Wondering if anyone would have suggestions for possible root causes of failure for a blown out AT pan gasket that’s only a few months old. 1994 Toyota Pickup, 4 Cyl 22RE with a 4 speed automatic. I I replaced the gasket, along with the internal AT filter, a few months ago. The new gasket was rubber and instructions specified a thin layer of RTV on both sides, then torqued to specs, 4 lbs per bolt if I recall. It has been working perfectly, no leaks of any kind, until today after a drive up 121 to McKinney from Coppell.
If I remember correctly it should be like 65in pound on the torque spec ,how do the Threads looks did you happen to get it crossthread ? I always do a cross tightening pattern on pans is your torque wrench in spec
Use straight edge to check pan surface is flat 4. Verify RTV you are using is rated for ATF 5. Coat new gasket with ATF rated RTV Probably doesn’t need RTV per @jast
Re-apply gasket
Re-install Trans pan, using cross tightening pattern
My immediate reaction to that is “How odd…”. It would be new to me for any manufacturer to actually specify RTV with a gasket. General rule of thumb is “either/or”. I’ve done a fair number of auto tranny fluid changes in my time, on equipment of this era, and make, and never had problems with dry gasket installation, so I don’t know why they’d change that.
Which having said, make sure, if it does, the gasket maker is rated for that duty. Double check flatness of both surfaces never a bad idea. Double check torque, but honestly, for that application, they aren’t usually THAT finicky… Did any other weirdness happen, like the dipstick blew out? There’s just not a lot of things that would cause pressure in the tranny case, other than heat, which might have been greater than usual if you were at higher speeds than usual. In which case I would be checking for overheated fluid evidence, plugged vent ports, etc. But I would expect a blown dipstick before a blown pan gasket if those were the culprit.
RTV silicone and auto trans fluid don’t react with each other. I suspect the use of RTV in addition to a gasket mechanically caused a sealing failure. Rubber doesn’t seal against a rubber surface and silicone doesn’t bond well to anything but silicone, so you’ll tend to see leaks at the point where the gasket and silicone meet.
Appreciate all the feedback. I’ll double check the RTV I used when I replaced but I think it was Black and rated for Transmission fluid. The instructions definitely called for RTV. Otherwise all the noted items, clean pan, level, cross pattern, torque specs and others were followed. The only stand out is that I was cruising along 121 at about 80 mph which is about as fast as I go in my truck.Then parked and noticed about an hour later I had a puddle going on!
I need to get a new gasket and drop the pan to get a better look. It looks like it might have failed at a bolt hole and I’m wondering if perhaps I damaged it somehow on installation or it was damaged at that point and I didn’t realize. I may not be able to tell, just a thought.
Anyway, I appreciate all the feedback. I’ve never seen a blown out transmission gasket like this before, I didn’t think the case had any pressure to speak of on that gasket and I’ve done a couple of these, including one on this truck years ago.
OK, update: I picked up a new kit and did some cross checking. I mixed up instructions; Haynes manual says use RTV on the gasket, the kit itself is quite clear, don’t do that. So … human error (me) is the likely root cause of this failure.
Thanks for all who contributed comments and props to those of you who pointed out RTV + Rubber != success
At least that one’s an easy fix, once you’ve realized it! Better than chasing your tail with weirdness of unknown cause…
Keep us posted!
(PS I’m secretly thrilled to hear we are continuing with no known manufacturers of gaskets specifying RTV on their “rubber” gaskets. )
The sealing surface on the pan is only about 1/4" wide down the center of the rim and thinner around bolt holes. The gasket is about 5/8" wide, so there’s a lot of overlap and it’s quite thick, maybe 1/8".
Is this RTV damaging the gasket material + bolts doing something or ? Strange to me. This failed gasket was torqued to 4 ft-lbs (Haynes manual instructions) and the kit says “No more than 12 ft-lbs”. I used a craftsman torque wrench, indicator type, not click, and I think it’s reasonably accurate.
Looks like the pan surface may not be flat to mate properly with the transmission and it’s pinching the gasket. This can happen if it’s tightened by a gorilla previously.
Jphelps,
That is a mechanical failure in the gasket, not a cross contamination failure.
Looks like you may have unknowingly pinched it with a bolt. No biggie happens often.
The good thing is that you noticed it in time.
P.S. the transmission fluid pan is NOT pressurized.
Better than 
)
