Two issues. Noise when leeting off accelerator and knocking noise at rear.

This is my first post since join a whole hour and a half ago.

I just bought an '85 300zx. I do realize it needs some work, and I'm hoping u guys can help me out.

Driving it home I noticed two things:

first issue,

When i let of the accelerator after giving it abit, there seems to be a slight grinding noise. The same noise can be heard when putting the car into second or third gear.
Sounds like a wrecked gear box?

Second issue,
When driving along a road, going around corners or over slight bumps on a highway there is a knocking sound at the rear end. The previous owner said the rear drivers shock is 'leaking'. I had a look and it looks like a hydraulic shock. (I know almost nothing about cars - yet - I plan to learn alot!)
Can shocks make that noise?

Cheers. Z

 

an 85' would be a Z31, i doubt shocks would make that noise unless they were completely loose.

 

Yeah it is a Z31.
cheers, I don't think they're loose though. I'll check in the morning.

 

Kind of sounds the same problem that i had too, but with my z32 with that grinding noise. Turned out to be the tail shaft center bearing

 

How was it cost wise for parts and labor?

 

Your noise could be gearbox but I'd first check the tailshaft centre bearing.
I had my centre bearing replaced about 6 months ago for $250 parts and labour but that also included some welding on the exhausts.
Repco sold me a pair of rear shocks for $195 and my mechanic fiited them for $50 (I removed and replaced all the boot lining panels for him)

 

Yeah, have a look at tailshaft centre bearing - if it's not there it might have fallen off.