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Captain Obvious

My New Diff Mount and Strap Project

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On 8/12/2016 at 8:44 PM, Zed Head said:

The leather one?  Won't you need to apply conditioner on a regular basis?  Or the timing belt?  Probably only good for 80,000 miles.

https://zcardepot.com/driveline/rear-axle/differential-arrestor-band-goto-240z-260z-280z.html?search=differential

https://zcardepot.com/driveline/rear-axle/differential-diff-arrestor-band-belt-rear.html?search=differential

I like the nylon strap.  Same material as towing strap, it could be rated for 30,000 lbs.  https://www.amazon.com/Smittybilt-CC330-30-Recovery-Strap/dp/B001CF4UXU

I converted mine to metal.

 

Done.JPG

I'd like to have one of those!

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Socket head cap screws ... excellent idea ... wish I'd known that LAST weekend. To tighten the bolts on mine I took off both rear wheels, got a long flex-head ratchet on the top bolts with the handle pointed toward the gas tank, and reached through the fender wells to grab the handle. I was only able to turn the nut a single ratchet click or two at a time. To an outsider I'm sure it looked like I was artificially inseminating the car.

I'm an EE too, but this Z sometimes makes me wish I was a mechanic/welder/bodyman/psychic instead.

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Haha! Sorry. I had the work done before the prior weekend, but was too rushed leading up to Zcon to get something posted. File it away and if you're ever psychic enough to find yourself messing with that thing again, do the hardware switch then!

And as for your posture working on yours... Pics or it didn't happen.  ;)

 

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On 8/12/2016 at 9:30 PM, Namerow said:

After measuring for proper length, I sewed the loop on the second end and it looks like this. Like I said, I'm no seamstress. I was focused more on strength than looks:
P1090664_zpstntwmmcr.jpg

Question for CO:  How did you do the stitching?  By hand?  Household sewing machine?  Jobbed out to your local shoe repair shop? 

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I stitched that blue one myself on an old household strength Singer machine that came to us from my Mother-In-Law. Here's the whole story about the sewing process...

I made that blue one as proof of concept. Easy peasy. As soon as proof of concept was a success, I pulled the trigger on the higher quality material from McMaster. The black webbing arrived and I started making a better strap to replace the blue one. First thing I did was doubled up the black webbing for additional strength. That worked fine, so I figured "If two layers was OK, then three would be even better."

Well not so... I blowed up the sewing machine. Ripped the teeth off one of the plastic gears inside. I knew I was overtaxing the poor old girl, but I pushed ahead anyway and she made it clear that she just couldn't handle the strain.

So since then I have learned more about sewing machine repair than I ever wanted to know, and I have purchased and installed a replacement gear as well as clean, adjust, and lube the whole thing. So at this point the machine is back to better than before I started, but I haven't gotten back to working on the final strap yet. I do know, however, that my household grade machine can deal with two layers of that black stuff, but not three.

I really didn't need to triple it up anywhere, but it was the over-engineer in me. When I get back to it, I'll either farm out the final sewing, or I'll limit my layers to two. :)

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I do too, and I looked at using them for this project. They're very flexible and I think that kind of webbing would work fine, but the reason I didn't use them was because of the age. Most plastics deteriorate with time and I didn't want to use 40 year old plastic webbing. I wanted new. I wouldn't use the old stuff. Webbing is cheap.

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On 8/16/2016 at 5:01 PM, Tomcat said:

I'd like to have one of those!

Thanks Tomcat.  Maybe Ryan from zcardepot can work up his own variant.  I'm surprised he doesn't have something like the RT style mount, considering how fast his development work is going on other areas.  His new Ford diff mount shows some imagination.

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One of my off season projects for this year was to replace my temporary light duty nylon web diff strap with a more substantial version made using a stronger webbing which I purchased from McMaster. I also figured out a simple way to adjust the webbing tension to account for stretch that may occur over time.

Here's what I started with. The blue webbing is whatever the local hardware store had on shelf. Worked great for the six months it was on the car, but I had already planned on replacing it after proof of concept. The black webbing is McMaster P/N 3510T83 - Shock-Absorbing Nylon Webbing, 1-1/2" Web Width, 5100 lb Breaking Strength:
P1090775_zpsxbbyjete.jpg

To adjust the strap tension, I designed a new adjustable anchor bracket for the driver's side mount. I had originally planned to put these new brackets on both sides, but the diff doesn't sit in the middle of the tunnel, and it was an uncomfortably tight fit on the passenger side. With the help of our resident sheet metal magician @disepyon doing the bending for me, here's what I came up with:
P1110729_zpsv0e5thfi.jpg

Here's the adjustable anchor assembled. The strap loop goes around the center shaft and the bolt slides in the slots to adjust:
P1110731_zpsuatgetyx.jpg

Here's my new strap in place. Original anchor on the left in the pic my new anchor on the right in the pic (driver's side):
P1110740_zpsknspxrda.jpg

And here's my adjustable anchor bracket in use. Loosen the bolt, pull down until desired tension is achieved, and then tighten the lock bolt through the middle:
P1110741_zps544f4c9g.jpg

Works great!! Thanks again disepyon for the help!!

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8 hours ago, sweatybetty said:

i would like to see if the bolt moves in that slot over time and stress

I was wondering that too. Might want to make some witness marks to keep an eye on it.

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Thanks guys! That pinch bolt is pretty tight, and I really doubt that it'll slip, but you're right that it could happen. I'll keep my eyes on it.

I can just reach the strap with a couple fingers with the car on the ground. That way I can check tightness without jacking anything up and crawling underneath. Makes it easy to tell without much difficulty if anything has loosened up. I'll keep you posted!

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Overkill, but you could put a jack under the nose of the diff and put some lift on it.  Disconnect the bottom mount so that you don't damage it.  Won't be surprised if you can lift the back of the car off the ground with it.  Assuming that the mating surfaces were oil/grease free.  I'm surprised sometimes that we don't consider the surfaces when bolting things together that require friction to do their job.  I'm sure that you did but it's often overlooked, with greasy parts assembled and bolts/nuts torqued.   You might even use some Loctite or similar to buy some shear strength if it slips a bit.

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Original pic links were dead (because photobucket sucks!!), so I refreshed the pics below.

I recently did some work on my front diff mount and strap and here are my findings from the project. It was my first time messing around with these parts.

Here is a pic of the old mount and original hardware. I'm replacing the mount because the rubber is soft and squishy. The original hardware holding the mount to the diff is hard to remove because the mount itself is partially in the way. It's much easier with the whole diff out of the car, but if you're trying to replace the mount without dropping the diff it's a pain in in the butt. I think you're supposed to remove the hardware using an open end wrench on the bottom and a box end up in the trans tunnel hump on the nut up top:
P1090619.JPG

I decided that since my original mount was already 75% split and squishy, that I would just split it the rest of the way and pull the bottom part of the mount off which allowed me to use a standard socket on the bolt head. In other words, I finished the destruction of my old mount to get to make getting to the hardware easier. Here's my old split squishy mount:
P1090627.JPG

When it came time to put my new mount in, I changed the mounting hardware scheme to socket head cap screws instead of the original hex head bolts. I don't know if this is old hat or not, but my custom hardware looks like this. Socket head cap screws on the left in this pic:
P1090774.JPG

So what's the big deal about using SHCS there instead of hex head bolts? The SHCS allowed me to use a hex driver on my ratchet like this:
P1090779.JPG

And tighten the bolts from the bottom like this. The hex driver clears the bottom plate on the mount so you don't have to deal with the original hardware anymore. If I ever have to mess with this thing in the future, it will be much easier to R&R. Box end wrench braced against the diff body to hold the nut on top and hex drive to tighten from the bottom, I found this much easier to work with than the original hardware scheme.

(Edit for new info) Only update I would make to the original procedure is that I would use a grinder to notch the diff mount plate a little bit to clear the heads of the socket head cap screws. The reason for that is the heads of the SHCS are taller than the original hex head hardware and even though I don't think I'm having a problem on my car, I can see the possibility that the lower plate of the diff mount may hit the heads of the screws if the mount is twisted enough. So just to be sure, I would take a little metal off the diff mount to clear the new screw heads.

But in any event, here's how easy it is to access the SHCS heads with the modified design:
P1090781.JPG

I used 1/2-13 x 4 inch long socket headed cap screws. You could also use M12 SHCS if you can't deal with the English hardware on the Metric car, but since the English stuff is so much more prevalent and cheaper for me, I used Engilsh. I used the black oxide hardware below to test fit, but for my final install, I bought some new zinc plated hardware for corrosion protection. This pic was before I had the zinc plated parts bolts on hand:
P1090642.JPG

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Good idea, I didn't think of that and used a grinder to make a notch in the mount for standard hex socket clearance.

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22 hours ago, Captain Obvious said:

You could also use M12 SHCS if you can't deal with the English hardware on the Metric car,

Hey Captain, i can't deal with english hardware on a Metric car!!! … I hate it!  ?  ….   btw... isn't that hex head called an allan key?   or is that tipically English to call it that? I've never heard of a SHCS bolt?  what does it stand for?   ( when Volvo made the p1800 there were also english bolts and things on it for a few years because they made them in England!  normally a Metric swedish car..)

 

EDIT... haha.. SHCS.... google... says   :  a socket head cap screw….  pfff..  we call it (Dutch) a: "inbusbout"   haha..  a bolt with an IN(side)  hex-hole... simple…  

Edited by dutchzcarguy

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Yes, the Allen key is what goes into the head. I've heard them called all sorts of things here including Allen screw, but I believe the official name (here) is Socket Head Cap Screw (SHCS).

I'd rather call it an inbusbout.  LOL  I like it.

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21 hours ago, Captain Obvious said:

I've heard them called all sorts of things here including Allen screw,

I prefer the Allen-bolt.

21 hours ago, Captain Obvious said:

I'd rather call it an inbusbout.  LOL  I like it.

Let's make it:  an inbusbolt!  :beer:

More on the subject,  My feb 1971 240z car does not have the strap, also the mounts are not there..  I ask myself don't they have one ( the early cars?)  Is it why my car shakes so much when going over 200kph?  (Last summer on the german highway, around 210 on the clock… totally Original engine!  ? )  Got the feeling.. any moment it's going to take of!!  ROFL

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