hi all have I have a 910 bluebird it is an automatic. it start making this cracking sound when I knock it back to first. Then it started making it as well when I put it in reverse and gave it a bit of power. Now it does it when I have it in first and put the power down and when I back off as well. it is not diff noise. That is there as well. It sounds like metal on metal. I pulled the back seat out trying to see if there is a crack where the lower trailing arm Joins the floor. But I can't see anything.
has anyone ever experienced this before?

nik

Sounds to me as though you have a worn bush(es) and something is contacting? Aside from the cracking in the floor, I'd look in that area next.

At least it is getting worse so it will become really obvious soon what the problem is

I have changed the lower trailing arm bushes. Not the upper, though they look to be ok.
Your right about the getting worse thing. I just hope it doesn't become to obvious. Like my dad did the back brakes on his 85 hilux not that long ago and fogort to tighten the the wheel studs when the car was back on the ground and sure enough he was dragging his bum along the ground. not much damage but still a stuff around. I found it hilarious.
That said I don't want that to happen to my car.

I would be checking the drive shaft uni joints for slop.
Try wobbling the shaft in all directions by the joints and see if you can detect any abnormal movement.

_________________
Regards, Graeme
Just trying to help...
http://nissanman.shutterfly.com/
graemes@internode.on.net

It also happens under hard braking.

Is your rear end brakes disk or drum? If they're disk, it could be something as simple as your pads moving inside their calipers, which would be due to either the retaining springs not having enough tension, or not being there at all.

This is interesting as it pretty much eliminates the U joints. Braking pulls the rear wheels to the back as the body tries to keep moving forward. I would look at all control arm bushings at the rear cross member and the mounting points for the cross member to the body. Better check the differential mounts including the mustache bar.

Its very common for 910's to tear the rear trailing mounts of the floor.You will have to jack it up,throw stands under sills.Grab your wheel and try and push in and out and side to side...With a lever/pry bar see if you can get any movement out of anything under there....

_________________
68 510 - soon to be restored into a replica 68sss
69 510 - current build - L20b turbo
91 GT turbo legacy
GET THAT DATSUN DIFFERENCE!

It turns out that the upper trailing arm where it bolts to the car. the hole in it is a little worn so the bolt was moving around and creating a cracking sound. So I just did the bolt up as tight as I could so it would squash up against the crush tube and walla, no more noise.