Ebay Progressive Limited Slip Differential

[jp5Touring]

The shop I help out has made those before for DSM's Eclipse,Talon's.

My understanding they worked pretty well.  IIRC they where like $195.    

Hmmmmm

[323IJOE]

I'm interested in these too, been looking for a reasonably priced LSD lately. When I started my build they were going for around $300, kicking myself now for not getting one then.

 

those who ordered already give us an update when they come in 

[2joejoe2]

This is probably obvious to everyone.....since this is not original carrier to to the diff you are putting it in it will probably require some shimming to get the correct backlash....

 

I looks to me like this kit works by creating a friction surface between the spider gears....am I right?  Seems kinda sketch...will it just wear out the surface of the spider gears over time? 

[jwill214]

The pictures show clutch disks so to speak. The spider gears in the diff should be a much harder material than the disks so it will wear the disks rather than the gears. At least that's how it should be...

[Dudeland]

Let's be realistic.  The diffs that we pull out of a wrecker will have questionable clutches at best.  If you get one rebuilt they will be 1000-1500$.  A rebuilt one will outperform one of these kits I am sure.  The fact is that most people don't rebuild them, they check the gears, maybe the backlash, new seals and away you go. I think that this will outperform a worn out LSD. 

 

I will let you know, as well as publish the install instructions. 

 

 

[midnightmotorsport]

Because there seems to be a lot of discussion here about merit without a lot of discussion about how an LSD actually works or what these inserts do...

 

Firstly, what does a clutch-type LSD do?  In (very) brief, it uses ramped clutch packs to apply pressure to your carrier side gears (the ones splined to your output flanges and thusly bolted to your axles), effectively "clutching" your axles to drive at the same rate.  The more your axles spin at different rates, the more the clutches engage to grip both axles together and force them to spin at the same rate...  The more one wheel spins, the more power is applied to the non-spinning wheel.

 

How do these inserts differ from a stock-style clutch plate LSD?  Position of the clutches!  A stock LSD carrier is built so that the clutch plates are outside the side gears, applying friction between outer sections of the lsd carrier... which is a big, heavy machined part with large friction surfaces that is engineered to take the force of the clutches pushing against them.  The side gears/output flanges/axles are splined into these clutch packs so they have the clutch force applied to them while the load of the clutches binding is taken up by the carrier, as it is designed to do:

 

 

Now, how do these LSD inserts work?

 

Well, they put the clutch packs inside the side gears, applying the clutch force against the faces of the differential side gears.  These gears have a much smaller friction contact surface, and are relatively small-and-not beefy, and not at all engineered for pressure to be applied to them in such a manner.  More to the point, there is not really any "set of clutches" with the insert, so any "drag" is created between the face of the gear and the metal of the insert, thus scraping the two metal surfaces against each other.

 

CAVEAT: This particular LSD manufacturer seems to have improved on this slightly, by adding a single "friction shim" between the metal insert halves and the gear face.

 

Nonetheless, this is still not a real clutch pack set, designed for wear as the friction/metal surfaces scrub against each other...  Your gears are not designed to do this, and you will wear away the "hardened" metal in the contact area (or the face of your side gears).  Shear stress is also applied to the center pin connecting your spider gears (which is actually what applies real ramped pressure to the "clutch" faces against the side gears as the carrier loads, not those little springs).  The center pin in an open differential is not designed for this load.

 

To quote Jack's Transmissions, a reputable manufacturer of FWD racing transmissions:

 

"It is common for people to want to install a cheap LSD in their FWD trans for better traction. You get what you pay for, the cheap insert type LSDs are terrible, don’t work, and have a very high failure rate.

The way the inserts work is they jam two steel plates in between the front diff spider gears. The plates are spring loaded and they put pressure up against the gears. Good idea, but the problem with this is you have a metal plate pushing against metal gears. Over time the gears will dig into the plate which will leave metal shavings in your trans. When they wear in far enough either the gears break (if you’re lucky) or the front diff pin can wear and break away from the diff housing with no where to go but through your trans case."

 

 

 

 

 

CONCLUSION:

 

Well, we do have one major advantage over the FWD guys who have typically tried these "LSD inserts" thus far...  Our differentials are isolated from the rest of the drivetrain!  So when your differential inevitably ends up with metal shavings through the gears and/or broken side gear chunks and a center pin floating around in there, you'll only grenade a cheap open differential, not your whole FWD transaxle.

 

The engineer can see where these inserts go wrong; they are creating stresses the open diff carrier was not designed to carry, and apply those stresses to parts never designed to be stressed in that manner.  They do so with parts designed to create metal-on-metal wear in a system full of tight clearances and bearings that do not like extra metal bits floating around.

 

BUT... the realist can see that OEM clutch pack LSD's are getting expensive as hell (I remember regularly buying good used LSD's for $100-$150), and open differentials are cheap as hell, and we have no definitive test of just how quickly these inserts will wear out diff parts and break.  The FWD world is full of horror stories, but also full of reports of people beating on these things with decent results.

 

SO...  Just be knowledgeable about what you are getting into.  We as humans do shit all the time that we know is bad for us, but acceptably so.  If you choose to install a cheap insert rather than a "real" LSD, you probably know in the back of your mind that it is not a real proper solution, but you also are probably doing so because you are not planning on racing, autocrossing, or otherwise beating the crap out of your car with that diff insert.  You are probably planning on installing it yourself, and thus you are only risking a small amount of money and your own time if/when the thing grenades.

 

But if you are planning to buy one and pay somebody like me to install it...  Well, for the money it would take to pay for your diff to be removed, disassembled, LSD bought and installed, and diff reinstalled (and then the whole process repeated again later when the differential insert breaks off some side gear teeth and it all implodes), well, you can probably afford to suck it up and get a "real" (OEM or Quaife) LSD.

 

Sorry for the long rant.  Don't let me talk you out of trying the insert (don't let me talk you out of a cheap eBay turbo either!), but please go into it understanding what the hell it is actually doing and what you are risking.  In this case, maybe the risk is moderate enough (and self-contained enough) to be worthwhile.  Or maybe it isn't.  But it is important to discuss these things in more depth than just "hey look it's cheap on eBay".

Edited January 24, 2018 by midnightmotorsport
grammar

[2joejoe2]

Its definitely clever 

[Dudeland]

12 minutes ago, midnightmotorsport said:

Because there seems to be a lot of discussion here about merit without a lot of discussion about how an LSD actually works or what these inserts do...

 

Firstly, what does a clutch-type LSD do?  In (very) brief, it uses ramped clutch packs to apply pressure to your carrier side gears (the ones splined to your output flanges and thusly bolted to your axles), effectively "clutching" your axles to drive at the same rate.  The more your axles spin at different rates, the more the clutches engage to grip both axles together and force them to spin at the same rate...  The more one wheel spins, the more power is applied to the non-spinning wheel.

 

How do these inserts differ from a stock-style clutch plate LSD?  Position of the clutches!  A stock LSD carrier is built so that the clutch plates are outside the side gears, applying friction between outer sections of the lsd carrier... which is a big, heavy machined part with large friction surfaces that is engineered to take the force of the clutches pushing against them.  The side gears/output flanges/axles are splined into these clutch packs so they have the clutch force applied to them while the load of the clutches binding is taken up by the carrier, as it is designed to do:

 

 

Now, how do these LSD inserts work?

 

Well, they put the clutch packs inside the side gears, applying the clutch force against the faces of the differential side gears.  These gears have a much smaller friction contact surface, and are relatively small-and-not beefy, and not at all engineered for pressure to be applied to them in such a manner.  More to the point, there is not really any "set of clutches" with the insert, so any "drag" is created between the face of the gear and the metal of the insert, thus scraping the two metal surfaces against each other.

 

CAVEAT: This particular LSD manufacturer seems to have improved on this slightly, by adding a single "friction shim" between the metal insert halves and the gear face.

 

Nonetheless, this is still not a real clutch pack set, designed for wear as the friction/metal surfaces scrub against each other...  Your gears are not designed to do this, and you will wear away the "hardened" metal in the contact area (or the face of your side gears).  Shear stress is also applied to the center pin connecting your spider gears (which is actually what applies real ramped pressure to the "clutch" faces against the side gears as the carrier loads, not those little springs).  The center pin in an open differential is not designed for this load.

 

To quote Jack's Transmissions, a reputable manufacturer of FWD racing transmissions:

 

"It is common for people to want to install a cheap LSD in their FWD trans for better traction. You get what you pay for, the cheap insert type LSDs are terrible, don’t work, and have a very high failure rate.

The way the inserts work is they jam two steel plates in between the front diff spider gears. The plates are spring loaded and they put pressure up against the gears. Good idea, but the problem with this is you have a metal plate pushing against metal gears. Over time the gears will dig into the plate which will leave metal shavings in your trans. When they wear in far enough either the gears break (if you’re lucky) or the front diff pin can wear and break away from the diff housing with no where to go but through your trans case."

 

 

 

 

 

CONCLUSION:

 

Well, we do have one major advantage over the FWD guys who have typically tried these "LSD inserts" thus far...  Our differentials are isolated from the rest of the drivetrain!  So when your differential inevitably ends up with metal shavings through the gears and/or broken side gear chunks and a center pin floating around in there, you'll only grenade a cheap open differential, not your whole FWD transaxle.

 

The engineer can see where these inserts go wrong; they are creating stresses the open diff carrier was not designed to carry, and apply those stresses to parts never designed to be stressed in that manner.  They do so with parts designed to create metal-on-metal wear in a system full of tight clearances and bearings that do not like extra metal bits floating around.

 

BUT... the realist can see that OEM clutch pack LSD's are getting expensive as hell (I remember regularly buying good used LSD's for $100-$150), and open differentials are cheap as hell, and we have no definitive test of just how quickly these inserts will wear out diff parts and break.  The FWD world is full of horror stories, but also full of reports of people beating on these things with decent results.

 

SO...  Just be knowledgeable about what you are getting into.  We as humans do shit all the time that we know is bad for us, but acceptably so.  If you choose to install a cheap insert rather than a "real" LSD, you probably know in the back of your mind that it is not a real proper solution, but you also are probably doing so because you are not planning on racing, autocrossing, or otherwise beating the crap out of your car with that diff insert.  You are probably planning on installing it yourself, and thus you are only risking a small amount of money and your own time if/when the thing grenades.

 

But if you are planning to buy one and pay somebody like me to install it...  Well, for the money it would take to pay for your diff to be removed, disassembled, LSD bought and installed, and diff reinstalled (and then the whole process repeated again later when the differential insert breaks off some side gear teeth and it all implodes), well, you can probably afford to suck it up and get a "real" (OEM or Quaife) LSD.

 

Sorry for the long rant.  Don't let me talk you out of trying the insert (don't let me talk you out of a cheap eBay turbo either!), but please go into it understanding what the hell it is actually doing and what you are risking.  In this case, maybe the risk is moderate enough (and self-contained enough) to be worthwhile.  Or maybe it isn't.  But it is important to discuss these things in more depth than just "hey look it's cheap on eBay".

 

You hit it right on the head.  No autocross for me, I just need a little more traction as I live in a place where it rains 65 days a year.  And talking of from a stop light I often am spinning one wheel.   This will help me with that.  Also the most HP I will be putting through this is about 120-140, so no large stresses here.  If I get 2-3 years out of the rear end, I will consider myself lucky.  It is old but still in ok shape, when it grenades I will be at the stage where a full FI stroker etc etc.. will be happening.  Until then a good shorter term solution. 

[ray_]

Dudeland, what tyres are you running?

 

My 13" Michelins hook up pretty well.

 

Cheers,

[jp5Touring]

I wouldn't worry to much about breaking that diff.  Agreed a LSD would be better,best.

The older DSM cars are turbo with quite a few putting out 500 whp,with very little tuning you can get 

250-300 whp.  Something that a 2002 won't be doing. That Jack's article is a bit sky is falling since they want you to buy their transmission. That design has a very low failure rate caused by lots of whp.   For the average 02  guy I think you'll be fine.

[AceAndrew]

I dealt with these type of units back in high-school drag racing club days (i.e. stock HP srt4's, 240sx's, mustangs, etc.).  Remember all the issues then, got to the point where we'd laugh if a new guy bragged about putting one in.  I guess time causes memories to fade.

 

As someone who goes through rebuilding a fair amount of differentials, I would not advocate the use of these.  "There is no free lunch."

[Dudeland]

44 minutes ago, ray_ said:

Dudeland, what tyres are you running?

 

My 13" Michelins hook up pretty well.

 

Cheers,

15" Crapolla brand from Shitco...   They were installed by the PO.  They are fine in the dry, but in the wet, they are sketchy, especially when I am doing a hill start. 

[ray_]

2 minutes ago, Dudeland said:

15" Crapolla brand from Shitco...   They were installed by the PO.  They are fine in the dry, but in the wet, they are sketchy, especially when I am doing a hill start. 

 

Well. There's your problem.

 

?

[Dudeland]

If I get into it in the dry, I will also get a one wheel dragger. It is a 75 so I think it is 373 or something close.  That with a 5 speed is geared pretty low. 

 

 

 

[TobyB]

Quote

Sounds too good to be true

 

You beat me to it, Patrick.

 

I would Lincoln lock a diff before running a center clamp...

 

oh, wait, I do.

 

t