Can anyone isolate this leak?? Or, 'Depends' for an FJ40...

[Solace in Solitude]

I drove 44 about 165 miles yesterday... All but 8 miles on pavement... Generally around 60-65 on the highway... Occasionally, up to 75, while passing.

This morning, I find thick, black blobs under the rear end.. From shock mount to shock mount.

The rear end, itself, was glistening, from the horizontal welded seam to the bottom, only on the front side. The bottom three nuts (front) on the pumpkin were also glistening.

The rear driveshaft was dry... As are the two rear wheels.

I checked the diff... It's properly full of clean gear oil.

I cleaned the mess off the rear end and found the two bottom-left-most nuts slightly loose. I re-snugged them and jacked the rear up and put it on stands... Then, I started 44 and went thru all four gears several times.

No obvious leaks...

No noise, no problems that I'm aware of... Just the obvious shine and the blobs on the floor...

Can anyone look at this pic (sorry, best I could get) and tell me where they think the leak might be?

Is this a leak that would only repeat when driving highway speeds, with the wheels on the ground?

All insights are welcome!!

 

[GA Architect]

Do you know if it is gear oil or motor oil?

Didn't you just have some oil pan leak issues? You may be blowing motor oil out of engine compartment or gear oil out the tranny and spraying the rear members?

 

[Solace in Solitude]

Do you know if it is gear oil or motor oil?

Didn't you just have some oil pan leak issues? You may be blowing motor oil out of engine compartment or gear oil out the tranny and spraying the rear members?

The black blobs were VERY thick and VERY black... I couldn't merely wipe them off of the epoxied concrete floor... Had to use brake cleaner to get it up... So to speak.

The diff, tcase and tranny oil is clean and golden... As is the motor oil... And the oil pan leak is a distant memory... As is most everything else nowadays.

Since the rear drive shaft is dry, I suspected it was grease out if the whatchamacallit ( it's after noon, I'm losing my vocabulary... The things that connect the driveshaft to the rear end... Oh! U-joint)... The rear U-joint.

Is there something that could be amiss that would cause grease to be sprayed out of the rear U-joint?

 

[JackA]

That does not seem like grease to me. Looks like some gear oil that sprayed out from the front and landed on the rear diff at highway speeds. Any leakage around the rear output/parking brake?
Touch it and smell your finger, you should easily be able to tell if it's gear oil or not. Mine does something similar from some leakage at the tcase.

 

[diogenese]

I'd guess that it is out of your transmission and has blown back to the rear axle. maybe the blackness is from road dirt captured by the oil leak?
There wouldn't be that much grease in all your UJ's!
I'd check all your oil levels as a clue to it's origin

 

[Solace in Solitude]

Thanks guys! That's three of you... Sounds like a consensus... I'll drop the skid plate and check the levels.

I've had a very slight leak back there all along, but never saw it beyond the skid plate ...

I thought that, since the driveshaft was clean and dry, it wasn't from the tcase or tranny.

Thanks!

 

[diogenese]

The aerodynamics of the underneath of a vehicle at highway speed can get oil into some very strange places

 

[cooney]

That does not seem like grease to me. Looks like some gear oil that sprayed out from the front and landed on the rear diff at highway speeds. Any leakage around the rear output/parking brake?
Touch it and smell your finger, you should easily be able to tell if it's gear oil or not. Mine does something similar from some leakage at the tcase.

This gets my vote. Sounds like a double seal housing from Poser in your future. Does he still make those? @Poser


Sent from my iPhone

 

[Solace in Solitude]

This gets my vote. Sounds like a double seal housing from Poser in your future. Does he still make those? #poser


Sent from my iPhone

Thanks!

Do you still do the double seal @Poser?

Please PM me with specifics.

I'll drop the skid plate in the morning and look closer at the tcase and tranny.

Thanks!

 

[JohnnyC]

I vote rear pinion seal ... Does the pinion have some play?

 

[Solace in Solitude]

I c

I vote rear pinion seal ... Does the pinion have some play?

I can't see/feel any play Johnny... But describe what you mean by play... We may have different tolerances... Thx!

 

[slickrock]

Did you smell it yet? Gear oil, tyranny fluid, motor oil, brake fluid, and steering fluid all smell very different. If you must, by a quart of each and dip some on you finger and get the nose working and find your fluid.

 

[HJ45]

I vote rear pinion seal

x2 or diff gasket where nuts were loose.

How do you find the airbags comfortable ride?

 

[JohnnyC]

Slight movement up and down

I have had leaks all over from the transfercase to the crank pulley ... Never has any sprayed like that

It's from the rear end area... could have possibly been because of the loose bolts ...

If they are now tight ... Clean it all off and go for a run? See if it's still an issue

If your vent is clogged the pressure will escape and find the easiest way out (if the vent is plugged) ... The path of least resistance

 

[Solace in Solitude]

Did you smell it yet? Gear oil, tyranny fluid, motor oil, brake fluid, and steering fluid all smell very different. If you must, by a quart of each and dip some on you finger and get the nose working and find your fluid.

Only when I first found it, I cleaned it up and can't smell it X again unless/until it leaks again... It smelled like gear oil to me. It hasn't leaked since I snugged my nuts

But, has only ran on stands. I'll take it for a drive before Monday, but I have some things to do before I drive her.

 

[Solace in Solitude]

x2 or diff gasket where nuts were loose.

How do you find the airbags comfortable ride?

So, having snugged my nuts, I may have stopped it... I'll drive her as soon as I can... Before Monday and see what I see.

I love those airbags!!

 

[Solace in Solitude]

Slight movement up and down

I have had leaks all over from the transfercase to the crank pulley ... Never has any sprayed like that

It's from the rear end area... could have possibly been because of the loose bolts ...

If they are now tight ... Clean it all off and go for a run? See if it's still an issue

If your vent is clogged the pressure will escape and find the easiest way out (if the vent is plugged) ... The path of least resistance

No pinion movement up and down.

I have to remove the hump to get to the tcase vent... I need to tie it into my raised axle vents. I'll do that this weekend, but I don't think it's blocked.

I'm really leaning toward gear oil being forced out thru the loose nuts area of the rear pumpkin. Now that they are snugged back down, I want to raise the tcase vent and make sure it's clear before I do a road test.

Once I remove the hump and raise the vent, I'll run over to the car wash and pressure wash the rear-half-underneath and take her for a drive.

Here's hopping... Edit: well, here's hoping...

Thanks everyone!!

Happy New Year!!

 

[handcannon]

This probably isn't the culprit (long shot anyways), but what kind of condition are the knuckles in? Any leak from the knuckle area most likely would leave a longer grease trail that would start farther up towards the front. I'm thinking more in terms of gear oil mixed with the grease in the knuckle.

Don

 

[Solace in Solitude]

This probably isn't the culprit (long shot anyways), but what kind of condition are the knuckles in? Any leak from the knuckle area most likely would leave a longer grease trail that would start farther up towards the front. I'm thinking more in terms of gear oil mixed with the grease in the knuckle.

Don

They're still in good shape. No mess in the front 2/3's. Thanks anyway!

 

[honk]

Could you have gone over some seaweed, a dead catfish, or maybe someone's charbroiled infant?

OK, the infant is a bizarre example but I'm trying to bring the possibility that the blobs are not a failing of your truck at all but instead a result of something you encountered while driving your truck.