REAR LSD insert / no bolt design

[NHerron]

I'm open to opinions on this one, even unsure ideas just give me another choice to look into! Also, this is a different question than most threads found on LSD's.

Anyway, I'm not looking into holding the power down but rather, more traction in snow / mud slipping conditions. See I live in Montana and would love to have a weather-proof climber. The reason I'm interested in the rear LSD setup is that I already have the advantage that FWD cars have with the weight of the front end but the rear end is pretty light. Plus I don't want to mess with an expensive Shepherd built trans

I have verified I don't have a rear LSD by the sticker on the diff case as well as the telltale orange sticker which is not present on any door jamb. So these are the options I have found over a few months:

-Finding a stock rear LSD for my 97 GSX
-Possibly LSD insert
-Maybe Evo diff

To be honest I can't find much info on the design of my rear drivetrain because my rear drivetrain does not have a 3 or 4 bolt design it's more like the front with a splined hub. Can I convert to a 4 bolt LSD?

Finding lots of LSD inserts (Phantom, BM, etc) for the front diff, but is there one for a rear diff?

I've seen a little info on the Evo swap but can't even fathom the price/availibility of that

 

[1990AWD]

I'm not the biggest expert of 2g cars, but I understand all 2g diffs are 4 bolt and you can just swap a stock LSD rear into your car no problem.

 

[NHerron]

I would love to do that. I sure don't need a beefy setup so that would be easy enough once I find a 2G GSX in a local yard. Why is my car odd with the no bolt / splined hub? I also don't have ABS, doesn't look like it ever did either.

 

[NHerron]

Who knows about the 2G splined hub rear axles? My diff is labeled BFB. Can I switch to a 4 bolt rear end easily. I haven't been able to find much info on this. Or where can I get an LSD insert for the rear end

 

[NHerron]

Okay I got a couple pictures and another link to show what I'm talking about. I can't find hardly any info on this, and why it's so hard to even find the LSD BFH pumpkin.

If I did find a BFH LSD rear, is it a direct swap? How come I can't find anyone that ever wanted to swap their BFB non-LSD for LSD?

This guy has the same exact setup as me:
Need help with Rear Diff! - DSM Forums: Mitsubishi Eclipse, Plymouth Laser, and Eagle Talon Forum: DSMtalk.com

And here's my pictures,
Overal diff:

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Drivers side axle cup where it slips into hub assembly:

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Passenger side:

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NOTICE NO 3 OR 4 BOLTS

 

[Awdspyderman]

hey man I see what your saying, I have both diff's right now in my garage. I have a 1g four bolt and a 2g lsd so i've compared them. The first gen rear is smaller than the 2g so i don't see it working. I also have yet to find anybody who has a four bolt rear in there 2g, it's becuase the four bolt design is for the first gen not the 2g. Our 2g's use the spline thru the hub setup, the axels are longer also but if your trying to save money, look for some one who is selling the rear lsd on here or craigslist by you if you have ABS make sure the rear end has ABS or vice versa. It's a strait swap but not an easy swap which you will have to remove the axles also so plan a day to do it. Some guys can do this in a few hours but just give yourslef some time. If you have to drive a little ways for one that my be your best bet. I'd sell you mine but I promised MITSUMISSILE i'd trade for a set of knuckles so im sorry man hope this helps. goodluck

 

[black_gst]

All you have to do is swap in a LSD diff from off a 2G and you will also need the swap axles as well, or just the LSD axle (which is the passenger side axle IIRC) you cannot swap to a 1st gen diff (3 or 4 bolt)

 

[black_gst]

also you can swap to an Evo rear diff, you have to actually swap the differential itself and you will also need the Evo inner axle cups as well to work with the evo diff. i know of a couple local people that have done the evo swap, its a much better diff

 

[turboglenn]

The right hand LSD axle has an extra extended part on the spline into the pumpkin, other than that 2g to 2g bolts right in. When i did my AWD swap i got a non-LSD rear in the subframe and swapped in the BFH LSD unit with little work. the axles MUST be changed though (at least the right one but something makes me think there might have been a difference on the splining in general but i can't remember honestly)

 

[black_gst]

The right hand LSD axle has an extra extended part on the spline into the pumpkin, other than that 2g to 2g bolts right in. When i did my AWD swap i got a non-LSD rear in the subframe and swapped in the BFH LSD unit with little work. the axles MUST be changed though (at least the right one but something makes me think there might have been a difference on the splining in general but i can't remember honestly)

i thought the splines were the same, and thanks for confirming that its the passenger side axle that has the extended part for for the LSD i couldent remember for sure

 

[Mr PopUps]

For clarity, 2G's do NOT have outer cups which would be 3 or 4 bolt cups, they are like the front joints with splines going into the hubs. And the orange sticker was for the center diff viscous coupler not the rear LSD. Absence of it would point to a FWD->AWD conversion or someone simply removed the sticker.

 

[NHerron]

Please don't spread misinformation, its already confusing enough on the subject. On the orange stickers they directly refer to the rear differential.

"This vehicle is equipped with a viscous coupling type limited slip differential in REAR AXLE"

Thanks for the other confirmation though, do you have anything helpful to add pertaining to my original question?

 

[jtmcinder]

Aye, Herron. It is annoying.

And the orange sticker was for the center diff viscous coupler not the rear LSD.

Gotta talk to Chris about having the ability to give a person a second red chicklet....

-

One point to consider is this: for performance, there are many better LSDs than a VC. But for simply not getting stuck in snow, a VC is actually a very good option. BFH might be your best choice.

 

[Mr PopUps]

While i havent seen the sticker in a 2G in quite a long time, even if the rear is limited slip, it is referring to the VC in the TRANSMISSION that sends power to the rear wheels regardless of the type of rear end you have. Towing is what kills the VC in the transmission, not the rear diff. You do know how a VC works right? Thus the reason for NOT towing it with either front or rear wheels up and 'locked' to the tow truck.

Im not spreading mis-information, you just dont know everything (neither do i). Dont assume my low post count means anything other than i never joined/posted till 10 years after production stopped.

That said, your OP is a bit fuzzy. Are you planning for this, or are you experiencing this 'deficiency'? I can see in extreme circumstances that you might get one wheel or the other to spin, but you would still have 2-3 wheels with traction. Having only had a 3 bolt stock LSD and a 4 bolt swapped in LSD i cant offer any driving differences, but can tell you that even with bald tires resembling slicks more than anything my 90 AWD still would not get stuck anywhere, and forcing them to spin under boost the car would start to rotate, but slam right back in line when i let off the gas as if i were on rails.

Gotta talk to Chris about having the ability to give a person a second red chicklet....

Seriously? I got the first one from a n00b who is a donkey rear that took a bad attitude with me when i joined because he thinks he knows everything and that post count means everything as well. Its called discrimination.

 

[jtmcinder]

I actually have no clue how differentials work. I took a look at the tech threads linked to here http://www.dsmtuners.com/forums/drivetrain-tech/251295-diffs-lsds.html but they were way over my head. All I know is that the orange sticker tells people who are incapable of bending over to look at the rear pumpkin that the car has a VC in the back. For all I know, that means that we're still at war and a very small and very angry SouthEast Asian is hidden inside, ready to jump out and kill a Yanqui. But I have a suspicion that I'm not thinking of the right kind of VC.

 

[Mr PopUps]

, thats funny

Yes, the rear is a viscous coupler type vs. a clutch type LSD, but it still allows the rear wheels to turn at diff speeds. I tested this theory when doing my 4 bolt swap after a 3K clutch drop killed my left axle, by having someone hold one end while i turned the other, and it did, just very tightly as designed. If you doubt me, try revving the engine and dumping the clutch while turning left or right and see if the inside rear wheel spins, and it will for a short time till the LSD kicks in.

But the center diff in the tranny also has a viscous coupler that normally splits the torque in a 50/50 full time variable split. It can send up to 100% of the power to the front or rear diff's (as seen on a drag launch with the front wheels spinning but you are still moving fwd), but doing this with all 4 wheels free is not dangerous. Its when one set or the other (f or r) are 'locked' that it will cause damage to the viscous coupler in the tranny, not the rear end.

Trust me, im not wrong on this, but i may be on the sticker as i have seen a 2G one in a very long time (think like 11-12 years) and i dont have mine in the driveway at present to go take a pic of it.

 

[bryanwheat]

While i havent seen the sticker in a 2G in quite a long time, even if the rear is limited slip, it is referring to the VC in the TRANSMISSION that sends power to the rear wheels regardless of the type of rear end you have. Towing is what kills the VC in the transmission, not the rear diff. You do know how a VC works right? Thus the reason for NOT towing it with either front or rear wheels up and 'locked' to the tow truck.

Im not spreading mis-information, you just dont know everything (neither do i). Dont assume my low post count means anything other than i never joined/posted till 10 years after production stopped.

That said, your OP is a bit fuzzy. Are you planning for this, or are you experiencing this 'deficiency'? I can see in extreme circumstances that you might get one wheel or the other to spin, but you would still have 2-3 wheels with traction. Having only had a 3 bolt stock LSD and a 4 bolt swapped in LSD i cant offer any driving differences, but can tell you that even with bald tires resembling slicks more than anything my 90 AWD still would not get stuck anywhere, and forcing them to spin under boost the car would start to rotate, but slam right back in line when i let off the gas as if i were on rails.



Seriously? I got the first one from a n00b who is a donkey rear that took a bad attitude with me when i joined because he thinks he knows everything and that post count means everything as well. Its called discrimination.

Again, stop posting things that you know nothing about

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[Mr PopUps]

I said, i might be wrong about the sticker, but i am NOT wrong about the viscous coupler in the transmission.

Proof...

1000 Already Answered Questions - Index page

Sorry link doesnt work like i planned, so here is the post:

Why can't I tow an AWD [DSM]?
My AWD [DSM] was towed [at some time]! Did anything break?

You can tow an AWD DSM. The trick is to have all four wheels off the ground while it is being towed. This can be done using a flatbed tow truck, or putting the front wheels on dollies.

The reason that AWD DSMs should not be towed with two wheels on the ground is the limited-slip differential (LSD) which is present on many AWDs. The function of the LSD is (surprise!) to allow a limited amount of speed difference between the front and rear wheels.

[Please note that the operation of the LSD has been simplified here for the purposes of discussion. This is not a dissertation on the LSD itself.]

Under normal driving conditions, the front and rear axles rotate at the same speed. (This is what differentiates AWD from older 4WD vehicles - on 4WD vehicles, it is assumed that the front and rear wheels usually rotate at different speeds while the 4WD is engaged.) During this time, the LSD does no work, and is 'open', providing no coupling between the front and rear wheels of the car.

The LSD is a viscous (fluid-based) device, and contains no mechanical interlocks. When one set of wheels begins to slip, plates in the LSD rotate at different speeds. The speed difference creates friction, and therefore heat, in the LSD fluid. When enough heat is generated, the LSD fluid abruptly changes state from 'open' to 'closed' providing a semi-solid junction between the two plates. With the fluid now 'locked' the plates are forced to rotate at near-equal speeds, which is turn forces the axles to turn together. When the slip condition disappears, the LSD quickly loses heat and returns to an 'unlocked' state.

So, the raison d'etre of the LSD is to prevent excessive wheel slip between the front and rear axles. The only problem with this occurs if two wheels are forced to slip, while the other two remain stationary. This occurs, of course, if two wheels are on the ground (rolling) and two are stationary (lifted) while the car is being towed.

In this scenario, the LSD will quickly build up heat and 'lock', attempting to rotate both axles equally. Unfortunately, it is unable to do so, since the stationary axle is locked securely into place by the tow operator. The other option is to halt the rolling axle, but the LSD does not have the strength necessary to resist the force provided by a tow truck designed to pull much larger vehicles. So the LSD plates continue to slip, even when the LSD is 'locked'.

When placed into such an impossible situation, the LSD does the only thing it can do - build up heat until it self-destructs. The tow truck driver, driving a dually burdened with the added weight of a 3000 lb car, is unlikely to notice either the extra resistance provided by the LSD or the lack of resistance once the LSD burns out. By the time the car is again dropped to the ground, the LSD is literally toast.

This situation can easily be avoided by only towing the car with all 4 wheels off of the ground. The exact method used is not critical. And no, it isn't going to hurt the LSD to load the car - technically, the front and rear axles are never going to rotate at exactly the same speed during driving, so the LSD plates are always rotating at slightly different speeds. Obviously, this doesn't hurt it, since it runs in 'open' mode normally - the problems occur when it is 'locked' and still cannot equalize the axle speeds.

Those interested in the exact operation of the LSD can read all about it in their technical manual (you do have one, right?).

Those interested in the details of the AWD system should read Eliot Lims Introduction to AWD Systems.

 

[bryanwheat]

I don't think that anyone was arguing that you can tow an awd with a set of wheels on the ground.

 

[Mr PopUps]

You mean cant, typo i guess.

Then why did you say i knew nothing when i have been talking about the VC in the tranny being the point more so than the rear? If you disconnect the driveshaft the rear end wont care if you tow or flat bed it.

 

[bryanwheat]

You mean cant, typo i guess.

Then why did you say i knew nothing when i have been talking about the VC in the tranny being the point more so than the rear? If you disconnect the driveshaft the rear end wont care if you tow or flat bed it.

I just don't understand why you are talking about towing and the center diff viscous coupler when it wasn't mentioned at all in the thread.

 

[eclipse gsx]

i towed a 98 gsx from Indiana to Texas it ad no vicious lsd but it had the bfb and i took the drive shaft off and i put the front tires on a dully so the rear where on the ground. which it had no drive shaft and its running perfect.

 

[NHerron]

Mr. PopUps

I have no idea how you got so off track. I haven't gotten the chance to read all the useless SH*IT you posted in my thread but I'm talking about traction in snow, remember, I live in MONTANA where we get 1-2ft of snow. Obviously these cars have low clearance and it's easy to get high centered. I know I don't have an LSD axle front or rear. With that said, I only have 1 wheel drive on the front and one on the back, WHILST being high centered. So I want an LSD in the rear to solve this problem. The way I see it is, the FWD vehicles have the benefit of the weight of the engine keeping traction on the front axle, while the rear axle has less weight. That's why I choose the rear LSD axle. I also don't want to tear into my expensive ShepTrans, either.

I want to know the easiest way to get LSD in the rear, since most go with LSD in the front. But from the helpful info. from everyone else, I think I might go with an EVO differential. I didn't mean to be sarcastic or a dick in my earlier post but you clearly posted misinformation. I'm still open to any HELPFUL info you have to give me but just don't give me an attitude about it.

 

[eclipse gsx]

yeah i get what your saying. go for the vicious lsd or the evo diff and try to take your time remember its better to take it slow that to do it twice.

 

[NHerron]

Well I figured I would have enough money from taxes to go with the EVO LSD since it seems like a direct swap. I also picked that one as it is serviceable since it has a clutch pack. I have looked for an LSD insert but they all say they are for the front. Anybody have any idea on that, where or if I could get that, for the rear BFB diff?