LSD unit question
01-01-2012, 09:04 PM
#1
Thread Starter
LSD unit question
got my self a used LSD unit and in the process of taking it apart i notice something odd.. each side of the unit only has one internal splined (clutch material) disc, and 3 external splined discs. 2 external spline, then clutch disc, then external , then diff gears......
PET shows external, 2 internal, external.....
thoughts?
PET shows external, 2 internal, external.....
thoughts?
01-01-2012, 10:48 PM
#3
Former Sponsor
They "bounced" around quite a bit on what pieces they installed. Lots have two friction discs, but they are touching each other, without an outer lamina between them. The result is the same...there are only two friction surfaces touching outer lamina on each side.
That friction disc is completely toast. The moly coat is worn down so that the "peaks" are almost all gone and the surface is virtually worn flat. The next step is for that surface to start "smearing" the peaks and valleys together.
If you want to build a "better" limited slip, buy yourself 4 new inner friction discs, instead of just the two....from Porsche...or from someone that bought them from Porsche (do not use aftermarket friction discs....they are not of adequate quality.)
Assemble each side this way, starting from the "inner pressure ring" and working your way towards the outside:
Inner Pressure ring
Inner friction disc
Outer lamina
inner friction disc
Outer lamina
Spring washer
Start with 1.9 or 2.0 outer lamina pieces.
Assemble the entire unit, using a gear oil with the proper friction modifiers that work with this style limited slip. Mobil 1 LS is easy to get and ecconomical (Auto Zone).
Bolt the entire thing together. Install 6 temporary bolts and nuts (with washers on each side of the differential to not damage the surface where the ring gear sits), where the ring gear normally bolts (to make sure the unit is completely squeezed together.
Install a CV stub axle on each side. One stub will have two 10mm bolts (or studs) inserted 180 degrees apart. You will clamp these two bolts into a vise.
For the other stub, you will need to make a little flat plate that bolts across the flange with two 10mm bolts 180 degrees apart. In the center of this plate, weld a 17 or 19 mmm headed nut.
This nut will allow you to turn the limited slip with a torque wrench. measuring the amount of friction the unit has. You can turn it 20-30 times to get the inner friction discs to "settle" in. Now use a torque wrench to turn the unit. I think that the "ideal" friction, for new friction discs is right about 40 ft lbs. You can switch the "outer lamina pieces" to adjust this pressure. They come in 1.9, 2.0, and 2.1mm thicknesses. You should be close, if you assemble the unit like I described. If your pressure is very low, install new "spring" washers on the outside...they get "soft" over time.
If you don't understand, I can take some pictures of the flat plate with the nut all mounted in the vise.
I've got a couple of these things to "set-up", next week.
If you have any trouble finding any of the pieces, I stock all the pieces, multiple times over....including new prssure rings, inner friction discs, outer lamina (in all three sizes), spring washers, and thrust washers.
That friction disc is completely toast. The moly coat is worn down so that the "peaks" are almost all gone and the surface is virtually worn flat. The next step is for that surface to start "smearing" the peaks and valleys together.
If you want to build a "better" limited slip, buy yourself 4 new inner friction discs, instead of just the two....from Porsche...or from someone that bought them from Porsche (do not use aftermarket friction discs....they are not of adequate quality.)
Assemble each side this way, starting from the "inner pressure ring" and working your way towards the outside:
Inner Pressure ring
Inner friction disc
Outer lamina
inner friction disc
Outer lamina
Spring washer
Start with 1.9 or 2.0 outer lamina pieces.
Assemble the entire unit, using a gear oil with the proper friction modifiers that work with this style limited slip. Mobil 1 LS is easy to get and ecconomical (Auto Zone).
Bolt the entire thing together. Install 6 temporary bolts and nuts (with washers on each side of the differential to not damage the surface where the ring gear sits), where the ring gear normally bolts (to make sure the unit is completely squeezed together.
Install a CV stub axle on each side. One stub will have two 10mm bolts (or studs) inserted 180 degrees apart. You will clamp these two bolts into a vise.
For the other stub, you will need to make a little flat plate that bolts across the flange with two 10mm bolts 180 degrees apart. In the center of this plate, weld a 17 or 19 mmm headed nut.
This nut will allow you to turn the limited slip with a torque wrench. measuring the amount of friction the unit has. You can turn it 20-30 times to get the inner friction discs to "settle" in. Now use a torque wrench to turn the unit. I think that the "ideal" friction, for new friction discs is right about 40 ft lbs. You can switch the "outer lamina pieces" to adjust this pressure. They come in 1.9, 2.0, and 2.1mm thicknesses. You should be close, if you assemble the unit like I described. If your pressure is very low, install new "spring" washers on the outside...they get "soft" over time.
If you don't understand, I can take some pictures of the flat plate with the nut all mounted in the vise.
I've got a couple of these things to "set-up", next week.
If you have any trouble finding any of the pieces, I stock all the pieces, multiple times over....including new prssure rings, inner friction discs, outer lamina (in all three sizes), spring washers, and thrust washers.
01-01-2012, 11:13 PM
#6
Thread Starter
i got it! :-)
got to clean this unit up before i start getting it back together. the trans it came out of looked like it fell off the boat on the way over from germany
got to clean this unit up before i start getting it back together. the trans it came out of looked like it fell off the boat on the way over from germany
Trending Topics
01-02-2012, 12:15 AM
#8
Former Sponsor
01-02-2012, 12:22 AM
#9
Former Sponsor
Wondered if anyone would notice.
Thought I'd start out the New Year, passing on information to my friends on Rennlist.
Only took me 15 years to figure out what pressures work the best and what combination of pieces work well.
Nothing to it....
01-02-2012, 12:43 AM
#10
Man of many SIGs
Rennlist Member
Rennlist Member
They "bounced" around quite a bit on what pieces they installed. Lots have two friction discs, but they are touching each other, without an outer lamina between them. The result is the same...there are only two friction surfaces touching outer lamina on each side.
That friction disc is completely toast. The moly coat is worn down so that the "peaks" are almost all gone and the surface is virtually worn flat. The next step is for that surface to start "smearing" the peaks and valleys together.
If you want to build a "better" limited slip, buy yourself 4 new inner friction discs, instead of just the two....from Porsche...or from someone that bought them from Porsche (do not use aftermarket friction discs....they are not of adequate quality.)
Assemble each side this way, starting from the "inner pressure ring" and working your way towards the outside:
Inner Pressure ring
Inner friction disc
Outer lamina
inner friction disc
Outer lamina
Spring washer
Start with 1.9 or 2.0 outer lamina pieces.
Assemble the entire unit, using a gear oil with the proper friction modifiers that work with this style limited slip. Mobil 1 LS is easy to get and ecconomical (Auto Zone).
Bolt the entire thing together. Install 6 temporary bolts and nuts (with washers on each side of the differential to not damage the surface where the ring gear sits), where the ring gear normally bolts (to make sure the unit is completely squeezed together.
Install a CV stub axle on each side. One stub will have two 10mm bolts (or studs) inserted 180 degrees apart. You will clamp these two bolts into a vise.
For the other stub, you will need to make a little flat plate that bolts across the flange with two 10mm bolts 180 degrees apart. In the center of this plate, weld a 17 or 19 mmm headed nut.
This nut will allow you to turn the limited slip with a torque wrench. measuring the amount of friction the unit has. You can turn it 20-30 times to get the inner friction discs to "settle" in. Now use a torque wrench to turn the unit. I think that the "ideal" friction, for new friction discs is right about 40 ft lbs. You can switch the "outer lamina pieces" to adjust this pressure. They come in 1.9, 2.0, and 2.1mm thicknesses. You should be close, if you assemble the unit like I described. If your pressure is very low, install new "spring" washers on the outside...they get "soft" over time.
If you don't understand, I can take some pictures of the flat plate with the nut all mounted in the vise.
I've got a couple of these things to "set-up", next week.
If you have any trouble finding any of the pieces, I stock all the pieces, multiple times over....including new prssure rings, inner friction discs, outer lamina (in all three sizes), spring washers, and thrust washers.
That friction disc is completely toast. The moly coat is worn down so that the "peaks" are almost all gone and the surface is virtually worn flat. The next step is for that surface to start "smearing" the peaks and valleys together.
If you want to build a "better" limited slip, buy yourself 4 new inner friction discs, instead of just the two....from Porsche...or from someone that bought them from Porsche (do not use aftermarket friction discs....they are not of adequate quality.)
Assemble each side this way, starting from the "inner pressure ring" and working your way towards the outside:
Inner Pressure ring
Inner friction disc
Outer lamina
inner friction disc
Outer lamina
Spring washer
Start with 1.9 or 2.0 outer lamina pieces.
Assemble the entire unit, using a gear oil with the proper friction modifiers that work with this style limited slip. Mobil 1 LS is easy to get and ecconomical (Auto Zone).
Bolt the entire thing together. Install 6 temporary bolts and nuts (with washers on each side of the differential to not damage the surface where the ring gear sits), where the ring gear normally bolts (to make sure the unit is completely squeezed together.
Install a CV stub axle on each side. One stub will have two 10mm bolts (or studs) inserted 180 degrees apart. You will clamp these two bolts into a vise.
For the other stub, you will need to make a little flat plate that bolts across the flange with two 10mm bolts 180 degrees apart. In the center of this plate, weld a 17 or 19 mmm headed nut.
This nut will allow you to turn the limited slip with a torque wrench. measuring the amount of friction the unit has. You can turn it 20-30 times to get the inner friction discs to "settle" in. Now use a torque wrench to turn the unit. I think that the "ideal" friction, for new friction discs is right about 40 ft lbs. You can switch the "outer lamina pieces" to adjust this pressure. They come in 1.9, 2.0, and 2.1mm thicknesses. You should be close, if you assemble the unit like I described. If your pressure is very low, install new "spring" washers on the outside...they get "soft" over time.
If you don't understand, I can take some pictures of the flat plate with the nut all mounted in the vise.
I've got a couple of these things to "set-up", next week.
If you have any trouble finding any of the pieces, I stock all the pieces, multiple times over....including new prssure rings, inner friction discs, outer lamina (in all three sizes), spring washers, and thrust washers.
Happy New Year!!!!!
01-02-2012, 01:29 AM
#13
Former Sponsor
