Afterwards a slight whistling noise between 80 km/h and 115 km/h.
My dealer drained the rear differential.
But the noise is still there.
So I'm going to drain the two differentials and the transfer case myself.
Concerning the front differential and the transfer case the information is clear:
Castrol transmax or syntrax saf-xo 75w90 and shell TF 0753.

Concerning the rear differential:

-open differential l405 without hybrid model:
Castrol saf-xo 75w90

-open differential hybrid model
Castrol bot 750b

-locked differential
Castrol bot 720

Photo :





After a lot of research on the web I was able to find the viscosity of the different oils:


Castrol syntrax 75w90
101 mm2 /s (101 cSt) at 40°C
15.4 mm2 /s (15.4 cSt) at 100°C.


Castrol bot 750b
51 mm2 /s (51 cSt) at 40°C
9.6 mm2 /s (9.6 cSt) at 100°C.

Castrol bot 720
83.1 mm2 /s (83.1 cSt) at 40°C
13.8 mm2 /s (13.8 cSt) at 100°C

Looking at these figures I think that put This viscosity oil in the rear differential is the cause of this slight whining.
I think that jlr's choice to offer this oil is linked to electrical operation to preserve satisfactory autonomy: there must be as little friction as possible in the differential.
My question do you think I can upgrade to the Castrol syntrax 75w90?
This won't void my warranty if there is a differential failure

Click image to enlarge

Click image to enlarge

So I drained all the front and rear differential fluids and transfer box.

The whistling noise therefore comes from the front differential because I found a lot of Metal chips on the cap.

But on the open rear differential I removed 1.1l of oil ????

While the recommendation for open differential is 0.82l!

Even with 1.1l of oil, this one didn't flow from the filling cap??

While on some videos we can see that 0.85l is enough to overflow the oil through filling cap?

Can you help me with those who have already done it?

The references of my rear differential are:HPLA-4A213-BA

Thanks in advance