Not sure it really matters, but I think the 55425-N4300 is the strap for the 280's with the R200 diff.

if you've got a 240, then I believe you want the 55425-E4100.

My measurements indicate that the two straps are different lengths.

Does it really matter ? I can't seem to find 240 straps. I do have this one also, but the previous one snapped:

 

Datsun 240Z 260Z 280Z Differential Arrestor Band Belt Rear 413 | eBay 

1 minute ago, bartsscooterservice said:

Does it really matter ? I can't seem to find 240 straps. I do have this one also, but the previous one snapped:

 

Datsun 240Z 260Z 280Z Differential Arrestor Band Belt Rear 413 | eBay 

if i put this one, next to the used oem one from the 280z they are the same length and width 

On 9/21/2023 at 3:39 AM, Captain Obvious said:

My measurements indicate that the two straps are different lengths.

🙄

Something I’ve run into more times than not is Sellers assume that what they are advertising fits the entire series. I’m sure there is not a lot of research going on before running the add.

All the pics are dead, but here's a thread I put together a bunch of years ago about my diff strap project:
https://www.classiczcars.com/forums/topic/55955-my-new-diff-mount-and-strap-project/

And here's a couple of the pics that don't show up in that thread anymore. Here's the older and newer side by side:

 

I found early strap to be 537mm and the later strap to be a little shorter at 529:

And here's what I ended up making for my car. I used heavy duty nylon web strap and made my own:

Edited September 23, 20231 yr by Captain Obvious

2 hours ago, Captain Obvious said:

And here's what I ended up making for my car. I used heavy duty nylon web strap and made my own:

How has it held up? How much abuse has it received?

creative, i like it !   Would those few mm really matter ? I can put the oem 280 strap on, or the one pvc one, that snapped only after 2 years.

 

I doubt the difference in length really matters. I just wasn't sure if you were going for a complete stock result or not. From a functional standpoint, I think you'll be fine.

21 hours ago, Patcon said:

How has it held up? How much abuse has it received?

I haven't even really thought about until this thread came up. So the good news is my diff isn't clunking, but I haven't looked at it since I put it in. Maybe checked it once to make sure everything looked OK, and then completely forgot about it. So... I'm guessing it's fine? 

the oem 240 belts are almost none to find anymore, i'll use the 280 one then, I bet it was more flexible when new haha, it became stiff, like old people 

3 hours ago, bartsscooterservice said:

it was more flexible when new haha, it became stiff, like old people 

I get that!! 

280 nos belt is on. Seems fine to me... 

 

Removed the taillight panel to get that original look and treat surface rust beneath the rear panel...

 

Fun thing is i found a photo of one in the Nissan museum that is glossy? 😂