Updates - Oil Consumption, Rear Diff Leak ...

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Spiguyver

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Is the diff fluid just resting on the cooling plate now though?
No, it seems to be doing the trick. I even made sure it was fully serviced and I’ve had no issues, even after very spirited driving!
 
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I should also add that I have been trying to see what the GT4 car uses for cooling, and I have yet to be able to find a picture of the underside.

I have only found this picture so far, which appears to show one side exhaust and what appears to me, to be a cooler of some type to the left of the rear right passenger wheel.
Edq-bwzWkAI4BGU.jpg
 

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Maybe I'm just not seeing it, and I'm assuming here, but you're stating that it appears the diff was leaking due to you driving the car hard and it was overheating, and after the Verus Engineering diff cooler was installed, the issue has gone away?
 
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Maybe I'm just not seeing it, and I'm assuming here, but you're stating that it appears the diff was leaking due to you driving the car hard and it was overheating, and after the Verus Engineering diff cooler was installed, the issue has gone away?
Yeah, I think that's why he's alluding to. The car gets hot, and the oil bubbles through the vent. The cooler reduces temps quite a bit.

1633370687338.png
 

underdonk

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Yeah, I think that's why he's alluding to. The car gets hot, and the oil bubbles through the vent. The cooler reduces temps quite a bit.

1633370687338.png
Alright, I'm glad I wasn't the only one interpreting it that way... and honestly it's good to hear it. It's an easy fix if that's the case (though of course one we shouldn't have on this kind of car from the factory). I've had one of these sitting in the garage to be installed for a while now, it just falls into the "damnit I need to jack the car up which is kind of a pain so I'll do this next time I'm under there" category. I have a Cusco rear brace sitting around for the same reason. I'm lazy.
 
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Maybe I'm just not seeing it, and I'm assuming here, but you're stating that it appears the diff was leaking due to you driving the car hard and it was overheating, and after the Verus Engineering diff cooler was installed, the issue has gone away?
Not to say the Verus part does not work, however in this situation I am doubting the differential is overheating, if it was you would have an error on the dash due to the diff having an oil temp sensor built into the drain plug.

Members who have had this looked at, had the differential drained and refilled - probably actually setting the level correctly.

The diff should only be taking the following:
Hypoid Axle Oil G4
Standard differential oil capacity:
1.0 liters (1.1 US qts, 0.9 Imp. qts)

My car sits in the garage as a non rain weekend toy has 650 miles on it and had this happen - while I drive it hard when I can, I am not doing any burnouts, drifting ,etc that would cause this issue.

I have my new scope and will have to crawl under the car to take a peek where it is coming from (probably the breather).
 

MisterSkiz

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I had an opportunity to get the car up in the air a bit, disassemble things, use my scope and poke around with my hands.

I pulled off the mass damper from the rear subframe, and found diff oil over the top of it. (note: the BMW Z4 does not have this piece - maybe due to subframe connectors for the convertible reducing NVH)
20211005_162639.jpg

20211005_161946.jpg


I found oil in bottom/corners of the rectangle that is just below the breather house/tube, along with oil surrounding the fill plug, drain plug and on the bottom of the fins.
20211005_162000.jpg

20211005_162013.jpg


The scope did not show any oil on the bottom of the rear trunk pan (ie: no oil spraying UP), and showed no sitting oil near the breather tube - which doesn't mean much, as the heat, etc would have caused most of the oil to pool/drip down the differential cover.

The fill plug and drain plug are tight and not leaking - no leaks were found around the outside of the differential cover and carrier housing.

There is no crush washer on the fill plug, but rather an O ring that must sit on the plug.
20211005_163920.jpg


I cleaned up whole back with brake cleaner and wiped clean, and the car was taken for a 10 minute drive at around 25mph, came back home and reinspected - no leaks were present from fill/drain plug or the breather.

My current belief is the differential is overfilled from the factory and at highway speeds when the fluid is up to temp (~200F for normal car differentials) small amounts of fluid come out from the small hole on the back (not top - this appears to be sealed - its not just an open hole) of the breather - however I will not be able to verify until I get a new crush washer from Toyota for the drain plug and new diff fluid. I am going to drive and monitor for now.
 

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Note: here is the top view of the breather tube.
i-img1000x1000-1623401403sosbsb269641.jpg

i-img1000x1000-1623401403dqcqcm269641.jpg

Rear-Axle-Differential-Carrier-3154-Ratio-OEM-41110WAA05-Toyota-Supra-2020-304090551355-2.jpg
 
 
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