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twsutt

What's its purpose?

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Okay, I'm reassembling things after replacing the bushings on a 1975 280z.

This piece fastens to the differential crossmember. It's made of 1/2" steel plates and weighs about 10 lbs. What's its purpose? Does it have a name? Is it necessary?

not to scale:

unknown.jpg

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That piece looks a bit different than the standard piece on the 240Z I'm accustomed to looking at which is a simple rectangular piece, but assuming it is connected to the bottom of the front diff member, it's the same piece and is a vibration damper designed to minimize the transfer of vibrations to the body caused by the drivetrain.

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Thanks =Enigma=.

Sorry about the illustration, but I'm drawing from memory and the last time I saw it was several days ago and I had been working past my bedtime.

I hate to admit it, but I kinda' forgot which way it's supposed to attach to the front diff. crossmember - does the "built-up" part face the front or back of the car?

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Good question. I'll have to leave this to one of our 280Z owners, however I'm not sure it would make much difference. If it were me, I'd put the large end towards the back.

Unless you have a good reason for wanting to remove it, I suggest you leave it in place. The official name is "PLATE DAMP DIFF MTG - RR".

The part number are as follows:

pre 12/74 = 55418-N3000

post 12/74 = 55418-N3701

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Enigma was correct as far as I know. If I rememeber correctly, only the automatics had this vibration dampener. So if the car was originally an automatic, then that is most likely what it is.

Not totally sure of anything nowadays,

Dave.

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My 240Z in not an auto and I have one of these. I belive they were originally added to the 240Z as part of a multi part fix for the vibrations caused by the forward placement of the diff. This placement issue was later fixed by moving the diff back, but it seems the dampener remained for good measure.

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I'm the third owner of my Z, and as far as I know the 4-speed in the car is original equipment. I've looked through tons of pictures here and on HybridZ.com and on the few pics that show the front differential crossmember none have this dampener on them. In the case of my car, since it's not just something that a P.O. put on the car, but an actual Datsun part, it will go back on. Besides, it makes a great, solid jacking point. (I just hope that I can figure out which direction to face the darn thing.)

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I've got a 75 280Z with the OEM 4 speed and it has it as well. If I remember correctly the tall portion goes in the back. If nothing else see about lining up the holes with the bottom of the case...should only fit one way....Let me put that another way (LOL)...more than likely someone could probably install it wrong tho if they tried real hard...(LOL)

webdawg1

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Is this what you guys are talking about? (I'll be embarrast if it's not). When we bought my car several years ago, it was lying on the passenger side floor, and ever since I've always thought it was just some piece of medal welded up that the previous owners had left in the car as it doesn't look professionally made. For some reason I've kept it (not knowing why), but here it is. Is this crucial to have on the car if this is what you guys are talking about? Anybody have a picture of one mounted on their car? My car is a 4 speed by the way too.

mountmb3.png

mount2mh6.png

What's up with this?!?

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I wondered about the thing when I was reassembling my Z 3+ years back. I could see no real reason for it and left it off. I cant see any difference one way or the other.

Gary

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Hmm. None of the three '71s I've had (both manual and automatic) have had this part. Was it something Datsun came up with later?

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76Datsun280z,

Yep, you got it. That's the peice. Thanks for posting photos.

And I agree with you that it looks like a homemade part - it doesn't have the fit and finish that everything else on the car has.

Webdawg1,

I wish that it were as easy as just bolting it up the only way that works, but with two bolt holes-and nothing blocking the raised part on either side of the front differential crossmember-the part can be attached two ways (four ways actually, but we wouldn't even consider placing the tall part downward.)

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twsutt,

I'll check when I get home tonight and see if I can see the outline of when it was actually bolted up to the bottom. (Read lack of dirt/mud/dead bugs/vermits/and lots of grease) (LOL)

That's why I restated my comment about it being possible to install it wrong. (LOL)

webdawg1

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webdawg1,

If it can be installed wrong - I'll be the guy that does it. :stupid:

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My 77 had similar piece. Very homemade looking with bad welding. It was loose and rattling around, couldn't find anything about it so i took it off.

Vince

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In my second picture, do you think that's how they made it, or do you think it got bent? Dumb question, but don't see how it could have been bent unless it was under some real stress as that thing ways a ton.

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Austen,

I don't think that yours got bent, I think that they were put together haphazardly. Here's some pic of mine taken from the back of the car looking forward.

100_1616a.jpg

100_1614a.jpg

100_1612.jpg

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Thanks for pictures! That really helps show where and how it's mounted. I think I'll probably just leave it off as I don't really see much of a reason to put it back on, unless you guys think it's pretty crucial to have on there.

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Great Pictures! Now I'm going to have to go out and see if I have one...?

Thanks for the info.

Chris

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From what I can tell there was a design change in Dec. 1974. This is from carfiche.com.

carfiche.jpg

Does anyone know what the "ICA" column means?

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