Resealing Transmission Sump Pan.

Here's a little something that I have recently learned the hard way, this I have posted in the Transmission Group, yet post it here too for the benefit of those who don't venture down into the Group Dungeons.

This little job can catch you out in many curious ways, please pay great attention to every detail of this apparently simple job.

The best way to do this is the same as Mr T, clean both faces with brake cleaner, then run a continuous 5mm bead of RTV around the centre of the pan sealing face routing inside the bolt holes and torque the bolts up to 6.5 ft lb.

The above system is perfect when the transmission is out of the car and upside-down, however, when it's the right way up under the car, it can be difficult to keep the transmission sealing face free of ATF that will be creeping down from above.

The slightest drip or smear of ATF and the RTV will not stick and consequently, the joint will leak.

"Use a gasket", I hear you cry!

"Use gaskets with caution", I reply!

I have learned the hard way that transmission sumps become addicted to gaskets!

The pan is pressed from light gauge steel and the 6MT bolts have a small spring washer only, with a squidgy gasket underneath 6.5 ft lb pulls the pan around the bolt hole into the gasket.

This means that the originally flat surface around the perimeter of the pan has become a rollercoaster by a millimeter or two between the bolt holes.

The gasket however, will seal up nicely, nevertheless, the problem may surface next time the sump is removed.

Gaskets come in both rubber and cork flavours, with the cork version being twice as thick as the rubber.

These different gasket thicknesses cause different size rollercoasters and you will find that you can't use a rubber gasket after a cork one has been used, but you can use a cork one after a rubber one has been used.

If you are not aware of this, the job can become a proper wind-up.

If you need to drop the sump, let the car stand overnight with the drain plug out, then when the transmission is opened it will be a lot drier inside and a good dabbing around with an absorbent cloth should then allow the faces to be cleaned with solvent to be free of ATF and with care, RTV only will do a good job.

If a gasket must be used, use a rubber one the first time, which could then be followed by a cork one the next time.

I left mine for hours (in the car with sump off) and was still having to keep drying up the ATF that was creeping down from the internals, took me about 6 hours to do the job (simple sump pan change ...or so I thought) and as a result I still have a slight weep where it didn't seal properly.

Next time I WILL be leaving it overnight to dry up completely,

Cheers David.

Very helpful. Thankyou for that David.

You're welcome.

In automatic transmissions the gears and clutches are at the top of the box and which are lubricated by means of a set of jets on top of the valve-body.

It takes about 12 hours without the engine running for the ATF to stop dripping from the gears, so it makes sense to rest it with the plug out.