landstuhltaylor

iTrader: (6)

Broke an Auburn Racers differential this weekend, it had 7 days of autocross on it. I have been fighting wheel hop under braking which I think did all the damage, as well as the rear suspension binding over bumps and causing the car to skip over parts of the course. I'm hoping if I fix these issues the next one should last much longer. It has never seen any wheel hop under accel

Relevant info:
LS1/T56
Intake/exhaust/pulley/tune
Quartermaster Optimum RR clutch (7.25" twin disk)
Aluminum rear LCA, decoupled torque arm and Watts link
Solid pinion spacer and TA diff cover
Auburn 542088
Motive orange box 3.42 gearset
315 Hoosier A7
3350lb race weight





And here is the cars final runs. Binding suspension in the beginning of the clip likely put the nail in the coffin, broke on the 2nd run after that. It has been hopping in every brake zone with a decent bump so I will be taking care of that first and foremost. Video in link

FirstYrLS1Z

iTrader: (4)

Campell's Chunky soup.
How many miles on it ?
The Auburn cone clutches appear to be worn out past their service life. That's what causes spider gear destruction. As the cone clutches wear,the springs push them further into the carrier,as they go further into the carrier the spiders move apart also(as they're part of the cone clutches) and then the spiders are not running full tooth contact.Eventually just gear tips are contacting/meshing and the tips don't have the strength of full tooth mesh.

landstuhltaylor

iTrader: (6)

Under 1000 miles. Two 2-day ProSolos on concrete, two days of locals on concrete, and one local on asphalt so 37 runs total. It broke one tooth off the ring gear and none on the pinion. Might try conventional gear oil in the next one and not the Heavy Shockproof I was using. Great for lockup, not so great for wear. I was still able to drive it when it broke but it was functioning like a fully open diff and was clunky on tip in. I'm assuming the spider gears are what broke and then the debris took out the ring gear.

dailydriver

yes, but;

Do you drive this thing on the street at all??

If so, how does that racing style clutch perform in traffic, slow driving?

Can it be slipped at all, or is it the proverbial 'light switch' like most other small diameter, alloy cover, racing set ups?

79_T/A

iTrader: (1)

I have no idea how they got such a good recommendation, but an auburn racers diff simply does not work in one of these cars if you drive it hard. The cone clutches are too small in a 7.5" diff. They work for about a day of abuse and are gone. Then you get what you see here. Killed 3 in 3 years with a mix of HPDE, autocross, and a few light street miles. Tired of replacing them, just put a truetrac in my car.

landstuhltaylor

iTrader: (6)

I drive it to every event, whether that be 30 minutes down the road or 13 hours to Lincoln (although I'm trying to avoid that it's not looking good). Drove it to an event in the rain and it was impossible not to spin the tires starting from a stop on the random brand 225 street tires I use.

Bought the twin disk instead of the triple because it has a more heat tolerant clutch material. It chatters, it squeals, but it has also tolerated a traffic jam or two. Would be more street friendly with the stock master it is designed for but I am using a Tick unit. It became much more on/off when I made the switch. It's not what I would call fun, but pedal effort isn't that much more than stock it is easily doable for something that's not daily driven. Would not recommend it unless you really wanted that last little bit though. Extra cost was worth it for me due to the 30lbs off the nose.





It's in this so frankly I don't give two ***** about street manners.

landstuhltaylor

iTrader: (6)

If I break another one, that's what I go with next. Going to give the DREX program a shot at least once. I definitely had setup issues that contributed. Fixing the binding of the rear bar, adding a proportioning valve with weaker rear pads, and switching to the Penskes should help. I'm planning yearly replacements before nationals every year so as long as it doesn't explode again I'm OK with it.

79_T/A

iTrader: (1)

If replacing them doesn't bother you, then go for it. They work pretty decent until the clutches burn up. Unfortunately for us with a 7.5 diff, that happens pretty quickly, and the way auburn designed the unit, it can't be serviced by the user. I'm sure the same diff for something like a ford 9 would be much better and have a longer life.

You can try a mineral oil, but I would still look for one made without the friction modifier. You won't be happy with the performance if friction modifier is used. It allows the clutches to slip more, I was getting a little bit of inside wheel spin, and it beat the clutches up even more because of constant slipping.

What's your braking setup if you are still getting hop under braking with that torque arm. We run a very similar setup, and my car rarely hops even with race pads in the rear. You have to crank a lot of preload into the brake link. Should only de-couple about 1/4 inch.

landstuhltaylor

iTrader: (6)

Preload was going to be my next thought. It is decoupling a lot more than that, the zip tie was more than half way down when running on concrete, so I will tighten it up. Current and future setup is below. I'm not convinced the brakes are the issue so much as the shocks. I put too much rebound in the 3rd gen Konis and it was causing lots of issues over any kind of bumps. Combine that with a sway bar link that backed off ending up with ~1/4 inch of clearance to the housing cover at ride height, and it was bound to be a nasty ride.

I spun the hell out of this diff everywhere, partly due to setup. I'm going to start conservative on this next iteration and dial it up as far is I can. It may end up with the HP+ in it by then end, but I would rather start low. I was already going to pickup a second GoPro so I'm going to use the old one to get a better idea of what the rear end is doing under load. As long as it doesn't explode again a ~$150 rebuild every season is no big deal. As long as I try to chase a jacket in ESP I'm stuck with making this pile of crap 10 bolt work for me.

Before setup:
800/400lb spring
35mm solid, 22mm adjustable
Koni singles, 3rd gen rear (tried many settings, they just don't work for what I need)
98 DTC-30, 94 HP+
J&M aluminum LCA
Watts link
Motive orange box 3.42
Solid pinion spacer
TA diff cover
Auburn Racers Differential
Blainefab spoiler towards the end

New:
1200/550lb springs
Penske 7500/8300 by Jason at UBE
Rod ended rear bar links
SJM brake bias valve
DTC-30/parts store premium

dailydriver

It might be because Sam has suggested them due to their D-REX replacement program, and not much else being available for the 10 bolts, save for what you're using, and the Eaton Posi I am using.

I am guessing that neither Wavetrac, NOR Quaife will EVER make anything for these weak, obsolete, 'out of print' 10 bolts (and yes, I DO remember the 10 minimum group purchase that one fraxx member tried to get going for the Quaife diffs a few years ago).

dailydriver

That thing sure is PURDY!
And the car is cool as well, with that sweet Blaine Fab spoiler and Penskes on it !
(How many f bodies have PENSKE dampers?!?! )

But yes, I will probably be going with the 38 lb. Ram dual disc/aluminum flywheel street set up next, since this is my ONLY car at the moment.

landstuhltaylor

iTrader: (6)

I did talk to OS Giken and they said they do make custom pieces. Pricing would be for a minimum of two units at $2500 each, which isn't that bad considering how much a normal one costs. Doesn't seem like it would be worth it for something that will break though.

landstuhltaylor

iTrader: (6)

It's more so I hate losing, and losing costs money. The car has had the raw pace to win both national events it's been to, but unfortunately it hasn't happened yet. Toledo the car was fast Saturday but I found out the hard way fuel starve is at 3/8 tank, then the diff broke before I could put in a time. The car feels like an oxcart over bumps right now and it's almost impossible to find a set of Koni Yellow doubles unless I bought the remaining new ones I've found ($1400), and then I would likely have them revalved. That's already the cost of race Bilsteins and the extra cost of Penskes seemed like an easy choice for their quality, weight, and adjustability.

That and every time I don't win I lose out on $760 worth of Hoosiers.

dailydriver

OUCH!

Quaife was only asking ~$975.00 or so, but for a 10 or 20 minimum order, so for the R&D OS G would have to do for that low production number, I guess that IS a 'fair' price.

I wonder what a 10 order, group buy would cost from Autotech/Wavetrac??

The OS Gikens are a MANY MANY MULTIPLE ring, carbon clutch pack diff (MANY times more than my Eaton) with a big pre-load on them, correct?

landstuhltaylor

iTrader: (6)

Not sure on the details of the OS Giken, but for most platforms it's already in the $1800-$2000 range.A 25% upcharge for a custom unit is more than fair in my eyes. A good majority of the front running cars that can have them do, but I think a big part of that is the ability to tune them to each customers needs and preferences.

I only talked briefly to Lugod since he works there and is a fellow autocrosser, but he said it should last 10+ years with regular fluid changes (they warranty only their own fluid at $50/liter). I know he isn't familiar with the 10 bolt in our cars so I'm not sure how accurate that information would be. I assume there aren't any gears to break though, just clutches to wear out.

The boost buggies were kicked out in 2015, something I did not agree with. Competition is basically all Mustangs with the odd G35 or other things thrown in. The local national events are usually a mix of 08 Shelby GT, a GT500, Boss 302, and 2015+ GTs (which I think will dominate far and away once a top tier driver is in one).

2QWK4RU 06 GOAT

iTrader: (1)

The wavetrac has been structurally sound in other small gear applications. Haven't seen any break, that might be a good move. Just make sure if a company decides to build, they get the tolerances correct .

dailydriver

Yes, I looked at the rules again after posting this and realized that the Nippon rally meisters were no longer in E/SP, but most of those other rides still in the class are no slouches either!

I've seen that Giken gear oil for up to $75.00 a liter!

79_T/A

iTrader: (1)

If you think the price on he giken oil is bad, the smell will give you nightmares. Don't know what they put in it, but you can smell it through the metal bottle it comes in. Gear oil doesn't bother me, but that stuff will test your gag reflexes.

I wouldn't bother spending big money on a high end diff like that. The root issue is the size of the diff. Simply too small to handle the power and traction of a properly set up - and driven hard- 4th gen. Can't expect anything to last when it's so undersized for the application.

landstuhltaylor

iTrader: (6)

I've been seeing some numbers of what the 5.0s are making in ESP trim and combined with the gearing the days of the 4th gen being on equal terms are over. I'm not going to spend big money on a diff for this car. I'd like to campaign it for a few years in ESP, hopefully at the very pointy end of the field, while saving for a 9". At that point with just a mild heads/cam setup and some easy weight reduction the car would be very competitive in CP and to a lesser extent SM right out of the box. If I added some ballast and picked up street tires it would even be a good CAM car as well.

In the mean time, a working rear suspension should make the next diff last quite a bit longer than this one did.

Chris Paveglio

iTrader: (2)

At a recent local/semi regional AX event, a good driver in a new Mustang GT 5.0 crushed the other 3 of us in ESP by 4 seconds. That includes some pretty good nearly-national level guys in a 05 or 06 Mustang, and me in my 4th gen TA with all the allowed parts, on hoosiers. Just can't compete with the new 'stang that has +85 hp over me (tuned even), 3.73 gears, and IRS.