This weekend I plan on changing out the gear lube in the rear diff. I went and bought a new gasket and planned on getting the oil as well, but neither mobil 1 or royal purple make a 80w90 that my truck demands. I wanted to put the best in there, any suggestions?? Also any how-to on the project would be greatly appreciated. Am I right thinking the differential holds around 2qts. Thanks all.

 

I put Castrol semi-synthetic in. It was what A zone had at the time.

 

Just make sure it has the proper additive for chevy cars and if you are right about what it takes. If you are then valvoline, penzoil, castrol, etc all make a perfectly good 80-115 or so lubricant that will do the job. The proper listing for being used on chevies ought to be printed right on it and any popular brand should be fine. If it is not listed right on the product you purchase, there is a proper additive made for chevie rears that ought to be used.

Yes, about two quarts, but spillage can easily make it into the third quart. Buy an extra one and use the left overs for chores requiring a good solid oil.


Be careful removing the plug, dont strip it out with inferior tool.

 

my autozone has mobil 1 75w90 full synthetic, will this satisfy the 80w90 requirement? Are there any risks in using a 75w? I read on the mobil 1 website that it meets all gl-5 classifications??? has anyone put this in their trucks??

 

I used this on both the front and rear diff of my old '97 Dodge Ram. Never had a problem with it. This is what I will be using in my Bravada this summer.

 

Kyle, did your dodge ram recommend 80w90? Your comfortable about putting in the 75w in your bravada rear end? I'd really prefer to use it, but I don't want to screw anything up and be stuck with a huge repair bill.

 

Yes, the Ram spec'd 80w90. The 75w90 will do fine. It's kind of like running 5w30 for winter engine oil, but being able to run 10w30 in the summer (in some engines and climates). It's alittle lighter when cold, but the same weight when up to operating temperature.

Have a read thru this:
HowStuffWorks.com - What does the weight mean on a can of motor oil?

Here's a link to Mobil's website, specifically the 75w90 gear oil. This oil contains the friction modifiers for the limited slip so no additive is required unless you are really worried about it...:
Mobil 1 Syn. Gear Lube 75w90

Heck, I'm running 10w30 in my Bravada engine right now because it was leaking oil past the oil pan o-ring on 5w30, but that was before I tightened down the pan. Doesn't show any difference even over this past winter (as mild as it was). Next oil change will be back to 5w30 though.

 

ok then I'll put in the 75w, thanks for mentioning about the additive aspect. I didn't even know that was requiered in some oils, or should I say existed. So, I assume I can just drop the pan, put on a new gasket and just fill until the bottom of the plug (2qts) and be done with it without any additives?

 

Should be good to go. I'd take and clean out the diff with some brake parts cleaner. When I did both the front and rear of my Ram, I just used some black RTV (no gaskets - none were available) and 2 cans of brake parts cleaner (one per diff) to clean out all of the old oil. This cannot be done on the front diff of the blazers, but I'd alteast drain and refill the front. The rear, you can pull the cover off and really give it a good cleaning. Allow the brake cleaner to fully evaporate before putting the cover back on and refilling it.

If you have any rust on the rear cover, now would be the time to get it cleaned up and repainted. You do not want your diff cover to rust through!

*EDIT* - Front has a capacity of 2.6 pints (very roughly 1.5 qts) and my references state 1.75 quarts in the rear, but like everyone has said, it'll probably take 2 qts or more if you spill. If you get 4 qts, you'll have more than enough to do both axles. 3qts would not do it.

**EDIT** - Here's something interesting that I have found. TSB 01-00-90-001A Subject: Rear Axle Lubricant: See attached images...


[IMG]local://upfiles/667/51638CC753694273BF5C23A1740BF126.gif[/IMG]

[IMG]local://upfiles/667/AAD16298506C436AAA35D9A1F1B81C80.gif[/IMG]

 

interesting read, thanks for everything. While I'm picking your brain we have standard differentials not locking correct? And the blazers rear end is a limited slip? Also if you have access which seems to be very top secret info the location of the egr valve on 02+ blazers. Napa sells one that looks just like the previous years but its not sandwiched between the alt/compressor.