2nd Gen Non-Engine/Transmission Rear Differential Gear Oil

[Behr]

Last nite... I took a couple of minutes and crawled under my trick to check the gear oil level in the rear differential.



Pulled the plug... stuck my finger in... and yeppers. . plenty of oil there... but its black... .



Is it suppose to be black... I thought the oils were semi clear.



Not many miles on it... only about 20 K



Its the original gear oil from the factory.



Any comments would be appreciated.....

 

[dieselsam59]

I changed mine at 17,000 miles Not Black maybe a little brown

I have a limited slip for what thats worth , I'm not sure if the clutches could blaken the oil or not



I would recomend a change, 4-5 quart , if the parts man says 2 qt. dont believe him

 

[Hohn]

I would change it. The factory stuff isn't the best (lowest bidder) and it's no doubt got all the break-in metal and clutch perticles in it.



BTW-- color doesn't mean much. I am basing this on it being the original oil.





Redline is my favorite. ANY synthetic is going to be much better-- mobil 1, amsoil, etc. Go with heavier stuff (80w-140) if you tow heavy for a lot of miles.



ALSO-- the previous post is right-- 5 qts is more what it takes. Don't worry about overfilling... far better to overfill than underfill. Don't worry about foaming with the better (synthetic) gear oils.



HOHN

(ps-- I am running mobil 1 now, but will switch to the Redline Shockproof Heavy next change)



http://redlineoil.com/redlineoil/spgoti.htm

 

[EricBu12]

I got the Amsoil 75W/90 Synthetic for the diffs.



Also get the Mag hytec diff cover. Doubles the capacity and it is way easier to change the oil. no more removing the cover to change the oil

 

[RustyJC]

With the 4x2 Dana 80 cover, 3 quarts of Royal Purple 85W-140 "overfilled" mine - it was up to the bottom of the fill hole.



Rusty

 

[pwr2tow]

Drive the truck down the road ten miles or so and back to warm everything up good, then pull the fill plug, use a $7. 00 suction gun from wal-mart to pull the oil out and you don't have to worry about takeing the cover off and makeing a mess or if the new silicon sealant will leak.



Ron

 

[Royal]

I have a 99 2wd with a Mag Hytec cover. When I installed the new cover at about 5K miles the oil was dark/black. I used Mobil Syn. oil . The cover has a long magnetic rod type dip stick to check oil level. When I pull the stick after several K miles, there is a collection ( glob) of black wear metal on the stick near the bottom end,but the oil at the upper end by the full mark is as clear as the day I filled it. If it were not for the magnet catching the wear metal it would mix with the oil. There is also a large magnet on the bottom drain plug which probably has a bunch. I now have 25K on the truck and will change oil soon and see how the drain plug looks. The MT cover does more than hold more oil & provide good looks in my estimation.

 

[Dennis Garrett]

Even with synthetics, if you have a limited slitp, you better change the oil about every 30k or whatever the book says. I tried to go 100k with Amsoil 75-90, and the carrier bearings went out. I didn't realize the normal clutch wear on the limited slip will eventually contaminate the fluid. Had to do a rebuild, and replace all the bearings including all four wheel bearings which were lubricated with the same contaminated oil. The oil looked like it had silver spray paint in it, and the microscopic steel grit from the failed bearing ruined everything else. I do use Royal Purple 85-140 now, but will change it every 30k or so. A point driven home : "oil is cheap, machinery is expensive"

 

[Behr]

I just want to thank everyone's comments and posts here.



I think just for pease of mind I will change over the gear oil. I doubled checked again this morning the fluid... . and its more of a dark dark brown... . but like Dennis said... . oil is cheap but machinery is $$$$.



Also going to look into getting one of the Mag-hytec diff covers... . I like the whole concept of them. Going to be kinda anxious to see what has actually gathered iin the bottom of this thing.





Gordon...

 

[amsoilman]

Dennis,

Did you by chance have the gear lube analyzed? It would have been nice to see if infact the gear oil was broke down and caused the failure of your bearings.



My last truck had the mag-hytec cover and I had the gear lube analyzed at 60,000 miles. Gearlube was still like new as far as chemical analysis was concerned. Infact the lube still appeared blue in color at that time. Truck has since been sold with over 155,000 miles.



Wayne

amsoilman

 

[KFroese]

i finally changed my rear diff fluid this week... . i figured after 175,000 mi i'd give it a treat from the origional fluid.

fluid was brownish but hardly any metal on the magnet.

 

[tgrfan2]

Lube Change

Dennis, I don't think your extended change had much to do with your trouble. I changed the fluid in my 98 every 15K and used Mopar fluids. The left carrier bearing still went at 85K spinning the race and ruining the housing. I still have not changed the fluid in my 95 with 187k, but it does not have limited slip. It seems to me that for some reason the Dana 70's around 98 just were not holding up. Sam Memola even said it sounded like the caps were not properly torqued to allow this to happen. The tech that rebuilt mine worked for GMC and he was getting plenty of practice doing rear ends.

 

[Dennis Garrett]

I really can't blame it on fluids, I think it might just have been a bad bearing. It didn't spin under the cap, the race on the passenger's side was spalled out about 1/3 the way around making it slightly elicptical. The rollers were all starting to etch away as a result. It was noisey, & I found it trying to pin down a rumbling noise comming up through the bed when both wheels were jacked up off the ground, & the truck was in "D" at about 45 mph. I should have checked it, changed it, or at least sampled it every 30k or so, but I only checked it's level a few times & didn't notice any metal particles. It got noisey over a couple of months, and it was the last thing I checked trying to pin down the source.

 

[AMF]

My owners manual recommends 75w140 syn. in the rear differential for towing. Why not the front differential as well?

 

[Rman]

You can put the 75-140 in the front diff, it certainly won't hrt anything, the manual doesn't advise it because you tow haul heavy equipment in 4wd. The reason they recommend the oil is because of the intense heat and friction encountered while towing for long periods.