Hello all,
I'm pretty sure I've got a transmission leak somewhere. I was gone on a year long deployment and into the second month my wife had told me there was a big oil puddle forming under the car. I've taken a look underneath to see if I could tell where it is coming from and I saw this puncture in the plate next to the engine oil pan. I've tried looking in the chevy service manual, my restoration guide(which is pretty useless) and looking for diagrams online of the transmission to see if I could tell what that plate is called. Here are some pics.
Any thoughts? Could that be causing the leak?
I'm about to head over to the autozone to pick up some break cleaner to clean up down there, a new tranny oil pan gasket, engine oil and oil filter to start bringing it up starting state.

 

The first picture is the flywheel cover. Looks like either rear main seal or maybe the intake gasket leaking down for that. Take the cover off, 4 bolts, and see whats going on. I would do this ASAP as that hole was from the engine out so maybe a bolt came off.

The transmission could be many little things. Start with replacing the pan gasket and then clean the trans and watch to see where any others are.

 

Looks like the cover was somehow pushed up into the flexplate which chewed it up.

Pull the cover and make sure there is no leak from the converter or front of the transmission.

Look at the dipstick tube carefully as sometimes the o-ring seal needs to be replaced.

Check every fitting on the transmission.

I had 3 different leaks on my '73 all contributing to the mess under the car. One was a fitting for the cooling lines needed to be tightened, one was the dipstick tube o-ring which was the worst leak, and finally the pan gasket needed replacing.

DC

 

The damaged area of that lower inspection cover is NOT causing any oil leakage. It may be allowing a leak from the front transmission seal (or other possible leak sources) to dribble on the ground. But, where that damaged areas is should be a 3/16" diameter hole that is there to allow trapped oil to drain out of the inspection cover!!! The ring gear just ate through where that hole was placed!

You can spend money to fix that cover. But, what you have is not doing any harm. If you seal that opening back up, any collected oil would just accumulate until it came out the side seams or the ring gear threw it around in there.

 

Check...
I figured the cover might not be causing the leak or I would of noticed a significant amount of oil under the car at all times. I'll take a pic of the oil that leaked out on my driveway. I pushed the car back in to the garage once I cleared room for it this weekend. Now I'll be able to do some work on it.

Question though. My service manual and from what I know is good practice says to warm up the transmission fluids before draining and before diagnosing e.g. checking levels. I currently have the gas tank out since it was shot and I'm waiting for the new one. I accidentally ordered the LT1 tank which only has one fitting for a fuel line and my car supports two.

Right, the question. Would it be wise of me to just take the transmission pan down and change the filter, o ring, and pan gasket without being able to warm up the fluid?
I've checked out the passenger side for possible areas of leaking, I didn't see any oil by the cooling lines(at least what I think are the cooling lines, service manual says they are on that side)

Tomorrow I'll get back under there and check the drivers side. I think I did see something there that was leaking or looked moist with oil.

If it ends up being the front transmission seal, is that something that can be addressed with the tranny in the car or would I need to take it down?

Thx for your help so far everyone. I'm trying to do as much of this myself as possible to learn. I just don't feel comfortable taking the transmission out on my own.

 

The cooler lines are both on the right side- 5/16 tubes that come out of the trans and immediately turn to the front, running past the starter and along the block. Also up on the right side is the dipstick tube, the o-ring on that could be leaking too. One thing that is often overlooked- some cars have a TCS system- transmission controlled spark. The switch for that is on that side of the trans also. IT's a simple oil pressure switch that tells a solenoid the trans is in 3rd gear and allows vacuum to the distributor. (or shuts it off, I don't remember)

 

I agree with all above on the leaks Plus another place that will leak is the shift lever shaft. It takes a special tool Snap on has them, & you can order one on line. GM SHIFT LEVER SEAL TOOL
A cold transmission is ok to change the fluid in. In fact I'd rather it be cold than hot.
So for trans seals get Pan, dipstick tube seal, shift lever seal, vacuum modulator oring, oring for govenor cover and output yoke seal and TCS Switch oring if it has one.
Find a trans shop in your area & pick up all the seals there. Local auto chains probably wont have them.
All those seals can be changed with the trans in the car.
Here's a full seal kit though you wont use the seals for the front pump&input shaft
External seal kit

 

Warm trans fluid flows faster than cold fluid. GM service mechanics are expected to do their work FAST. I would never work on a hot tranny either. Just fill it to the "cold" line on the dipstick. When you get a chance to drive the car, recheck the trans fluid level when it gets hot, then add some if you need to.

 

Hey everyone,
So I got some time to get under the car yesterday and I cleaned up the area with some brake cleaner and took down the transmission pan. I'm leaning towards the pan on this leak as the bolts were way too easy to come off. I didn't have to use much force at all. I believe the service manual states 12 lbs of torque to tighten them, and I hope thats not how loose they sit torqued to those specs.

Since I have the pan down and cleaned up, I was thinking about touching it up. Have any of you painted your trans pan before? I'm not sure if I'm going to wire brush it and use some POR13 gray or black. Or maybe take it to someone to have it along with the tank support sand blasted.

What's your input?

Also, the kit I got from autozone contains a rubber gasket. Rubber or cork? I've seen threads stating both have solved leaks for the particular individual.

 

I prefer rubber myself with a very small amount of ultra black silicone on both sides.

For painting the pan it will not hurt (the outside only of course) and if you want to do it now is the time.

 

Torque required to remove a bolt is about 1/2 of the amount used to set it. So, it's a lot easier to remove bolts than install them (that is, if they're not rusted in tight ). So, don't overtorque them when you go back together thinking that will help. It won't. Also, make certain that the oil pan 'rail' is not deformed...especially not dimpled at the bolt positions. It needs to be flat--except for the stamped-in strengthening groove.

 

Ok everyone.
So I cleaned up the pan and painted it. I'll post some pics soon. Now...I'm trying to put the new filter on and put the pan back on. Only issue is, every time I put the filter on, the pan does not fit. It almost seems like its hitting the filter end where the pick up tube connects to filter to case. When I remove the filter, the pan fits just fine. Just once I put the filter on.

When I put the pick up tube on the filter, I'm putting it in all the way until the lip hits the gasket/seal. Same thing when I put it up in to the transmission. Is there a trick to doing this? What am I doing wrong?

 

TH400- there is a tube that runs from the pump down to the filter. Tube has O-rings on the upper end. Make sure you got the old one out of the pump, lube the new one and push the tube up into the pump. There should be a couple of "wings" on the tube to get it in the correct position so the filter will set correctly and allow the bolt and spacer to hold the filter. (some just have a shoulder bolt and no spacer)
The 2 big dimples in the pan are what the filter actually sets on when the pan is installed so it lifts the filter and gets it off the bottom of the pan.

 

I believe that you may have the same problem I have with my '82. When the car sits for several weeks in storage, the trans fluid drains from the torque convertor down into the pan, effectively overfilling it and causing fluid to overflow up the dipstick tube. Tie a rag around the dipstick tube the next time you store it and if you come back and find the rag soaked with fluid you'll know that's the problem. The only cure is to start the car and shift the trans back and forth a couple of times and let the torque converter refill and you'll start the process all over again.

 

Ok, I feel embarrassed. I tried to put the pan on again and this time when I put the filter on I put my palm right under the pick-up tube area and pushed after I had everything set in place. I heard a click and the filter had slid right into place. One side wasn't hanging down lower any more. I don't know how I didn't get it to do that the first time. I supposed I was worried about pushing too hard and having the car slip off the jack stands.

Anyhow, its on now but...while tightening the pan bolts I noticed where the shift linkage goes up towards the engine bay, that cable was completely loose. The cable was dangling near the holder that it should go into. I put it through the holder; however, I'm not sure where it connects. Anyone know what I'm talking about?

Another thing. In that same corner where the linkage bolts to the pan, those bolts are longer than the rest of the pan bolts yes?

Those two bolts are longer for me, and they don't tighten up all the way. They just keep spinning once I tighten them to a certain point. Seems like either the transmission threading is stripped or the bolts are not correct fit. Anyone else run into this issue?

 

Updating this just in case anyone else runs in to these same problems.

That cable that was loose that mounts with the transmission oil pan and runs up toward the engine was what I found out to be the "interlock cable". The retainer was gone along with the C-pin that would be holding it in place.

I just ran it through the bracket and hooked it back up and put in a washer and new C-Pin. I'll try to get a hold of one of the retainer clips.

I ordered a new set of ARP Auto TH350/400 Transmission bolts and installed them along with solving the mystery of the longer bolts.

The longer bolts do go in the area of that cable linkage mounts and there is one that is longer than the rest that goes in the rear driver side. One I put the longest one there, it tightened up all the way. For the other bolt that was the front most for the linkage(closer to the engine), I just had to push up more when I was tightening for it to catch correctly.

I now have the transmission pan installed nice and cleaned up and ready to be filled up with oil again. Now on to the install of my gas tank.

 

Those "longer" bolts go into the shift cable brackets....because they add thickness and require longer bolts. It sounds like you stripped the threads in the two holes where you [mistakenly] installed the long bolts. The only way to resolve that problem {it WILL leak wherever you aren't able to tighten a bolt} is to remove the pan again and repair the stripped threads with Heli-coils. You can get them at auto parts stores and/or Fastenall stores. You can make this repair with the transmission left in place. Just use a good electric drill and try to hold the drill as perpendicular as possible to the pan rail. Also, hold the drill tightly, as it will want to 'pull' into the soft aluminum rail, once the drill gets a good bite into it.

This will not be a 'cheap' fix, as you have to buy a full kit...including the properly sized drill to clean the original threads out, tap to put in threads for the Heli-coils, and the Heli-coil inserts...if you don't already have one. But, it's a "must do" situation.

In the future, when disassembling anything, look at each part you remove and note any differences with other (similar) parts. It may save you from problems like this. It would also be valuable to have a copy of the AIM and to review it carefully before doing any DIY task on your car.

Please don't take this negatively; it is meant to be useful advice for you and for others who may find themselves in similar a circumstance. Just take your time and plan what you will be doing...especially for the first time!!

 

7T1Vette - I'm not sure if I confused you when I was writing the previous posts up. I actually didn't put the longer bolts in any other spot. I had them all placed in a shoe box that I slotted up in the pattern/shape they go back in to the pan. I think there was one bolt out of the two that were long that was supposed to go in one specific spot. All the bolts tightened up and didn't spin freely. For my first time, I probably wasn't pushing up on the pan correctly to get that thick autozone gasket squeezed down enough to start the threading.

I did however purchase a copy of the AIM. It helped big time when putting my gas tank back in.

 

Hello all, I can't believe it's been a year since I tried addressing this issue, but I'm revisiting it. So the leak is still persistent. Just to review, I changed out the pan gasket and put a set of ARP bolts for the TH350/400 bolts due to the old ones looking so nasty. When I drive my vette daily, I get no leaks. It's only when I haven't driven it after a week or two that it will leak. When the leaking does begin, it really comes out. I'm going to check some of the previous advice given above such as dipstick o-ring, cooling lines, and so forth, but has anyone else ran into this? No leaks when daily driving but gushes out after a week or two of non-op.

I know fitzrade said he had a similar issue when storing his car. I would really like to find the source of the leak though.

 

Check the tail shaft seal (where the transmission connects to the drive shaft) it could be leaking there once the car is parked up and the oil from the torque converter drains back into the transmission bringing the "tide" level up to where the seal is. FWIW I have the same problem and that is where it is leaking,not sure if I can fix it without dropping the trans (mine is a 200R4). The oil leaking out is red yes? I don't believe you said in earlier posts.