Even MORE gearbox trouble: any ideas please?

[smallspeed]

Just like to point out i don't have experience from a g.box building point of view but have spent the last 12 months trying to resolve a similar transmission lip-seal issue for a large scale vehicle manufacturer so picked up a few thing along the way.. I'm no master but my job is to be a jack of all trades

glad the specialist is going to resolve it; he sounds like he knows what hes talking about based on previous builds and things; Love your car, and really enjoyed having a sneaky nose around it at mikes "reveal party" so hope it back up and running again soon!

[smallspeed]

Sorry if the first sentence sounded a bit "up my own arse", it wasn't meant to! I was trying to say i don't really know what im talking about just putting forward a few ideas we were able to rule out at work

[911hillclimber]

Bruce is right, it is a 'seal' that in the event the lip seal fails stops the oil seeping down the input shaft and to the clutch.
You do need a 6mm hole drilled in the tube at the bottom obviously for the leaked oil to escape and seep down the wall of the bell housing out to the road/clutch arm/heat exchangers and futher afield....

Read about it on Pelican after a Google search on the subject Andy.

I have to find time to pull the trans out, de-oil everything and get it up north a 3 hour ish drive one way.
Also need to focus on the other Porsche thing in my toy box, far more perplexing.

[myatt1972]

To save you a day I bet someone on here would be heading in the direction of the specialist and willing to drop the box off for you ?

[911hillclimber]

Nice thought, but I don't know when I'll pull it all out again, certainly not in the next 10 days.
Thanks for the idea though.

[andytat]

Sorry to butt in I don't normally stick my nose in, but I had a thought while reading your thread Graham. I'm very familiar with the 915 box and input shaft seals don't usually have problems like this. Years ago I had a leaking 915 after it had been freshened up and it covered the clutch lining in oil. I fitted a new clutch lining & input shaft seal thinking this was the problem but after 20 or so miles it was leaking again. After removing the box and scratching my head I realised that the leak wasn't from the input shaft. The breather plug on top of the box had been removed & refitted with the hole facing the wrong way round so the oil was being thrown off the ring gear, out through the breather hole and directly into the bell housing, there is a large-ish opening at the top of the bell housing where the oil was going in. Because the box was clean and the oil new, it wasn't completely obvious wher the oil originated from. It might be worth taking a look with a mirror if you can get under the car, or perhaps the breather is blocked causing a pressure build up in the box.
Good luck with solving the problem & please don't give up on your Porsche's.

Andy

[911hillclimber]

Andy:
Your thinking is sound as a pound.
I know about the direction of the breather.
On my 911 it is correct and clean, the 915 box above in the race car is mid engine so the breather goes in 180 deg to the normal.
The same specialist did both boxes.

When I removed the box after 201 miles the case was dry outside the inside of the trans bell housing was wet and the underneath drenched.
Now, after 50 miles and a new seal the oil is coming out of the housing cut-out.

I have not done many gearboxes in my life (3 of them and non Porsche) but I have never had lip seal probs with boxes or engines.

In time I will get the box out again and REALLY check to see it is not coming from the O ring in the guide tube, but it has to come out..

[davep]

A good start to the "dam seal" fix for the 915:
http://forums.pelicanparts.com/6870795-post5.html

My thoughts on your problem are: the bearings fell out, and the case had to be repaired; the input seal wears rapidly in one spot. If the shaft was not supported or warped then I would expect that the shaft would wobble, and the seal would not wear in just one spot. If the shaft was misaligned, then I think you would get the result you have. I suspect that the bearing is not perfectly centered, thus causing a slight (but significant) misalignment. If you can determine the "clock" position of the wear on the seal then this might help point out where the problem is.

[911hillclimber]

I see your thinking, but the gearbox is silent in the gears, with the typical '915 chatter' when in 5th at 40 mph under load.
The bearings were loose in the case, they don't fall out just shuffle round with the outer race moving may be a 0.25mm here and there.

I think it is a simple case of the seal was in the box dry and burnt on the shaft witht eh 2 hours of constant 3000 rpm to see Mike's RSR and then the same back, 201 miles.

The new seal I've fitted I think is running on the black trace on the input shaft which is uneven enough to allow a leak.