Hi,
Recently I changed front diff, rear diff and transfer case oil in my 2007 gx470 with 200k miles with Mobil one 75W90 synthetic gear lube.
Transfer case fluid which came out was very dark but diff oil was relatively clean and slight milky.
At 160k mile service I asked my local shop to change all three oil but not sure if he changed transfer case oil.
Question:
Is it normal for transfer case oil to be that bad?
Car runs sluggish and fuel economy dropped after this change. Any idea what can be the problem?

Thanks

 

Too thick of a fluid can slightly impact your mpg but you should have no issues if using Mobil 1 75W90. I would not go back to that wrench if I were you. The diff fluids will usually come out darker than T case but with only 40k miles since last change, diff shouldn’t be milky and Tcase should look clean. DIY it next time- it’s a very easy job!

 

Thanks.
I did DIY this time hence realized what’s going on with oils. If transfer case fluid hasn’t been changed for sometime will it cause any issues if changed now? I heard people advising against transmission oil which has gone longer interval to not change.

 

Milky diff fluids may be an indication of water contamination. It’s relatively cheap so I’d do another drain/fill just to make sure it’s completely clean inside (but that’s just me). That theory regarding transmission fluid may be true, who knows. But you’re talking about your T Case here. New fluid new blood. You’ll be fine. Your sluggishness issue may be something else ie plugs, coils, fuel, filters, etc. Checked your transmission fluid level recently?

 

transmission unit is sealed and can’t check oil level without a trip to dealer I heard. I’ll try to change diff oils one more. I did few patch of water puddles few months back FYI. One more data point. On idle/stationary in D it makes slight humming noise and which goes away in P. RPM is constant on 600s. No warning code on dash.

 

'04+ have "sealed transmissions" which basically just means no dipstick, but they are serviceable all the same, with some extra monkeying around to get the fill level correct. There is a procedure to put the truck into "service mode" to set the trans fluid level, or it can be done via tech-stream software and a cable same as Toyota techs would use at a dealership.

 

The trans pan has two bolts, one is a overflow check tube. You can do the check procedure at home.

xfer case (diff) oil? Send sample to Blackstone. Other than that, just change the oil. Changing the oil should have no impact on MPG's or cause "sluggish". I use same Lucas full synth 75-90 in all 3 areas (3 diffs), never an issue.

 

The maintenance supplement for my 2004 shows differential fluid change interval is every 15k miles and transfer case is every 30k miles.

I do them every 30k miles, along with a drain + fill of the transmission.

For fluids, the differential and transfer case get good commercial fluids that meet the spec. Transmission fluid is Toyota-brand WS.

Chip H.

 

I think that short service schedule for front, rear diff and transfer case change is for towing….full synthetic like Amsoil should be good for 100,000 miles. I just went through schedule listed on this site and there is no scheduled change listed except for towing.

 

It was in the thinner Lexus manual with maintenance info. Agree that if you tow or go offroading you should change more frequently.

Chip H.

 

They call it “sealed” so you can spend your money at the dealership. I just finished servicing my transmission few weeks ago, running 14 quarts of WS through the system. I used my Scangauge II to monitor trans fluid temp then opened overflow plug the set the desired fluid level. Easy peazy. Now the humming, that could be anything really. First thing I would check is loose body parts or under the hood parts. Possible something not tightened or missing push-plugs. Start there.