can oil without LSD additives cause low power and poor gas milage

96Finder · Jan 26th, 2008, 04:23 AM

Hello there.
Can regular gear oil in rear differential (without LSD additives) cause rear differential (which is LSD) to decrease power and cause poor gas mileage on my 96 LE 4x4 auto?
I've got about 13 mpg on average in 2wd mode. Low power is especially noticeable at higher speeds (above 50 mph) when it tends to switch to a lower gear when going up the hill.
I also hear whining noise from rear at those speeds, especially when turning. Can that be caused by the wrong oil or is that something else? Thanks

**88pathoffroad** · Jan 26th, 2008, 06:00 PM

No idea on the whining noise, but gear oil generally won't do that, no. Not unless your rear diff is just about completely stuffed and about to break itself.

Check which kind of fuel you're using...10% ethanol will generally cause a 5-10% decrease in mileage, plus winter formulation gas will also cause a decrease.

95'BlackP-Finder · Jan 26th, 2008, 10:05 PM

Cool, I didn't know a few of those things, but I can tell you that gear oil without the LSD additives made my 95 Pathy pop, crack and grab when turning, added the additive and stopped immediately. I assume the clutches were grabbing. I'd recommend the additive.

michen00 · Jan 28th, 2008, 11:37 AM

Did your problems start soon after you changed your differential oil? If so, I would definitely change it.

96Finder · Jan 28th, 2008, 07:08 PM

this problem I've had for quite a while... and I don't know if the previous owner put the right oil in there... the oil I put just recently had this label saying that it's good for LSD but I'm wondering if there still any additive needed...

Danmuzicman · May 31st, 2008, 08:40 AM

if its wining the pinion gear/bearing could have excessive wear on it. its makes a whrrrrrr-ing sound correct that increases and decreases with power?

rbo1577186 · May 31st, 2008, 02:52 PM

Not having the LSD additive shouldn't hurt anything, it should just act like an open diff.

Change the diff oil (the correct oil + additive). There may be some very tiny metal flakes in there. It's normal on a higher mileage diff.

Like 88path said, it could be on its way out, especially if the oil level got too low for a while. In order to lubricate the outer pinion bearing, the oil level should be correct, If it got really low the inner pinion bearing and carrier bearings could starve also. A bad pinion bearing will be noisy. Danmuz is on with the sound, the faster you go the louder, the slower the quieter. Sometimes, not often but sometimes a rear end will "roar" at a certain range, even from the factory. Sometimes after it breaks in it goes away and sometimes it doesn't. It's just the way Ring and Pinions are sometimes.

If your problem continues inspect the bearings/differential if you can. If this isn't it.... A whining noise with decreased mileage/power sounds more like an automatic transmission starting to slip a little.

minnight · Oct 10th, 2008, 10:38 AM

Can anyone recommend a good gear oil for the front and rear diffs?I have a 92 auto with 130k miles and i live up in nortwestern ontario,canada where the winters can get reeeeaaaal cold at times.I have the 4 wheel discs so im assuming the rear is LSD?

thejaron · Oct 10th, 2008, 09:20 PM

if your pf is equipped with LSD then it's best to get penzoil... otherwise unexpected results may occur. I filled mine (97 pf le) up with generic 80w90 gl5 and it was making weird noises... seems like what you got, so I shopped around for several hours for this stuff

Pennzoil® Gearplus® SAE 80W-90 GL-5

PENNZOIL® GEAR OILS

I found my bottles of that at Fred Meyer

VA06TITAN · Oct 12th, 2008, 09:50 PM

Quote:

Originally Posted by minnight

Can anyone recommend a good gear oil for the front and rear diffs?I have a 92 auto with 130k miles and i live up in nortwestern ontario,canada where the winters can get reeeeaaaal cold at times.I have the 4 wheel discs so im assuming the rear is LSD?

I would recommend AMSOIL Severe Gear 75W-90 (GL-5) for the front:
AMSOIL SEVERE GEAR EP lubricants excel in hot and cold temperature extremes. By design, they resist breakdown from high heat, preventing acids and carbon/varnish formation. Their waxfree construction also improves cold flow properties, and cold weather shifting: https://www.amsoil.com/storefront/svg.aspx.

I recommend AMSOIL Severe Gear 75W-90 for the rear also. Assuming that your Pathfinder has the Controlled Slip Differential. Even if it does not, you can still use this weight of gear oil. You'll find that this product may be a bit pricey compared to other brands, but you're purchasing a very high quality product. I hope this helps.

Feel free to use this application guide for future use. I find it to be rather handy. https://www.amsoil.com/scripts/runis...msoiloaf:index