dankfrye@charter.net

After replacing all the bushings, struts and springs and putting in a Ron Tyler Diff mount, I finally found out where the famous rear clunk problem is on my 1978 280Z. It is clunking where the axle flanges go into the side of the differential. I can push, pull and rotate the flange and feel the slop while I'm staring at it. My question is; is it usually the side output bearing that goes bad or or the gear teeth on the companion flange to the diff gear itself? Can I replace this bearing with the diff in the car? Most of these rear clunk problems seem to come from other areas such as the diff mount or the U-Joints. Mine are good. Thanks for any info! Dan Frye

I have a '78 also and had the same problem. After replacing all my hoses and such, I still had a high idle so I removed my BCDD valve at the bottom of my throttle body and capped it. This solved my problems. You should be able to turn your idle screw all the way and kill your engine. If you can't then you have a vacuum leak. The seals in the BCDD valve get old with age and leak air, bypassing the throttle body. It is just an emissions device on deaccelation anyways.

Thanks! I've had it all together several times but I just have to keep taking things apart! I guess that's what makes old cars fun though!

Thanks Guys!!

My speedo cable is drooping down and hitting the steering coupler. Does anyone have any good pics that shows how it is supposed to be secured? This cable is in the dark on all of the pics that I have found. Here is a pic of mine. Thanks!

Thanks! I've done alot of reading too but there are so many contradictions. Some people even wish that they would have stuck with their stock manifolds. I would not be thinking of headers, of coarse, if my stock manifold wasn't damaged in so many places.

I discovered that my exhaust manifold has a crack at the #6 stud and I also broke all three of the large rusty studs at the flange the the exhaust. Instead of trying to get the exhaust manifold repaired, I thought about getting some MSA headers since I have about a $200 credit. I know that I will not see any extra performance with the engine stock and I don't want a very loud noise. Can anybody give me any comparisons between the 6-1 and the 3-2 headers. I will be attaching them to my stock exhaust for now. Iwas also wondering if one fit and installed better than the other. Thanks, Dan

Thanks! Great pics!

I've read all the comments about worn out parts causing the rear clunk but mine is just the opposite. I have a 1978 280Z that made no rear clunking noise what so ever with the old rubber bushings. I just replaced the mustache bar, inner control arm and sway bar bushings with energy suspension poly and now when getting on and off the clutch I get the clunking. I used lots of grease and I torqued all the bushings down to spec. When I dropped my diff down, I did notice a piece of thick rubber fell off the top of the diff ander the arrestor strap. I put it back in where I thought it should go. Is this a factory piece (it looks kind of like a piece of tire rubber) or did a previous owner put it there to eliminate the clunk in the first place? I now have a better handling car but also have the dreaded clunk! Thanks, Dan

The exhaust manifold might have a slight warp but now it is very small and the noise is barely audible. I never remove the exhaust manifold because the 3 bolts on the flange were very rusted and would not budge, even with much PB blaster. I did wire brush qand clean the are good and put some high temp exhaust/muffler sealer on it. I'll see if that helps. If it don't then I'll tear it all down later. I would rather get my new rear bushings on now.

Did the Sea Foam treatment through the brake booster hose. Besides smoking up my garage and half the neighborhood, I did find an exhaust leak at the bottom of #6 exhaust bolt on the manifold. I tightened it up along with all the others and readjusted my valves the right way. The car seems to run quieter and stronger. I still have a light tick when engine is warmed up but it's not near as bad. My valves were all tight because the guy that showed me how to do a valve adjustment said to put the feeler gage under the tappets on the drivers side instead of directly under the cam lobes. This apparantly makes a pretty big difference. Thanks for all you guys help!

Yes. It stopped ticking when I removed the plug wire to #6. When I swapped #5 and #6 plug wires, though, it started ticking again. I pretty much ruled out the plug wires, plugs and injectors by swapping them out. I also have brand new NKG plugs and plug wires.

Thanks! I'll try that.

Thanks for your suggestions. I was contiplating using Gunk valve medic or something similar but I was afraid that I might break some deposts loose and clog up my oil pump. My valve train does look prettty clean though so I might try it. I have cleaned my intake and throttle body both off and on the car so I think it's pretty clean. I have also taken my injectors out, cleaned them and tested the spray pattern. I guess the exhaust manifold could possibly have a leak. I have some sea foam and might give that a try.

I have already replaced the gasket. It don't go away when it's hot though. It starts ticking when it gets hot; just the opposite. Thanks