Captain Obvious

My New Diff Mount and Strap Project

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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_zpsrzprmtdy.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_zpskkjlcjjb.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_zpsurfbvjx5.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_zpse0y2zapl.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:
P1090781_zpsezywmqol.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_zpskfexu6jx.jpg
 
 
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Just my opinion Captain.....why wouldn't you install the R/T mount and never have to do the job again? The bump stop from above keeps the rubber from separating on the diff mount below.

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Ron Tyler is one of the most calm and considerate guys on the whole internet.  You are way off base Blue.  If you have something concrete to show, you should show it.  Your general frustration with the world is getting out of control.  

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Besides that, he lives out here in Oregon.  How would you know anything besides some internet posts?

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Don't really care what his personality is......he made a great contribution to the Z community......his R/T mount works great! I'm grateful.

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I just installed the stock strap ( new) with new mount on the 72 . I saw the strap mount bolts ( large ones) were going to be a PITA with the amount of tension on that strap. I had the diff out and had the diff mount mounted-( mouthful). I pulled the crossmember and bolted it to the diff mount and jacked everything in place at once. I used a trans jack and it was quite effortless . I didn't see anyway I was going to get that strap in with the diff there. I was actually impressed how snug and well it all fit and thought - why the hell I did the RT mount.


Sent from my iPhone using Classic Zcar Club

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Diseazd , I went with the stock type system because it's just simple and easy. I really didn't want to drop the diff, and while I've heard that installing the RT mount is possible with the diff in place, I've also heard that it's way easier if you pull the diff first. Doing what I did, I didn't have to pull the diff or mess with any of the driveshafts. My thinking is that the original stock mount lasted the first forty years and if I use a tight strap to keep the front of the diff from lifting, I should be able to get the next forty years out of the new OEM lower mount I just put in. And with that in mind...
 
sweatybetty, Where did I get a new strap? I sewed myself a new one! As proof of concept, I bought some cheap blue nylon webbing at the local hardware store and sewed loops on the ends. I'm no seamstress, so please be kind... Sewed a loop on one end:
P1090648_zpsd4xit30s.jpg

Here's how the loops fits over the mounting rod:
P1090652_zpsck0wawsh.jpg

In order to determine where to put the other end loop, I installed it in the car and measured for length by looping around both end mounts and removing the slack. If you look carefully, you can see my Sharpie marks:
P1090662_zpsgbawfy6k.jpg

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

Wrapped around both end mounting points and installed above the diff, it looks like this:
P1090668_zpswgm2i4vy.jpg

Summary... Here's all my parts. Old mount stuff on the right, new on the left:
P1090772_zpso5jvwjek.jpg

That lightweight blue webbing strap got me to Zcon and back, but it's really a temporary install. It's a thin gauge webbing of unknown origin and specification. Since making the original strap, I've purchased some known quality webbing from McMaster and I will make a second strap to replace it. Here's the better webbing from McMaster:
P1090775_zpsxbbyjete.jpg

So I don't have any data as to the longevity of my strap solution, but I can tell you that cheapie blue one has been in there for about a month and is still going strong. I can also tell you that it's doing a whole lot more for retaining the diff nose than my original stretched out crispy factory strap.
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13 minutes ago, Captain Obvious said:
Diseazd , I went with the stock type system because it's just simple and easy. I really didn't want to drop the diff, and while I've heard that installing the RT mount is possible with the diff in place, I've also heard that it's way easier if you pull the diff first. Doing what I did, I didn't have to pull the diff or mess with any of the driveshafts. My thinking is that the original stock mount lasted the first forty years and if I use a tight strap to keep the front of the diff from lifting, I should be able to get the next forty years out of the new OEM lower mount I just put in. And with that in mind...
 
sweatybetty, Where did I get a new strap? I sewed myself a new one! As proof of concept, I bought some cheap blue nylon webbing at the local hardware store and sewed loops on the ends. I'm no seamstress, so please be kind... Sewed a loop on one end:
P1090648_zpsd4xit30s.jpg

Here's how the loops fits over the mounting rod:
P1090652_zpsck0wawsh.jpg

In order to determine where to put the other end loop, I installed it in the car and measured for length by looping around both end mounts and removing the slack. If you look carefully, you can see my Sharpie marks:
P1090662_zpsgbawfy6k.jpg

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

Wrapped around both end mounting points and installed above the diff, it looks like this:
P1090668_zpswgm2i4vy.jpg

Summary... Here's all my parts. Old mount stuff on the right, new on the left:
P1090772_zpso5jvwjek.jpg

That lightweight blue webbing strap got me to Zcon and back, but it's really a temporary install. It's a thin gauge webbing of unknown origin and specification. Since making the original strap, I've purchased some known quality webbing from McMaster and I will make a second strap to replace it. Here's the better webbing from McMaster:
P1090775_zpsxbbyjete.jpg

So I don't have any data as to the longevity of my strap solution, but I can tell you that cheapie blue one has been in there for about a month and is still going strong. I can also tell you that it's doing a whole lot more for retaining the diff nose than my original stretched out crispy factory strap.

OK, this -- along with the socket-head cap bolts substitute -- wins my vote for, 'best improvised maintenance fix of the year'.  If you'd been a Nissan Service employee when these cars were in production, CO, they probably would have given you an award!

 

Who said chemical engineers can't think outside the box? LOL

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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

Edited by Zed Head
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Yeah, that blue webbing stuff is of questionable origin and specifications, and that's why it's a temporary install. The black stuff I got from McMaster is thicker and has known specs. The black webbing is McMaster P/N 3510T83 - Shock-Absorbing Nylon Webbing, 1-1/2" Web Width, 5100 lb Breaking Strength.
 
I was considering 2" wide material, but I'm figuring that 5100 lb breaking strength of the 1 1/2 inch wide stuff ought to be enough. And I used the shock absorbing rated material to deal with any sharp shock loading.
 
My blue temporary webbing has been in place for about a month and I've been reaching up there to check the tension occasionally, and so far, so good. So even for a temporary installation, it's holding it's own.

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Zed Head, I like your metal mount.

And about that leather looking arrestor band... I don't think that's leather. I think that's Super-Grip Rubber Flat Belting from McMaster - "Commonly used for material handling and light to medium duty power transmission, this belting has a textured rubber cover on both sides for a better grip on material than urethane. Inner layers are cotton. Width tolerance is ±1/8". Color is tan."

Something like McMaster P/N 5753K424. Three ply 1 1/2 inch wide:
5753k425p1-d03bl.png?ver=1407843356

I looked at a lot of flat belting before I decided to try my web strap approach.

 

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33 minutes ago, Namerow said:

wins my vote for, 'best improvised maintenance fix of the year'.

Who said chemical engineers can't think outside the box? LOL

Haha!! Thanks! I may have won the "more free time than money award", but other than that, I'm not so sure.

And I'm electrical, not chemical. But what's a discipline between friends?  :D

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12 minutes ago, Captain Obvious said:

And about that leather looking arrestor band... I don't think that's leather. I think that's Super-Grip Rubber Flat Belting from McMaster - "Commonly used for material handling and light to medium duty power transmission, this belting has a textured rubber cover on both sides for a better grip on material than urethane. Inner layers are cotton. Width tolerance is ±1/8". Color is tan."

Something like McMaster P/N 5753K424. Three ply 1 1/2 inch wide:
5753k425p1-d03bl.png?ver=1407843356

I looked at a lot of flat belting before I decided to try my web strap approach.

 

You're right, I accidentally ran the magnifier over it on his site and you can see the fibers.  Leather sounds tougher though.

That other one sure does look like a timing belt though.  I was just joking around, 

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20 minutes ago, Captain Obvious said:

Haha!! Thanks! I may have won the "more free time than money award", but other than that, I'm not so sure.

And I'm electrical, not chemical. But what's a discipline between friends?  :D

Well, I meant electrical, of course.  Chemical engineers just play with reactions and stuff.  Nothing useful.

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9 hours ago, 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

ZH, your metal strap design does everything the R/T mount does but is simpler, easier to install and lighter, thinking of going into production?

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I had the same clearance problem accessing the bolt when I changed my broken original mount.  On the new one, I used a die grinder to remove a little metal from the mount so I could use the original bolts.  Got good access with a standard socket and ratchet.

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Yup. That works. I considered doing the same thing as well, but decided that the SHCS option was easier and a little more forward compatible. I mean... I sure don't expect that I'll need to replace that mount again, but if I ever do, I won't have to grind clearance on each new one that goes in.

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While messing around with the diff straps, I noticed what may be some obscure Z car trivia...
 
Here are the two belts I have. Top is from my old 260 (stamped with P/N 55425-E4100), and the bottom is the one that I just took off my 280 (stamped with P/N 55425-N4300):
P1090682_zpsqcw6f0rb.jpg
 
I wanted to know the circumferences of the two, so I put some tape on the inside like this:
P1090577_zpsz10mv23v.jpg
 
And then peeled the tape off and measured the length like this. It's not an extremely accurate way to make this measurement, but was probably good enough. The measurements I got showed that the 260 belt was a little longer than 21 inches in circumference while the 280 belt was a little shorter than 21 inches circumference:
P1090578_zpswy2f0cr7.jpg
 
But the neat potential trivia part is that there are numbers molded into the ID side of each belt. The 260 belt has a "537" molded in:
P1090576_zpsnlrgj6hy.jpg

And the 280 has a "529" molded into it:
P1090616_zps1mbsqcwm.jpg
 
And if you interpret those molded numbers as millimeters, you'll find that the math works out almost perfect. So I don't know for sure if those molded-in numbers were in fact the circumference length from the factory, but it sure appears that way to me. It's also interesting to note that the 280 belt seems to be designed a little shorter than the earlier belts, even though it's for a R200 instead of a R180?:
P1090683_zpsrgcgkrtl.jpg
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On 8/13/2016 at 4:49 AM, grannyknot said:

ZH, your metal strap design does everything the R/T mount does but is simpler, easier to install and lighter, thinking of going into production?

Thanks GK.  I don't think that one product would be enough for a business though.  Plus I didn't keep the jigs, which were a patio expansion crack and a saw kerf in a log.  And a spare parts car in the garage for trial fittings.  I did it mainly for the challenge and because the new rubber stock mount was $70.

I think that somebody with a big metal brake could pop out one piece steel mounts that would use the four mounting holes in the body.  No welding, just two  bends and five or six drilled holes, depending on GM mount or snubber..

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