JDM vs. USDM differential

[arminder_d]

Hi guys. This is my first time posting on this forum so please be patient with me. I tried searching for this but unfortunatly i coudlnt find anything that answered my question. Here is my conundrum.

I recently imported a 91 180sx from japan. It shows characteristics of a Posi diferential...but when i talked to the importing company he said it was because i have a 2 way lsd. So i have two questions.

1) Will a 2 way LSD cause the car to shudder doing any sort of turning and cause the outside wheel to skip across the pavement like a limited slip with its spiders welded would?

2) If my differential is shot (theres a lot of driveshaft play also so i know theres too much pinion>ring gear clearance) will a USDM 240sx diff bolt up? From what i know the inside flanges for the half shafts are different. However, if i could get a 240sx differential that included halfshafts would it fit inside of my 180sx? The second question if very important because im going to tear my diff apart tomorrow and see what things look like inside. If theres damage i need to replace it quick.

Thanks in advance.

[Irukandji]

Hi guys. This is my first time posting on this forum so please be patient with me. I tried searching for this but unfortunatly i coudlnt find anything that answered my question. Here is my conundrum.

I recently imported a 91 180sx from japan. It shows characteristics of a Posi diferential...but when i talked to the importing company he said it was because i have a 2 way lsd. So i have two questions.

1) Will a 2 way LSD cause the car to shudder doing any sort of turning and cause the outside wheel to skip across the pavement like a limited slip with its spiders welded would?

2) If my differential is shot (theres a lot of driveshaft play also so i know theres too much pinion>ring gear clearance) will a USDM 240sx diff bolt up? From what i know the inside flanges for the half shafts are different. However, if i could get a 240sx differential that included halfshafts would it fit inside of my 180sx? The second question if very important because im going to tear my diff apart tomorrow and see what things look like inside. If theres damage i need to replace it quick.

Thanks in advance.

1) Yes, 2 way will occasionally cause your tires to "skirt"
2) Yes. Just get the 6 bolt half shafts (or axels) and swap them out.

[EchoOfSilence]

alright. 'posi' = LSD.

Yes, an lsd would cause tire shudder. it's what happens when both tires spin concurrently, such as with a welded differential or an LSD.

[driftenthusiast]

Every 2 way i have driven (Kazz,ATS,Tomei) caused a chatter when turing at low speeds.

[arminder_d]

Hmmm....i talked to a few shops down here and they said that its definitly not normal for even a 2 way lsd. Also on the note of a posi = lsd, an lsd still gives way to power differentiation through compression on a clutch pack (if clutch type is used). a posi will transfer equal power to both wheels all the time which is more like a 2 way lsd rather than a 1.5 or a stock viscous, or so ive heard. Thanks for the help though guys.

One thing i still dont get though is....are the 240's half shafts 6 bolt or the 180's? Because if the diff combo im picking up comes with 240 half shafts i should have to worry the outside is splined rather than flanged correct?

[driftenthusiast]

In a clutch type two way you will ALWAYS hear the chatter, those shops must not have done any of those type before, even when brand new during break in( and yes mine were put togeather with correct backlash and pinion depth). Ive seen many 240 rear ends from japan, so are 5 and some are 6 bolt, so just check what you have.

[arminder_d]

ahhh ok. But like....when this thing shudders....i feel my whole car lurch....and it shakes the whole car....and my right side rear tire (driver side) twiches back and forth. Now, i could just be tripping and the wheel hopping could be mistaken for axial movement or i think i may have a LCA thats dunzo. Is it really supposed to be THAT violent? Also from external tests ive figured out i have a helluva lot of pinion>crown clearance.

[cdlong]

LSD is a general term; clutch, viscous, and helical are the three main types. there are also the fancy computer controled hydraulic clutch types.

"Posi" is a trademarked name used by GM for their LSDs in the muscle car days. i think it was a helical, it's short for Positive-traction. i think you are thinking a posi is like a welded diff. every LSD "gives way to power differentiation", how much depends on the design of the diff.

2 way or 1.5 way are clutch types, the number refers to when it locks up. 2 way, full lockup in accel and decel, 1.5 way, full lockup under accel, partial lock under decel.

open diffs put equal power to both wheels (torque actually), any type of LSD will transfer torque to the tire with more avaliable traction. which one works best for you depends on how you use the car and your preferences.

you might have a welded diff in there or a clutch type that is really tight. some are adjustable. just pull the thing apart and see what it is. show us pictures if you need to. you might have a shot bearing on the pinion, you might be best off buying a new VLSD if everything is screwed up.

[driftenthusiast]

2ways are alot louder than most people how havent driven one before expect, you would hear a loud clicking sound coming from the rear, with a welded the car would shake and tire would skip. Without hearing it or seeing it its hard to really say what exactly it is. If you take the cover off and post pics i can give you a good idea of what it could be.

[arminder_d]

Yea. Ive driven an offroader with welded spider gears and it feels prety similar. Thanks a lot for you help guys youve been really resourceful and answered questions i couldnt get the answer to anywhere. Ill take pictures once i get the diff out!

[arminder_d]

Alright so here's an update. I tore apart the differential and realized i did infact have a nismo 2 way lsd and it was in good working order. All other measurements were TO SPEC (including backlash and contact patterns). Also i found out that my LSD was 3 level adjustable...so i set the little puck to the lowest level (level closest to the spider gears) and the breakaway torque is supposed to be something like 40 ft lbs. I then waited like 4 days for my gasket to come in from edmonton and finally got everything back together today. I rolled the car off the hoist...only to realize my wheel was still twiching and diff still clunking. Not quite as bad as before (or so i think) but its still there. Now the problem is that im most likely not gonna pass inspection with this occurence. Does anyone know perhaps if i may have adjusted the puck wrong....if its supposed to come out as far as it can for the lowest level of adjustment? Also anyone that has owned a Nismo 2way could you please tell me EXACTLY what it drove like. I know i have a lot of questions but im stuck right now. Thanks in advance.

[O.D.]

2 ways will chatter during small turns