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Ironhead

ANOTHER Datsun Z/LS3/T56 Swap Thread

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Posted (edited)
27 minutes ago, softopz said:

First thing off epic build thats some crazy stitch welds never seen that many. I was once told by an old timer that too much could be overkill and be counter intuitive if god forbid accident since these are areas that need to be crumple.

 

With that said torque usually raises the diff up and most of your mount/bracing is targeting to the bottom. Hence I see why you want to do a 3.0 maybe just a simple brace from where you already have the mount like attached in the pic in yellow? you can go straight or do a little bend with a slight gusset.

diff design.png

 

 

Thanks for the input....

 

I am definitely going to use what I have made, particularly now since the cross-member is part of it.  I am just considering whether to add some bracing similar to what New Zed sketched as insurance.  By my thinking, it shouldn't matter  much whether the steel supports are above or below the diff tabs, unless there was a chance of the diff snapping the two grade 10.9 M12 bolts holding it in place (I don't think there is...).  But what was sketched would add even more strength and rigidity by introducing another chassis tie-in location.  I just cannot decide at this point if it would be overkill or not....

Edited by Ironhead

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Posted (edited)
14 hours ago, Ironhead said:

 

 

Thanks for the input....

 

I am definitely going to use what I have made, particularly now since the cross-member is part of it.  I am just considering whether to add some bracing similar to what New Zed sketched as insurance.  By my thinking, it shouldn't matter  much whether the steel supports are above or below the diff tabs, unless there was a chance of the diff snapping the two grade 10.9 M12 bolts holding it in place (I don't think there is...).  But what was sketched would add even more strength and rigidity by introducing another chassis tie-in location.  I just cannot decide at this point if it would be overkill or not....

 

Making that double sheer would certainly be stronger, but like you said it is likely overkill. 

 

I would however get a larger diameter thick washer on the top, large enough to support the whole bushing. Like this:

 

 

98.jpg

 

 

Then, where is going to go? It's not going to bend that mount, you could pick up the whole car from that mount. The diff would have to sheer the bolts, which for 10.9 M12 is like 15,000lbs or something (Someone will correct me I am sure)

Edited by LLave

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23 minutes ago, LLave said:

 

Making that double sheer would certainly be stronger, but like you said it is likely overkill. 

 

I would however get a larger diameter thick washer on the top, large enough to support the whole bushing. Like this:

 

 

98.jpg

 

 

Then, where is going to go? It's not going to bend that mount, you could pick up the whole car from that mount. The diff would have to sheer the bolts, which for 10.9 M12 is like 15,000lbs or something (Someone will correct me I am sure)

 

Yeah I have the big washers, just haven't been using them when mocking things up...

 

Is that your car in the picture?  Just wondering how that mount has held up.

 

Regarding the strength of the bolt, I did some math.  A grade 10.9 bolt is rated at 150,000 PSI tensile strength.  In other words, a bolt with a cross sectional area of one square inch would fail at that load.  An M12 bolt has cross sectional area of .17".  So, .17 X 150,000 = 25,500 pounds of tension, or just shy of 13 tons for the bolt to fail.  And that of course is for one bolt, and the mount uses two.  

 

If that isn't enough for us, an ARP stainless bolt is not only pretty, but is rated at 180,000 PSI tensile strength....which without doing the math I'm guessing would knock us up to between 15 and 16 tons of load per bolt.  So you could lift a small-medium bulldozer off the ground with one of those bolts.  And those ratings are minimums, so it might actually exceed those figures by a fair bit before it broke.

 

So whatever might fail here, I'm not really worried about the M12 bolts.

 

Thanks for the input.

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2 hours ago, Ironhead said:

 

Yeah I have the big washers, just haven't been using them when mocking things up...

 

Is that your car in the picture?  Just wondering how that mount has held up.

 

Regarding the strength of the bolt, I did some math.  A grade 10.9 bolt is rated at 150,000 PSI tensile strength.  In other words, a bolt with a cross sectional area of one square inch would fail at that load.  An M12 bolt has cross sectional area of .17".  So, .17 X 150,000 = 25,500 pounds of tension, or just shy of 13 tons for the bolt to fail.  And that of course is for one bolt, and the mount uses two.  

 

If that isn't enough for us, an ARP stainless bolt is not only pretty, but is rated at 180,000 PSI tensile strength....which without doing the math I'm guessing would knock us up to between 15 and 16 tons of load per bolt.  So you could lift a small-medium bulldozer off the ground with one of those bolts.  And those ratings are minimums, so it might actually exceed those figures by a fair bit before it broke.

 

So whatever might fail here, I'm not really worried about the M12 bolts.

 

Thanks for the input.

 

Nice! I was somewhat close on my wild guess. Many many pounds of force. 

 

That is not my car, another members here. I can't seem to find the original thread but check it out here:

https://www.diyauto.com/manufacturers/nissan/generations/240z/diys/differential-cv-lsd-hp-torque-r160-r180-r200-r230-diff-mount-faq-by-jmortensen

 

 

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46 minutes ago, LLave said:

 

Nice! I was somewhat close on my wild guess. Many many pounds of force. 

 

That is not my car, another members here. I can't seem to find the original thread but check it out here:

https://www.diyauto.com/manufacturers/nissan/generations/240z/diys/differential-cv-lsd-hp-torque-r160-r180-r200-r230-diff-mount-faq-by-jmortensen

 

 

 

Thanks!  Wish I had seen that link a couple of weeks ago.

 

That mount looks quite a bit less beefy than mine, so if that car has an LS swap and the mount has held up, I should be sitting pretty.

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Installed the Apex Engineered cross-member and braces today.  Seems like a good product, although I am kind of dubious how much rigidity it will add, since the front and rear control arm mounts are directly on the frame and are very close to each other.  I do like the multiple adjustable pivot locations the setup provides.  I have no idea whether the LS3 oil pan and other ancillaries will clear these parts.  I am just going to have to drop in the engine and find out.

 

It took a fair bit of grinding and brute force to get these things to line up, but considering Apex has to produce a "one size fits all" product to fit 45 year old cars, pretty amazing it goes on at all.

aiXMmZ1.jpg

 

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oICjjPN.jpg

 

KqSQgAe.jpg

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Posted (edited)

Just a bit of scattered progress...

 

I was planning on relying on the fill port on the rear diff cover for a return line from a cooler...but there wasn't clearance...the T3 support blocks for the control arms were too close.  Same for the threaded plug I welded on the other side for a diff temp sensor.  So I had to weld on new fittings.  Not a big deal, but the whole "welding aluminum" thing is still kind of a mystery for me.  Sometimes it goes OK, sometimes it doesn't, and I never know why.  They don't look great, but I got them welded on...don't think they will leak or fall off.

 

SkCsHhK.jpg

 

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Mocked up the front brakes, just to make sure everything fits as intended.  I drew up the hats and caliper brackets with a CAD program, then had them machined and anodized locally.  Seems like everything fits as intended, but I initially drew things up with the discs sitting too far inward, where the caliper brackets would have interfered with the steering arm.  There were a variety of reasons I did not want to go with one of the assorted "bolt on" BBKs that are available for the Z, but getting this setup done was enough of an expensive PITA that I should have.

 

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And finally, got the door hinges stripped and rebuilt with new hinge pins and bushings, then painted them.  In the photo the paint looks a weird greenish color, but it is actually just a medium gray that I am going to use for the interior of the car.

 

UjPdJpd.jpg

 

87MphWI.jpg

 

Thanks for looking.

Edited by Ironhead

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Posted (edited)

I am running a clutch type LSD with this project, and the manufacturer of the LSD in their documentation recommended the differential gear oil be changed after every race or track event if a diff cooler was not used.  Since that would be a huge PITA, I decided early on to include a diff cooler in the build.

 

I spent the last week or so figuring out what would go where and fabricating mounts for the cooler and the fluid pump.  There is not much room under the back of a Z, and I could not come up with a mounting scheme wherein the cooler would both be somewhat protected from road hazards and also get decent air flow.  So, I decided to use a couple of 4" Spal fans instead.  The setup will be wired to come on at a preset diff temperature, which will turn on both the diff oil pump and the fans.

 

Below is my progress thus far.  I have plumbed in the supply line, but haven't totally figured out yet where I will route the return line.

 

Thanks for looking.

 

ccrzi4L.jpg

 

AywCiNT.jpg

 

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MKFS4B3.jpg

Edited by Ironhead

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1 hour ago, LLave said:

Stout! This car is not going anywhere. Looks great. That should do the trick. I can't image a diff with one time use fluid, that sounds like a lot of maintenance. 

 

Thanks dude.  I freely admit to having a tendency to over-engineer parts a bit.  I was going to make the mounts out of aluminum, then reasoned the weight difference would only be a pound or so, and I already had the steel lying around, so I just went that route.   Plus I avoided having to confront my fear of welding aluminum.

 

Got the steering rack mounted today.  Had to have custom outer tie-rods machined due to the combination of threads I am using with the new rack, the T3 parts I planned to use would not work.  Woodward power steering machined the tie rods for $35 a piece...which seems like a smoking good deal.  Most machine shops won't even chuck a part into a lathe for less than $100.

 

On the advice of Tony at Woodward, and other stuff I have read, I moved the rack backward so that it sits roughly 1" behind the point where the tie rods pivot on the steering knuckles.  This apparently improves the Ackerman and general steering geometry for a performance oriented car.  Time will tell if the change also introduces bump steer or other undesirable characteristics, but since everything on the front suspension and steering setup is completely adjustable, I am confident I will be able to sort out any problems that might arise.   I am not super familiar with the principles of steering and suspension geometry, so this part is proving to be a bit of a learning curve for me.

 

I am also wondering if the engine will interfere with the steering rack...again...time will tell and I will deal with it if it does.

 

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