This can't be good

[oil pan 4]

Today I pulled the diff cover off my 1984 6.2L (non turbo) diesel 2x4 half ton chevy suburban.
When I pulled the cover I saw the ring gear had copper colored discoloration on it where the pinion drives the ring gear. Knowing it's not some kind of copper addtive rubed on ther it can only be heat discoloration from metal being heated to a straw color, about 450'F.
The old oil was only filled to about 2/3 to 3/4
Now I have 2 gear oils, I was going to use one of them. Both are 80-90 weight, both are GL-5, neather are synthetic.
One is penzoil the other was cheap-o in a gallon container for $9. I don't think I want to use eather one of those any more.
I bought this turck for the long interstate hauls up to 1000mi each way, some times trailering a car. Z28 camaro + trailer = all most 6,000lb.
I have pulled quite a few covers, never seen a ring gear that looks like this.
The gear oil VOA page didn't have ****. Only found 1 oil that I could/would buy.
Is this bad?
Its only a 170Hp engine w/auto transmission, it can't dish out that much punishment to the rear can it?
I'm guessing every one will say grab synthetic?
What is a good gear oil?
I got 80-90 weight for the possibility of better fuel milage, should I maybe think about some thing different, heavier?
It wouldn't be hard to rig up a rear end cooler with pump and filter, should I install one before the next long tow maybe?

 

[acewiza]

Put some 75w-140 synthetic in it and button it up with a finned cover. Should be good to go if it is still intact.

 

[Pablo]

Differentials get hot - towing or hauling - they get REAL hot.

Since you have some new fluid, just use that as a short flush. Then go with a good synthetic 75W-90 or better a 75W-140 GL5:

Severe Gear 75W-90
or
Severe Gear 75W-140

 

[oil pan 4]

The rear is in tact, it didn't come close to the point of no return.
I asked around and herd stories of blued gear teeth and so on.
I allways wanted one of those fined covers.
IMO they cost to much, never needed one before. I should check ebay I guess.
My inferred temp just got in, I guess I'll have to point it at the diff some time soon.
When I tow I use all 170hp when I run into hills.

 

[TheLoneRanger]

OilPan, did the gear teeth look scored? If not and they were still smooth, I think you're OK.

I agree with using a syn 75W140. You need all the protection you can get. Forget about the better mpg with the lesser weight oil, it's not worth it in your case.....

 

[1040 WreckerMan]

As TheLoneRanger said, as long as the teeth are still in good shape don’t worry. A little discoloration will not hurt them (blued is another story) and those gears will last a long time. It’s real common to see 225+ *F in a diff, especially when towing. A good 75w140 is what I would use, probably syn would be a wise choice as well. Mobil, RedLine, SF all make good 75w140 gear oils. If you want a deep cover, PML (at www.yourcovers.com) make sand cast covers for a decent price. Mag-Hytech is also very nice, but quite a bit more expensive usually.

 

[oil pan 4]

The ring gear teeth look normal and smooth just a straw/copper color where the pinion rubs and contacts it.
Also the guy that owned it before me put a few coats of rubberized under coating all over the diff and cover.
Yea I bet that helped the heat a lot, build up I mean.
That is why I all ways in the past cleaned the diff cover off and threw on a coat of paint.

[ August 16, 2006, 04:13 PM: Message edited by: oil pan 4 ]

 

[Steelhead]

don't waste your money on one of those boytoy chromed fin covers
just use the Amsoil Severe Gear 75w140 in those severe service towing conditions...change ever 50k

which is more cost effective, 75w140 with long rear end life or 1 mpg gain in fuel mileage and rear end replacement at Joe's Rip Your Rear End Off Auto Repairs in Timbuctu?

that GM 6.2L stoker smoker may not have high rpm horsepower put she puts lots of diesel torque to the back end, just what you need freeway towing for long distances....
the dino bacon drippings GM 75w90 turned to vapors and left that hot diff.

 

[unDummy]

As mentioned, use the gear oil you have as the rinse.

Then, buy ANY 140wt SYNTHETIC gear oil for the next change.

I truly doubt that you will notice an MPG change with just a rearend fluid change.

 

[acewiza]

Yeah forget about the finned cover. Who cares if the heat hardens the seals, causes a leak and kills it that much quicker. Just buy an extra couple quarts of that expensive Amsoil gear lube and keep adding it. Problem solved!

 

[oil pan 4]

Well I grabed some Mobil 1 75-90 weight $8.88/qt.
Didn't put it in yet.
I wanted to get the 75-140 weight but it was $15.somthing a Qt !? Over $60 to fill my rear!
It took over 3qt's of the cheap by the gallon stuff.
I will change it out, I had to rush it into service so I could go buy a starter for my Z28 and buy the Mobil 1 gear oil.
(turns out the starter wasn't bad just the selonoid connection was crusty)
I know that thing was getting hot, the inside of the rear carrier and every thing in side was blackened unlike any other rear end I have ever seen.

 

[acewiza]

Wow. I remember getting some ST 75-140 syn at Wallyworld a couple years ago for alot less than than. Don't remember exactly how much it was, but it had to be alot less than that. Got some Mopar 75-140 off a guy on eBay last year for about $10/qt. as I recall. Gotta shop around, but I guess if the rig's down you gotta do what you gotta do, been there too.

 

[TheLoneRanger]

I was at WallyWorld the other day looking at gear oil, and the syn 75W140 is indeed about $14/qt. A GALLON of dino 85W140 is only $9. It's really hard to spend the extra bucks on the heavier weight syn, but consider it's a one-time cost and should last 100K miles. The dino will need to be changed probably 3 times as often to gain the same protection. Then there's the time and trouble of changing it.

When all these things are considered, the syn looks more cost effective. I'm in the process of changing all 3 of my vehicles to syn 75W140, and then I'm going to forget about gear oil for a LONG time.....

 

[acewiza]

That's pretty much the same thing I've been saying about the engine oil all along as well.

 

[1040 WreckerMan]

Summit Racing has RedLine 140wt for 7.95 per quart. My local NAPA has Royal Purple 75w140 for about 8.95 per quart. I think that a larger cover is well worth the money if you are having heat problems. The Mag-Hytec cover lowered my diff temps by about 40*F while towing (refilled with the same brand and viscosity oil before and after install). Good syn oil and a bigger cover, button up the diff and forget about it for the next 75-100k miles.

 

[acewiza]

I was looking at those mag-hytec covers, dang they are the really nice good ones aren't they!! A bit pricey, though...

But I guess maybe they are worth it:

"These differential covers are one of the most innovative products available for serious truck owners. Cast in A356T6 aluminum, Mag-Hytec aluminum differential covers feature increased lubricant and cooling capacity and they are equipped with a magnetic drain plug, 1/8 NPT temperature sender fitting, lube reference plug and a magnetic dipstick for checking fluid level and condition. Dipstick, drain, and reference plugs are MS 33649 and fitted with AS 568 O-rings, as is the cover gasket, which requires no sealant or gasket. All hardware is stainless steel, and the differential cover is texture-powdercoated in black with contrasting machined cooling fins. What more can a truck ask for?"

 

[1040 WreckerMan]

Although I've rarely had problems with the stamped covers leaking, I really like the O-ring seal on the Mag-Hytec covers. If you shop around you can get them at a reasonable price. I found a Mag-Hytec for the same price as the PML with a little shopping. They are still expensive, but it was well worth it on my tow rig, IMO.

 

[Ken2]

Try taking your gallon jug to a truck repair shop and buy some of the synthetic for the differentials that get the 750,000 mile warranty. They buy this gear oil by the drum. Call ahead, but the price should be right.


Ken

 

[oil pan 4]

Now that is the best Idea I have herd all day.
Also I have driven my truck a little.
When I did I brought my craftsman inferred temp gun.
On a 20 mile round trip to the parts store. I was driving it like a mad man flooring it off every stop light to smoke people out. For fun.
I got home it was about 80'F out and pointed my temp gun at the diff cover and it showed it at 115'F to 118'F.
That was with the brand new 80-90 weight dino oil with 20miles on it.
On a high way trip I'm sure it would be hotter. On a high way trip towing a car it would be a lot hotter.

 

[SpitIX]

quote:

---

.....the dino bacon drippings GM 75w90 turned to vapors and left that hot diff. [/QB]

---

Those same "bacon drippings" worked OK for the last 22 years.
Drain it, refill it with whatever the book says and drive it for another 22 years. You can use a finned diff cover if it makes you feel better. Or not.
Thanks.