4 replies to this topic

[LXCHEV]

Popped the head under the Torana earlier this week to investigate a trans fluid leak. I'm running an aftermarket alloy pan on the TH350 - with a nylon style washer. No longer in one piece. No idea if I've simply over-tightened it at some stage in the past, or if it's just worn out...

 

 TH350_pan.jpg   445.69K   0 downloads

 

Anyway - I was digging through my spare parts - and found a spare dowty washer (pictured far right) - which is something that the boys down at Pirtek had put me onto years ago for replacement sump plug options. They reckon they're great - and common in hydraulic applications. It's a beautiful snug fit on the trans plug - so I've installed it and we'll see how it goes. This washer is an aluminium outer / rubber inner combo.

 

Just curious - is there any reason not to use this for transmission fluid? i.e. is there a reason sump plugs typically have copper washers for engine oil, and transmissions have nylon washers for trans fluid?

 

 TH350 drain plug washer options.jpg   574.25K   0 downloads

[greenhj]

The hydraulic washer is about as good as you can get but they are less tolerant of "not flat" surfaces than the others.

 

The copper/fibre/plastic washers will deform more and seal better in non ideal circumstances.

 

 

Edited by greenhj, 09 November 2025 - 01:29 PM.

[Bruiser]

The rib around the plug hole thread doesn’t look very flat at all
Would the rubber inner section of the hydraulic washer diameter match
and make a good seal against it?
If it does, it should be flat enough, how would even it become un-flat?

[rodomo]

With a coarse thread (virtually self centering) like that, annealed copper would be my choice. 

[LXCHEV]

Since the new washer is smaller in diameter - it sits beautifully on the rib. Pic below.

 

So far, so good. Looks mint, and zero signs of any weeps. If I have any dramas I'll swap it out for copper. But I think I'm onto a winner...

 

 LXCHEV TH350 Plug.jpg   468.98K   0 downloads