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Ironhead

ANOTHER Datsun Z/LS3/T56 Swap Thread

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9 hours ago, Invincibleextremes said:

That's amazing how rust free your car is.  Mine is literally about to fold in half, but it's on the road and I'm having fun.  Any reason you went with the short nose r200 instead of a longnose or a ford 8.8?

I got pretty lucky for sure on the lack of rust.  I gave the car a very thorough inspection prior to buying, after looking at several cars in which the floorboards consisted of hardware store galvanized sheet metal held in with rivets or duct tape.  But I bought the car in Palm Springs, and I think it spent its entire life there.  I would imagine most Southern California cars have little or no rust.

As far as the diff, I am planning to use the TTT rear end conversion kit, which is designed around Nissan components, so I was not really thinking Ford.  Also, the short nose came with a 4.08 on the 300ZX....all the other R200 diffs had ratios in the 3.XX range.  Turns out I am using a 4.6 gearset from the front of a Pathfinder, which if I understand Nissan diff interchangeability at all would not work in a longnose R200.

I just hope the diff is beefy enough for a 525 HP LS3...as it did not come on any  Nissans with anywhere near that output.  But all the advice I got from people who claim to know this stuff said that it should be fine.  Besides my only stronger Nissan option was the R230....which comes with something like 3.5 gearing....not good for my purposes.  And AFAIK there are no other R230 gearsets available.

 

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3 hours ago, LLave said:

That sucks man. Of course the thread gets boogerd the very last time it comes apart... Figures. Getting a threadsert in dead straight is not easy. 

The car is looking great. Keep it up.

Thanks,

The worst part....I was just starting to set up the new diff housing today....and it is going to require completely different shims than the prior one.  Starting completely over, but I guess that should not be a surprise.

Edited by Ironhead

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Finished welding in the Bad Dog frame rails today.

Doing this actually killed two birds with one stone.  My floor pans were kind of wavy and bowed inward from decades of improper jacking and other abuse, and I was not having much luck straightening them with mallets and 2" X 4"s.  I just drilled through the Bad Dog rails and through the floor pans and used longish M5 bolts to draw them tightly together.  This not only positioned the rails properly for welding, but the rails were rigid enough that the bolts forced the floor pans straight.  Not sure why that did not occur to me sooner....

I experimented a bit with what sort of stitch weld to use on the rails so as not to grossly distort the floor pans.  I initially was going to use 1" weld beads spaced 1" apart, but quickly found the heat from the longer bead was pulling/distorting the floor pans.  So I resorted to 1" spaced plug welds in the flanges, and larger 1" spaced spot welds between those.  Seems like this should be more than strong enough and kept the distortion to a minimum.  I only used long weld beads where the rails mated with the thicker steel of the car's OEM frame.

I know others have enthused about them for many years, but I wanted to add again that the Bad Dog rails seem to be a great mod for a tired beat up car (which all "Zs" are to different degrees).  They were also far easier to install than I expected.  Great product.

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Beyond that I have been working primarily on stitch welding all the OEM joints.  Really a grind of a job, had I fully known what would have been involved I might have skipped it entirely, but now that I have gone this far I have to go all the way right?

The welding is the easy part, what is driving me crazy is trying to get all the metal clean enough of primer and seam sealer so I can wind up with decently solid welds, rather than gonad-looking porous monstrosities.   Probably 10X as much time is spent working assorted wire brushes and dental picks than actually welding.

Thanks for looking.

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Finally got my diff more of less sorted...

 

As I mentioned previously, I am using an R200V from an N/A 300zx, which comes with a 4.08 ratio.  After doing the math and pondering it a bit, I decided the 4.636 ring and pinion (I bought on Ebay) would meet my needs better.  As best I can determine, these come out of the front of assorted Nissan 4WD vehicles like Pathfinders.  It is a 51/11 gearset.

 

On first trial assembly, I was a bit confused because the input flange would bottom out before the pinion bearings had even tightened up....  It soon became apparent that the 4.636 pinion gear is significantly shorter than the 4.08 pinion:

 

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This fact somewhat complicates setting up the diff with the new gears, as the prior spacing pretty much has to be thrown out the window...there is no using the original diff shims and hoping it will leave you in the ballpark...  You kind of have to start from scratch, and without having the specialized diff setup tools (who has those?) the only recourse is a lot of trial and error via assembly and disassembly.

 

If it helps anyone, I wound up needing 5.75mm spacing between the inner pinion bearing and the pinion gear.  Checking the Nissan shim charts, the minimum thickness available (if you can find them) was around 3mm, and the max I believe was 3.66mm.  So none by themselves are thick enough, and two of even the smallest would be too thick.

 

To get around this, I would up using these 2.5" ID shims https://www.onlinemetals.com/merchant.cfm?id=1217&step=2&top_cat=1175.  They are not an exact duplicate of the OEM shims, not being metric and all, for example they are slightly looser around the shaft....but they are close enough to work fine.  Like I said it took a lot of experimentation...assembling and disassembling until things were close enough to leave a recognizable pattern in the gear engagement dye:

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In this picture you can see the pinion was too close to the ring gear....

 

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After a lot of experimentation I wound up with the pattern below, which I think is about "right".  If nothing else this process will make you an expert at tearing down and assembling a differential....

 

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Once the contact pattern appeared correct, the backlash seemed to take care of itself and measured out within spec at .004".

 

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Once that was done, tear everything down AGAIN, paint it (yes, freakin orange!) start final assembly, new seals, and stub axles.  The six bolt stub axles are for a Skyline GTR, which I used so I could use the beefy Q45 axles (which are also good because I have a set).  The OSG LSD is also the model intended for the Skyline GTR so things like spline counts and lengths would all be compatible.  Mike Hanson at Whitehead Performance helped me with the Nissan diff parts interchangeability questions, which had me completely confused (be forwarned, a lot of the info circulating in the 'net about Nissan diff parts compatibility is just plain wrong) but Mike seemed to have this stuff down, fortunately.

 

The only other aftermarket parts required were the Nismo M12/M13 ring gear bolts...because the 4.636 ring gear has M12 threads but the OSG LSD has 13mm holes.

 

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Someone will probably weigh in now with a much simpler way I could have done all this....but such is life.

 

 

 

Edited by Ironhead

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3 hours ago, Geno750 said:

It's probably due to how ABS was done on the R32's (4.36) and it was done via the drive shaft side, the diff on those cars is slightly longer to accommodate the sensor. Any plans for that 4.36 final?

I think I am going to keep it and eventually build a second diff.  I have so many parts lying around I might as well.

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1 hour ago, LLave said:

That stitch welding is some of the best I have ever seen. Great work. I am inspired to slow down a bit, stay patient, and measure them all out. 

 

Thanks....I just use one of these https://www.mcmaster.com/#compasses/=1akhiyh set at 1" and a Sharpie to mark where the welds are going.  Obviously it is just about aesthetics and precision is not needed.  It only adds a few minutes to the process.

 

As I said....it is removing the primer and seam sealer prior to welding that is driving me nuts.  And of course, after I make a string of welds having to go back and grind down/redo all the contaminated ones that look like a donkey dick....

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