Leaking everywhere...!

I have a sbc 350 with a th400 tranny.

So after driving my truck a few weeks I've started to develop some leaks and they are frustrating the hell out of me. The tranny seems to be leaking from the shift shaft (don't know if it's a seal or o-ring) and around the pan (changed the gasket 3 times already and can't stop the leak). I'm using a ratchet shifter and don't know if maybe the linkage isn't lining up the shifts well enough or if there is some other malfunction. Do I need to just go through and replace all the seals and o-rings?

I have recently started spewing oil from what appears to be my pressure sender (can't tell if it's the sender or maybe a rear seal but looks like it's coming from the sender). Oil is flowing down the bellhousing and dripping out of the torque converter cover. This only seems to happen when I fire it up and drive it a short while.

When at idle the oil pressure seems fine, but when I drive it it drops (don't know if this is a failed sender or sender not working properly from leaking oil). My water temp gauge has stopped working (could be something unrelated). I'm using Dolphin gauges.

The motor sounds great but I can't pin point these leaks. Is there a common factor here?

Hey Kelseydum - easiest way to locate the leaks, is to clean off the trans, put it on a rack and start it up and just watch - on the oil sending unit, if it's running down the outside of the bell housing it's likely to be the unit and not a rear seal or it maybe one of those pluged holes in the back of the block. If you have to take the tranny pan off - look very closely at all the bolt holes to see if there are any cracks or the hole itself is dimpled in and not flush with the pan surface.Best beat is to replace all your seals,gaskets and maybe even the pan.

kelseydum said:

So after driving my truck a few weeks I've started to develop some leaks and they are frustrating the hell out of me.

Click to expand...

I had the same problem and it was the drive shaft. I bought a new one & it has a hole that is supposed to be plugged but wasn't. Plugged it & then all was good!

Beercan

rustybeercan said:

I had the same problem and it was the drive shaft. I bought a new one & it has a hole that is supposed to be plugged but wasn't. Plugged it & then all was good!

Beercan

Click to expand...

Yeah ive had that happen to me.

OK first If I recall there is a shifter shaft seal on those. You can can get one at the parts store. Kind of a pain to get the old one out in most cases. Next what kind of trans pan gasket are you using rubber or cork? Rubber ones always leak. Once you tighten them up the gasket compresses at the bolt holes and they leak. Torque specs on pan bolts are very low so dont crank them down and get a cork gasket.

As said before clean off the oil and watch the sender to see if thats the leak. if it is replace it. I use a dye that glows under a black light to find oil leaks. great if it is a hard leak to find.

as far as the oil pressure every sbc I ever had would show low oil pressure once it warmed up at idle. my truck went to 0 on the gauge once warm. But i think the spec is like 5psi warm at idle. it dont need much.

rockabillyrat said:

I use a dye that glows under a black light to find oil leaks. great if it is a hard leak to find.

Click to expand...

That's how I found the leak in my Nova. It was the oil sender tube. Had a small crack in it!

BoB

check the dip-stick tube, the o-ring will leak and make you think the pan is leaking, the shifter shaft will also make you think the the pan is leaking there is a seal, and it is a real bear to change, DO NOT use a seal snook hook to pull that little seal out, I have seen the snook hook tools scratch the shaft and the seal will not seal up, I use a pocket screwdriver, and drive it into the steel around the seal and work it out of the hole, it has a step inside the tranny and the seal will not push all the way through, use a socket big enough to go over the shaft and small enough to fit the seal and drive the new seal in.
oil pressure switches are fairly cheap, if in dought replace it.

I had a brand new ford crate engine 302, that would leak all the time,this went in for a month,any thing over 2500rpm,so i finally called ford racing,told them they knew right away.there was a extra dip stick hole on the drivers side that wasnt plugged i was very happy it was such an easy fix.

Found the leaks!

I found that the tail shaft seal and the shift shaft seal are both leaking pretty bad and seem to be the main leaks here on the tranny. Any advice on replacing them? I have no manual and am going to just jump into it. It doesn't seem too difficult.

Can the rear pump seal be changed without pulling the transmission? I thought I might do this too just in case.

Do I need any special tools?

rockabillyrat said:

Rubber ones always leak. Once you tighten them up the gasket compresses at the bolt holes and they leak. Torque specs on pan bolts are very low so dont crank them down and get a cork gasket.

Click to expand...

This is a myth. the rubber seals work fine as long as you don't over tighten the bolts which most people do. Also make sure your pan rail is still flat. if the bolts were over torqued then the holes will all be bumped up and it will leak no matter what seal you put in it. Second, make sure you are using the correct fluid. Dexron 3 can be used with a cork gasket but if you put dexron 6 in the tranny it will leak like a sive with a cork seal. The molecule size of dexron 6 is 3 times smaller than dexron 3. it will lubricate better but in older trannies it usually leads to leaks. GM went to a rubber seal in the mid 90's and they are reusable as long as the bolt torque is correct.

I replaced the shift shaft seal, the tail shaft seal and replaced the vacuum modulator. I started her up and let her warm up as I was putting the ATF back in. I put almost 6 quarts in. I ran through all the gears to get some fluid moving and once she was warmed up I put her in reverse. She moved back... put in neutral, was able to push her forward, put it in D and didn't feel it kick in gear. I gave it a little gas and nothing. I put it back in park and it shifted back into park but it doesn't seem to want to shift into first gear at all! I had to remove the shifter linkage and the shift shaft to swap out the seal... is it possible I didn't get something hooked back up properly? Is the shift linkage not finding the gear right?... Any ideas?

No leaks as of yet... but?

I want to have my wife sit in the truck and smash on the brakes so I can unhook the linkage and try to shift through the gears with my hand and see if the shifter linkage is not hitting gear or something. Other than that... maybe just don't have enough ATF???...................WTF?

umm... when you put the shaft back in you forgot (or missed) putting the little rod on the shaft itself into the center of the slot on the manual shift valve. You will know when you drop the pan and look at the end of the shift shaft as to what I am talking about. Only once you have made this mistake do you recognize when it happens to someone else. been there, done that! [S

Yeah, that linkage fell out when I unhooked the shift shaft but I was almost positive I put it back in correctly. I'll try to post more pics of what I did in a minute. I could have just taken this to a tranny shop, but I WANT to learn about this stuff... even if it costs me a little extra right now... the knowledge is almost priceless.

That shaft your talking about goes into the top of the gear plate with the teeth and the other end rests in between the manual shift valve... correct? This is how I hooked it back up. Maybe it slipped out when I was putting the pan back on or something? I'm going to re-check the fluid level first then go from there.

Thanks for hanging in there with me and helping me figure this out.

in the end of the manual valve that sticks out of the valve body there is a groove that goes all the way around and is like 3/8" deep. the "pin" on the back of the shift shaft (also has the detent plate on it) goes into the groove. if it is behind it it wont shift right at all. It will seem to have gears at first then it all goes haywire. I did the same thing on the th400 in my truck when I rebuilt it

Are you talking about this end...


or this end?

kelseydum said:

Are you talking about this end...

Click to expand...

I was talking about the first pic and you have it together correctly. The second pic is just the park pall. So back to square one as my idea didn't pan out.

Well, some other people I've been chatting with have said these transmissions can hold up to 9-12 quarts so I'm going to add fluid 1 quart at a time and see if this is the problem.

I'll let you guys know.

If I have them apart and the converter drained I usually start with 10 qts then add from there

Wow, I feel stupid... but relieved. I ended up putting 9 quarts in it and drove it to the grocery store and back. It seems to be okay now. That scared me for a minute. I had no idea these could hold so much fluid if the converter drains out too.

Thanks for all the help!

Cool! Glad you got it up and running. And didn't have to resort to a tranny shop either![cl