limited slip diff.
12-30-01, 02:00 AM
#1
SPORKY
Thread Starter
Join Date: Mar 2001
Location: Mill Creek, WA
Posts: 422
Likes: 0
Received 0 Likes
on
0 Posts
limited slip diff.
ok, so I've asked this before, I know I can do a search, but all of the answers I've gotten haven't worked.I have an 86 mazda rx7 base with the sports package. I've heard that some came with it, some didn't. how can I tell if mine has it or not? I've tried peeling out, but since it has independant suspension, it'll leave 2 tracks anyway, right? I tried spinning one of the wheels and for some reason it was very hard to spin it. it would only move a little bit, so I couldn't tell. My friend said that it was that way on some limited slips (like his AE86) and that you have to spin the driveshaft. is it that way? if it isn't then I have something wrong with my brakes or my e-brake. at any rate, I'd really like to know so that if I don't have it I can put it on, or if I do so I can put some fluid in. thanks
12-30-01, 04:42 AM
#2
Put one tire on the grass and one on the pavement on the side of the road and floor it. Limited slip will leave rubber on the pavement, open will transfer all to tire on the grass. I'd say if you can't easily tell which you have by driving it you don't have enough HP that you need limited slip-but I've been wrong before...
12-30-01, 06:26 PM
#4
SPORKY
Thread Starter
Join Date: Mar 2001
Location: Mill Creek, WA
Posts: 422
Likes: 0
Received 0 Likes
on
0 Posts
I was doing some things on the car and I decided to try it again. I spun one wheel, the other stayed still. I spun the other, only one spun. the other wheel is kind of stuck/sticky, but I think this concludes that I don't have limited slip. now, to find one...
12-30-01, 07:12 PM
#6
SPORKY
Thread Starter
Join Date: Mar 2001
Location: Mill Creek, WA
Posts: 422
Likes: 0
Received 0 Likes
on
0 Posts
there was no tag. is it possible for the tag to be taken off? anyway, I'm pretty sure that I don't have LSD. Spinning the wheel, the other didn't spin. the other wheel is kind of sticky, but if it was LSD the other wheel would have either stopped spinning or gotten harder to spin, at least I think it would. I'm wanting to replace it with LSD, but I need to know a few things. 1st, I know that the series 4 and series 5 are different. as I remember, series 5 is viscous (something like that) and series 4 is clutch. which is better? will the series 5 fit a series 4? just some things I want to know before getting them.
12-30-01, 07:35 PM
#7
Full Member
Join Date: Sep 2001
Location: ny
Posts: 122
Likes: 0
Received 0 Likes
on
0 Posts
Taken from se-rx7.org :
RX-7's actually came with 4 different differential types:
- open
- clutch-type limited slip
- viscous limited slip
- Torsen
Zack described the open differential sufficiently -- torque is split
between the driven wheels, with the greater going to whatever wheel is
easiest to turn, e.g., based on the differential rotational speed.
The clutch type LSD, like on my old '86 GXL, has multiple plates (4 or
6) on each side which resists rotational speed differentials between the
two driven axles. These work like an open differential, but the friction
of the plate (hopefully) ensures that a percentage of the torque on the
slipping wheel is transfered back to the non-slipping wheel. The plates
are considered a wear item and may require service before the car has
reached the end of its useful life. The Mazda Competition Parts catalog
indicates that alternate thickness plates may be used, modifying the
friction LSD characteristics. It is because of the plates that a special
LSD additive is required on RX-7's equipped with this kind of
differential.
HE then goes into the Vicious type LSDs.
The viscous type LSD, like on my 1990 GTUs and on Turbo II's of the same
year, has multiple plates with viscous fluid between them, kind of like
a plate sandwich. The plates are not in physical contact with each
other, as I understand it. The differential fluid has the magical
property of changing viscosity depending on the differential rotational
speed between the two driven axles, and therefore the plates. When the
differential speed is high, the viscosity increases leading to a torque
coupling via the fluid back to the "slow" axle. These types of
differentials are very common place these days. They are relatively
cheaper to manufacture and do not require maintenance. No special LSD
additive is required. They also require slip to occur before they react,
with a corresponding time lag. I have not driven my GTUs sufficiently
hard yet to comment on the degree of slip that occurs when accelerating
hard out of a corner.
Some have said that the viscous type LSD is not the hot setup for
racing. I suppose this is because the viscous type will allow a certain
amount of slip before reacting, above the amount required to allow a
turn to be navigated. The clutch type will resist any kind of slip, with
the friction creating a force that must be overcome, even when executing
a simple turn. I would further suppose that the clutch type LSD will act
as a locked differential up until the point where the static friction of
the clutch plates are overcome. After that, sliding friction of the
clutch plates remains to provide the LSD mechanism.
Torsen type differental.
The last type, Torsen, is not strictly an LSD at all, and comes on all
93-95 RX-7's and some 94-97 Miatas (R's). It is similar in concept to
the Quaift Automatic Torque Biasing differential. Those interested can
read technical details on this differential at:
http://www.mindspring.com/~audidudi/Torsen.htm
http://www.quaife.co.uk/index.htm
Basically, the Torsen uses worm gears, which prohibit, or more correctly
limit, torque transfer in an "opposite" direction, but function normally
in a "forward" direction, kind of like a diode, but for torque. The
mechanism is such that torque is always routed to the "slower" spinning
driven axle, which is, we hope, the wheel not slipping. The differential
does not actively try to limit slip or control differential rotation
speeds.
The design, while clever, is not foolproof, and the 'Net is filled with
anecdotal stories of instances where drivers were less than pleased.
Despite these comments, in my opinion, the Torsen would seem to be the
best choice of differential.
Mazda actually offers a "Type 1" and "Type 2" Torsen, which differ in
the bias ratio. The bias ratio refers to the percentage of torque which
can be transferred. The bias ratio is determined by the pitch of the
threads on the worm gears. I have no information yet to determine which
ratio is best for an FC3S.
I have heard that it is possible to retrofit a Miata Torsen into an
FC3S, but I do not yet have all the details. I believe that it will be
more difficult, and more expensive, to swap a Miata Torsen into an FC3S
with viscous LSD like mine -- the drive shafts are slightly unequal. I
also question whether the Miata Torsen would be reliable in a Turbo II.
There are at least 2 other types of differentials that deserve mention
here.
Locked - no differential rotational speed is allowed. Provides best
traction on marginal surfaces, but increases wear and tear on high grip
surfaces. These are common on 4WD vehicles.
Detroit Locker. This differential works a little bit like your Craftsman
socket wrench. There is a ratcheting mechanism in the differential to
prevent one wheel from spinning excessively.
So concludes my core dump on differentials for now. Although I have
raised more questions than provided answers, I will continue looking
into the Torsen situation and share what I learn.
This article can be found on http://www.se-rx7.com/techtips/lsd.htm
Wicked
RX-7's actually came with 4 different differential types:
- open
- clutch-type limited slip
- viscous limited slip
- Torsen
Zack described the open differential sufficiently -- torque is split
between the driven wheels, with the greater going to whatever wheel is
easiest to turn, e.g., based on the differential rotational speed.
The clutch type LSD, like on my old '86 GXL, has multiple plates (4 or
6) on each side which resists rotational speed differentials between the
two driven axles. These work like an open differential, but the friction
of the plate (hopefully) ensures that a percentage of the torque on the
slipping wheel is transfered back to the non-slipping wheel. The plates
are considered a wear item and may require service before the car has
reached the end of its useful life. The Mazda Competition Parts catalog
indicates that alternate thickness plates may be used, modifying the
friction LSD characteristics. It is because of the plates that a special
LSD additive is required on RX-7's equipped with this kind of
differential.
HE then goes into the Vicious type LSDs.
The viscous type LSD, like on my 1990 GTUs and on Turbo II's of the same
year, has multiple plates with viscous fluid between them, kind of like
a plate sandwich. The plates are not in physical contact with each
other, as I understand it. The differential fluid has the magical
property of changing viscosity depending on the differential rotational
speed between the two driven axles, and therefore the plates. When the
differential speed is high, the viscosity increases leading to a torque
coupling via the fluid back to the "slow" axle. These types of
differentials are very common place these days. They are relatively
cheaper to manufacture and do not require maintenance. No special LSD
additive is required. They also require slip to occur before they react,
with a corresponding time lag. I have not driven my GTUs sufficiently
hard yet to comment on the degree of slip that occurs when accelerating
hard out of a corner.
Some have said that the viscous type LSD is not the hot setup for
racing. I suppose this is because the viscous type will allow a certain
amount of slip before reacting, above the amount required to allow a
turn to be navigated. The clutch type will resist any kind of slip, with
the friction creating a force that must be overcome, even when executing
a simple turn. I would further suppose that the clutch type LSD will act
as a locked differential up until the point where the static friction of
the clutch plates are overcome. After that, sliding friction of the
clutch plates remains to provide the LSD mechanism.
Torsen type differental.
The last type, Torsen, is not strictly an LSD at all, and comes on all
93-95 RX-7's and some 94-97 Miatas (R's). It is similar in concept to
the Quaift Automatic Torque Biasing differential. Those interested can
read technical details on this differential at:
http://www.mindspring.com/~audidudi/Torsen.htm
http://www.quaife.co.uk/index.htm
Basically, the Torsen uses worm gears, which prohibit, or more correctly
limit, torque transfer in an "opposite" direction, but function normally
in a "forward" direction, kind of like a diode, but for torque. The
mechanism is such that torque is always routed to the "slower" spinning
driven axle, which is, we hope, the wheel not slipping. The differential
does not actively try to limit slip or control differential rotation
speeds.
The design, while clever, is not foolproof, and the 'Net is filled with
anecdotal stories of instances where drivers were less than pleased.
Despite these comments, in my opinion, the Torsen would seem to be the
best choice of differential.
Mazda actually offers a "Type 1" and "Type 2" Torsen, which differ in
the bias ratio. The bias ratio refers to the percentage of torque which
can be transferred. The bias ratio is determined by the pitch of the
threads on the worm gears. I have no information yet to determine which
ratio is best for an FC3S.
I have heard that it is possible to retrofit a Miata Torsen into an
FC3S, but I do not yet have all the details. I believe that it will be
more difficult, and more expensive, to swap a Miata Torsen into an FC3S
with viscous LSD like mine -- the drive shafts are slightly unequal. I
also question whether the Miata Torsen would be reliable in a Turbo II.
There are at least 2 other types of differentials that deserve mention
here.
Locked - no differential rotational speed is allowed. Provides best
traction on marginal surfaces, but increases wear and tear on high grip
surfaces. These are common on 4WD vehicles.
Detroit Locker. This differential works a little bit like your Craftsman
socket wrench. There is a ratcheting mechanism in the differential to
prevent one wheel from spinning excessively.
So concludes my core dump on differentials for now. Although I have
raised more questions than provided answers, I will continue looking
into the Torsen situation and share what I learn.
This article can be found on http://www.se-rx7.com/techtips/lsd.htm
Wicked
Trending Topics
12-31-01, 10:36 AM
#8
Former Moderator. RIP Icemark.
On your car, with the rear end in the air, if you turn one wheel the other should move the opposite direction if you do not have an LSD.
If the other wheel does not turn or turns the same direction that points to having a clutch type LSD. This test only works on the clutch type. The Fluid or Viscous uses a different test (one wheel turned one direction, then reveresed and turned and then reveresed back again and turned, then the rear should lock up and both wheels turn).
It sounds to me based on your description that you have an LSD that the wrong gear oil (the 84-88 clutch type used an LSD additive or a specific for LSD gear oil) was used in or that the rear end is worn out.
If the other wheel does not turn or turns the same direction that points to having a clutch type LSD. This test only works on the clutch type. The Fluid or Viscous uses a different test (one wheel turned one direction, then reveresed and turned and then reveresed back again and turned, then the rear should lock up and both wheels turn).
It sounds to me based on your description that you have an LSD that the wrong gear oil (the 84-88 clutch type used an LSD additive or a specific for LSD gear oil) was used in or that the rear end is worn out.
01-01-02, 05:37 AM
#9
SPORKY
Thread Starter
Join Date: Mar 2001
Location: Mill Creek, WA
Posts: 422
Likes: 0
Received 0 Likes
on
0 Posts
happy new year. anyway.
so if that points to the clutch type lsd, would it be as simple as new oil? or would it be something more like rebuild/replace. I would doubt that it'd be warn out, seeing that it has 92,000 miles on it, but its always a possibility.
so if that points to the clutch type lsd, would it be as simple as new oil? or would it be something more like rebuild/replace. I would doubt that it'd be warn out, seeing that it has 92,000 miles on it, but its always a possibility.
01-01-02, 05:43 PM
#11
Rotary Freak
Join Date: May 2001
Location: Hampton Roads, VA
Posts: 2,340
Likes: 0
Received 0 Likes
on
0 Posts
Is it Easy or Cheesy?
Anyway, since you have a clutch-type LSD, you probably are going to have to look into rebuilding the rear end. Clutch-types should allow minimal slippage before allowing the other wheel to turn, if properly adjusted (shimmed). I had one off the car, and if I tried turning one stub shaft and holding the other, I couldn't do it; the stub shaft I held got jerked out of my grip. I tried holding one in place with a crow bar, but then I couldn't get the "free" shaft to turn. As I said, this was OFF the car.
One of the 86's I had that has a clutch-type LSD exibited need for a rebuild at about 130k, or, at least, that's when I noticed it. I had inadvertantly gotten stuck with one tire on pavement and one on wet grass, and I just spun the tire on the grass. I know for a fact it had LSD. When I got home that day, I jacked the car up and checked it out. I could spin either wheel and the other would turn in the same direction. However, if I grabbedd one of the halfshafts and spun the opposite wheel, the shaft I held would stay still. This indicated to me that the clutch plates were in sad shape.
By way of comparison, I tried to do the above to my 944 turbo. I damn near broke my wrist holding on to one shaft while I had a friend try to spin the opposite wheel. Bad idea.
All that said, however, I wouldn't condemn the LSD until you determine whether you rear brakes are locking up. Try the spin trick with both calipers removed.
Ren
Anyway, since you have a clutch-type LSD, you probably are going to have to look into rebuilding the rear end. Clutch-types should allow minimal slippage before allowing the other wheel to turn, if properly adjusted (shimmed). I had one off the car, and if I tried turning one stub shaft and holding the other, I couldn't do it; the stub shaft I held got jerked out of my grip. I tried holding one in place with a crow bar, but then I couldn't get the "free" shaft to turn. As I said, this was OFF the car.
One of the 86's I had that has a clutch-type LSD exibited need for a rebuild at about 130k, or, at least, that's when I noticed it. I had inadvertantly gotten stuck with one tire on pavement and one on wet grass, and I just spun the tire on the grass. I know for a fact it had LSD. When I got home that day, I jacked the car up and checked it out. I could spin either wheel and the other would turn in the same direction. However, if I grabbedd one of the halfshafts and spun the opposite wheel, the shaft I held would stay still. This indicated to me that the clutch plates were in sad shape.
By way of comparison, I tried to do the above to my 944 turbo. I damn near broke my wrist holding on to one shaft while I had a friend try to spin the opposite wheel. Bad idea.
All that said, however, I wouldn't condemn the LSD until you determine whether you rear brakes are locking up. Try the spin trick with both calipers removed.
Ren
01-04-02, 05:27 AM
#13
Rotary Freak
Join Date: May 2001
Location: Hampton Roads, VA
Posts: 2,340
Likes: 0
Received 0 Likes
on
0 Posts
Should be two bolts on the inboard side of the caliper. Of course, I can't remember right now, and I don't have my car with me... naturally. This sucks. AAAAAARRRRGGHH!!!!!! I need to see my babies again, I'm going through withdrawal.
Good breakdown available in the service manual...
Actually, you wouldn't have to remove the caliper completely, just the pads. That should free up the rotors to turn.
Ren
Good breakdown available in the service manual...
Actually, you wouldn't have to remove the caliper completely, just the pads. That should free up the rotors to turn.
Ren
02-03-04, 08:28 PM
#15
Senior Member
Join Date: Jun 2003
Location: Burnaby, B.C.
Posts: 427
Likes: 0
Received 0 Likes
on
0 Posts
Bringing up an old thread because I don't want to start a new one.
What happens if i have a viscous lsd and normal diff fluid is in there?
Will the test still work?
What happens if i have a viscous lsd and normal diff fluid is in there?
Will the test still work?
02-03-04, 08:57 PM
#16
Former Moderator. RIP Icemark.
Originally posted by Ronac
Bringing up an old thread because I don't want to start a new one.
What happens if i have a viscous lsd and normal diff fluid is in there?
Will the test still work?
Bringing up an old thread because I don't want to start a new one.
What happens if i have a viscous lsd and normal diff fluid is in there?
Will the test still work?
So unless you busted open the actual diff itself (and not just opened the pumpkin/housing) you would only find gear oil.
And if you are doing it on your car in your signature (an 89 GXL) it won't matter, as you won't have a LSD anyway unless someone added it after the car left the factory.
02-03-04, 09:03 PM
#17
Senior Member
Join Date: Jun 2003
Location: Burnaby, B.C.
Posts: 427
Likes: 0
Received 0 Likes
on
0 Posts
Well.
I think my car is a whole different story..
My car has been totaled and rebuilt before I bought it. It even has a turbo hood . I'm not sure if my car has been pieced together with other car's parts. Also, I live in Canada, I'm not sure if the GXL are the same as the ones in the states.
I think my car is a whole different story..
My car has been totaled and rebuilt before I bought it. It even has a turbo hood . I'm not sure if my car has been pieced together with other car's parts. Also, I live in Canada, I'm not sure if the GXL are the same as the ones in the states.
02-03-04, 11:30 PM
#20
Jesus is the Messiah
Rebiulding the whole differential:
$250-$300 in labor
$120 in parts for the bearings (I got mine from a local bearing shop)
$35 or something like that in seals from MazdaTrix.com(one front, and two side seals)
$250 or around that for the clutch parts from MazdaTrix.com
$11 for the Crush Tube from RacingBeat.com
$7 for the Lock Nut from RacingBeat.com
$21 for 3 bottles of Mobil1 Synthetic gear lube (use your own if you want)
After spending all that $, why not buy a set of 4.3 gears? $~430 new from racing beat I belive. I've also got a set for sale with an S5 NA vLSD (No stub shafts tho!) I also have an S5 NA standared diff with a 4.1 ratio that has stub shafts and is in fantastic condtion. And I have a standard carrier with a broken tooth that you can have for free if you just pick it up :-p
Rebiulding just the clutch unit:
4-6 hours of work for the first time you do it (Dont dissasemble anything exept the carrier and count the turns of the side screws and return it where it came from. CLEAN EVERYTHING AND KEEP IT CLEAN.)
$250 or something around that in clutch parts from MazdaTrix.com
$21 for 3 bottles of Mobil1 synthetic gear lube
If you want help on how to do this, you can PM or IM me.
$250-$300 in labor
$120 in parts for the bearings (I got mine from a local bearing shop)
$35 or something like that in seals from MazdaTrix.com(one front, and two side seals)
$250 or around that for the clutch parts from MazdaTrix.com
$11 for the Crush Tube from RacingBeat.com
$7 for the Lock Nut from RacingBeat.com
$21 for 3 bottles of Mobil1 Synthetic gear lube (use your own if you want)
After spending all that $, why not buy a set of 4.3 gears? $~430 new from racing beat I belive. I've also got a set for sale with an S5 NA vLSD (No stub shafts tho!) I also have an S5 NA standared diff with a 4.1 ratio that has stub shafts and is in fantastic condtion. And I have a standard carrier with a broken tooth that you can have for free if you just pick it up :-p
Rebiulding just the clutch unit:
4-6 hours of work for the first time you do it (Dont dissasemble anything exept the carrier and count the turns of the side screws and return it where it came from. CLEAN EVERYTHING AND KEEP IT CLEAN.)
$250 or something around that in clutch parts from MazdaTrix.com
$21 for 3 bottles of Mobil1 synthetic gear lube
If you want help on how to do this, you can PM or IM me.
Last edited by Tofuball; 02-03-04 at 11:42 PM.
02-04-04, 01:13 AM
#23
Jesus is the Messiah
Auto gearing LSD? If it is an aftermarket unit, it may require a special fluid. Read the documentation or contact the company that sold you the unit.
For the stock differentials in most cars, they usually want 80W-90 weight gear oil. Sometimes they take ATF.
I'm using Mobil1 75W-90 Synthetic in mine, and it works very well.
For the stock differentials in most cars, they usually want 80W-90 weight gear oil. Sometimes they take ATF.
I'm using Mobil1 75W-90 Synthetic in mine, and it works very well.
02-04-04, 07:25 PM
#24
Full Member
Join Date: Jan 2004
Location: CA
Posts: 228
Likes: 0
Received 0 Likes
on
0 Posts
ice man.. about your post you put up there..
>>On your car, with the rear end in the air, if you turn one wheel the other should move the opposite direction if you do not have an LSD.
If the other wheel does not turn or turns the same direction that points to having a clutch type LSD. This test only works on the clutch type. The Fluid or Viscous uses a different test (one wheel turned one direction, then reveresed and turned and then reveresed back again and turned, then the rear should lock up and both wheels turn).<<
yea.. does that really work.. what if when i do spin it and only the one that im turning is spinning.? does that mean i got lsd on that car.? or the clutch type.? curious. i saw your forum, and was just curious and tried it out.. ehehe.. but yea.? just wanna make sure...
1990_whitecomet
>>On your car, with the rear end in the air, if you turn one wheel the other should move the opposite direction if you do not have an LSD.
If the other wheel does not turn or turns the same direction that points to having a clutch type LSD. This test only works on the clutch type. The Fluid or Viscous uses a different test (one wheel turned one direction, then reveresed and turned and then reveresed back again and turned, then the rear should lock up and both wheels turn).<<
yea.. does that really work.. what if when i do spin it and only the one that im turning is spinning.? does that mean i got lsd on that car.? or the clutch type.? curious. i saw your forum, and was just curious and tried it out.. ehehe.. but yea.? just wanna make sure...
1990_whitecomet