an open diff when needed, and puts the power down to the wheel with traction.
     
  18. Sky Render

    Sky Render Stig's Retarded Cousin

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    You have absolutely no idea what you're talking about, do you?
     
  19. Pentalab

    Pentalab forum member

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    The torsen / eaton tru trac puts the power down to the outside wheel, when flying around corners. The carbon fiber clutch plates on the GT-500... melt, pita. The eaton tru-trac just runs and runs and runs, zero maintenance item, just use the correct oil..and install it correctly. Install it once, then forget about it. The rear axle catch can is a must item though, regardless of what LSD you use. You don't require a differential cooler with either a eaton tru-trac nor a torsen.
     
  20. Juice

    Juice forum member

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    I guess you would want to road race or autocross with a spool rear then. Try that.
     

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