Originally Posted by Madvlad

The AWD service does a fluid drain and fill on your t-case and your front/rear differentials and it is separate from an actual transmission service. Not 100% on these cars if the t-case fluid is shared with the transmission, from my years as an used car tech I only saw the FWD based AWD set ups have that type of design but with a RWD based AWD system you tend to have all independent from each other from what I've seen. I assume they're separate cause both dealers quoted me independently for drain and fill on both front and rear diffs and the t-case. Yes, mixing old fluid with new fluid is very bad juju cause of the oxidation rates and what not, it'll cause more damage than help honestly. I have yet to find a shop that would actually do an actual full flush on it, not sure if it's because of the transmission design or what honestly, they can't really clearly tell me why. I've yet to look under there and see why they don't offer this service but they do offer a drain and fill which I find surprising as most shops have stepped away from that.

Originally Posted by GNS

I was watching a DIYDan video when he did the transmission fluid change on his GS350 and he said somewhere that the T-case fluid is shared with the transmission. I don't know if this is true or not?

Originally Posted by Madvlad

Looking at the video, it looks to me like he meant that it uses the same type of fluid but doesn't look like it shares the actual fluid directly from the t-case to transmission. T-case fluids tend to be the same type/viscosity as transmissions and differential fluids go more along the lines of gear fluid (75w-90, etc).

Originally Posted by GNS

Okay. I know about the differentials, but I didn't know about the transfer case being a separate thing from the transmission. I will ask my mechanic (a former Lexus Master tech) about it next time it's on the lift. It's a long time before I'll need to do it (planning to do it at 80000 km, it's at 20000 km right now) but I'd like to know anyway.

Originally Posted by Madvlad

Yeah it's attached to the transmission but it's not part of it as a whole. Here in Colorado at least when I worked as a tech at Infiniti we tended to do them every 30k miles along with a full transmission flush, mainly if you're doing a lot of mountain driving as it'll beat the crap out of your fluids (or if you tow). Not sure what Lexus recommends as far as mileage/km intervals for the AWD service but it'd be a good thing to ask your buddy since he's very familiar with these set ups.

Below is a picture of an actual 16' IS 300 transmission/t-case set up and as you can see the t-case is attached and sealed with silicone to the transmission but it's not all one piece. The IS/GS being a RWD based AWD will have this type of set up and you see it in the video as well. Meanwhile the RX/ES AWD, although the same basic idea but their attaching set up will look different because they're FWD based AWD and the engine/transmission are mounted transversal and not longitudinal like the IS/GS are.

Originally Posted by GNS

Oh interesting, thanks! That T-case is what's sticking into the driver's side footwell, right?

Originally Posted by Madvlad

Nah, I believe the infamous hump (not sure why people make such a big deal out of it honestly) is to give the front diff and the driveshaft space for fitment.

Originally Posted by GNS

I have an AWD and the hump doesn't even touch my leg. I didn't even notice it on the test drive, and I don't even care it's there.

Originally Posted by GNS

I have an AWD and the hump doesn't even touch my leg. I didn't even notice it on the test drive, and I don't even care it's there.

Originally Posted by s3v3n

Same here. I sit too low and it actually serves as my leg's resting spot. It also makes my foot stay flush between the gas/brake pedal.