Rear end service-before/after/during?

[ColoradoSpringsToDaMAX]

OK,

I have done a number of searches and read a whole lot more than I consider healthy about rear end lube change. However, I am not sure what to do in my case. I have a new 2003 D/A CC with about 800 miles on it (love it so far!). I have only towed my boat about 60 miles so far, and will probably only tow it another 100 miles or so before I leave on a 1100 mile one-way trip two weeks from now. The boat/trailer weigh 5100 lbs.

Now to my question. Everywhere I read that I should change the rear end lube after 500 miles of towing. In this case, 500 miles is going to hit about 1/3 of the way through my trip. Does anyone see any major problems with changing it when I get to my final destination...or should I change it before I leave...or worse yet is it important enough that I try to take the "kit" with me and change it on the road somewhere. Any thoughts out there on my dilema? :eek:

[TxDoc]

Do you have the Eaton G80 locking differential? If you are not sure, look at the codes in your glove box.

If so...Eaton says:

"Mr. Ralph Holmquist of Eaton, the maker of the locking differential:
"The maintenance schedule for the rear axle was developed by American Axle &
Manufacturing and GM truck based on multiple tests. The Eaton locker does
not require additional maintenance nor does it add heat to the lube. The
lube will darken due to the carbon wear on the clutch surfaces, much the
same as a disc brake pad & rotor. This does not damage axle components such
as seals or bearings. However, a new axle can produce excessive
temperatures (plus 350 degrees F) due to the ring & pinion breaking in that
will break the lube additives down. Avoid high loads, trailer towing and
high speed extended driving during the initial break in of the vehicle.
After the break in period axle temps will level at a much lower figure.
Lube changes are a good idea because the additives are replenished and
contaminates such as casting sand are eliminated. The axle is filled at the
factory with a synthetic 75w90 GL5 rating made by Texaco under part # 2276.
The GM service # is 12378261. This is the only lube we have done extensive
testing with to insure locker compatibility. The only negative to using one
of these other lubes is an increased potential for clutch chatter. This
really doesn't hurt anything and can be corrected by changing the lube. I
noticed in the latest GM owners manual the term "or equivalent" when
referring to the lube specification. Look for a GL5 rating on the bottle to
make sure the ring & pinion, seals & bearings are protected. Limited slip
additive is not needed."
The following information outlines the type of
rear axle lubrication utilized in GM Truck axles.
I. Fluid Type
II. The 1500, 2500 and 3500 GMT 800 Trucks utilize SAE 75W-90 Synthetic Axle Lubricant. The GM part number is 12378261 and the specification is 9986115.

[ColoradoSpringsToDaMAX]

Yep, its the G80.

[ColoradoSpringsToDaMAX]

OK, after reading your reply a couple of times...I finally noticed the bolded section. So, I guess I need to get more specific (cause I had seen this same response in other posts). Is 5100 lbs considered heavy towing for this truck? Since it is rated to 15K, my guess is no, but with 4 people, a topper, gear etc. the load for the 1100 miles will be more like 6500 lbs. Heavy towing? Still probably a bit light, but I want to do the right thing as I plan on keeping this truck around for a while. Thanks.

[dmaxalliTech]

TxDoc, can you email me a copy of that letter you posted, thats very good info. Thanks

[Jelisfc]

I'll be the nay sayer. 15000 miles and I have no immediate plans to change my rear diff fluid. Granted I don't tow that often and when I do it's about 5K. My 1/2 ton G80 held up towing the same weight. I certainly hope this monster rear will do the same. I'll be the guine pig and see how long it lasts. The only rear end I've blow was a snapped pinion shaft from applying too much Hp. smile.gif

I'd wait until you get home. You know Murphey...he loves to go on vacation. Don't temp him.

[ChevysRus]

It's kind of a dilema, you don't have enough miles before you leave and maybe too many by the time you get back. It's about a $130 deal to change the 4 qts of grape juice and you don't have enough time to mail order the stuff at a discount, unless you work fast and order tomorrow (email Dmaxalli, he may be able to ship the stuff quickly). They just changed the bottles and the hand pump doesn't fit anymore, but you can still pump the stuff out. It's an easy change and can be done anywhere, no need to jack the truck up, just a 3/8 rachet to remove the bottom drain plug and the fill plug, a pan to catch the fluid in and the hand pump from any parts store for about $5.00. 4 qts will do ya, but it will take about 1/4 more so you have to buy 5 bottles the first time and save the rest for next time. I changed mine at 8K and just a week or so ago at 30K. No need to do it again for a while, maybe I will do it again at 100K if I can fine that 3/4 full bottle by then LOL :D

I guess in your case you can do it when you get where you are going and it will most likely be OK to do it when you get back as well. It will take you 30 minutes at the most and I would do it when you get where you are going. If you can buy the stuff cheap and get it shipped quickly, take it with you (don't forget the 3/8 rachet or breaker bar).

Another reason to use the expensive GM Grape Juice is to avoid any warranty issues if you should have a problem (I know it's not legal, but easier to avoid issues than fight in court).

Enjoy your trip, the truck is awsome!

[Nixter]

Just change it when you get back from your trip or a couple thousand miles after. It is cheap and easy to do yourself. You may be suprised at the amount of metal fragments that are stuck to the magnetic plug. I intend to change mine about every other year or 25k miles. GM wants us to get our trucks beyond the warranty period. I want mine to last forever so I will have to take personal responsibility for it. --Nick

[56Nomad]

TxDoc wrote:

"I would recommend that you stay with the GM synthetic, not Mobil 1"
TxDoc,

Just as with anything..... ask 10 physicians about a malady and you

[Nixter]

I don't think that Mobil 1 syn has "fallen out of favor". It just hasn't been tested for compatibility by Eaton for the G80 locker. Correct me if I'm wrong.

Also FWIW, you don't need a pump to inject the fluid if it comes in a squeeze bottle with a pointed tip. Just squeeze in as much as will readily go from each bottle and then combine the remainders into 1 to finish. Its a 1 beer job even for a chump like me. --Nick smile.gif

[Turbo Al]

I had the same problem as you, went on a 1,600 mile trip towing my trailer. Just changed it when I got to where I was going (800 miles). It was actually pretty painless, except for the mud, snow, Grizzlies, Mooses etc.

[ram/tx]

I can't agree with the "Not Mobil 1" statement. I changed mine at the 1000 mile mark and used Mobil 1 and I now have 28000 miles towing a 4000 lb boat all over Texas in hot and cold weather and have not had one problem with the rearend. No chatter or leaks. :D

[TxDoc]

[quote]Originally posted by 56Nomad:
[b] TxDoc wrote:

"I would recommend that you stay with the GM synthetic, not Mobil 1"
TxDoc,

Just as with anything..... ask 10 physicians about a malady and you

[sonofagun]

Colorado,

I think you are towing enough, especially in summer heat, to consider following the towing guidelines. That said I wouldn't worry too much about your trip. If you can conveniently change it at your destination I would but if not I would order it from dmaxalli and do it when you get home.

I did install a Mag-Hytec diff. cover on my truck when I got it. I has a magnetic dip stick as well as the magnetic plug (like the OEM cover has). I check my fluid level with the dipstick each time I change my oil and EVERY time the dipstick magnet was COVERED with 1/8 inch or more of metal paste. The only way to clean it off with the OEM cover is to change the fluid and folks don't do that. I am quite pleased that that metal is in the trash and not still roaming around in the differential. You don't know it's broke until it tells you so but you can prevent or delay it with good care.

good luck,
Bob

[MadDuraMax]

Colorado,

I don't think there's much difference either way, frankly. You're not towing that severly to expect problems. If you're the type to worry about it change it with a reasonably priced syn before you leave and again with the syn of your choice when you get back.

The GM lube (grape juice) is actually a Texaco synthetic, so don't pay the long dollar at the dealer. GM will warrant the OEM Eaton G80, so meet their specifications, Eaton only warrants the aftermarket variants. Mobil 1 meets the GM specification listed in TxDoc's post as do most other full syn axle lubes.

Hope this all helps.

Mark

[AbqGeorge]

I'm at 15,880 Gross Combined Weight. I didn't change my rear end fluid until around 1800 miles with all but the first 550 miles of that towing.

Should have saved my money. I saw hardly any sign of metal paricles or any other particles and very, very little of the "gray sludge" described by others (and I looked, carefully!). The fluid looked/smelled exactly like the new stuff. The recommendation for a "severe duty" 500 mile change out was in the 2001 manuals. I cannot find those words in the 2003 manual??

As they say, "your mileage may vary". Maybe I got a "lose one".

Geo.

[xamarud]

have 16,000 miles on '02 dmax, just now thinking about changing rear-end grease. may use castrol syn, it has Mac H rating. good luck

[JimWilson]

I don't see where you'll have any problems changing it when you get back. If you want to save some money do it yourself, but use a good quality synthetic (like Amsoil, Mobil 1, Royal Purple, etc).