best diff and atf fluid

[farmboy]

hey guys ive got a '96 chevy z71 w/ the 5.7 and 170,000 miles. i am about to change the diff fluid and atf fluid. its time to do both anyways, but there is also a whinning noise coming from my rear diff. i havnt looked at the existing fluid but i suspect it to be the problem. anyways, what would you guys suggest for my application?

personally for the diff i was going to use either valvoline durablend 80/90 or lucas 80/90 (lucas claims to revive diffs and eliminate whinning noise...) but i would like to see what others have to say. thank you for your help! any input is welcome!

 

[AzFireGuy79]

I had a similar problem in my 96 SS camaro a few years back when it was stock. It turned out to be a bad pinion bearing. This is a common problem with the 10 bolt rears of that era. Not sure which diff you have ( probably an 8.5 10 bolt) but you might want to look closer at the noise. I highly doubt it is the gear oil, although this is the cheapest and easiest approach to the problem. Just dont get your hopes up that the fluid is the culprit. When does it make the noise? Highway, in town, all the time?

 

[farmboy]

it happens all the time. it whines w/ the movement of the gears... for example, it will get louder as u accelerate etc.

a pinion bearing eh? ill have to look into that. i just assumed it was bad fluid, as i have heard trucks do that as fluid deteriorates in quality. but i could be imagining that too . thanks!

any thoughts on a good fluid brand?

 

[AzFireGuy79]

Yeah its almost impossible to diagnose a problem via the internet as you know but I have seen what you are desribing on my GM vehice and quite a few others. Its a good place to start if nothing else. Could be a bad ring and pinion or bearing etc...

As far as a good gear lube I have always had great results with Red Line. I also use Amsoil Severe Gearas well. Both are great choices. For a good ATF look to Red Lines D4 ATF. I have used this in countless GM applications with greatly improved duability, extended drains and the ability to handle the blistering Arizona summers with ease.

 

[1WildPig]

Just another thought to consider but a wheel bearing may be worn as well causing some of the whinning noise - happened to me on a Crown Vic Police Interceptor I have...the rear end does whine and I thought it was getting worse but it turned out to be a front wheel bearing going bad adding to the noise. Any good gear lube, synthetic being better, should do fine..Luck to ya...

 

[pickled]

For that application amsoil universal ATF and Severe Gear 75W110 (SVT) would be the ticket. It will be interesting to see how much gunk is on your differential cover magnet.