Why does my $5K diff/rear end setup not lock when lifting a tire? - Miata Turbo Forum - Boost cars, acquire cats.

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Old 09-14-2016, 01:35 AM   #1
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Default Why does my $5K diff/rear end setup not lock when lifting a tire?

Literally the only reason I bought an OS Giken was so I would never get stuck when driving up steep driveways, or in the backcountry roads.

The lifted wheel just spins. I'm still getting stuck. I wasted 3k in parts and 2k (not including new axles, seals, hubs or bearings) in labor for nothing.

I guess I just assumed the best diff for a miata would actually lock, but, yet again... I am idiot.

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Old 09-14-2016, 04:34 AM   #2
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My understanding is without Lsd my mx5 loses 75ish % power when a wheel spins.
Somehow your magical Lsd still provides the grounded wheel with its power. But the other wheel still spins?

Again I don't have Lsd.
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Old 09-14-2016, 04:49 AM   #3
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Quote:
Originally Posted by thumpetto007 View Post
Literally the only reason I bought an OS Giken was so I would never get stuck when driving up steep driveways, or in the backcountry roads.

The lifted wheel just spins. I'm still getting stuck. I wasted 3k in parts and 2k (not including new axles, seals, hubs or bearings) in labor for nothing.

I guess I just assumed the best diff for a miata would actually lock, but, yet again... I am idiot.
Sounds like a torsen, even my old worn out clutch type didn't act this way before I rebuilt it so a new OSG should definitely not. And yes, that is the most annoying feeling, tripoding a curb and having one tire free wheeling

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Old 09-14-2016, 06:42 AM   #4
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A limited slip, is just that. It limits slip. It is not a locked differential. I'm not sure what the torque split numbers are for your diff, but you are exceeding it, sounds like. A really steep hill with lots of traction and one light tire, that puppy will spin.
My understanding with the OS, was that it is a more controlled diff. It has different ratios of tire controll when accelerating and decelerating.

Am I wrong on these points
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Old 09-14-2016, 07:14 AM   #5
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IIRC a clutch diff will act as an open with one tire stuck in the mud. You'll have to provide enough force through accel to push on the clutch plates to send power to both wheels -- so the one tire in the mud will still spin, but now equal power is being sent to the other tire.
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Old 09-14-2016, 07:25 AM   #6
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From the OS website...
Superior Overall Performance

- The OS LSD standard spec allows for low preload while still retaining a fully progressive 100% lock capability; basically, the vehicle will feel like driving on an open diff in slow turns / street driving, but can still transmit maximum power to the drive wheels under load.
- Operation is ultra quiet, and the progressive locking allows for smooth, predictable locking. Especially when replacing an open diff, equipping OS LSD will completely improve the driving experience while maintaining everyday drivability.
- Due to the precision manufacturing, high-grade materials, and unique design, a break-in period nor rebuild is required for OS Giken LSD’s. OS LSD is purposefully over-engineered to offer the best performing, most durable clutch-type LSD available.
- Aside from the performance advantage and stock-like feel at slow speeds, vehicles equipped with OS LSD are more stable in all road/weather conditions, allowing for a safer driving experience.

Tunability

- Initial torque can be adjusted by using thicker / thinner cone springs
- Lock progression timing can be adjusted by using stiffer / weaker pressure ring springs, allowing the progression of full lock to be fine-tuned to the vehicle/driver.
- Ramp angles can be customized by swapping the pressure ring and iron cross for even more tuning possibilities.
- TCD spec disks can be installed for increased oil cooling and even smoother operation.


Sounds like:
A. Low speed situation like yours, it won't do much.
B. There is room for tuning and improvement.
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Old 09-14-2016, 02:37 PM   #7
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Another defective part. A VLSD should be able to tackle that task, wanna trade?
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Old 09-14-2016, 02:41 PM   #8
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I have an OSG in Acamas that doesn't do that. Yours is broken. Jack up one rear corner, set the e-brake, and put the car in neutral. Take a torque wrench to the center axle nut with the wheel off. Measure the torque required to turn the wheel. Take that measurement, call OSG or whoever you bought your diff from, and ask them if it sounds right (it probably won't).

I did this early on to Rover's OSG - never figured out why, just popped the diff out and sent it back to OSG for them to freshen up. Diff shop charged me ~$100 to reassemble since they didn't have to re-set pinion depth.

e: see below for less derp

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Old 09-14-2016, 02:53 PM   #9
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Quote:
Originally Posted by Savington View Post
I have an OSG in Acamas that doesn't do that. Yours is broken. Jack up one rear corner, set the e-brake, and put the car in neutral. Take a torque wrench to the center axle nut with the wheel off. Measure the torque required to turn the wheel. Take that measurement, call OSG or whoever you bought your diff from, and ask them if it sounds right (it probably won't).

I did this early on to Rover's OSG - never figured out why, just popped the diff out and sent it back to OSG for them to freshen up. Diff shop charged me ~$100 to reassemble since they didn't have to re-set pinion depth.
Wouldn't setting the e-brake totally mess with the required torque to turn the wheel?
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Old 09-14-2016, 03:04 PM   #10
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Yeah, you'd want a way to hold the other wheel without interrupting the wheel with the torque wrench on it. Maybe someone with a breaker bar on one axle shaft, and a torque wrench on the other. That's what we would do for our cam and pawl for FSAE.
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Old 09-14-2016, 03:13 PM   #11
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Quote:
Originally Posted by aidandj View Post
Wouldn't setting the e-brake totally mess with the required torque to turn the wheel?
Derp, yes. You would need to remove the brake rotor and caliper, re-insert the rotor in the caliper, then set the ebrake.
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Old 09-14-2016, 04:29 PM   #12
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I would just leave one wheel on the ground and jack the other one up.
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Old 09-14-2016, 07:21 PM   #13
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Quote:
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Another defective part.
Is this true? 949racing better be prepared to reimburse the labor too. That **** cost more than the diff itself.
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Old 09-14-2016, 09:56 PM   #14
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In various scenarios, I have lifted the passenger corner or the driver corner tire, both of them spin, and barely any power goes to the tire on the ground. I even got stuck again. Had to push.

There are few feelings worse than spending multiple 10's of thousands of dollars to make each aspect of a car the way I want it, but none of it worked the way I wanted.
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Old 09-15-2016, 07:06 AM   #15
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install an AWD system into your miata.
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Old 09-15-2016, 07:47 AM   #16
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Not sure what one you purchased, but the site says that it IS adjustable. Maybe it is in a very light setting. It also says that at low speed, it will act like an open diff. How fast are you driving up these rutted out embankments?

I have just the factory LSD, and although it made a difference, I can absolutely still get stuck turning around on a small rise in my grass backyard, when the car is light on one side. Not the same as an OS, but not a world apart either.
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Old 09-15-2016, 08:09 AM   #17
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Did you buy the OSG from 949?
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Old 09-15-2016, 08:35 AM   #18
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Quote:
Originally Posted by Braineack View Post
install an AWD system into your miata.
A badly tuned setup with too many adjustable parameters will still be stranded with only one wheel spinning...

Paying full price for the labor of adjustments of the diff will require a well described working order with all the procedures and before/after test values etc.
If not it will only be very expensive oil changes.
The knowledge needed to tell someone else do the right thing is not insignificant.

Was the torque tested during installation and what is it now?
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Old 09-15-2016, 09:28 AM   #19
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Why dump an ***-ton of money on an OS GIKEN just to get up your driveway when a TORSEN will drive uphill with a lifted wheel all day?

I've done it a couple times, especially going in/out of a driveway with a deep raingutter at the road - if the tire lifts, then engage the e-brake about halfway and continue driving through your obstacle.

If the 4x4 guys saw a bone stock Miata doing this, they'd probably crap their pants - "OMG SPORTZ CAR HAZ LOCKERZZZ!"
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Old 09-15-2016, 10:09 AM   #20
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the giken will probably work in the same manner, just needs a bit of torque to engage the clutch discs which sends power to both wheels.
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