H55F mounting bolt holes

[HZJ75 FARMER]

I removed a H55F transmission today and one mounting bolt hole underneath started leaking oil.

Is this common?

Cracked housing?

Faulty casting?

 

[Eurasiaoverland]

Was it a steady leak or just a dribble?

 

[HZJ75 FARMER]

Was it a steady leak or just a dribble?

A steady dribble. But I only left if for about 10 minutes as it was making a mess.

Less than what comes out of a drain plug. More than what would fit in the hole if it had somehow been used as a thread lubricant.

 

[Eurasiaoverland]

I've seen it before where oil has wicked up into bolt threads and sits in the void below the bottom of the bolt. But if it definitely leaked more than can be stored there (the hole is quite a bit deeper than the length of the bolt), then it must be cracked. I would try filling up again and see if the leak starts again.

Was the oil that came out of the drain hole the same colour?

 

[HZJ75 FARMER]

It appeared to be gear oil.
I'll investigate further.
I intend to dismantle and rebuild it. So I was thinking I should be able to make up an adapter fitting and connect an air hose to it and see what happens.

 

[Eurasiaoverland]

It's hard to imagine a crack in the cast iron which only goes through to the bolt hole and does not reach any external surface of the housing.

 

[HZJ75 FARMER]

Yes, makes me wonder if it's more likely to have been drilled just slightly too deep perhaps.

 

[Eurasiaoverland]

Yes, makes me wonder if it's more likely to have been drilled just slightly too deep perhaps.

Mine goes 27 mm deep. Uness the bolt was threadlocked in, I think it would have leaked continuously before taking the mount off.

 

[LDowney]

It's hard to imagine a crack in the cast iron which only goes through to the bolt hole and does not reach any external surface of the housing.

Yes, makes me wonder if it's more likely to have been drilled just slightly too deep perhaps.

I am envisioning a combination of your thoughts.
Due to variations in casting; if the wall thickness was thinner than nominal and if a longer bolt* had been used, the bolt might have bottomed out and broken through the cast iron to some extent. Due to this, there was no oil leak while the bolt was tight but there was oil coming out once the bolt was removed.

*including debris in the bolt hole which effectively gives the bolt added length

Just a thought as you investigate. Good luck at tracking this down.

 

[HZJ75 FARMER]

How often does this happen?

What do you reckon - put thread sealant on the bolt and shouldn't be a problem?

 

[Eurasiaoverland]

Wow, I've never seen that before. Not that that means much as I've only stripped and rebult my own H55F, but I've probably read a good proportion of the useful threads on here and have not seen that get a mention. I wonder if someone hydraulically locked a boly at some point, or use a bolt which was too long. Or just a casting fault.

I don't see why threadlock would not work, there is not really any oil pressure there. For all we know it might have been like that from the factory. And it doesn't look like a crack that will propagate further.

Thanks for sharing the picture.