truck maintenance question

[dos gris]

How often do ya'll change out your differential and transfer case fluids? I do it once or twice a year but I recently had the Chevy dealership owner by the house tell me that you really never should have to change it out unless it gets contaminated with water or something.

What are ya'lls thoughts on this? [img]images/smiles/icon_confused.gif[/img] [img]images/smiles/icon_confused.gif[/img] [img]images/smiles/icon_confused.gif[/img]

[torch]

Dos I own a shop and they are correct. You really don't need to unless you get water or something in it.

[dos gris]

these fluids don't break down over time?

[WNE Driver]

Dos -

The lubricants don't break down over time. Heck, they have been sittin in the ground for millions of years prior to getting refined. Oil of all types has 3 jobs - lubricate, cool and hold contaminants in suspension.

What does break down with time is the additive package that is added to the oil. Most of the time these are anti-foam agents, detergents and friction modifiers.

What causes the oil to break down is heat (hence differential coolers on 200mph Winston Cup Cars) and "shearing" of the oil between the lubricated components. The other concern is the amount of contaminants in the oil (metal mostly) that can be held in suspension without any damage occuring.

Having said that Dos, I swap my dif lube at about 30K and my transfer case at 50-60K unless I have immersed either in which case I change it immediatly.

[goosebruce]

30k miles, or anytime I get water in them. Most of the time, they run out clean, and yeah youd be ok not changing them. But why not? No more than it costs, you cant know if they are low or contaminated if you dont check them, and you might as well change them if you gonna ck them. travis

[goosebruce]

I guess I should mention, you might want to actually check what the manufacturer reccomends. For years we've always went by 2 years or 30k on all the fluids, but 2 years ago, toyota changed their reccomendations to 1 year 15k on diff & trans fluids, so we changed our schedauls accordingly. But for some odd reason, they dont list a coolant change interval....2 years on that too, and on an old truck, once a year is a good ideal. travis

[H2OFowl]

Contamination is gonna be your biggest problem. Check all oils for this at each engine oil change and change diff and trans oils once a year. I manage a 250+ fleet and have done the math. It's cheap insurance.

[dos gris]

So, from the advise given above:

* I shouldn't have to really ever change it out unless it gets contaminated.

* Change out every 30,000 miles.

* Change out once a year.

So basically I'm pretty much where I started from... [img]images/smiles/icon_confused.gif[/img] [img]images/smiles/icon_confused.gif[/img] [img]images/smiles/icon_confused.gif[/img]

[walt333ms]

watch out ....your going to really mess up...

depending on the make, model and options on your vehicle...will depend on what to do as to the rear axle...and transfer case,,,,

1...does your vehicle have locking diff.or posi-traction...(can take a type of grease, or a hydrolic fluid...or synthtic blend....

most gm older vehicles have a silver tag on the rear axle...also a stamp on the axle housing under the spring hanger...

first find out what u have ...and i can tell your about what to do....

uncle walt and sam

[walt333ms]

also because of heat expansion,,,,rear axles are vented...some on the rear flange with a spring loaded valve...some with just a rubber tube that attaches to the bottom of the truck bed....

like i said ...watch out...wrong type of oil,grease of syn fluid and u have spent a bundle...

old axles with posi-locking diff were clutch type, they take a high grade thin fluid...

old axles without posi-locking diff take a grease that is thicker....

new cam type locking- posi axles take a very thin synthitic fluid ....

like i said watch out...

and as u look at the rear axle, most are made now without an inspection plate....

just knowing the year, make, model, and gear ratio is not enough....

if it is gm i can help....

uncle walt and sam

[BigOleDucker]

I was told it should be changed out every 50,000 miles or 30,000 if you are towing heavy equipment: large boats, horse trailers, etc.. and it should be change at 30,000 for a a new truck to see if the gears are alligned and not shearing.