2001 Nissan Sunny power stearing problem

Your mechanic could be right, but I wouldn't agree with his diagnosis until I inspected the car myself. Rack and pinion steering gears rarely make noise without there being some other real obvious steering problem. Also, it is extremely rare for a mechanic to rebuild a steering gear. If the parts are even available, they will cost more than a professionally-rebuilt gear with a warranty. You'll pay more for the parts and labor than for the rebuilt gear, and you'll have to hope the work was done correctly and won't have to be done a second time. Leaking seals is the most common failure, but they usually start leaking because of nicks or corrosion on a metal part, or wear in the housing that allows a metal part to move away from the seal. Rebuild kits don't include those metal parts, so that damage will destroy the new seals. Those are the three things your mechanic is worried about. Parts cost more, he might make a mistake, and the new parts might get damaged right away which may not be his fault. All of those things are addressed by the professional rebuilder. Those rebuilt gears are real inexpensive today.

The more common causes of rattles and clunks are worn ball joints, tie rod ends, lower control arm bushings, and anti-sway bar links and bushings. I would have the vehicle inspected at a tire and alignment shop for a second opinion. They're experts at finding the causes of rattles and other noises.

Yes it is hard to say without inspection.. but i want to tell you that i replaced and repaired ball joints, tie rod ends, lower control arm bushings when i install new shock absorbers and its mounts. but i don't know if i do anything about anti-sway bar links and bushings. i replaced all the above things and none of them work a little bit. when my mechanic adjust power steer rack it reduce little and after 10-20 km it whent to trouble again...

Like i said earlier i put my car in to testing where have huge bumps but there is no huge sound only when travelling in gravel kind of roads.. i felt little vibration to the steering column when this happens. power steering is very much smooth and when my mechanic adjust it it become little harder and he says it cannot be adjusted anymore and if it does power steering may fail. either way adjusting power steering rack didnt work...

the only thing i think to replace is power steering rack and the thing you mentioned (anti-sway bar links and bushings)...is problem will be okay if i replaced power steering rack ?

And you are right about the cost .. repair kit is way too pricy..

Please help...

Since you're only looking for the cause of a noise, here's something else you might consider. There is a tool you might be able to borrow or rent from an auto parts store that borrows them called the "Chassis Ear". It is a set of six microphones, a switch box, and headphones. You clip the microphones to suspect points, then drive around while listening with the headphones. You can move the microphones around to zero in on the source of the noise. Be aware that many mechanics have never seen or even heard of this tool. Suspension and alignment mechanics use it to find rattles, squeaks, and other noises.

The tool is available from the guys who drive the tool trucks to repair shops each week, but you can also find them on Amazon for about half the price. The original model used six wired microphones. On the newer model four of them are wireless.