justagoodolboy

It time to change my rear differential oil, and I have a quick question. I know my rear end is not positive track, so do I need the additive? I used 80-90w gear oil last time with 2 bottles of additive you get from the dealer, which by the way cost me through the nose! I know after reading the forum there has to be some better & hopefully cheaper options than going through the dealer, but I came up empty in my search results.

Thanks!

Jeff

timb

I've allways used 80-90 in my truck with good results so far. All original bearings and gears at 360,000 miles.

Ace

That liquid gold the dealers sell can be had on eBay for half the price if you want to keep using that. I'm surprised they even sold you the additive if your diff is a non-posi unit. If you do much towing and since you are in TX I'd recommend going with a 75/140 synthetic. Any GL5 gear oil will work fine, but the 75/140 syns hold up better under higher load/heat and you don't need to change it as often. More than offsets the cost, depending on your change interval.

dpuckett

No posi = no additive. I did the same thing in 00 when I bought my first 4x4. I had just gone through replacing all the clutches, etc, and wanted to make DANGED sure I didnt burn anything up this time round. Later, I found if you have a rounded carrier, you have an open diff. Still good insurance IMO.

DP

wannadiesel

What Ace said. The rear axle on a truck used for heavy towing is an excellent place for synthetic. Otherwise, plain old 80W-90 will do fine.

And no need for additive in the open diff.