So I bought a Limited Slip Differential yesterday. The guy claimed it was a series 5 Naturally Aspirated Limited Slip Differential. Does mean its a GTU's LSD? Is it possible to tell by the casting number on it? It says M055. Let me know thanks

 

you bought it and you don't even know what it's from? interesting.

 

He said it was an s5 so instantly i thought it was a GTUs one. I checked out the part though and it works perfectly no grinding. Just curious if it's a GTU's or if its a series 4 regardless I am going to install it on my car.

 

look at the bottom of it if it has a raised "circle" in the middle then it could be a s4 if if does not more than likely it is a s5

a s5 gtu is a open diff "spin one side the other side goes the other way"
a s4 gtu is a vlsd "which what i have seen acts the same way untill the fuild locks up"

hope this helps

 

i didn't see a raised circle
here are pictures of it

 

while i am at it
which plug is to drain the differential fluid? and what weight of oil does the differential use?

 

You want to use the bottom plug to drain it. As far as weight I would refer to the FSM because it all depends on the driving conditions. I have used the Royal purple Gear Oil and have felt a world of difference compared to the conventional oils. But that is really more about preference.

The differential that you have is definitely S5. I have never seen or possibly never notice the casting on the side of the differential. Your one lucky bastard if it is GTU's. One way you can find out is by driving at 60 MPH on 5th gear. The RPM should be slightly higher due to the changed gear ratio.

 

Another way you can find out, since it is sitting out in the open all pretty like... turn the input shaft and count the number of rotations the input shaft does, per revolution of the output shaft.

 

Useless ******* post.

He bought something and the seller said what it came from. He come to the list to make sure, since the seller could be wrong or ******* with him. We don't have pictures of the different Diffs in the archives and stickies last time I checked.

 

pfsantos - don't waste my time if your not going to help or if you are here just to run our moth
Puck - i will try that
Boost or Bust - thanks and thats what i plan on using Royal Purple Gear Oil

 

Gabriel - I quoted the other post for a reason. It was not meant for you. Cheers.

 

Alright, I usually get people who are just trying to run their mouths and not help thats why, sorry about that

 

okay drained the oil =]
it smelled funky and it had a little bit
i got two bottles of royal purple 75w-90 gear oil, Boost or Bust how many quarts did you put? i have the haynes repair manual and i can't find how many quarts to use.

 

It should be specified in Chapter 1 for the amount, also in Chapter 1 it decribes how to check / replace the diff fluid so If I were you i'd look it over.

 

Puck i did 4 revolutions in the input shaft for 1 revolution on the output shafts

 

Hard to tell from this still, because that's essentially 4:1
Our diffs are 4.10:1, or 4.30:1
It could be tough to distinguish between the two.

 

wow this is harder than i thought it would be

 

That would be 4.10. So that is not a lsd.
Thanks Robert

 

actually it is an lsd both out put shafts turn the same way

 

Not always indicative of an LSD.
An open diff will do this if no load is on either output shaft or the driveshaft.

Also, someone could have put an LSD of any type in an S5 open diff 4.10:1 ring and pinion.

Only way to know is to look inside.


I usually turn the two output shafts to the same position and mark them with chalk or tape... Then I turn the input shaft and count the revolutions of the output shafts, making COMPLETELY sure that they stay in the same relative positions...

If it's from a "GTUs" model, it'll have the coveted 4.30:1 gear ratio... That'll give you a little better launch torque, but take you down a bit on top speed.

.10 is 1/10th of a rotation... Like from 12 o'clock to a little past 1 o'clock.
.30 is almost 1/3rd of a rotation... Like from 12 o'clock to a little before 4 o'clock.
So the difference is easy to tell.


One good way to find out if it's a tight LSD is to block ONE of the output shafts and let the input shaft turn... Take a torque wrench to the lugs (Works well if this is on the car.) of the unblocked shaft and turn. It should turn, but it should take a LOT of torque to do it...

Viscous LSDs will not react this way... (They need to already be slipping to heat up the fluid.) Worn out clutch type LSDs (better than an open diff... Clutch packs are cheap.) won't react either because the clutches won't grip.

Like I said before...Only 100% sure way to know is to crack it open or look inside.

 

well right now the Differential is on the floor
and i just but new gear oil =/

 

i don't exactly understand what you are trying to tell me
turn the input shaft, make sure the output shaft are aligned
then what
turn the input shaft 4 times and see what rotation the output shaft is at?

 

Pele
i figured out what you were trying to say after a while
so i turned it exactly as you said and i got a 3'oclock turn hence .30
so i got myself a GTU's
thanks for helping and everyone else who helped me out
RX7Club FTW

 

Good job! Congrats!

 

Good that you figured it out, because I just reread and realized I fucked up...

You mark both the output shafts AND the input shaft.
Turn the input shaft until the output shafts come back to the same position (ONE full rotation)
Count where you come out at with the input shaft.