Help Me Identify These Parts (Photos Included)

[sopwith21]

Hi all;

Questions about my 1974 260z race car...

1. 206z REAR BRACE PHOTO. When I decelerate quickly or when I shift gears, I hear a big metal-to-metal "clunk" sound that is clearly from the rear end of the car. I thought it was a drive shaft issue or perhaps a rear diff mount, but upon examination those seem secure.

Please look at the rear frame bracket (first photo) that holds the rear end to the frame. The joint holding that piece to the frame is circled in red. Note that the photo was taken with the car on a lift, so the suspension is relaxed and extended.

Is there a name for this bracket? Is there perhaps a gasket here that could be worn or missing? Could that account for the big "clunk" described above?

2. 260z HALF SHAFT PHOTO. This is a picture of the rear drive shaft/half shaft. The passenger's side has no play it in whatsoever. The tire will not rotate when the car is in first gear, with the car on a lift, attempting to turn the tire by hand.

However, the driver's side has a bit of play. With the car in gear and on a lift, I can slightly move the tire and see the tiniest bit of play in this half shaft joint.

Can you tell me the proper name for this joint? And can you tell me if a slight amount of "play" is acceptable, or is that cause for immediate replacement of the joint? We had to replace this part several seasons ago and I am concerned that it might go out again.

When answering, please bear in mind that this is a race car.

Many thanks. You guys are the greatest!

[jfa.series1]

In picture 1, that is commonly referred to as a moustache bar, Nissan refers to it as a compression member - differential. Picture 2 is just a half-shaft U-joint. The moustache bar has a big rubber bushing pressed in at each end, yours may be well worn from track stresses. Swapping them out is a bit of a PITA. There should be no play in any U-joint - driveshaft or half-shaft.

[siteunseen]

I replaced mine with Hyper Flex polyurethane. It wasn't too bad with this Tech Tip for reference, thanks Blue.

http://atlanticz.ca/zclub/techtips/moustache/index.html

[Zed Head]

It's hard to tell when the diff mount is bad. The rubber will look okay but if you stick a long screwdriver or pry bar between the top and bottom plates and pry you'll probably find that it is weak and separates easily. When you accelerate the nose of the diff will stretch the rubber and when you let off the gas it will drop down and the top and bottom plates will hit, or the front of the top plates will hit the cross-member. Check the distance between the top and bottom metal at the front of the mount. There is a actually a spec. for the distance between the two plates.

Everything that you're asking about is described and illustrated in the Rear Axle chapter of the FSM. The diff mount is called an insulator and the "half-shaft" is called the drive shaft. What we call the drive shaft is known as the propeller shaft.

Index of /FSM

[EuroDat]

I agree with Zed Head. If the mustache bar rubbers look like that then the diff mount it probably shot as well. Replacing the mustache bar rubbers with originals is a right PITA. Redat on ebay sells them, but most people change over to PU bushes. Siteunseen posted a link to a great sight to get detailed info on how to do this.

The uni-joints are easy to replace and readily available through Rock Auto, MSA etc. I would change all four, but that is just me.

Chas

[sopwith21]

Fantastic - many thanks everyone! Double check me here...

• I've done biz with Rock Auto before and will get the U-joint through them.
  
• 
  
• I think I'll get the Differential Carrier "Mustache Bar" Bushings here - Spring Works - energy suspension polyurethane auto bushings nissan.
  
• 
  
• And I'll try the new aluminum solid diff mount here on this site: Motorsport! Solid Differential Mount, 70-78* 240Z-260Z-280Z - The Z Store! Nissan-Datsun 240Z-260Z-280Z-280ZX-300ZX(Z31/Z32)-350Z-370Z Parts
  

I think this should eliminate the "clunking" sound, eliminate any shifting and wear on the stock diff mount, and pre empt any failure of the u-joint.

Do you guys agree? Are these the right parts, and is there anything else I've missed here? Thanks again!

[Zed Head]

The parts look good individually, but the combination might not be the best. The solid front with the flexible back concentrates much stress on the front cross-member mounting point. Here's a thread from Hybridz that mentions it along with some other facts and options.

What is the deal with solid diff mounts? - Drivetrain - HybridZ

[sopwith21]

Read the whole thing, thanks.

I'd like to stay with the Spring Works polyurethane mustache bar bushings, but...

My searches are turning up lots of solid diff mounts, but few aftermarket urethane/rubber ones. Any suggestions? I think it's a cheap fix that probably needs done... now I just need to find the right part. Will keep looking.

[Zed Head]

The popular option is in the link, called the RT Mount. There are a couple of places to get them. Many people on this forum use it to get rid of the clunk. But others say that a new rubber mount and strap will accomplish the same.

http://www.classiczcars.com/forums/engine-drivetrain-s30/35995-ron-tyler-differential-mount.html

TechnoVersions - Home of MeterMatch, TachMatch, Diff Mount and MotorMatch

[EuroDat]

I would go with a standard front diff mount and the Ron Tyler diff mount to replace the strap.

Hardway has a great thread with lots of photos of the rear end and the Ron Tyler mount. It would be a good read to get an idea of what you want to do.

http://www.classiczcars.com/forums/open-s30-z-discussions/47863-lime-green-machine-restoration-thread-1972-240z.html

Cheers

Chas

[sopwith21]

Okay guys, many thanks. I've studied all the links provided, which really helps me visualize the issue since I am a race driver, NOT a mechanic. I'm buying the parts and overseeing a mechanic doing the work.

So please tell me what you think of this, based on your input above:

Keep the parts list intact (see above) but replace the solid diff mount with the TechnoVersions semi-solid mount with the urethane stud in the center.

This car has a racing engine that puts out an estimated 210 hp, so I'm afraid of going with a strictly stock mount. I'm sure we're stressing the rear bushings considerably more than intended.

Do you guys think this is a winning combination? Thanks again.