dnmacdon

I just replaced my input shaft bearing and am reassembling the transmission. I applied what I thought was an even bead of RTV (Permatex Ultra Grey) to the clean mating surface of the clutch half of the case, along the inside of the surface and around all the bolt holes. I got the other side back on, finger tightened the bolts, and then, as the Permatex package directs, waited an hour before torquing the bolts down.

A little while after I torqued the bolts down (criss-cross pattern according to service manual), I noticed this squeeze out in a few places (example on left side of picture). It looks to me like the even bead at the bottom is from when I initially finger tightened the bolts, and then the "broken line" pattern above it would have squeezed out of the partially cured RTV.

I also noticed a couple of places where there's no visible squeeze-out on the outside of the case, as you can see in the middle and towards the right side of the photo.

So, before I put the transmission back into the car and put everything back together, can anyone offer thoughts on whether this is OK and likely to have sealed properly?

Thanks!

ezone

Oh no no no no no.
You assemble and torque this as soon as it goes together. You DO NOT WAIT.
You do not want sealant to cure/harden before torquing, and that sounds like what happened.


Here's the basic simple instructions that apply to almost everything assembled with any type of RTV sealant, pay close attention to the "NOTE" part:



HTH

doggedpursuit

The technical data sheet gives different directions depending on whether you are applying the product as a "form-in-place" gasket or using their trademarked "Powerbead" dispenser. https://www.permatex.com/wp-content/.../tds/82194.pdf
I have always done what you did: get the fasteners finger tight and let it sit for an hour or two before torqueing. My thought was that if you torque immediately it would squeeze out all the RTV and leak. I don't understand why using a dispenser would change how long you wait before torqueing the bolts. But the manufacturer would know best, so who am I to argue.

ezone

I assemble immediately because I want the RTV to adhere to both of the mating surfaces. If you let the RTV "skin over" before assembly it doesn't adhere uniformly to the second surface, and may leak.

Squeezing them together just squishes out the excess, there is still plenty enough sealant left between the surfaces to seal.

dnmacdon

Got it all off, cleaned, resealed and reassembled. I found the Permatex much harder to get off than the original stuff, maybe because it was fresh. Just in case though I sprang for a tube of Hondabond. Actually, I may have the chance to test them side by side to see which is easier to get off. But I'll put the details in a new thread.

doggedpursuit

Have you tried using a brass or nylon wheel on your drill to take off old RTV? You have to be careful if the parts are aluminum but I find that works best. They make the stuff to bond and seal, not to be easy to remove.
I learned a lot from this thread. I have been using too much RTV sealant and waiting too long to torque it down. Also, the rate of curing is dependent on humidity and not just the temperature.

rattlenbang

From what I understand you're supposed to let it set up a bit before tightening. If you torque it before you can squeeze out most of the sealant. The sealant works in two ways: one way is through adhesion to the mating surfaces, but the other way is forming a physical gasket. If it has a chance to set up a bit before tightening, you in essence have made a silicon rubber gasket between the parts, not just gluing them together.

ezone

I don't give a rats *** what the instructions on the package say.

The trans case is designed to be fit "metal to metal".....so are many other parts that require RTV sealant.

If someone mis-using RTV sealer creates unwanted clearance between case sections, that can alter important clearances inside the trans.

doggedpursuit

Allowing the RTV to set up for an hour was the way I understood it. But the manufacturers technical data sheet says different. The oil paper that most automotive gaskets are made from has a thickness - in the range of 0.4mm if I remember correctly. The parts must be machined to allow for that gap, but the way the manufacturer says to use the product would leave almost no space between the mated parts. The RTV sealant would only fill the imperfections between the mated surfaces if it was torqued immediately. It also means you would use almost no sealant in parts that were closely machined to avoid gobs of dried sealant from ending up in oil galleys.

ezone

This is how it works.