We put an 8.25 rear from a junk yard 4 banger xj in my brothers xj. It wines when geting up to speed. Was hopeing for an easy 4.10 gear upgrade but the noise makes me wonder if it needs more then fresh fluid. I have the front axle to match but want to get the rear figured out befor puting it in. Any idea what the noise could be. Any help would be appreciated.

 

Could be carrier bearings or axle bearings.

 

As GOD has said, could be bearing. From my experience it's usually a pinion bearing but it could be any of them.

Did you replace the fluid once it pulled it from the JY?

 

Fresh fluid was put in when we put it in the jeep. Where gona do axle bearings and go from there. Thanks for the responses.

 

Does it only whine on acceleration or does it whine all the time?

 

All the time.

 

My XJ 98 sport was doing this from mile 85,000 when I bought it to over 200,000. No real increase in noise over that whole period. But I got sick of it and had the axle swaped for a D35. I was told it was the pinion bearing. At that time I was not doing repairs myself and went for the swap. Although this is not what I will suggest you to do I think I could have gone another 100,000 miles with the same noise..