Bought my truck about 3 weeks ago (67 C-10) and last week noticed the tranny was leaking from around te seal. Replaced with new filter, oil, and gasket. Looked to be ok. Looked under there last night and its dripping from near the modulator area with fluid on the bolts again.:mad:

I know there is an o-ring around the modulator. Never replaced one but it looks easy. Is this common for one to leak? Its a TH-400.

I am going to replace it and then retorque my bolts and wipe it all down again. Tranny fluid is expensive to keep peeing it all over the garage floor.

Simple fix and you can do it without loosing much fluid by putting something over the opening when you take it out. Just have another person that can change the o ring.

Is it a standard size o-ring that I can replace myself? The mod. is $12.00 new from advanced auto parts. If its a quick o-ring fix, then I will go that route.

Yes it's should be a standard size o-ring, nothing special.

ok, cool. thanks!!