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Was the factory LSD's breakaway torque any good?


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The WD21s had a breakaway torque of 260-289. I presume this was still streetable...but was it good enough for the trail? I'm rebuilding a LSD to replace the open diff in my R50 and trying to determine a suitable target number. Thoughts?

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Depends how often you lift a tire, and how badly... The stock LSD certainly is better than nothing, but some people rebuild them with an extra friction disk to stiffen them up. MY1PATH has a good write up on this IIRC, but isn't the only one.

As for streetable, yes, they are, but you have to be careful turning in lower gears when it is wet unless you enjoy pirouetting, especially if it is a manual transmission.

With your build, have you considered a mechanical locker?

 

B

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Yep, the rebuild will not only change the disc-to-plate ratio (from 2:9 to 5:6), but also add 1mm to the total clutch stack (which doesn't sound like much, but I'm at the very minimum stack height, and the range is 2mm more).

 

I'm hoping to quantify the amount of torque when both ratio and thickness are changed, just to understand if the WD21 specs are a reasonable target. Better than nothing, no doubt. But I also would like to know to justify costs. $170 gets me the 5:6 ratio, but $340 gets me the ratio and max thickness. I'm trying to gauge if that basically spools it, but without knowing what the OE stack height was for WD21 (FSM doesn't specify this), it's trial-and-error.

 

None of the write-ups really talk about that. MY1PATH's was very useful, but the lack of pictures on the Laxman one really kills the technical info that could be inferred.

 

I posted in the WD21 forum because the LSD spec in question was last used in 95 (well, maybe in HBs, but I didn't check). Think this is better suited for the Garage forum?

 

I would go with a locker, but it's the 33-spline and I'm not ready an air locker. The front is getting a Lokka, though.

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I'd say this is in the right place. Let's see if anyone else chimes in with anything not in the write-ups.

 

I see what you are saying, without having a stock stack up height value, the first try will be a Hail Mary. Does the FSM have thickness range or spec for the individual parts (ie to determine if they need replacing)? You might be able to work it out from there. :shrug:

 

Is the 33 spline VQ35 drive train specific? I thought the Lockright lockers that fit the WD21 also fit the R50.

I hear you on the air lockers though. Be nice to have but way to expensive for me...

 

B

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Exactly...without knowing the stack height that actually came in certain LSDs, I can't make the correlations I'd like to.

 

The FSMs do specify a stack height range per side (19.24mm-20.26mm), as well as wear and warp limits for the individual pieces. The pieces have nominal thicknesses of 1.4mm, 1.5mm (standard), and 1.6mm, with the exception of 6mm spacers that replaced 4 friction plates per side in 03-04 LSDs. Each side had 13 pieces (1-2 springs, 2-6 friction discs, and 5-9 friction plates), except for the ones with spacers (2/2/5 + spacer).

 

These FSM specs didn't change from 94-04, so there's some degree of standardization there, and both the nominal and actual (sum of pieces) stack heights basically guide any repairs/rebuilds.

 

I'll spare the theory, but I'm estimating 205 ft-lbs if I match the 5:6 ratio commonly found in the stronger LSDs, and replace friction plates with thicker friction discs.

 

Funny you ask about the Lock Right. There were actually two of them (3210-LR and 3220-LR). The 3210-LR is for 31-spline only because it includes new side gears; it fits older D21s (pre-94) that have 1-piece 2-pin open carriers. The 3220-LR offered some hope: it re-uses the side gears, making it spline agnostic. However, the 33-spline 2-piece 4-pin carrier it'd need to work in simply never existed (33-spline open carriers are 1-piece 2-pin). My cross-refs suggest that 33-spline side gears would fit the 31-spline open carriers commonly found in WD21s, D21s, and 99-00/01-ish D22s that the 3220-LR was designed for, but the tooth cut on the 33-spline side gears would likely not mesh properly with the drivers (but it is the same tooth count, 16).

 

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You have obviously done a lot of thinking and research on this, I'm interested to see how it works out.

 

Yes, I have the 3220-LR in my garage awaiting an open carrier; for some reason I thought it could be installed in the R50's as well, but apparently not...

 

B

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Ha, yeah, waaaaaaay too much time thinking about it...not getting enough sleep! I'll try to document both processes (LSD and Lokka) to see if I can get more technical information in them.

 

Would you mind taking measurements and pictures of the 3220-LR? The best observations I could make about it were from the Nissan Nut's website...unfortunately, I usually can't make sense of most of the stuff he writes, but the pictures really say everything (some of the pic links don't work, but the larger pics do exist...just need a little trickery to see them). It'd be nice to get a close-up of the teeth on the drivers.

 

IIRC, you have machining skills, so you likely have a good idea of useful measurements. I can confirm whether it at least physically fits an open (likely) or LSD (doubtful) 33-spline carrier. Dimensions/drawings of the tooth face would be huge. Wishful thinking: maybe we can arrange a loan so I can test fit it?

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*snort*

I understand, sometimes I get caught up in projects as well. Please do take good notes though, this might be the next big R50 mod! ;)

 

Yes, I can measure and photograph it for you. I don't have access to a metrology lab right now, but I have all my machining/measuring tools and a granite plate so I should be able to get some accurate dimensions. We'll start there to see if it is even close, and loaning it isn't out of the question, depending...

 

Give me a few days on that though, my chore list is long... :rolleyes:

 

B

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Yeah, these projects. I'll breathe a sigh of relief tonight when I've got my monster list of parts ordered to move everything forward.

 

And no rush on anything. I'm not home until next Friday so there's not much I can do with the info yet anyway. Except dream.

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Great info, hopefully I'll get to that point of knowledge. Still learning all about my 94. I am enthusiastic beginner.

 

Sent from my XT1254 using Tapatalk

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No sweat, B. In fact, let me post up a pic of the side gears and some basic dimensions first, then you can decide if it's even worth your time.

 

I've got two LSDs fully disassembled and sitting in a box now (all marked and bagged, of course). It's been an interesting project, but going a lot slower than I'd hope due to availability of Nissan parts. The friction discs are holding up the show. I switched focus to the pair of R200s, and installed a Lokka in one. Just waiting on new seals and gaskets to call the first one done, before doing it all again on the other.

 

The 2nd LSD has the "ideal" ratio I've been talking about in terms of friction discs. It's spec'd for 65-80ft-lbs, and came in at 68. Its stacks are only 0.1mm thicker than the 1st LSD, which does help correlate some numbers for me. I had to change my order for discs, but it ends up being the practical approach...won't be nearly as thick as I wanted, but still better than nothing. I'm estimating around 110-130 ft-lbs, which is no where near the WD21s, but they'll be much better than any stock R50 LSD.

Edited by hawairish
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Well, good thing I did finally remember to look, there is a tiny bit of surface rust starting. It'll be fine once I brush and oil things...

 

030_zpsg9sja70s.jpg

 

Measurements: Initial caliper based readings, I can take more specific measurements if needed.

OD: 100.95mm, 3.974"

ID: 72.1mm, 2.838"

Grooves: 4.5mm, .177"

Teeth: 13.9mm, .547" wide outside, 10mm, .393" inside, measured at the base 2mm, .079" deep

 

Gonna have to get back to you about the radii on the back, the face angle and the OD bevel. :shrug:

 

B

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My first try with this mod I added one disc to each side and it was basically a spool.
My third try sill has one extra disc but the outside two have .015" machined off them (-.030 total) so that the the surface facing the side gear and the surface facing the spring stack are smooth.
It's streetable but locks up under torque because the spider gears push outward against the side gears just enough to make it a spool when you punch it.
It is also like a locker on snow and ice which can lead to fish tailing if you are not careful.

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B: Those OD/ID numbers pretty much killed it, at least for using an LSD carrier and side gears. The ID is just a little smaller than the OD on the side gears (sorry, don't have my measurements handy to give exact numbers). Even if the numbers were better, the cut on the teeth surely wouldn't mesh right:

 

IMG_3443.jpgIMG_3445.jpg

 

Getting somewhat decent measurements was tough with all the angles and round edges/faces.

 

I'm not surprised by the results though. In the pics I've seen of the 2-piece open carriers and 2-piece LSD carriers, the LSD "center" is noticeably smaller (there's a gap between the center and the ID of the ring gear). Haven't pulled the open carrier yet, but I think I've seen the side gears look very similar, which makes this a no-go.

 

MY1PATH: Do you remember if your stacks were still within OE spec after machining them down? I'd still love to know what the original stack height was to pull those OE torque numbers.

 

Edited by hawairish
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MY1PATH: Do you remember if your stacks were still within OE spec after machining them down? I'd still love to know what the original stack height was to pull those OE torque numbers.

 

 

No, it was taller than stock. I have one extra disc on each side but two on each side are machined down by .015" (.030" total)

Assuming 1.5mm disc (.059")

 

.059-.030= .029

 

So my stack height is .029 taller per side.

Adding a .030" shim (full hard Steel) to each side may have a similar lockup as mine and that's probably what I would do next time since I no longer have access to a Blanchard grinder with a magnetic hold down. (IMHO that's the only proper way to take such a small amount evenly off an entire hardened clutch disc)

 

 

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Yep, I get the extra disc part; you added a disc to each side, and each is essentially half-height. I wouldn't be able to tell if you were in or out of OE spec without knowing your initial stack height (which is what I'd really like to know). In my case, I could do what you've done and still be in spec.

 

The two LSDs I broke down had very low stack heights, and consequently low break-aways. I was surprised to see that 150% more friction surface and .1mm (.2mm total) only produced another 25 ft-lbs. The "better" LSD has the same disc:plate setup as the WD21, but produces 25% of the OE WD21. The standard size part was 1.5mm, and assuming the stack used all standard sizes, that'd only be 19.5mm (mine are 19.3mm and 19.4mm; both will be 19.6mm). That all said, the WD21 must've had some 1.6mm to go above 19.5mm. If you went over with your shims, you must've had at least that. Do you recall having any 1.6mm discs/plates in those stacks?

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Honestly I didn't measure all of them. They all appeared to be in good shape and same thickness (to the casual eye) and that's as far as I went.
I wasn't going for repeatability in other pathfinders I was just going by trial and error until I achieved the right amount of lock up.

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Word. So was tightening up your LSD because the stock one wasn't enough? That was the original conclusion I was hoping to understand (from anyone), since it would've played into what diffs, discs, and what nots to look for and purchase.

 

Not really relevant now, since Nissan didn't have as many discs as I originally wanted. I scaled back to what was available (yet the dealership apparently still has their thumbs up their a's, and all my projects are postponed...) The nice part is that I can bench test everything before taking apart the truck, but it just gives me a number and not a "feel".

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Have you talked to Rob Lacy (Alkorahil) about getting the parts? This sounds right up his alley...

 

B: Those OD/ID numbers pretty much killed it, at least for using an LSD carrier and side gears. The ID is just a little smaller than the OD on the side gears (sorry, don't have my measurements handy to give exact numbers). Even if the numbers were better, the cut on the teeth surely wouldn't mesh right:

 

Well, there it is, photographed and documented... :shrug:

 


Adding a .030" shim (full hard Steel) to each side may have a similar lockup as mine and that's probably what I would do next time since I no longer have access to a Blanchard grinder with a magnetic hold down. (IMHO that's the only proper way to take such a small amount evenly off an entire hardened clutch disc)

The best and easiest way, I would say, but not the only! It could be done with a magnetic or vacuum fixture on a mill, or with a magnetic or vacuum face plate on a lathe, utilizing a tool post grinder or even just facing it with single point turning. It's all in the set up and method... ;)

 

B

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Have you talked to Rob Lacy (Alkorahil) about getting the parts? This sounds right up his alley...

 

Been thinking about it. Been to the website, too. The prices between them and my norms are about the same, but I usually go with Courtesy because of the Nico discount, which has basically covered shipping ($40 in this case). Now, if there's an NPORA discount...

 

CP has been good about things, but they dropped the ball this time. We had some delays sorting out numbers/availability for these discs, which took too long to sort out. Found out this morning that they've been holding the older for a back-order item that they optioned to me to split off, and I took the option. SFD install: delayed. Lokka install: delayed. LSD rebuild: delayed.

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Word. So was tightening up your LSD because the stock one wasn't enough? That was the original conclusion I was hoping to understand (from anyone), since it would've played into what diffs, discs, and what nots to look for and purchase.

 

I wanted more...I was wheeling a lot back then*

Stock does pretty well with both tires having contact and the e-brake trick helps balance the torque if one tire has limited contact.

But once one tire is completely floating in the air and your front tires are trying to move over some rocks it does not do much anymore.

 

Have you seen my video? I've had 3 pathfinders and only one of them can drive of a jackstand in 2wd.

Look at the painted stripe in the video of the last pathfinder there is Zero slippage when it comes off the jack. It requires pavement actually forcing the inside wheel to slow down for my "LSD" to actually "S" the "D"

 

 

 

*now I seem to enjoy the creature comforts of my wife's stock 4dr

Edited by MY1PATH
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Saw the video, too. An obvious difference, and that's the concept I'd like to go for should I be in wheel-up scenarios. But, I'm the type who needs something quantitive to describe that. I mean, is that 80 ft-lbs, or 280 ft-lbs?...can't tell without measuring. Were you just idling in for the modified take?

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The modified LSD in in a 5 spd MT yes, just idle and let out the clutch. It locks up even harder when I goose it.
The unmodified was in an automatic so I had to give it some gas to get the driveline moving.

 

Its probably somewhere in the 300 Lb ball park.
I will have to create a long arm jig I can bolt in place of the wheel and put a big torque wrench on it to find out my exact breakaway. My concern is that I will move the vehicle long before it slips even if I try to block the tires.

 

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Nice! Yeah, I have length of steel that'll serve a similar purpose to bolt to the hub. I made something out of scrap that does the trick for now.

 

The good news is that I'll get everything before the weekend, but not sure it leaves me enough time to rebuild everything and get the SFD on. I'd love to tackle all this stuff before I have to go back out of town for a couple weeks.

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