That Lead Noise Damper for the Differential

[Gary L]

In Wick Humble's book HOW TO RESTORE YOUR DATSUN Z-car, In the chapter on technical bulletins he mentions that in 9-5-1975, in order to dampen rear differential noise, Nissan made available a 10 lb lead weight that bolts ATOP the differential to quiet noise from the ring-and-pinion gears. Has anyone ever seen one of these and has a pic of one that they could post ? And I'm not referring to the one that attaches to the differential's rear mounting support studs to cut down on vibrations or the stack of metal plates that hangs (bolts) beneath the differential's front cross member. This is supposed to be a lead weight ATOP the differential?

I just put a rebuilt diff in my 77 Z and although it is quieter that the original one, there is still some whining which must be from the ring and pinion since the bearings are all new.  I've read that even when these cars where new the diffs were a little noisey and I'm never going to get it completely silent, but I'm wondering if one of the lead weights Wick mentions would help. So if anyone has a pic of one of these I'd like to see what they look like.

Thanks

Gary

 

[EuroDat]

Me too

[Zed Head]

I want to see the companion flange with the rubber damper that comes with the kit.  Humble posted a kit number but it seems to be for the earlier 240Z R180 kit, not the 1975 kit.  99991-20000

[Jarvo2]

You mean this one...

 

[Zed Head]

No, that's the standard factory issue damper plate.  It's actually shown in the Rear Axle chapter of the FSM.  Gary L is talking about a retrofit kit that Nissan produced,with a lead weight on top of the diff.  (Don't know why he used atop, a bit archaic there Gary L...)

[Gary L]

No, thats the language used in Wick's book - atop; probably due to the original Japanese bulletin interpretation !

Below is taken from an old post on another Z web site at the following link

http://www.zcar.com/forum/10-70-83-tech-discussion-forum/40849-differential-damper-plate.html

"9-5-1975
A remedy for excessive noise from the early-style or R180 differential was isssued by Datsun in 1975. This is not to be confused with the kit used in 1971 to correct high vibration levels of the differential. It is not applicable to the alter R200 differential, which has no side-bearing retainers whith their five distinctive bolts. Nor is it recommeneded for 2+2 models due to interference with the rear seatbelt-attachment bolts. The noise was identified as coming from the meshing of the ring and pinion gears, then amplified by virbratiions in the body. Datsun's solution was to add mass - a 10 pound wight bolted to the differential housing. Also included was a replacement companion flange that included a torsional damper that helped absorb torsional vibration inthe drive line. The parts were cataloged under the part number 99991-20000, which included mounting hardware. The companion flange includes a disc section, much like a crankshaft vibration damper. It is easy to distinguish from the previous part. Installation was the same as that descrbied in the service manual. The mass damper is a solid lead weight that bolts atop the differential pinion-gear housing with two 7/16 inch bolts.
"

 

But Zed is correct, I'm not talking about the one pictured in 4 above.

 

Edited August 29, 2016 by Gary L

[Zed Head]

Edit - here's a cheaper version - http://www.ebay.com/itm/1978-Datsun-Technical-Service-Bulletins-Manual-Nissan-/371690698878

The right part numbers might be in here - https://www.amazon.com/Datsun-Truck-Technical-Service-Bulletin/dp/B017PZ7GMM?SubscriptionId=19FZ002EVKGD47C50K82&tag=datsun280zparts.com-20&linkCode=xm2&camp=2025&creative=165953&creativeASIN=B017PZ7GMM

Maybe they just took that early R180 weight, that bolted on to the bottom, and bolted it to the top of the diff nose for the 280Z.  Same part numbers.  Odd that they used 7/16" bolts.  I'm guessing that they used the two back unused holes of the R200 diff mounts and just strapped it on there.  The companion flange must be a fine piece of engineering though.

Edited August 29, 2016 by Zed Head

[Gary L]

I was actually thinking of picking up a sheet or bar of lead weighing 10 or so pounds and bolting it on top to those 2 unused holes Zed mentioned.

It'd be nice tho to see how NIssan fashioned/configured such a weight.

Bars of lead are fairly inexpensive but the sheets are a little more costly for example

http://rotometals.com/lead-sheet/sheet-lead-1-4-16-lbs-sq-ft/

And I'm sure the companion flange must be a precision, well balanced piece as Zed mentioned.

 

 

 

[Zed Head]

Funny how many translate the "lead" in to steel and what Humble references, in to the factory issued piece shown in the FSM.  On the other hand, Humble seems to be the only person that actually knows about the parts, and he got his part numbers confounded with the early part numbers.  He did a lot of writing about it.  He has to have seen hundreds of the big L-shaped steel plates though, that bolt on to the bottom.

Who knows.  I just want to see one of the differential companion flanges with a rubber damping piece, like a harmonic damper.  That would be cool.  Seems like it might be a unicorn though.