I had the transmission fluid and pan/filter replaced around 6 months ago. Twice I have noticed that after the car has been sitting for prolonged periods of time, transmission fluid leaks.

Both times the fluid puddles were fairly large.

I don't think the shop replaced the mechatronic seal.

What do you think is the cause? If I use the car regularly, I see no leaks.

 

I have had a very slight leak after replacing the pan.

I tightened the set screws in the area as much as I dared which stopped it.

The root problem IMO is that the gasket on the pan is a rubbish design and also

the plastic distorts a bit with the heat.

 

Switch over to the Ford steel pan, & filter if it fits your car, less cash, & it just don't seem to leak like the plastic one on my car did.

 

I've owned several classic cars and the ones with automagic transmissions all tended to leak in the same manner. The joke in the hobby is that if its not leaking, its empty. It was explained to me once that since classics sit for weeks or months at a time, the fluid in the top half of the torque converter drains back through old internal seals or worn check valves in the valve body, thus eventually overfilling the pan. Seals like on the side of transmission where sensors and linkages penetrate the case work fine against the liquid being splashed around inside, but were not designed to hold back the force of being under several inches deep of fluid. Even the pan gaskets are under greater pressure to leak.

 

That makes sense. I think my car is telling me to drive it more often.

 

Can't say your wrong, it (steel pan) has just helped me, with my issue, of the leaking plastic trans pan.

 

I found a steel pan on eBay. As long as it is for the ZF6HP26 it fits, right?

 

It fits on my 04 XJ8, with bolts, & drain plug, for $139.75 delivered to my door.

 

I just had my cat's transmission fluid level checked, it was perfect and no leaks at 90K miles, there's still color in the fluid. I want to do the oil change kit with seal, but don't want to open Pandora's box and have a dribbling cat.

 

Yup

 

There will always be claims that steel is better than the plastic. 99.9% of plastic pans are a non issue. Don't fret it. If you're uncomfortable with the plastic, buy the steel.

Steel pans are overrated IMO. Most modern cars have plastic pans today and you will find failures but unless you're off roading, your chance of a leak in plastic over metal are nil.

If you're old enough to remember GM's TH350, 400 etc, the pans were all steel and often leaked like sieves. I think plastic is an improvement. Often the leak is the result of tightening the pan bolts in the wrong sequence or over torquing the bolts.

It's your car. I've replaced on my X350 with plastic and my XK. My XK pan (same tranny as the X350), was an aftermarket bought from a German distributor and likely made in China. Doesn't leak a drop and I paid $64 for it, including the gasket and an entire new set of larger headed bolts.
Just a different perspective. I'm sure you'll be happy with either in the end.

 

Main reason i went with the steel pan was, plastic one was leaking, they tend to warp from what i read, also the filter is part of the pan, bad idea (my opinion). The steel one is reusable, as is its gasket, steel, & rubber, the filters are in the $20 to $30 range, so even if you replace the gasket every time the filter is changed, you still save some cash.