rearend fluid

[PONCH]

anyone running synthetic in the rear end? What are the results?

Thank You

[ADub]

I was under the impression that the trucks came from the factory with synthetic.

[DmaxMaverick]

Originally posted by Ponch:
anyone running synthetic in the rear end? What are the results?

Thank You The factory fill is synthetic. AAM, the manufacturer of the rear end, specifies ONLY synthetic lube. Using a dino lube would likely cause failure, and deny warranty coverage.

GM recommends their lube, affectionately refered to "grape juice", as the only replacement lube. Only place to get it is GM.

On the other hand, I (and many others) use a synthetic of another brand. My choice is Amsoil Series 2000 75-90. It has worked very well for over 80K. I have changed it twice since the original fill, and the lube appeared "good as new" each time. The first change, getting the factory fill out, was absolutely ugly. Definately follow the recommendations of the long term members here, including me (as well as AAM), and change that factory fill after no more than 500 miles of towing, regardless of what GM recommends, which seems to change like the weather. Once you pull the drain plug, you'll see why.

[angus]

I will be changing my rear end fluid this weekend. Does the plug on the rear end housing require any thread sealer, or is it a taper fit like the plug on the oil pan?
Thanks for any info.

[Idle_Chatter]

I'm not sure what you mean by "taper fit" on the oil pan, Angus. Mine has a shoulder with a sealing washer. The rear diff fill plug (on the rear of the cover) also has a shoulder and sealing washer (white nylon). The drain plug on the bottom of the diff has a shoulder and black rubber seal, also contains a magnet. Just make sure the washers are clean and reinstall, no sealant needed.

[k1rod]

Definately follow the recommendations of the long term members here, including me (as well as AAM), and change that factory fill after no more than 500 miles of towing, regardless of what GM recommends, which seems to change like the weather. Once you pull the drain plug, you'll see why. Yea and amen! I changed the oil in my differential last week and it was some of the vilest stuff I have ever seen. It was jet black with a high density of metal in it. It looked like metalflake black. Some of it looked to be about as thin as water and it blew nasty black bubbles as it drained. There were little chunks of metal and a metallic paste all over the drain plug magnet. The smell was something that will take paint off walls. I tossed my clothes into the laundry room afterwards and my wife about gagged when she went in there the next day. I only have 5400 miles on this truck and I have only towed a 6000 lb trailer for about 300 miles. If you haven't changed yours yet, I would do it very soon. Mine was so rotten, I am going to change it again in another 5000 miles. Best -rod

[PONCH]

dma

[PONCH]

DMAX IS THE AMASOIL YOUR TALKING ABOUT 75W-90 SYN EP LUBE?

[DmaxMaverick]

Originally posted by Ponch:
DMAX IS THE AMASOIL YOUR TALKING ABOUT 75W-90 SYN EP LUBE? It is "Series 2000 SAE 75W-90 Synthetic Gear Lube". I'm not familiar with "syn ep lube". The Series 2000 is what Greg Landuyt recommended early on (back when the question first came up in early 2001), and he indicated it is an upgrade from the standard syn. lube. It's not lacking anything that I can tell. The diff. temp seems to be under control, and it doesn't appear to have induced any wear. Rear end is still very tight and quiet. No seal leaks.

They also have the same stuff in 75-140, for frequent heavy towing in extreme heat. This is the viscosity GM recommends for those conditions. I haven't found a need for a lube that heavy, and I tow 12K# in CA summers (100

[PONCH]

AMSOIL ORDERED----They suggested severe gear 75-90 instead, so that's what we'll try!

Thank you all!
SEE YA BYE

[JD Diesel]

Have omly pulled my trailer 50 miles. Plan on changing rear oil about 4000 miles. yall think that would be OK. plan on using amsoil severe duty 75 90. :cool: P.S. I really love this place.

[ 05-20-2005, 06:08 PM: Message edited by: JD Diesel ]

[jbplock]

Moved to the 2500/3500HD Trucks & Drivetrain (http://forum.thedieselpage.com/ubb/ultimatebb.php?ubb=forum;f=11) forum.

smile.gif

[Kennedy]

I did my 2002 again just for grins the other day. First change was early on, and this one was unnecessary at 75k, but I had it warm from running on the dyno and changing it is so easy with these that I did it anyhow. The oil (Amsoil) was still pretty transparent and blue unlike the first change that was black...

[DmaxMaverick]

JK

Are you using the Series 2000?

I found the Syn. EP on Amsoil's website, and it wasn't in my ~1 yr. old catalog. It appears the Series 2000 has been replaced with it (no 2000 listed on the site anymore). I don't know if it is just a relabled lube, or something new.

Greg's site is still listing the 2000. We'll have to get with him to get the skinny on this.

[Ofbmicsafety]

Hello, this is my first post but have been visiting this page for years. Have had 3 F**d 7.3s, 1 D***e 5.9 and am working on my 3rd 6.6 GMC The info I have learned from you experts has been invaluable. Does anyone have a problem with using Mobile 1 in the rear end?

[jbplock]

Originally posted by Ofbmicsafety:
... The info I have learned from you experts has been invaluable.

..Does anyone have a problem with using Mobile 1 in the rear end? Ofbmicsafety,

Dittos! TDP is a great place with great people!

Regarding the rear diff fluid, many folks here (myself included) are running Mobil-1 75w90 (GL5) synthetic gear Lube. Checkout the following TDP topic ...

Eaton's Recommendations on Locking Rear Diff Service (http://forum.thedieselpage.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=7;t=002814)

The last time I checked there were no aftermarket gear lubes that were certified to "exactly" meet the GM spec but their are several good GL5 synthetics such as AMSOIL and Mobil-1 that folks are using with no reported problems.. If one were concerned about warranty coverage the low risk path would be to use the GM lube until the warranty period was over.

Here's another related thread on the BITOG forum. (note the second post)

Clear Answers for GM G80 Rearend Lube? (http://theoildrop.server101.com/cgi/ultimatebb.cgi?ubb=get_topic;f=16;t=001890)

smile.gif

[Kennedy]

Originally posted by DmaxMaverick:
JK

Are you using the Series 2000?

I found the Syn. EP on Amsoil's website, and it wasn't in my ~1 yr. old catalog. It appears the Series 2000 has been replaced with it (no 2000 listed on the site anymore). I don't know if it is just a relabled lube, or something new.

Greg's site is still listing the 2000. We'll have to get with him to get the skinny on this. This was series 2000 75w90 that I had on the shelf. Not sure about what the new stuff is about.

[DmaxMaverick]

Thanks John.

I've got enough of the 2000 for about 2 more changes. Maybe I'll get some new stuff, and stash the 2000 for other uses. I read Amsoil's spec. sheet on the EP, and it appears it is a little higher in high temp/pressure perfomance. Hmmmm. What to do....

[JeffsTowTruck]

I KNOW FIRST HAND... MY REAR END OIL WAS CHANGED, TO THE NORM 90W.(I DID NOT KNOW) WHILE I WAS IN FLA. ON VACATION FULLY LOADED THE REAR END GREASE BOILED OUT AND WAS SPRAYING ON MY TRAILER. WELL TO MAKE A 30 TO 40 HOUR TRIP SHORT;( NORM 12 HR). WENT TO THE DEALER AND THEY SAID THE SYN. OIL WAS THE CORRECT STUFF. TOOK REAR APART AND LUCKY ME NO DMG. AN ONCE CLEANED UP AND NEW GM SYN OIL PUT IN. 20 BUCKS A QT FOR 3 QTS.( THATS WHY THEY PUT OLD 90W IN :rolleyes: ).. NO MORE TROUBLE.

[LanduytG]

Series 2000 was discontinued last fall and now the Sever Gear has taken its place. It has been reforulated a bit. Its is totally compatable with the Series 2000.

I was not awear of the fluid level change till the other day. I have had my 04 to the old spec for over 30K miles and do not have a single weep or leak. To take it down 3/4 of a quart would be almost to the point you can't touch it. As long as I have no problems I will keep it where it is.

Greg

[DmaxMaverick]

Thanks, Greg.

You'll be hearing from me soon. Gotta' get some....


It's not on your site, that I can find. Is a phone order necessary?

[tanker]

Just changed mine at 4500 miles. Shocking though, the level was about 1-1/2" below the filler plug on the rear cover. I called my GM dealer, and was told that GM uses a measured amount of lubricant?? :rolleyes: He said they put them at about 1/4" to 1/2" below the fill plug. I was shocked to see all the gray matter on the drain plug magnet. The front diff had lots on the magnet as well. I used the Amsoil 75-90, maybe I should go to 140 in the summer. I'll do another change in about 5000 miles and see how the magnets look.
I had my vent spew out fluid on my 95 K-2500 suburban (different rear axle) and I drilled a new vent hole on the top of the axle housing between the wheel and center section, which solved my oil spray at high temps.
If you haven't changed the lube in your new truck yet, I'd do it first chance you get. Thats some nasty stuff in there. :rolleyes: