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Oil pouring out of 4 speed transmission vent while driving

2K views 16 replies 10 participants last post by  V6Opel 
#1 ·
As the title says, I have a strange issue with my GT that I’ve never seen mention on the forum. Whenever I drive my GT it leaks gear oil from the top vent (see photo with my purple gear oil pooling below the vent).

I’ve had this issue for years, but I’ve never known it was the vent until recently when my new silver spray paint allowed me to see it. (Also I just replaced all the other seals and they are dry.)

My transmission does not leak one bit in the garage while stored, but as soon as I drive it leaks everywhere. The oil pours out onto the trans mount and exhaust. The faster I go, the worse it is.

Anyone else have this problem? I guess my next step is to attempt to remove the vent and inspect it. Not much room up there now that it’s installed…

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Discussion starter · #4 · (Edited)
I think this was suggested on FB, but if the lube is too high (s/b a half inch BELOW the filler hole, due to the tilt in a GT), that might cause it.

Or the lube you are using is foaming. What brand and type and weight?

Or you are driving too damn fast around corners!!!
i don’t think it’s the oil. I’m using royal purple synthetic 75w90 that is brass safe. I run the same in my other GT and it’s dry even on the track. Of course it has the later style breather at the top.
I did lower my oil level to spec. And it’s unchanged.

no corners yet, I’ve just been doing some testing on the cam and taking it easy.

I took the vent out and it doesn’t seem clogged. I cleaned it up anyway. There was plenty of oil in the vent. I reassembled and put some sealer on the threads, but I doubt that makes a difference. I may try and do a breather extension to the engine bay for fun. Finding a barb with that strange thread pattern may be tricky.
 

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Discussion starter · #9 ·
I find it odd that you get any fluid out of that vent, it’s just the tail shaft that is inning back there, maybe the speedometer gear, so not really a bunch of stuff to faking oil I would think. if something is causing the fluid to foam or causing turbulence/pressure?
True. I don’t know. I’ve had the pan off before and everything looked fine except for a missing reverse tooth.

I will say that 3 out of 5 of my early spare transmissions show evidence of extensive leakage from the vent based on grime build up, while my 2 later style spares do not.
Opel may have changed the design to solve leakage.
Also one other thing. I drive differently than most opel owners. My car sees above 6000rpm every time I drive it several times. So my trans is spinning as fast as it can most the time.
 
Discussion starter · #10 ·
The thread pattern is m14x1.0. Not a common fitting size, but I managed to find one on eBay. I’ll install that Barb fitting and run a 3/8 emissions line to the engine bay with a 3/8” breather at the end.
It shouldn’t leak after that. If I do all of that and I still see leakage then I probably have a crack somewhere that opens under load and I’ll swap the transmission in that case.

having a vent to the engine bay will be useful though because I could use it to refill the trans too.
 
Discussion starter · #12 ·
I fixed the issue apparently. Not a drop leaked out from the vent or onto the trans mount at the track today. My guess is that vent was slightly clogged and pressure build up was forcing fluid or vapors up and out. I guess cleaning it out with compressed air worked even though it didn’t seem clogged. Or maybe enough fluid leaked out to prevent it from happening lol.

The only leak on my car now is a slow one from the speedo drive. I’ve replaced it with OGTS seals twice now. Their seals just aren’t quite right. It’s the inner cup seal that doesn’t work quite right.
 
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