Auto gearbox gasket sealing problem

[Robmsharp]

For a while now my BW 35 gearbox has been leaking fluid from the 15 bolts that secure the sump pan to the bottom of the box so I thought it high time to change it.
i bought a replacement from Paddocks and did the job last weekend. I noticed after removing the old gasket that oil had breached the seal and that it was compressed and had gone hard. I fitted the new seal and for good measure smeared Blue Hylomar on both sides of the gasket (the ROM suggested this was OK to do). I then refitted the sump and refitted the bolts. I couldn't find any torque setting so used a 1/4 drive socket to apply what I thought was sufficient tightness to the bolts. The test drive showed no leaking but after doing some more journeys I noticed the tell tale witness of oil on the bolts. So they were tightened even more, but I noticed that the gasket had started to squish out the side of the join and I can start to see the hylomar also being squished out. Unfortunately this has not cured the leak and I feel that more tightening of the bolts will only cause the gasket to squish out even more and eventually the gasket will fail.
Can anyone advise why the gasket has done this and what I can do to make an effective seal?

[stag8manod]

Hi Robin, Remove the sump again and run a straight edge over it to check it's flat and hasn't pulled down through the bolt holes.
Cheers Ian A

[sujitroy]

Early BW35 pans were steel . later used aluminium . I was able to get an aluminum one. I still have small leaks. Just a thought, there are torque setting for the gearbox bolts which is aluminium, find the same size bolt and its torque setting and use that as a guide.
Sujit

[Robmsharp]

Thanks for your replies, the pan is an aluminium one and when I inspected the mating surfaces they looked clean and flat. I was wondering whether it might be due to the grade of cork used to make the gasket and whether there were alternative types of sealing material available as it seems odd to me that the gasket should start squishing out.

[Nauts]

I have the same problem wit my BW35, I have tried to sort by having a custom made gasket from a local supplier, this was made from a blue food grade type material, its not quite as bad but still leaks from the bolt heads, I have come to the conclusion that the box's are porous and topping it up now and again saves me from doing an oil change.
Paul

[Peter707R]

The BW65’s are no better - tried a rubber gasket which is advertised as an improvement - certainly wasn’t so I’m back to cork. Biggest issue is the fluid draining back from the torque converter and the fluid comes out of most orifices!!!!

[elvimto]

I used an adhesive that is for the rubber trim to frame I put that on the pan fitted the gasket then bolted that up to the box dry and left it overnight then removed it and applied the adhesive to the dry side and fitted it up to the box it does not leak,

[TR5convalescent]

Having spent a small fortune on gaskets, new bolts and sealer and air vent tubes and God knows what else a couple of years back, I bit the bullet and got Clive a Tate to do a ZF conversion. One of its benefits is a dry garage floor. The other is much quieter cruising.

[DJT]

With my old (pre-ZF) BW35 I used a cork gasket acquired from a local transmission specialist and fixed it using Stag Wellseal. I also annealed the two copper washers for the dipstick tube banjo fitting. Never dropped any oil after that.

[Robmsharp]

Thanks for your replies - Paddocks supplied the replacement cork gasket so I'm going to talk to them. I'll probably end up getting another one and seeing as I've got some Wellseal I'll give that a go, but never having used the product before can anyone advise the best way to use it ?

[DJT]

Sparingly. Brush it on using a small artists brush or similar. It is quite runny and goes sticky quite quickly. Practice on a piece of cardboard first.

[sujitroy]

Here in the US I got a BW 35 gasket years back. It was made of paper and not cork. No sealer of any type used. It leaks. I have a large drip pan and card board under the car for drips.

I seem to recall someone mentioning that you should pre- soak a cork gasket in oil before fitting.

Sujit

[Robmsharp]

An update on my gearbox sealing problem - I talked to Paddocks and was disappointed in their reply as they said no one else had complained of this seal causing problems before, and they weren't willing to accept the seal was at fault, so I bought one from LD Part instead. When I removed the one supplied by Paddocks it was clear just how badly squashed the gasket was and it was no real surprise that it wasn't performing its job, however upon fitting the LD Parts seal I noticed that once again the seal was being squashed out the side again. This time however I smeared both sides of the gasket with Blue Hylomar so I'm hoping this will help effect a long term seal, but I'm not holding out much hope.
i wonder if what's really at the bottom of this problem is the fact that the new cork seals are of inferior quality to the ones made years ago. Has anyone else experiencing sealing problems with using new cork gaskets?

[thebadleys]

Is it possible that the sump pan bolt holes are a little distorted where they could have been overtightened and pulled the pan out of shape. I don't think there is a torque setting for them but perhaps over-tightening is indicated by the gasket being squeezed out.

Just a thought.

Nigel

[Alacrity]

I own a transmission business & we never need to use sealant on BW35 or 65 pan gaskets. just clean dry surfaces &, if a steel pan, make sure you tap the surface back down with a hammer before fitting. Ali pans are easy as they don't leak, the original gaskets were not cork/rubber but a thick gasket material but are NLA. It may be possible to get similar gaskets in a material called Farpak but not sure without checking.

The most likely cause of the leak is the two manual selector shaft seals which are just above the sump, these leak onto the joint between the sump & maincase & it then runs round & drips off the bolts. No amount of pan gaskets will cure it! Remember, as with all leaks ALWAYS look above where it is dripping from. There are also other places above the sump that are common sources of leaks - kickdown cable, inhibitor switch are very common. Also when filling it is easy to get fluid running down the outside of the filler tube & that can drip for days. A lot of people on here talk of converter drainback but in my experience it is very rare. Due to contracts we once had years ago we have built 1000's over the last 39 years I have been in this business & I have only known a few cases of it.