Assuming it's not over filled: Top cover gasket installed wrong would be my guess. Or worse, the center is cut out or torn. Tiger & Cobra tunnels do get quite hot enough for fluid expansion, but they need splash access to expel the gear oil.
Not overfilled... I don't know how you could anyway.... the gear oil should be at the bottom thread of the fill plug.. I would assume that the cover gasket hole should NOT align with the hole in the metal cover??
well, the new gasket kit has a hole in the gasket... if it doesn't have a hole, how would it vent?
if you happen to remember, give me a heads up! I'm guessing that he added a vent in the tailshaft housing near the flange where it bolts to the main case. That way it'd be away from the main supply of gear oil but would still vent through the mainshaft bearing...When I talked with the owner of Paradise Wheels he said and showed me a breather he added to top loaders to help stop their leaking out the vent. Sorry it's been 10 years so I can't describe it further..
If the gasket does not have a hole how can the vent be functional? On my survey of two there I'd say ho yes der b a ho ,
Maybe the gasket acts as a diaphragm and flexes
I imagine so!
I don't think that the vent is very well placed. It may just be that it's due to the way the car sits.. the rear ride height is higher than my personal car.. in any event, I had an old Jaguar gearbox vent fitting that is threaded 1/8" BSP and I installed it right behind the flange on the tailshaft housing... There is very little oil there, but as you found when fitting the drive shaft there is continuity for air travel. It could be that this car has fairly soft rear springs and what actually forcing the fluid out is the driveshaft moving in and out...
Now that makes sense , acting like a piston pump
exactly!
Would fitting stiffer shocks compensate for soft springs and reduce the amount of in / out of the driveshaft therefore less pressure needed to be vented from the gearbox and less oil puking
that'd be one way, another would be radius arms. I'm using both Koni's and radius arms (traction bars)... and yes, I still have the panhard rod in place. I have suspension travel, which is important if the car is going to handle worth a damn, but the suspension is set pretty stiff. I have Koni's in the front as well. They're all adjustable, just a royal pain to do it!
Here's my solution... Jaguar vent assy. It has an internal washer which stops fluid, but will allow air by. Kind of like a miniature PCV valve w/o the vacuum. It has a larger vent hole as well. As there is little oil in the tailshaft housing, and that's the source of the problem, I mounted it as close to the flange as possible.
The trans is no different than the rear end of the car. If the drive axle doesn't have a vent you'll find that the gears basically act as a hydraulic pump. The movement of the oil builds pressure in the housing and the pressure vents thru the path of least resistance. If there is no vent on a drive axle you'll find it usually blows thru the axle seals. The gears in the trans are constantly moving the oil and building pressure. The pressure vents thru the path of least resistance. That could be a weak or loose gasket or a marginal condition seal. I know of one Sunbeam running in SVRA that the rear axle vent had to be plugged off to allow the use of the rear sway bar. The axle seals starting leaking after several laps.
Sean. Do you know a way to stop the leak out the top without removing the engine/transmission?