Bench Racing: LSD When None's Available?

So say you have an imaginary FWD car. Said car isn't much loved for anything, and has zero aftermarket support. Then say, "Hey I want to build this unloved car into a insert motorsport car." Said car is probably going to need LSD in its transaxle's gear box to make it do what you want in that motorsport.

So what do ya do, how do you do it, and here's the catch, how do you do it on a challenge budget?

Anyone seen/heard of machining the carrier to fit clutch packs?

Take a bunch of measurements, then start disassembling transaxles at Pick-N-Pull in search of that needle in a hay stack that might work?

Welding the spiders isn't really an option.

Talk amongst yourselves.

• Lee

Find a similar unit, and drop it in?

Pull the existing diff, measure everything you can. E-mail measurements to Quaif, Torson, etc etc and ask what they have that is close. Either that or call phantom grip.

Does Phantom Grip have something that could be adapted to said imaginary, unloved car?

What you do is come here and tell us what make/model/trim the car is and if you can, the part number for the transmission. Then the Hive will use it's group think to reference all known parts bin compatibility options to explore and make suggestions. It may involve pick-n-pull dissection/exploration, but I'd be amazed if we couldn't help point you in the right direction.

sooooo, go.

Weeeeellll...

Not the voice of experience, but a few things that spring to mind:

• Seems more likely to find a junkyard LSD which can be adapted/machined to fit this trans than building non-LSD into LSD by adding clutches (I could be wrong about that)(EDIT: Boy am I wrong about that! Phantom Grip, huh?)
• Lots of stuff is related to lots of other stuff. Challenge conversations always end up being really abstract because people don't want to give away what they're working on, but there's a lot info there that may clue people into what else is likely to share a gearbox, or even just gearbox origins suggesting shared measurements for ring gears, bearings, etc...

Something like this?

http://forums.probetalk.com/showpost.php?p=1924133431&postcount=2

Or.... think about swapping a trans from a different car onto it?

I thought phantom grips were complete and utter garbage.......

yamaha wrote: I thought phantom grips were complete and utter garbage.......

They're like a phantom.

What's it for?

There's usually some crossover. For example, apparently Series 4 RX-7 and '94-up Miata rear diffs will work in a Ford ZX2 trans as long as you don't mind having no speedometer.

yamaha wrote: I thought phantom grips were complete and utter garbage.......

I've heard this, but I've also heard of them working with some tweaking. You definitely need to change the trans fluid often though.

As far as mods, many people use different springs with them, and I've heard of some machining down the block slightly and putting a motorcycle clutch disk in as a wear-surface.

You split the brakes left/right into 2 channels and when one wheel spins faster than the other you apply the brakes to that side to transfer power to the other wheel.

One might use the signals from the ABS sensors, a repurposed ABS pump and an arduino.

Giant Purple Snorklewacker wrote: You split the brakes left/right into 2 channels and when one wheel spins faster than the other you apply the brakes to that side to transfer power to the other wheel.

So... new Focus ST, but manually with two brake pedals to be operated with your left foot? I like it.

Swank Force One wrote:

Giant Purple Snorklewacker wrote: You split the brakes left/right into 2 channels and when one wheel spins faster than the other you apply the brakes to that side to transfer power to the other wheel.

So... new Focus ST, but manually with two brake pedals to be operated with your left foot? I like it.

BMW 135i's do this to fake an LSD so there is a controller out there to take care of it... might be easier to roll your own than to interface theirs though,

In reply to Swank Force One:

why limit to L/R? go whole hog and 4 small pedals arranged in a small grid! independent brakes each corner!!!

yamaha wrote: I thought phantom grips were complete and utter garbage.......

They're better than nothing and can work ok with the stiffest springs they make.

Giant Purple Snorklewacker wrote: You split the brakes left/right into 2 channels and when one wheel spins faster than the other you apply the brakes to that side to transfer power to the other wheel. One might use the signals from the ABS sensors, a repurposed ABS pump and an arduino.

Use a steering angle sensor to give the system some ESP and it can pre-brake the inside tire for you.

Use 2 electric motors, one on each wheel. Instead of braking the inside wheel, regen-brake to slow it down, but transfer that power instantaneously to the motor on the outside wheel. Less heat, more power.

Get a few other people with said FWD car with no support and call up Mfactory. They made some for Saturns... I can't believe there are many FWD cars with less support.

ProDarwin wrote:

Giant Purple Snorklewacker wrote: You split the brakes left/right into 2 channels and when one wheel spins faster than the other you apply the brakes to that side to transfer power to the other wheel. One might use the signals from the ABS sensors, a repurposed ABS pump and an arduino.

Use a steering angle sensor to give the system some ESP and it can pre-brake the inside tire for you. Use 2 electric motors, one on each wheel. Instead of braking the inside wheel, regen-brake to slow it down, but transfer that power instantaneously to the motor on the outside wheel. Less heat, more power. Get a few other people with said *FWD car with no support* and call up Mfactory. They made some for Saturns... I can't believe there are many FWD cars with less support.

Mazda MX6s would like a word with you.

But yeah... contacting MFactory with a group buy proposal probably isn't a bad idea. I've seen them go through with 15-25 guaranteed unit sales.

Giant Purple Snorklewacker wrote: You split the brakes left/right into 2 channels and when one wheel spins faster than the other you apply the brakes to that side to transfer power to the other wheel. One might use the signals from the ABS sensors, a repurposed ABS pump and an arduino.

You just described an "e-diff" which is fairly common on modern cars.

I know a guy who put a Phantom Grip in a Toyota C6x-series transaxle, he said it worked decently for drag racing.

Your MX6 is much better loved than the old Elantra. So stuff it.

My first instint: Weld the spider gears.

Bobzilla wrote: Your MX6 is much better loved than the old Elantra. So stuff it. My first instint: Weld the spider gears.

On a FWD car? I'd only do that if it's for drag racing, not street driven, and you have an air jack in the rear with a caster on it to make it easy to turn.

Swank Force One wrote: Mazda MX6s would like a word with you. But yeah... contacting MFactory with a group buy proposal probably isn't a bad idea. I've seen them go through with 15-25 guaranteed unit sales.

I feel sorry for MX6 guys. But then I don't, because your motor can make power, while the Saturn motor assplodes at like ~225hp.

FWIW, the MFactory Saturn buy in was 10 people.

another MFactory vote, they'll also do custom R&P's if you'd like to shorten the gearing. (Until 3D printing in metal becomes 10000x cheaper at least)

What kind of price is MFactory? I fear that something custom from them would blow a Challenge budget.

The Phantom Grip is interesting. So they don't actually use any friction material, just their plates rubbing on the spider gear?

Actually had a similar idea to Phantom Grip while day dreaming, though I was replacing the pin that the two non-axle spiders are on, instead of encapsulating it like Phantom Grip does.

My hair brained idea:

Black = New Spider Pin/Plate hybrid thingy
Green = Springs
Gray = "Pressure Plates"
Red = Friction Material
Blue = Axle Spider Gears

So it could be simplified with keeping the spider pin, and doing like Phantom Grip's design, so less parts for the LSD.

I mean I do have a HF X2 Clone Mini Mill, so "I can build anything!"
Plus I could be a shoe-in for the "Most Spectacular Failure," if nothing else.

I knew this was the right place to ask.

• Lee

Mfactory stuff isn't challenge friendly. It's very well-priced, but a diff through them still runs in the $800-$900 range.