The Stovebolt Site Forums The Shop Area Driveline How often do you change your gear oil?

I guess this is sort of a poll.

I probably change the gear oil in the tranny and rear end every 5 years or so. What do you guys do?

Kurt

You change your gear oil??

I'm a total nerd. I do it spring and fall. I drive in alot of rain, oil is cheap by the pail, and when you have a pail, you can use a pail pump. It makes it no chore, and kind of fun to fill it back up. Before I had a pump, I used to heat the oil up for the suction gun, as I had no garage either. That stuff is thick when its freezing!

Chris - how much rain do you get in the trans and differential??
I wouldn't be surprised if the oil in the trans and rear of my 58 was still the factory stuff

Bill

I would change the gear oil as a new owner of a truck or while rebuilding it. Another reason is to inspect what comes out for any particles.

I never change it.

Bill, you're right! I'm sure I change it too often, but if I don't, how can I justify the $43 I spent on the bucket pump? I'm just practising for my TT, I have get my strength up 'cause I'll be pumping 460wt oil in it.

I only change it if I am in there for some reason, other than that I just check the level.

I think the guys pretty much touched all the bases Kurt. But what the heck, I'll throw in my two
pennies worth just in case something was missed.

Change it if the truck is new to you as mentioned, just to see of there are any teeth in the
bottom.
Change it if you think it may have been in a flood or water over the running boards, they
can pick up water thru the vent or bearings.
Change it if you think it might not have the appropriate weight gear oil in them for the
weather ahead an plan on driving a lot, as Chris mentioned.

The main reason for changing the oil in the engine is contamination from the combustion
process. If the engine simply pumped air like a compressor then you would rarely need to
change oil, simply keep it topped off. The trans and rear axle are not exposed to
combustibles to contaminate them so they theoretically could go their entire life without
being changed.

However, even the theoretical non-firing engine will wear. Pistons, piston rings,
cylinder walls, bearings, cranks, cam & lifters all wear out. And with gear boxes and rear
axles the gears, bearings, bushings, syncros, shifting forks all wear out eventually also. What
wears off has to go somewhere so that alone would give reason to changing the fluids.
And this is the prime reason that the factory recommends changing the gear oil at certain
specified intervals.

Denny Graham
Sandwich, IL

Change if new to you and inspect gears and bearings.

Wow,

Denny, Lots of opinions.

Main reason I change mine is to remove any water due to the possibility of condensation, and I figure the oil will break down eventually and loose its lubricating properties, and finally, if something is coming apart inside, I'd like to know about it, so I always take a look at the drainings and run a magnet through it.

Kurt

Ken or Jerry should have more info on this but it’s my understanding that the biggest
enemy to oil longevity next to contamination, is heat.

Consider that there is a light film of oil present on the cylinder walls and on the piston at
all times. So every time the cylinder fires it burns off a tiny bit of oil the ash is eventually
washed back into the main pool of oil.
In petroleum oils with lower flash points the smaller molecules in the oil vaporize and
burn off more rapidly than the larger ones. The larger oil molecules do not flow as easily
and tend to coat the surface restricting the oil flow which would normally carry away
some of the heat thus adding to the heat problem. I also recall hearing that the pour point
depressant additives in multi-grade oils that keep the waxes from solidifying are used up
quickly, which also contribute to oil thickening up. So does petroleum oil break down
when subject to high heat in an infernal compression engine, sure does.

The synthetics stand up to high heat much better because they are compounded to have
that same size molecule so even as some of the oil still burns away it remains consistent
in its flow characteristics. Contamination heads up the list of reasons to change synthetic
rather than compound breakdown and its not unusual to see recommended oil changes in
the neighborhood of 10,000 miles using synthetic oils and a good filter.

And again, the transmission and rear axle is not subject to high heat like we see in the
engine so there is very little break down in the oil over time.
Denny Graham
Sandwich, IL

I thought of another reason to change it. This would be to stop worrying about it. I am not joking. Sometimes it is good just to have peace of mind about something like this.

There must be water in gear oil. I have a TF centre section sitting in half a pail of gear oil and the part that is submerged has rust whereas the exposed does not. Weird or what?

Oil is lighter that water so it's possible that you some how got water in the bucket and any part of the centere section that's at the bottom could get rusty. How long has the bucket been sitting? Where in the barn did you have it sitting? Where did the oil come from, it fresh of drained?

DG

The owner's manual on my 09 F150 says that rear gear oil never needs replaced. Whereas on my 02 Dodge, I believe it stated 50,000 or so. Personally, I would only change it If I suspected a problem. I know there's trucks out there with hundreds of thousands of miles, that have never been changed.

according to chevy... the new trucks are supposed to have all lubes changed ... i mean front and aback diffs, and transferr cases ... the new synthetic fluids do WEAR out..... good to use . overkill on older trucks ....my 2008 duramax just got changed... like 6 qts @ $14. ea... gm fluid is $35........progress???jm2cw..kev

spoda change the brake fluid also....absorbs water... rusts the system......kev

I take the approach that I don't know what is in there until I look. Someone mentioned that they change it if the vehicle is new to them. That is what I do so I know that the rear end most likely won't be a problem for me or the next person. I "assume" that the rear end grease has been in the rear end since it was new. So 50-60 year old used oil needs to be changed. I do it with out hesitation. I don't run synthetics in my old trucks either. I'm not saying synthetics are bad. Just saying I don't go through the expense of synthetics for my old trucks.