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Torsion Bar Spring Rates D21


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Okay, so for the D21 chump truck, I'm going to eventually need stiffer torsion bars.  On the last 620 I had, I just bought a set and they worked great.  However, since I'm on a budget and I'm doing this truck junkyard-style, I figured I need to investigate some torsion bar rates and spline counts.

 

Does anyone know if the torsion bars are the same rate between VG30 D21s vs. Z24/KA D21s?  And does anyone know if their spline count is the same, length, etc?

 

I've already re-indexed the torsion bars on the chump truck and adjusted the ride height accordingly.  It works just fine, but I can tell she's a little soft.  Probably has something to do with 192k torsion bars that are no doubt not as springy as they once were.  What I'm thinking is, what if I can just get a V6 D21, yank the bars out of that, and presto, a 100 lb increase in spring rate?

 

Ah hah, I'll leave that first bit since deleting is cheating, but I found a bunch of information in my old Nismo catalog.  From there:

 

99996-T4014 - 25mm 2wd torsion bar set D21

99996-T1440 - 26mm 2wd torsion bar set D21

99996 - T4012 - 4x4 torsion bar set D21

 

The 4x4 set is a 2 stage bar with an adjustable secondary stop.

 

OE specs for 2wd are depending on the model (probably V6/xtra cab or 4 cyl/std cab) 22.6mm or 24.4mm

OE specs for 4x4 are 25mm from 11/85-7/90 and 26mm from 7/90 on.  The note says this is a heavy duty part, NOT a lift kit.

 

So the bars are physically different sizes, which would indicate higher spring rates.  What I'm thinking is the bars are probably the same length.  So if I get the torsion bars from a 4x4 D21, and also retrieve the corresponding front and rear stays, they will likely bolt on, meaning I can use the 4x4 higher spring rate for a "free" junkyard torsion bar stiffness upgrade.  I'll have to do some digging in pull and save tomorrow to find out, but that would be awesome!

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4x4 definitely appears to be longer since the bars go into a different spot being they have wishbone control arms instead of the single lower stamped steel unit of the 2wds.  Haven't counted splines, was trying to make it a timely run.  Sway bars look like they will bolt in, but being a bare bones truck, I'm not sure the frame has bolts in it to accept the bar mounting points.  It has holes, but it seems there's nothing up there to bolt onto, but I'll investigate further.

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Its actually pretty ingenious. Under normal load, the entire bar rotates for the torsional resistance. On hard turns, the middle arm locks to the frame and then the unrestrained section becomes the 2nd stage torsion which is stiffer.

 

I recently saw a 3-stage unit. I have to find the pic.

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