Differential Lube

[MarkD51]

Been thinking of yanking the rear Diff cover soon on the 97 Tahoe (with factory limited slip), dropping out Mobile 1 which has been in there, do a nice drain, new gasket, paint the cover, and refill with Amsoil 75-90 Severe Gear Lube. Whattaya think?

I'm thinking 75-110W Amsoil might be unnecessary, but would like some input, and recommendations?
Mark

 

[Goodinblack]

I would go with factory fill spec stuff imo

 

[SunlitComet]

80w90 dino gl-5 or 75w90 synthetic will do fine. for factory lock no friction modifier is needed.

 

[MarkD51]

Let me just ask this question, about gear lubes, and addressing in particular, Amsoil Brands.

They offer 3 varieties in their "Severe Gear" full synth line, 75-90W, 75-110W, and 75-140W. All supposedly surpass GL-5, and many other specs.

What harm-foul would there be using 75-110W, or 75-140W Amsoil full Synth Lube?

As from what I always understood about all lubricants-oils, a multi-viscosity lubricant will be what it will be required to be, according to internal temps, loading, ambient temps.

In other words, 5-30W oil will "act" as 5W under cold conditions, and initial cold fire-up, and be no heavier than 30W ultimately.

I'll assume the same for Gear Lubes as well, and usually with synth gear lubes, they commonly have a lower temp pour point which is important in temp extremes, such as sub-zero cold.

I cannot forsee such wider range of gear lubes being a detriment, especially under extreme high heat, and severe conditions such as towing, racing, off roading, etc.

About the only worry I might have with Amsoil, is I know there were some service bulletins about certain RTV Sealants. being used as Gasket Sealers.

I'm guessing Permatex Black should be OK, provided some time is allowed to let set-dry, and I'm assuming there shouldn't be any issues at the Hubs on a Chevy Rear in regards to leakage?
Mark

 

[ccapehartusarmyINF.(ret)]

i just changed out mine with 80 90 royal purple
my tahoe is completely royalpurpled

 

[SunlitComet]

there was a time when a synthetic would eat up a specific rtv so it was not advised in the rear end unless it was manufactured after a certain VIN breakpoints. There was a number of different axles involved but the the but the 1/2 rears in our suv were clear of any breakpoints from the factory. Besides chemical formulations have improved over time. you can chose between two different gasket types for the rear if you like. the more expensive one is preformed like the valve covers, improved intake design and the oil pan. that one would require no extra sealant of any kind. the 75w-140 was initially recommended for the front axle when people had axle shifting issues when really cold outside but is permitted in front or back for consumer choice.With our GVWR specs 75w-140 synthetic gl-5 compliant is more then enough.

 

[Rangel]

i just changed out mine with 80 90 royal purple
my tahoe is completely royalpurpled

working toward this running the new HMX.

 

[MarkD51]

On my Tahoe, after about 5K, I swapped to Mobil 1 Synth Gear Lube, but did a makeshift evacuation, with suction gun, removing as much as I could after warming up, and "agitating" rear gear lube.

As they say, you never get it all, and perhaps the very last bit that I didn't get had the most amount of contaminants?

This time, the cover will get yanked, properly drained, new gasket,and refilled with Amsoil.

This should be the last time this rear axle will ever need servicing in this lifetime. I should be good until either the Tahoe dies, or I leave this world.

We encounter extreme heat here in the desert southwest, I'm only 30-40 some miles as the crow flies from the Trinty Site (1st Atomic Bomb), and 3 or so miles east of White Sands National Monument-Missle Range. While sometimes it doesn't "feel" like it, 108-110 degree temps on a daily basis occur here for 6-9 straight weeks in the summer months. At ground level, I'm sure eggs will fry. Not as hot as some parts of AZ, or CA, but sure hot enough.

Here's my Tahoe overlooking the City of Alamogordo NM.
Mark

 

[SunlitComet]

Well I need to do all my fluids before I go to AZ next month, both axles, tcase, engine, coolant and hinge lubing.

 

[MarkD51]

Well I need to do all my fluids before I go to AZ next month, both axles, tcase, engine, coolant and hinge lubing.

I would think the weather should be "perfect" by the time you go.
It's usually around late June-July that AZ starts getting those wicked 110+ degree temps.

 

[mattluttrell]

I see 5F in the winter and 100F+ in the summer. I always just put 75Wor80W-90W. I put the same stuff in the BMW, Escalade or Jeep with air locker and limited slip.
I've never had worn gears or bearings or oil go bad other than from being submerged in a river.

I'll pull carriers and gears on a car once a year so I'd see the damage. I've been lucky with the default gear oils I guess

 

[MarkD51]

there was a time when a synthetic would eat up a specific rtv so it was not advised in the rear end unless it was manufactured after a certain VIN breakpoints. There was a number of different axles involved but the the but the 1/2 rears in our suv were clear of any breakpoints from the factory. Besides chemical formulations have improved over time. you can chose between two different gasket types for the rear if you like. the more expensive one is preformed like the valve covers, improved intake design and the oil pan. that one would require no extra sealant of any kind. the 75w-140 was initially recommended for the front axle when people had axle shifting issues when really cold outside but is permitted in front or back for consumer choice.With our GVWR specs 75w-140 synthetic gl-5 compliant is more then enough.

I did ultimately decide to just go again with Mobil 1 75-90W, got 3 qts, a Felpro Gasket, small tube of Permatex Ultra Black Sealant, and a can of VHT Satin Black Engine Spray Paint. Will do the lube changeout hopefully this weekend if weather cooperates here.

My plans are to drive the truck a few miles, warm up, then drop.

I have read some here, about fill capacities, and how some fill to the side fill port, and others suggest not to, to fill slightly below this point. I've always filled till the Lube just began to flow out the Port, and capped? Any harm in this?

Vehicle is my 1997 Tahoe 4x4. (Rear Differential)

I plan on cleaning-prepping all mating surfaces, they'll probably lastly get a 91% alcohol wipe, and thought of just wiping a very thin coat of the Permatex evenly on both sides of the Gasket. button up, torque to 30 ft lbs (in 1/3rds approaching final torque values) and of course in a criss-cross fashion.

Let Sealant set up overnight, then fil the next day.

Sound OK?

 

[SunlitComet]

continue to do that voodoo that you do so well.

 

[mattluttrell]

I think the general idea is to get good oil on the metal surfaces. I think all the other decisions have little impact. I think your plan is good if not over the top. I'd just fill until it starts coming out and don't tighten the bolts so much that it warps the cover. It should be great.

 

[MarkD51]

continue to do that voodoo that you do so well.

That sounds like a go, and a thumbs up from you.

I'm going to sleep better tonight. Thank you SLC!
Mark

---------- Post added at 07:50 PM ---------- Previous post was at 07:37 PM ----------

I think the general idea is to get good oil on the metal surfaces. I think all the other decisions have little impact. I think your plan is good if not over the top. I'd just fill until it starts coming out and don't tighten the bolts so much that it warps the cover. It should be great.

Smartly, many years ago, when I worked for Amtrak as a Carman-Mechanic, I amassed an expenisve array-quantity of Snap On Tools. Some regrets later, as I probably could've bought twice as many Craftsman Tools! Got a few good Torque Wrenches though in the process, and my hands over the years have "a built in torque wrench."

Ahh, hindsight always has 20/20 vision, doesn't it?

A good plan I found, is to torque in 1/3rds, reaching required final torque values.

For sure, I'll eyeball the rear cover after removal, inspect, and finesse any weird dimpled bolt holes for trueness.

I'm hopefully going to enjoy doing this job, which I'm sure all will go well, love working on my Hoe, keeping it up, and looking-running good!
Thanks for the reply, and have a great weekend folks!
Mark

 

[SunlitComet]

Long live snap-on.

 

[MarkD51]

Dropped Rear End Cover this morning, lube looked fairly nasty, and the internal magnet had some "furr" around it, but no shavings, or anything large, so reckon that was a good sign, and that furr on the magnet of course can be expected. Cover came off easy, no wrestling.

All seemed to go smooth, took a wire brush attachment, and a drill, and cleaned up the outside of cover, cleaned, and got all mating surfaces clean.

All torqued up, but will wait till tomorrow, or maybe even Monday to fill. No rush, I figure the longer the Black Permatex Ultra sealant sets up and cures, the better.
Mark