TH400 gasket seal.

[cwilkie]

Hi guys. What is the proper way to seal a TH400 pan gasket? I have tried various things this past year and it still leaks. I torqued it to specs, tried different types of gaskets, a new pan, and nothing seems to work.

I heard from a friend I need to take the pan off. Wait for the fluid to drain. Put a new cork gasket on. Torque it to specs then wait a day for it to seal then add the fluid. I am confused.

[hugger6933]

I hate to sound like a smart tail but are you sure it is the pan? There are a lot of things that can leak so close to the pan it would seem that the pan is leaking when it really is not. Dipstick tube comes to mind, as does the shifter shaft seal. I had one in a nova once I thought the pan was leaking and it turned out to be the grommet for the dipstick tube was cut. I am sorry I don't have much more to offer on the pan idea except maybe try a neoprene gasket instead. If the oil level is below the pan top why would it leak sitting still? Jim

[cwilkie]

It's the pan. I prefer to have my fluid filled according to the dipstick. It seams like gaskets and I do not get along.

[jmorri34]

Originally Posted by cwilkie

It's the pan. I prefer to have my fluid filled according to the dipstick. It seams like gaskets and I do not get along.

Man I literally just got done with this same problem yesterday. I had 9 kindsa h$% trying to get mine to seal. I went through 3 gaskets and replaced the speedometer gear and replaced the tailshaft seal to make sure it wasnt running to the pan and making it look like it was. I think I might have gotten it but I gotta say I'm convinced the cure is luck lol. Im the same, other than try different gastets again and maybe cinch the bolts down a little more and gently is the only way to do it. Im sorry I also dont have more to offer but I know exactly how you feel. Im still not sure mine is sealed. its frusterating!!

[71 super]

Try putting a little wheel bearing grease on the gasket to housing surface, sometimes this helps to "fill" surface issues.

[GASoline71]

Make sure the pan rails are flat. The rails of the pan can get warped from overtightening over the years. Also... the pan gets torqued to somewhere around 140 INCH pounds (around 12 ft pounds)

Gary

[alsriv2]

I have always used the "Permatex" brush on Aviation sealant on both edges of the gasket before installing.
You can find it in better automotive supply stores. My local NAPA keeps it on their shelf.
Sealant always stays pliable, remains impervious to engine/transmission fluids and I have never had a problem with fluid leaks on my engines.

[Roger71SWB]

IMO cork gaskets will never seal. and every transmission shop i have ever talked to said the same thing. Dont use cork. Just my 2 cents

[71Dually]

I always use quality gaskets and a good sealer. I've found cheaping out on gaskets and sealer is just asking for leaks.

I use this stuff for sealer:



Heres a Jegs link: http://www.jegs.com/i/Permatex/775/85420/10002/-1

I've found it at AZ and with the part number it should be available wherever Permatex products are sold. I have found some places don't carry it. I think this may be that it is expensive so it sits on the shelf longer than the cheaper stuff. It's also been my experience that stores usually only stock what sells faster.

It's equivalent to hylomar (which works excellent). Like the "Aviation" sealant alsriv2 mentions in their post it's non hardening, stays pliable, fills voids. It may even be the same stuff as I believe hylomar is also widely used in the aviation industry. Old gaskets (even thin paper and cork) are easy to clean off when their sealed with this stuff, they peel right off, usually in one piece. No more scraping with a razor blade or gasket scraper, saves on expensive "gasket remover" spray too. Sealant residue wipes right off with acetone, brake cleaner, carb cleaner etc... again no more scraping. It's not silicone based either so it's safe for sensitive emission sensors also.

I'm unable to recall ever having even a small leak since I started using this type sealer about 20 years ago. I have even disassembled components and reused some old gaskets when I've used this. Great for checking valve clearances. It's impervious to lubricants, coolant etc... I apply a thin film on both sides of the entire gasket sealing surface. Seals instantly, no need to wait to fill with fluids.

I don't own stock or interest in the company either, I just like the product as it's made my life a lot easier.

As previously mentioned in GASoline71's reply, I also make sure the pan rail sealing surfaces are straight. I remove all previous over-tighting warpage and damage with a hammer and dolly and then only tighten to the correct torque with a proper torque wrench. I've found if gaskets are not torqued properly but rather by "feel" then gasket failure is very likely.

I also check for cracks or pinholes. Some of them little leakers from actual pan damage can be pretty small and easy to miss. I'll usually clean the inside surface with a fast drying solvent like brake cleaner or acetone. Then apply a penetrating oil (WD40, PB Blaster etc...) to the opposite side and then examine the "cleaned" side carefully for penetrant seepage. I use the non-aerosol WD40 applied with a brush for this and if needed a little added blue or red Dykem to the penetrant makes it easier to see seepage. Any Dykem residue cleans right off with solvent.

I will usually apply torque in 2 or 3 steps as I've found it helps prevent creasing, bunching or other deformation issues with gaskets. For example if an assembly requires 21 ft. lbs. I will torque to 7 ft. lbs., then 15, then the final 21 ft. lbs. value.

IMHO cork gaskets are OK but they relax after being tightened down. Cork gaskets need to be torqued several times before they will stop relaxing and seal properly. I always torque them down, wait a few minutes, torque them down again, wait again and keep repeating this until the gasket finely stops relaxing and the fasteners remain properly torqued.

With cork I also do the 3 step process but I only do the first 2 steps once and the final value is what I use to do the torque & wait procedure. It's a lot slower to do gaskets in this manner but after learning to do them this way I've had much greater success sealing gaskets the first and every time. I always keep in mind that assembling gaskets this "long" way does take a lot less time (and money) than repeatedly replacing gaskets that fail to seal. I've also found replacing engine oil pan gaskets in some vehicles requires a lot of work and I prefer to fix them in one shot over multiple attempts.

Also when possible, I'll check gasket fastener torques after several temperature cycles. After letting the component reach about 5 - 10 full operating temperature and complete cool down cycles I'll usually recheck for proper torque. This helps prevent fastener loosening from expansion and contraction which will ultimately result in leaks. (This reminds me I need to go check my valve cover gaskets after changing them last week)

Regarding cork gaskets I said they are OK, I have had great success with them. However sealing technology has come a long way since cork was developed and I usually purchase the rubber gaskets when available. I've had better success with them and they can usually be resealed multiple times where as the cork stuff is usually only good for one go around.

Good luck cwilkie with your trans pan leak. I sincerely hope my experiences on this subject can help with your concerns.

Best regards.

[cwilkie]

Now that is a little nicer out i decided to try and tackle this leaking transmission. Upon closer inspection i noticed the fluid looks like it was coming out on the speed gear housing. I took the housong out of the transmission and put in a new o-ring as well as a speed gear seal. That seamed to stop it but over night the area around the seal was good except i could see some fluid coming from the cable itself.

Is there supposed to be a gasket or seal on the speedo cable becore it is screwed into the transmission? I will have a picture or two of this tomorrow.