BNR34

iTrader: (1)

Just replaced the rear differential fluid myself on both my 05' LS430 and 06' SC430, here are my observations that I like to share with you guys.

On my LS430, is been 30k miles since the fluid was changed, so I decided to change it. I had the dealer did it last time because I was busy and the car happened to be at the dealer.

The procedure is very simple, is nothing to it, drain the fluid by removing the drain plug and fill up the case with the fill hole. I put in roughly 1.8 Qts of Valvoline Synpower Full synthetic gear oil 75-90W.

The observations is, the fluid is still very clean, I can hardly tell it got any dirtier at all. My theory is I drive this car very gently, I rarely floor it, it is mostly cruise at the speed limit.

I am continue to be unimpressed with the quality of Lexus dealer's service work. My theory is still correct, the only way to have anything done perfectly, is doing it yourself. The fill plug is half stripped and there is 2 washers on both the drain and fill plug, which means the guy put a new washer on without removing the old washer Luckily there is no leak. He did get the fluid level correct and the plugs are on with the correct amount of tightness. But still when I pay their ridiculous service charges, I expect the work to be 100% perfect. Nope, far from it, the typical rush it thru as fast as possible type of work I am so glad I did it myself this time. And my service advisor kept bugging me about letting them service my car. I be sure to let him know the crappy job they did on it and that is why I work on my car myself as much as I can

On the SC430, the thing I didn't like was both the plugs was on super tight, is like they tighten it with a huge breaker bar At least there is only one washer on each plug. The other curious thing is the fluid is starting to look unclear, and it had only been 15k miles on these fluid. It makes me wonder if the dealer really changed the fluid like they said they did Since the fluid on my LS is still very clear at 30k miles. But I do drive the SC a lot harder then my LS, so that might explain the difference in the fluid dirtiness.

That's it, oh and the LS got a lot more room to work with then the SC, both differential looks identical as expected

V8_Fan

It also depends what fluid you use. Some of the LS rear diffs are spec'd to use only synthetic 75w90, while others are spec'd using dino 90wt from the factory.

I put Mobil 1 delvac 75w90 commercial-grade gear oil in the front/rear diffs and t-case in my LX. After 33K mi, the front diff fluid looked brand new, rear diff fluid showed some loss of clarity but was fine. The t-case fluid was dark. So I know for that vehicle, I should change the t-case fluid every 30K but the diff fluids every 50-60K.

I recently had the dealer change the rear diff fluid on my LS using the M1 delvac 75w90 (tried to do it myself, but the exhaust was in the way, couldn't get the correct extension length). Dealer only charged me $50 in labor with me brining in my own fluid and gaskets. One drawback to the rear diff housing on the LS is it sure doesn't hold very much fluid.

BNR34

iTrader: (1)

Jim, thanks for your inputs, sounds like our observations are the same. Fluid is still clean at 30k.

But my SC's fluid is starting to get a little unclear at 15k

randal

I have the same issue in that I try to do all service myself. For one, I do not really trust another mechanic. Two, save money. Three, I want to do it myself for the pure satisfaction of knowing I can do it (its a prideful thing, I'll admit).

Also, wondering just how fluid in the diff can get "dirty" in the first place? Dirt getting past seals? From the heat buildup as the gears mesh? A combination?

Since there is no combustion going on, how do you believe the oil could even get worn/dirty? (I know it does wear/get dirty, but what are your thoughts on this?)

caddyowner

Should I fear where this thread is headed?

I think diff oil gets spent by heat from friction, the mechanical forces on the lubricant, and metal wear.

Kansas

The early 2001 LS430 maintenance schedule recommended replacing the differential fluid every 30,000 miles "Only if vehicle is operated primarily while towing a trailer or using a camper or car-top carrier." Otherwise, replacement was never indicated.

By the end of the LS430 run (2006), the maintenance schedule had been changed to only check the differential fluid every 30,000 miles. There is no mention in the 2006 LS430 maintenance manual of ever changing the differential fluid regardless of how the car is used.

IMO, it is completely stupid and wasteful to change the differential fluid on a rear wheel drive Lexus sedan every 30,000 miles -- but that is what I do too. Maybe I'm obsessive but maybe that kind of excess maintenance is what has helped my first Lexus LS, which I purchased new almost 21 years ago, get to something like 300,000 miles with it's current owner who is about as obsessive as me.

randal

Yes, be very afraid!

So, if the lube gets spent primarily by friction (ie:heat), what does that say about those differentials that DO get dirty in ~30K miles? More aggressive driving OR gears that are not quite dialed in correctly? It would be interesting to drive the car "normally" until warm, then point an IR (Infrared gun) at the diff and note the temp. Ambient air would obviously play a big part for comparison with other vehicles or driving conditions.

caddyowner

Just so we don't start talking about ATF.

campisi

FYI - Total waste of time and resources changing diff fluid after 30K miles. Doesn't help your car last to 300,000 miles. Period. End of story.

BNR34

iTrader: (1)

Yes I agreed after seeing how clean my diff. fluid was on my LS430. But it might only apply to cars that are driven very gently. Even my SC430 that I drive much harder, the fluid was starting to get unclear at 15k miles, and all my previous much more aggressive sports car's diff. fluid does get dirty.

So my conclusion is it all depends on how hard the car is used. Duh!

Jabberwock

One thing I am uncertain about - are the recommended maintenance schedules designed with a goal of keeping a car running for endless miles (say 500k+)? Or are the schedules designed to keep the car working well for 150-200k?

On something like a small airplane the required maint is regular and periodic and I think it assumes the aircraft is potentially gonna be used for years and years and thousands of hours. So in that application I don't think there are statements about "sealed for life" no maint required. Instead there may be a statement like replace every 2500 hours.

So maybe the car schedules should say differential (or AT as another example) needs no maint, replace diff every 250k?

With purely mechanical automotive systems like differentials, ATs, PS, etc it just seems intuitive that, all other things being equal, periodically changing and replenishing the lubricant would make the system last longer.

There really need to be a definition provided by manufacture of exactly what they mean by "lifetime" when they say a component or system needs no maintenance.

formerMB

I've done this at 90k intervals on the Benzes, seems to be perfectly adequate

BNR34

iTrader: (1)

Very well said, I agreed 100%

Only the manufacturer knows that and they would never tells you. But my guess is the recommended maintenance schedule is designed to keep the car running for 100k miles, 150k max. That is why I never follow the recommended maintenance schedule. I always drain the fluid myself to judge for myself.

Yes planes cost a lot more and it is much more critical that it doesn't malfunction in the middle of an operation. So recommended maintenance schedule is real for a plane. On a car, the manufacturers don't want it to last a long time and when it breaks down, is not a big deal, just tow it away.

I think the manufacturer's intention is they want the consumer to buy a new car every 100k miles, and most people do that.

Correct, the cleaner the fluid stays, the longer the mechanical parts last. The key is to figure out when the fluid get dirty. In my case on my LS430, it wasn't dirty yet at 30k, but my SC430 was starting to get a little dirty at 15k. So it is different for every car, for every one, there are variables for everything.

In my previous extensive research for the fluid replacement interval for the so call "sealed" 6-speed tranny in the 04'+ LS430 and 06'+ SC430, I found an offical Toyota document stating the definition of "lifetime" is 100k miles. So the way I read it, is the tranny and the fluid is definitely good for 100k miles, probably would go until 150k miles without changing the fluid, but will likely fail by 200k miles. So I change my tranny fluid every 50k

campisi

Just changed the diff fluid out. 85K miles. Clean and clear and very little 'pixy dust' on the magnet. It was actutally a little clearer-looking than the rear diff on my Subaru (though that car see's abuse whcih the LS does not) which I just changed at .... 30K miles! I don't think it needed to be changed at all.

ceedub53

I replaced the oil in my 2002 LS430 differential today. Needed a breaker bar to get the drain plugs out as they were on tight. Car has 124k miles and no mention of the fluid ever being replaced in the extensive service records I have. Fluid color was blackish-brown with a golden hue to it. Magnetic plug had small buildup of black dust but nothing else. Used Mobil1 75w-90 synthetic to replace. Glad I did it, not difficult at all.