Oil leak BW 35

[Deleted]

I have problems with my bw 35. The gearbox always starts to leak after 30-40 km driving. I have checked the oil level (very careful several times) I have changed front and rear seal. I have checked the converter for leaks. The oil seams to come from the upper side of the gearbox.
Anyone got any ideas ??

[harvey]

Normal places are the sump gasket and the selector shaft seal or possibly inhibitor switch. If it's coming from above those I'd suggest power washing the transmission, taking it for a run and then looking where it's coming from. They can get cracked casings but that is rare.

[Phil Nottingham]

The cooler pipes and filler tube/nut can also work loose - cleaning off and then seeing where its starts from is the best awy as Harvey suggests.

His first 3 supects are the most common - the sump securing setscrews actually work loose due the shrinkage of the cork gasket. retightening them may resolve thsi as long as they are not overtight as this just distorts the sump pan flange

[Deleted]

Thank you both, I will try to clean it up and see if I can see where its starts from.

Regards

Lars

[Deleted]

Tie a cloth around the filler just in case it is blowing up the tube. You will then be able to tell.
Another place to look at is the oil cooler connections.

[norvin]

I have the same problem but in my case the gearbox only leaks when the car is left standing for a couple of weeks, then i would say it will leak a couple of pints, this is the only snag on my car that i have not sorted.

[Phil Nottingham]

The ATF gardually drains back form the TC nad raises
ies sump level past gasket and inhibitor switch and selector seals etc - if these are worn it wil leak out

[norvin]

Thanks Phil, i will check this out when i have left it standing for a couple of weeks.

[stantondavies]

I have tried for 20 years to stop the BW35 leaking. Autolock in Crewe had an unsuccessful go, and Carvers of Reddish did a total rebuild. But the box continues to leak - erratically.
The car has recently spent a month immobile on a four-point side lift (another story!) Having been steam cleaned it is evident that the leak emanates from the inhibitor switch - no surprise there.
What flummoxes me is that there would be no leaking for days on end and then suddenly a pool of oil underneath the car. The car is stationary, hasn't been run, what on earth induces it to leak spontaneously? This revelation (to me) merely confirms my previous observations that there was no discernible pattern to when the box did or did not leak.

I collect the leaked oil in a tray - it isn't wasted, I use it to preserve the garden fence - I use old engine oil as well. As the fence is at least 35 years old and still going strong, I can recommend the practice to others with oil to dispose of, particularly if you have no convenient recycling plant nearby.

[Warwick]

Could it be that it accumulates in a hollow or depression and doesn't drip on the ground until the hollow is full? When you drive the car the air movement blows the hollow clean and it must then refill before dripping again appears?

[enigmas]

These boxes didn't leak when they were new and the unit went on into the 1980's in various guises in all sorts of vehicles.

A few thoughts on seals. A new seal fitted dry will burn it's sealing lip almost instantly before lubricant flows to it. Technicians and enthusiasts may fit new seals but may not give consideration to the sealing surface (fit a speedy sleeve). Hopefully the 'rebuilder' used thread sealant on every bolt that enters an internal space from outside. (i.e. the inhibitor/safety switch on the side. Coolant pipes exiting the case.)

Valve bodies (not all 35s have this) often have an anti-drain valve fitted so the torque convertor doesn't drain back. Oops...did someone forget that?
Speedo drive O ring and seal OK. Did anyone replace the old O ring/seal.
Side selector seals. Oops the old seals had gone rock hard and grooved the shaft. New seals and grooved shaft equals oil leak.
Most people focus on replacing internal components (bearings, clutches, bands, sprags, torringtons, thrust washers, etc) and the units function perfectly apart from the myriad and irritating oil leaks.
Aggravating isn't it.

[Phil Nottingham]

The resaon it leaks after standing a few days is that the ATF in the torque converter drains back down to the the outlet level. I have done this when changing fliuds and at least 3-4 pints come out this way.

This effect raises the ATF level above the sump pan gasket - another leak source - to the shift hole and inhibitor switch. Thread sealant can be used on the switch if its the non-adjustable type. I have heard of PTFE tape being used but I think unless this is fitted when the box is stripped that bits could fall in into the valve body and cause all sorts of problems

[stantondavies]

I understand that fluid drains out of the torque converter, but with the car being stuck on the lift the engine hadn't turned in weeks. Sometimes it would leak significantly, then for days it wouldn't and then again it would spontaneously leak. It doesn't make sense and I just can't get my head round why this should be!

[harvey]

Aug 24, 2008 11:50:01 GMT enigmas said:

These boxes didn't leak when they were new and the unit went on into the 1980's in various guises in all sorts of vehicles.

You obviously never worked on them when they were new then.........................

They were never an oiltight box in the same way japanese and ZF boxes tend to be, but they could be made reasonably oil tight with care. But they certainly did leak. The 65 was better than the 35 in this respect.

[harvey]

The anti drain valve for the converter is just a spring loaded ball bearing in the valve block, which IIRC serves no other purpose so could be left out without having any other effects. being just a ball bearing means that it could seat differently in different positions and cause it to work intermittantly.

[enigmas]

My apologies Harvey I was referring to the units built in OZ.

[harvey]

Aug 25, 2008 13:50:56 GMT enigmas said:

My apologies Harvey I was referring to the units built in OZ.

Maybe they were screwed together a bit better down-under!