I bought some Ravenol fluids to change the fluids in all of my diffs and transfer case. Only 20k miles but wanted to do the rear diff sooner. A lot of gunk on that magnetic drain plug and it's a good idea that it gets changed sooner to get rid of those break-in metals.

On my twin speed transfer case, I'm not certain of the fluid capacity. Can anyone confirm the capacity? I thought initially it was 2L from some service bulletins I have read, but I believe as I have come to find out that the capacity is only 1.5L, which would make more sense given the amount I was able to get back in.

Also, I apparently had the incorrect p/n's on the plugs for the transfer case; they were ever so slightly smaller. IYB5000020 is what I was told and what I have, but they seem like they are the plugs for perhaps the smaller single-speed transfer case.

 

Castrol shows 1.5L as does Kroon Oil in NL. Mine took a wee bit under that to refill so 1.5L makes much more sense. I didn't get 2L's worth out, that is for sure. Thought it was going to need to take 2L as some LR literature I have says (my local LR parts counter, as well,) but I took the fill plug out again this morning and it was dripping, so I did another pump or two and put it back together. The plugs I have for the transfer case are either the wrong plugs in both P/N bags or LR has their P/N's wrong. IYB5000020. New plugs I bought to use were ever so slightly smaller.

https://rego2oil.castrol.com/en_au/a...4x4_2016_2021_
https://www.kroon-oil.com/en/product...ponent:650838/

Here is the pic from the drain plug on the front diff. Lots of break-in gunk on it. Easy to do.

 

I am ready to change mine soon. Bought 2 liters but expect to only fill 1.5. Doesn’t matter as you fill until it spills out. What does matter is the fluid you use. For the differentials a quality 75w90 synthetic is specified. But for the transfer case there’s no aftermarket spec. Just the LR fluid and it’s been upgraded from the LR3 LR fluid part number.
Considering the transfer case probably costs over $6k if you could even buy one I wasn’t willing to save $50 on fluid.

 

I like Ravenol products because they publish their specs and they have a premium line (gold bottles) that uses the best base stocks available, (poly-alpha-olefin, or PAO.) Rarely will you find a comparable product with superior specs. Look at the pour and flashpoints to get a good indicator as to the quality of the base stock.

• If you have the electronic locking rear differential (service manual calls it the Electronic Torque Managed or ETM diff), you need Castrol BOT 720 spec. 1.21L wet capacity. LR p/n is LR019727.
  • Both diffs use the same drain and fill plugs. One each for each diff. TYB500060 is the fill plug (6mm hex) and TYB500110 is the magnetic drain plug. (I used the square 3/8's extension.
• The transfer case fluid spec is DTF-1 which is actually a BMW spec. LR p/n is IYK500010. I believe the capacity is 1.5L as I didn't even quite get all that amount in. I put in just about exactly what I got out.
  • Uses two plugs that use a small copper washer and a 6mm hex. I was told, I ordered, and my local LR dealer confirmed that IYB500020 is the part number. The ones that I received were a tad too small and would not fit. I had to reuse my existing plugs.
• The front differential uses the regular Castrol SAF-XO 75w/90 gear oil. Only takes 0.51L. LR p/n is TYK500010

 

I've changed the fluids.

-Rear locking diff had a bit of sludge on the magnet plug but not that bad (changed at 32k, no hard driving). Rear locking diff...eh, wasn't bad fluid but I wasn't convinced it would be good until 60k. I just re-used the plugs. I also used OEM fluids from the dealer (I think for rear locking diff, I have to).

-Front fluid at 32k looked new. Definitely could go until 60k. Front fluid is same fluid as in the LR3/LR4 front diff. Which is nice because I gave my left overs away.

-T-case. Yeah it hold about 1.5L but I'll tell you what, FUDGE THE GUY WHO DESIGNED THAT FILL HOLE. Its like refilling DEF, slow and miserable. First off, remove the little heat shield around the fill hole. I just removed 2 of the 3 lower bolts. Top bolt of the shield, I loosened and then moved the shield out of the way. Drained the fluid (once again, looked fine for 32k, can easily bump to 60k change). Refill sucked. I got a hand pump for the job. Main issue is that you gotta STICK the pipe in there at a weird angle. You'll see, there is a plate right behind the fill hole. You'll end up spilling fluid everywhere if you try to refill fast.

See attached information I have on D5 fluids (pre-ingenium engines) and T-case info.