Rear diff fluid going dark after a few months

[HoosierJeeper]

This is on my LR3, about 160k on it...running 75w90 synthetic in it. I've changed it every 70-80k ish (maybe a bit long). Last fall I changed them again and the rear diff fluid was like black. Figured it was just old and new will fix it. Fast forward to last month, I had to get an axle seal replaced and my guy noticed that the rear diff fluid was black again. He said it looked like coke. Put new fluid in it, and then this month it started leaking from the pinion seal and another axle seal again. Took it back to get it looked at, suspected a breather and he drained the fluid and it's black again. Impending diff failure? No weird noises or anything that I've noticed.

Edit: It's an open diff, no locker or limited slip.

 

[Motorsen]

Seems like a high temperature degradation problem. Your diff is running hot. Boiling oil cooks of the seals. Might have to look in to it further. Most likely an alignment of crown and pinion. If you have a temp gun try to shoot the temp after a longer drive.

Motorsen

 

[JLTD]

Sounds like it is time for a couple of UOAs to see what they find?

Or shorten the interval some. Is there a factory interval?

 

[SZR48207]

Those LR3s are pretty heavy right? Maybe the diff just has to work extra hard?

 

[zeng]

A sign that 75W90 isn't adequate for the applications.

 

[spasm3]

What gear oil are you using ?

 

[Ducked]

I'd bet you the price of a couple of UOA's that a lot of that "high temperature degredation" sticks to a magnet.

 

[HoosierJeeper]

At first 75w90 Mobil 1 and then Liqui-Moly. 75w90 is the factory spec.

Should I switch to a 75w140 or even go to a dino one?

 

[spasm3]

If its leaking, its hard to say how much oil is in there. I suspect its getting low, then getting hot! I'd probably run a dino,( just to save money since it leaks) and keep it topped up. If you correct the leaks and it stays in there then a synthetic.

A 140 might leak slower. I think its better to have gear oil in there than to have less of the lighter weight. I can't see it hurting to try it, unless you are in really cold regions.

 

[MaximaGuy]

The Brits gets nothing right - I am told the Rovers are more expensive to maintain than buying them (they aren't by any yardstick cheap).
Back in those days Aussues used to love their Rovers, now it all the Toyota Land Cruisers widely adopted and used since the 60s.

Brits really suck, do they even do anything these days that others buy (other than the RR engines).

 

[Snagglefoot]

I’d try another brand like Pennzoil and stay with 75w90 synthetic.

 

[zeng]

A dino in 85W140 is a bit on the thick side and 80W90 maybe adequate though a bit thin.
Yes,a synthetic in 75W140 of KV@40*C 170 cSt is quite a sweet spot, other than 80W140 (RL of KV@40*C 220 cSt) or 75W110 (of KV@40*C 140 cSt).
It's really your call.

 

[4WD]

IMO, just changing brands is not enough … you could try 140 … but get a sample out in 20k …

 

[1JZ_E46]

Originally Posted By: zeng
A dino in 85W140 is a bit on the thick side and 80W90 maybe adequate though a bit thin.
Yes,a synthetic in 75W140 of KV@40*C 170 cSt is quite a sweet spot, other than 80W140 (RL of KV@40*C 220 cSt) or 75W110 (of KV@40*C 140 cSt).
It's really your call.


75W-110 is my go-to differential weight for a daily driver. It’s a nice happy medium between 90 and 140.