some people said that differential oil should be changed every 15000 mile or 50000 mile depending on driving conditions, other people said it shouldn't change because after changing the oil a noise will appear from drive rear end. i need opinions pls, i changed differential oil once & till now 40000 mile has been driven on that oil

 

Think GM sez 100K... Your locale I would do it more often awful hot there...

 

The Owner's Manual indicates:
If changing the gear lubricant with the correct material, and the LSD additive causes "a noise (to) appear from drive rear end", you have a problem with the rear axle that needs to be addressed.

If it were my car, I'd change it every 25,000 miles.

 

Injuneer, depending on ur quote from GM manual they said differential oil should be changed ONCE after the first 7500 mile & i think they mean the first 7500 mile in car's life but what about after that 7500 mile? should be changed regularly?? I dnt have any noises from differential rear end except for a quite noise coming from rear side & it will come only when speed increased from 20-60 mile only & actually its unnoticable noise. the point is: are there any noises will appear after changing differential rear end oil??

 

You must use the limited slip additive from GM or the posi will chatter around corners if you have a whine it probably means the crush sleeve on the pinon has loosened up and you backlash is now wrong and eating up the ring and pinion. New fluid should make it more quiet... generally aftermarket gears are more noisier than GM gears...

 

Read EXACTLY what is says. There is also a chart in the manual that shows what service is done at each check (7,500, 15,000, 22,500, etc), and there is no indication at all that any service is required for the rear axle. GM is saying, leave it alone.

But GM is concerned about severe service - i.e. trailer towing. Since WE (gearheads) tend to have higher HP engines and drive more aggressively, I think its fair to say we SHOULD change the gear lube at some set interval, depending on how high the HP is, and how often you run the car to WOT/max engine load. With my 800HP/800lb-ft setup, I change it every couple seasons, if the car has been raced (unfortunately, not much any more). I put hardly any miles at all on the car, but if its been subjected to the heat of high engine loads, it makes sense to me.

As noted, I think you should consider every 25,000 miles.

AS I already responded - if changing the lube cause noise to increase, there is a problem with the rear and it needs service. Changing the lube in a healthy rear axle assembly will NOT suddenly cause noise to appear. I've been working on cars for more than 50 years, and I've never heard that changing the lube will cause noise.

 

I change every few years when the urge hits me. Diff oil has a much easier life than engine oil. GM's recommendation is reasonable, to me. But the urge to change it does occur to me periodically. I do it every two seasons on my race car and it come out looking new anyway.

Rich

 

now everything is clear to me. actually, my car is DD & im doing some races but not on a track & as u can see from my sig i dnt have much mods. my last question: is the wheather playing a role on differential oil?? as everybody know we got a very high temp here, sometimes it will reach 60 or 65 C. the reason for changine differential oil is the gear jerking which its bothering me specially if i applied hard acceleration from 0, so when tranny changed to 2nd gear the car will jumps. so i said maybe if i changed differential oil the jerk will be quiter

 

I really can't understand your comments about "jerks"..... might want to try and clarify that. A "jerk" is a sudden motion, not a noise. Do you mean when the tranny shifts, it looses traction?

 

yes i mean sudden motion not noise. its like during tranny shifting the whole car jump or move with the tranny shifting either between gears during driving or between R & D when car stopped, & yes sometimes i lost traction during tranny shifting & LOW TRAC light will come on & as u know it will disappear after moments. this problem really makes driving uncomfortable at all. can i have ur email if u dnt mind???