My New Diff Mount and Strap Project

[Captain Obvious]

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:

 

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:

 

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:

 

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:

 

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:

 

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:

 

 

[sweatybetty]

where did you get the new strap? i need a new one

[Diseazd]

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.

[240260280z]

RT is a jerk.  I would never buy anything with his name or credit.

[Zed Head]

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.  

[Zed Head]

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

[Diseazd]

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.

[madkaw]

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.


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[Captain Obvious]

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:

Here's how the loops fits over the mounting rod:


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:


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:


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


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


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:

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.

[Namerow]

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:

Here's how the loops fits over the mounting rod:


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:


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:


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


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


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:

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?

[madkaw]

Blue stuff looks a little weak compared to what I just installed from Z car depot or the stock one I took out.


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[Zed Head]

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.

 

Edited August 13, 2016 by Zed Head