4bolt LSD rear end info

[Kenny_Kline]

From the information I have gathered, 4bolt LSD rear ends came out of 92.5-94 Eclipses w/ or w/out ABS. If you have a Talon/Laser and you have option code C15, then you DO NOT have an LSD.

Discuss...

 

[3rdstrikedsm]

Every dsm I have owned or torn apart which is many has had lsd with or without abs.
I have never even seen a 4 bolt with no lsd but I know they are out there.

 

I'll let the pictures do the talking. Taken the day I got my Laser. 73k miles. Bought off the 2nd owner who bought it after the orinal owner rolled it over. No I did not install the shift knob.

Note: ABS

Note: Viscous LSD sticker

It's as simple as this.

90: No option for ABS. LSD optional

91: ABS optional. ABS = no LSD. NO ABS = lsd option.

92-94 : ABS and LSD in conjuction is possible and very common. Open diff is uncommon if non existant. (never seen one)

 

[Kenny_Kline]

Something to read: (found in the archives)

How our Viscous LSD works:
In the LSD is a cylindrical chamber of fluid filled with a stack of perforated discs that rotates with the normal motion of the output shafts. When one wheel spins faster than the other the heat generated expands the discs apart and locks the diff.

What happens when the rear wheels lock up together? The rear end comes around and you spin out of control. That is why early ABS was only on the rear of the vehicle. To prevent a spin out so the driver can remain in control.

How our ABS works:
The ABS controller senses wheel speeds and determines if a wheel is spinning faster or slower than the others. If it's spinning slower (Locked Up) then the ABS unit reduces hydraulic power to that wheel so until the speeds are the same again.

What happens when braking with an Viscous type LSD:

Now, If you are braking and one of the rear wheels locks up the LSD is going to lock also since the difference in speed is going to heat it up and force it to lock. Now the wheels are going to spin the same speed. In this case one wheel is locked. If the spinning wheel doesn't have enough traction it will lock as well brining the rear end around and leaving the driver without control. Hopefully the other wheel has enough traction and can break the brake's grip on the locked up wheel.

What happens with ABS on an LSD rear:
The wheels will technically hardly ever be activated since the difference in wheel speed will rarely ever be different. And since it's AWD it relays the speed difference to the front of the vehicle as well and the Viscous coupler will lock up and cause the front wheels to turn the same speed. So if you are locking up the rear wheels on an LSD car you are probably locking up all four wheels and ABS will not help you in that situation.

Now you do have to account for the G-meter. It senses any sudden motion and relays that to the ABS unit to engage. So if you are locking up all wheels and going slow enough the G-meter will not engage the unit.

I really think it was Mitsu's way of dodging law suits.

The above is only my theory on how the system works. If you have a better think on things then let's hear it.

 

[Kenny_Kline]

What is option code C15 and what determines if you got an LSD or not in a 92.5-94?

 

Enlighten us. Why do you keep saying 92.5? early 92's came with 4bolts also.

 

[ktmrider]

^^ That's the switchover for 6bolt to 7bolt engines but I have not heard whether it impacts the rear diff tho.
I always hope the factory diff sticker is still intact, B1H is the LSD 4 bolt.

 

[3rdstrikedsm]

Quoting blizz:
Enlighten us. Why do you keep saying 92.5? early 92's came with 4bolts also.


As a general rule 92.5 and up is 4 bolt although very few early 92's did come with 4 bolt's

 

[gtluke]

I thought all 92's came with 4 bolts, it was 92.5 when you find big brakes and 7 bolt
edit:
I owned a small brake 6 bolt 92 that had a 4 bolt

 

[Kenny_Kline]

The question is about 4 bolt LSDs and non LSDs. Yes the 4 bolts came in a few month earlier, I think May??? Regardless, thats not the discussion.

 

[iceman69510]

Quoting gtluke:
I thought all 92's came with 4 bolts,


Correct.

Quote:
it was 92.5 when you find big brakes


Incorrect. All from '93 model.

Quote:
and 7 bolt


Break point is by engine number, not specific model year or half year application.

Quote:
edit: I owned a small brake 6 bolt 92 that had a 4 bolt


That would be correct.

 

[iceman69510]

Quoting krkline2gdsm:
What is option code C15 and what determines if you got an LSD or not in a 92.5-94?



C15 is ABS. All '92 and up 1g Eclipse have LSD.

Chrysler kept it as separate option on Talon and Laser in 92-94.

 

[fivestardsm]

I had a dec. 91 -(still a 92 model) talon with 6 bolt, small brakes, and 3 bolt. It is all original...

 

[Kenny_Kline]

Well according to CAPS, it says the rear diff from a 92+ talon have a different part number than a diff with the C15 option code (ABS). LAst I knew, there was only 1 diff part number for the 4 bolt... system updated as of 2007.

I dont know. Much confusion. Many are saying there ABS talon has a 4bolt LSD from the factory. hmmmm.... Maybe the ABS wasnt the determining factor after all?

 

[iceman69510]

A couple things...

If you are looking at CAPS, you are not looking at Chrysler (therefore Talon) part information. CAPS will only have Eclipse info. It is for Mitsu dealers.

From 92 and up you can have a Talon with LSD and ABS, just like you can have an Eclipse with LSD and ABS. You can also have one without ABS w/LSD, or with LSD and no ABS.

The restriction of no LSD w/ ABS only applied to '91 MY.

 

Quoting fivestardsm:
I had a dec. 91 -(still a 92 model) talon with 6 bolt, small brakes, and 3 bolt. It is all original...



That's really interesting. Guess you learn something new every day.

 

[iceman69510]

Frankly, I don't believe it, or it was not untouched.

 

[H05TYL]

Quoting krkline2gdsm:
Something to read: (found in the archives)

How our Viscous LSD works:
In the LSD is a cylindrical chamber of fluid filled with a stack of perforated discs that rotates with the normal motion of the output shafts. When one wheel spins faster than the other the heat generated expands the discs apart and locks the diff.

etc

etc

etc





Except, a viscous lsd doesn't totally lock the wheels together, it can only limit the difference in wheelspeeds to a certain extent. (eg: 60/40 or 70/30 - this will be equal in both directions) Which is why when you launch hard and the car squats you spin the front wheels as the weight transfers to the rear.

Of course a plate type lsd that locked under deceleration would cause both rear wheels to lock up together, which is why OE units only lock under acceleration (1-way) in vr4rs, vr4rs evo, and evo1rs. OE units in evoII and evoIII's are 1.5 way, they lock under acceleration, but only partly under deceleration.

 

[Kenny_Kline]

OK so we are on all the same page that 4bolt LSDs come with or without ABS. So what was the determining factor of a 4bolt getting an open diff?

 

[iceman69510]

How the car was ordered.

As I said above, all Eclipse GSXs have LSD w/4 bolt.

Talons and Lasers have other variations.