What diff oil? (1 Viewer)

[crooozer]

Hi!

I checked my LSD rear diff oil last night for the first time and it's red.. and didn't smell unlike transmissiuon fluid. WTF? Is this likely correct?

Or should I drain it, and refill with something else? I will be doing the transfer case this weekend also, and someone here suggested I use 75w90 GL5 grade diff oil. , would this be a good choice for a LSD rear diff oil?

It's recently (in the past 6 months) developed a whine that I suspect is coming from one of the diffs.

 

[js93cruiser]

I use mobile one, I believe it's LSD rated if it isn't grab a bottle of LSD additive from the local parts store

 

[Jacques Villeneuve]

That's right; LSD is an additive; I had an LSD in a Pathfinder and bought the LSD additive from a GM dealer. Just dumped in the bottle into the LSD differential along with the 75w90. Unlike yours, the North American 80's did not get LSD.'s.

 

[crooozer]

Thanks guys. So the same oil for both trans case, and rear LSD, right?

Does anyone know why it's currently red?

 

[SZ01]

Thanks guys. So the same oil for both trans case, and rear LSD, right?

Does anyone know why it's currently red?

i also have the K295 axel set with LSD and after talking to the guys at Redline they suggested to use a GL-4 oil in the transfer case (and transmission if you have a manual) and a GL-5 oil in the front and rear diffs.

mobil 1 makes a GL-5 LSD oil and redline 75W90 GL-5 gear oil does not require the additive.

 

[Stevesnj]

It's just oil thats red it's okay. It may be synthetic.

 

[Bjohnston115]

i just replaced my dif oil with valvoline 80w90 and its holding up fine.

 

[crooozer]

Thanks y'all.
Is there any way to lessen the diff whine I'm getting, or should I just not worry about it?

 

[aclos3]

I replaced my front diff, rear diff and transfer case oil last weekend with Valvoline 80W-90 and it seems just fine (like it was before). I have owned the truck for the last 30,000 miles and had never replaced these fluids, nor do I have any idea when they were last replaced. The fluid that came out was the color of light honey -- like a wheat beer almost. The transfer case oil was ever so slightly darker than the diffs. The Valvoline oil I put in was the same color as the stuff going out.

All told, I should have used 8.3 US quarts of new fluid, but I only got in about 7.8 US quarts. The truck was on a lift and the front axle may have drooped forward a bit. I will check the levels this coming weekend and top up as necessary.

 

[Cruiserdrew]

Thanks y'all.
Is there any way to lessen the diff whine I'm getting, or should I just not worry about it?

If you know for sure it's a diff whine, you could try a higher viscosity diff fluid like 85w-140. It should lessen the whine but won't repair the worn bearings.

I did notice my t-case was quieter with Redline 75w-90 vs Mobil1 75w-90.

 

[Kernal]

crooozer: Mobil 1 gear oil, either 75W-90 or the heavier weight, is not red. Other brands may be, IDK. Not the expert but IMHO you have less options as to what you can dump into your Limited slip differentials compared to those of us who have open or locked differentials. I used a Moly additive for my locked rear diff for gear whine but you can't use that AFAIK. Using a heavier weight gear oil did quiet it down a tad.

Edit: ^^^ What he said^^^

 

[crooozer]

Thanks guys.

So, it's pretty normal on a truck with 200,000kms on the clock?
Will it last for ages before it goes bang, or is it likely to break soon, like everything else on it? Getting a little bit fed up with the 80 series..
It seems it's a truck for someone who just LOVES spending all their available time and money on. Not 'really' my kinda thing. But I love the way it drives!

 

[aclos3]

I'm sorry to hear that you're bummed about your 80. If taken care of, these trucks are not money pits at all, even at much higher mileages. You may just be suffering through some bad luck. If the truck has been neglected, it will be an expensive one to own. There are lots of large, expensive parts and systems on these vehicles, so it can be painful on the wallet if things start to break.

Does this whine go away or get very quiet if you take your foot off the accelerator? Does it only manifest at a certain speed range?

A diff whine, or any kind of whine is not normal on an 80 -- especially not a low mileage one like yours. However, us Americans are not familiar with the limited slip diffs, so maybe those wear faster. I would do the oil change and really watch what comes out. I would then check the diff fluid from the drain and not the fill port at every oil change to see if the diff was destroying itself. It is possible that the diff could survive this way for a very long time, or it could continue to get worse and eventually form a noticeable vibration and require replacement.

 

[crooozer]

Thanks mate. I will see if there are metal flakes in this weekends diff drain. Maybe there is and thats what I can hear, who knows.

It used to happen intermittently but now it's all the time, and at all speeds, speeding up and just coasting weather I give it power on remove foot from accellerator.
And it's almost impossible to narrow it down to the diff because I don't have a dyno (I'm guessing thats how you would listen for it) and it only happens when you drive of-course.

 

[crooozer]

Or could this be the frozen Viscous Coupler inside my transfer case I'm hearing?

I will be removing it this weekend. I have onbly one driveshaft connected right now.

 

[rove_mcanus]

Noise when coasting is a sign of worn pinion bearings. Try jiggling the flange/uni joint to see if there is much movement.

You probably notice it more with the front end disconnected as 100 percent of the engine torque is going though the rear, where as it would normally be 50 percent split with the front.

Certainly change the oil. It might be the wrong type. Diffs need a heavier oil then transmissions. Typically 90-140 where as transmissions are 75-90.

If the bearings are worn consider rebuilding as soon as possible. If it gets too bad it will chew out the gears, and getting a reconditioned replacement on a swap deal may be out of the question, and you will have to cough up for new gears (which is where it gets real expensive.)

 

[crooozer]

Thanks Rove. If you mean the driveshaft uni joint connection at the rear diff then there is no noticeable movement. Not quite sure where you mean.

 

[rove_mcanus]

That's exactly what I meant.

change the oil and see how it goes. If it is still quite noisy afterwards you might want to drop the diff and check it. On the bright side it's dead simple to remove. Don't even have to remove the wheels.

Finding the source of noises is usually down to experience. A rear diff will have a noise that comes from behind you. Folding down the seats and lifting carpets will help you to hear it better. A transmission noise will sound like it's coming right next to you since the tranny is nearly always right where the shifters are.

You could also isolate the rear diff by swapping driveshafts and running on the front diff

 

[aclos3]

Great advice Rove. I've never heard a worn out diff on an 80 before, but I have heard them on other vehicles. On a worn out diff, there is typically a very noticeable increase in the whine or vibration when you are on push the accelerator vs. coasting. Your description of the issue sounds like it might be something else. Definitely still change the diff oil though.

 

[crooozer]

Hmmm. I was trying to listen where it's coming from this morning on my way to work but really have no idea. And I found that it's more noticeable at around 40-80km per hour.

At first I couldn't even hear it (for the first 10 minutes) and then it slowly got worse, not like it's really loud or anything but it bothers me. I thought it might have been the tyres but I got new A/T's a few days ago, same noise. I wonder if it could be the VC.. Whatever it is it's put me ina grumpy ass mood again for the past fewe days and is totally pissing me off.