Transmission Leaks in reverse only! Front seal?
 

An easy one (I hope) for all you tranny experts: My 82 300TD has been leaking a significant amount of fluid when the engine is cold and I put it into reverse as i can always see a trail of fluid following me into a parking spot. based on the amount of fluid that comes out in reverse and how often I need to add transmission fluid (about 1 quart per 1,000 miles) i am probably also leaking a small bit when I am moving forward and know it leaks a bit at idle but not nearly as much as when i'm in reverse. The leak is coming from the front of the transmission where it attaches to the engine, ahead of but not from the torque converter.

Am I correct to assume it is the front main seal leaking? Are there any other seals I should replace when I drop the tranny or any other diagnostic tests I should run on it prior to dropping it? I have the filter kit and gasket.

I have to replace my starter so I have decided to go for the transmission at the same time with the help of a friend who has all the tools and has done this job many times. i'm feeling a bit apprehensive about such a big job but it has to be done. Any and all advice and support appreciated.

peace,
woody

It's possible that the front seal is shot, but I'm not sure about it leaking more in reverse. I'm willing to bet the leak is the same going forward or backwards, but you probably notice it more when you back up and the fluid sloshes out toward the front of the bell housing. Either way this is going to be a big job because you will have to remove the transmission to fix this. Once you get it apart however, replacing the seal is fairly easy!:D

I assure you it leaks a significant amount in reverse and very little in drive. I have been taking note of this for quite some time. If it leaked the way it does in reverse while moving forward I would have to be adding fluid after every couple hours of driving.

Now after rereading your post I hear you saying that when i am moving in a forward direction the fliud is pushed back toward the rear of the transmission an when going in reverse it moves to the front. this would make sense and would seem to explain what is going on. Any other opinions and theories welcome

what causes a front seal to go out? I know rubber will usualy stay good forever unless sun hits it. What im saying is why does his seal leak, while so many of the same mileage dont.

Might possibly be the o-ring around the reverse band servo (probably the front one ) is bad or not seated. IF that is really the case ( and not just a faulty "reverse only" diagnosis) you might not have to pull the tranny to get to it. Take a look at a manual to see where reverse band is located on the 722.3xx and see if that could be the leak area.

and

This really is not the case here. Apart from what tiny bit is left in the pan, the fluid is being carefully directed at the servos and clutches to make your car do what you tell it to do. There isn't anything "sloshing" near the bell housing.

Best course of action is to pressure wash your tranny, then get the car up on a lift and run it through the gears to see where the leak is coming from.

Rick

except for
 

Heat, oil and ground level ozone. Not being a smarty pants, but, unless we can find Viton or silicone seals leaks will happen.

Agreed. Fluids will slosh a bit as the vehicle moves, but it is minimal and they arent "forced" anywhere unless pumped. The front pump always runs when the engine turns, and is always maintained at a steady pressure no matter what the trans is doing, so what gear you're in will have no effect. Usually when that seal goes, you know it in a hurry, it will just spew like the dickens and you'll find yourself out of fluid in very short order. I'm banking on what Rick said, you have a servo cover leaking somewhere, one that is applied in reverse, maybe also in a forward gear but at a point where you don't see the trail due to being spread out from speed. I've also seen some posts on here about servo covers fracturing. Your leak could be running down the side of the trans to the place where you see it drooling off. Clean it off and watch for it before you pull the trans needlessly.

What manual would you recommend and where would I find it?


The leak is coming from the small gap between the front of the transmission and rear of the engine where they connect with one another.

Thanks for the input

If you are sure that's where it is coming from, you will have to pull it to fix it. I have no idea why reverse would affect the leak any more than a forward gear. As MM said, you are talking about the front pump that is always going the same direction under the same load. Good luck with that....

Correct. Fluid under pressure will not be sloshing around, but I was referring to a little that could be puddling in the bell housing as the front seal dribbles it out. The front seal should be under the same amount of pressure regardless of which way the vehicle is moving because the engine only rotates one way!;)

I'm not sure why it would be coming out more in reverse from in there with the system under pressure.:confused:

The only viariable I can think of is the bellhousing to engine bolts loose. Torque while reversing changes the direction of torque to the transmission case. This may change the alignment of the input shaft just enough to make a leaking front seal leak even more. Remember he said it pours out when in reverse. Also could account for the seals overall failure.
If you find the bellhousing bolts loose keep this in mind. A very long shot but something has to explain this oddity. If those bolts were really loose I might just tighten them up and test before pulling the transmission. If you do find anything unusual in the repair process let us know.

I am sorry to have to ask this question but what is a servo, what function do they perform, how many are there in the transmission and how do i check them to make sure they are all sealed correctly, not cracked etc....? In the meantime i will happily check the bellhosing to engine bolts to see if they are tight and hope they are not. if only i could be so lucky; please!!!

I am used to electrically controlled servos being used in other fashions. You could say the starter solenoid is a servo for example. Basically it is a device that a control signal makes perform a secondary function. In this case the controlled hydralic pressure activates the device and makes it tighten a band around a drum. Like an external brake lining on that band locks the drum up when it is tightened.
Just make absolutley certain you have the area where the fluid is coming out before pulling that transmission. Even if you have to put the back end of the car up on jackstands and run the car in reverse. I do not know for certain how many servos there are in this transmision. Two-three strikes me as about right. You at least are only concerned with leakage from them externally anyways. A shot gasket, O ring or cracked cover type of thing as a previous poster mentioned.
Search the archives on how to change front transmission seals and other related things. Others will post better information as well.
I am far from knowledgeable about automatic transmissions. What you are hunting for is within your abilities to find and repair. You are not going into the transmission. At this point you can easily understand why some people thought it was the reverse band solenoid. Hydralic oil under pressure is only directed to it when reverse is selected.

Tomorrow i am going to put the car up on Jack Stands, clean off under the bell housing, and run it in drive and reverse to make completely sure as to what is going on under there. from there i will make a decision to either pull the transmission and reseal or try and locate and inspect the reverse band solenoid before pulling the entire transmission out of the car. If anyone reading this has any idea how i can get to the reverse band in order to check it out I would greatly appreciate hearing about it as I have no clue where it is and have no manual that tells me such. As always thanks for the assistance.

If the transmission is leaking around an opening in the transmission with a small cover you will see it. Then describe it's location well and others can suggest what to do.
Repair should be managable without pulling the transmission then. If it is still originating between the belhousing and engine that is another story. Out with the transmission.
Also have a look to make sure the transmission dipstick tube appears inserted and dry around it. Thought about this yesterday but again do not know any mechanisim that would make it leak more in reverse than in forward gears. Sometimes things happen occassionaly that are hard to rationalise.

There are no servos in between the engine and trans, they will look like round covers on cylindrical protrusions on the side of the case. Think of them inside looking like a piston with a connecting rod in a bore, only the piston is flat so it only holds one O-ring or lip seal, and the connecting rod would be solidly attached, with a pointed end that would fit into a hole or groove in a band to push on the band when pressure is applied on top of the piston. There will either be counter pressure underneath the servo piston to release it or it would be springloaded underneath. I don't have a trans book so I couldn't say which one it would be for reverse. If it truly is coming from inside the converter area, you may have a fractured case (can happen from casting flaws or loose bolts) or you may have a pressure port plug that's come loose. There are small plugs in the end of some ports to cap off where the passage was drilled, and also serves as a test point to put diagnostic gauges on.

turbobenz, the reason a seal goes out is that the manufacturers use a spring-backed neoprene seal to prevent all oil leaks, because customers hate oil leaks and will make warranty claims to correct them. The problem with the neoprene seal is that, although it seals really well when new, after a zillion heat cycles it gets hard. When it does that, it will sometimes break, and the broken end will dig into the shaft, but more often it won't break but will just cut a groove in the tail of the crankshaft, or the transmission's input shaft, as the spring drives the hard seal into the metal. When you replace a seal like that, you can press a thin metal repair sleeve over the shaft, although it is a little tricky to do and sometimes the shaft has to be turned down first. What I prefer to do, however, is to simply not quite bottom the seal out in its carrier when I press it in. The groove in the crankshaft or input shaft is only about 1/8" wide, so if you leave about that much space between the seal and its carrier when you press the seal in, the seal will be contacting the shaft slightly farther out, where the metal is still there. Some people are afraid to do this because they fear that the seal will fall out of its carrier if not bottomed out. This is not true because the only forces acting on the seal during engine operation are radial in nature.

The manufacturers could use a different seal material that would last virtually forever, at the expense of minimal leaks, but their customers would hate the leaks too much.

Now, turbobenz, I suggest that you go float up some hills (inside joke).

Speed sleeves for adding a new surface area to worn seal riding surfaces might be had at large truck repair places or simular. Basically a very thin tube in stainless with an interior diameter the same or marginally larger. The new seal surface is slightly larger in od but usually works out okay. Saves a lot of time,effort and money ocasionally

Guys, we're talking about a trans pump seal here, not a crank or balancer seal. There is no shaft per se, it's just the snout of the torque converter which holds the seal, (which the input shaft actually fits inside of), which may as well just be replaced at that point rather than go thru the hassle and time of sleeving it. A reman converter can easily be had for about the same cost & guarantees you only do the job once rather than a few thousand miles later when the old converter decides to quit. I've never seen or heard of anyone wasting the effort to do that on a converter. Usually the pump seal fails either because it got hard, or because the pump bushing has become compromised and allowed the converter snout to develop a vibration or off to the side/off kilter position from excess slop. The "wearing a groove in the shaft theory" doesn't so much apply in this case, because we have to remember, the torque converter is mounted to a "flex plate". Why? Because it physically expands and contracts with speed and load/pressure, so it is constantly working back and forth in that seal, essentially preventing that ridgeline groove from happening. If one were to be able to mount a camera in there to watch it, the expansion change can actually be seen, so it's much more than the few thousandths of movement you get from an engine thrust bearing.

I get it

The front pump bushing is a pretty common wear item. When it's beat, the unit will leak out the front seal. - and i believe especially in reverse, since the reverse piston is mounted in tghe front pump housing. The good news is, the seal and bushing are easily replaced and cost less than $20 each. The bad news.......do you need to ask? However, this transmission is easier to remove than most.

Pete-

That doesn't sound like my idea of "good news".

What happened to the OP? Did he run off and sell the car in frustration?

Rick

Never, I'm committed for better or worse.

What did happen was i got it up on a semi-lift which I was at least able to sit under and, with one back tire off the ramp, watched as it significantly leaked in reverse. I wasn't completely convinced it didn't leak in drive but I am sure it leaked significantly more in reverse. I noticed for the first time the leak coming from behind the torque converter and thru the grated part in front of the transmission and not where i had observed it coming from while idling in the past.

Based on these observation I proceeded, under the partial guidance of someone who has done the job several times, to drop the transmission. doing the filter and seal before dropping it. when i got the torque converter out I saw the front seal was still in what looked like decent condition but r & r'ed it anyway. After taking out the front pump I replaced the O-ring, which was very hard, and the gasket. it took me the better part of two hours to get that gasket completely off the transmission. I was thinking perhaps it had been put in backwards being so stuck onto the transmission and then noticing where the side with adhesive lined up with the pump on the replacment. There was also a bunch of fluid in some of the hollow areas which were covered by the gasket. I wasn't sure if this might also indicate it had been put on backwards.

Transmission back in, filled with fluid, steady stream coming out. mildly freaked until i saw it was coming out of where the dipstick seats. the dipstick had bent forward a bit coming out and was not completely seated in a level position. out with the dipstick. a hammer and some silicon and back in, wait an hour, pray, fill again, Ok-no leaks. pray again (along with the counter lady at Popeyes Fried Chicken in Kentwood, LA-whole nother story). fire it up. looks ok, put it in reverse, no gushing, seemingly nothing. get under car, small leak coming from drivers side trans cooler banjo bolt, don't panic. tighten bolt, leak slows down but doesn't completely stop. I drive 100 miles home without incident. the major leaks have ceased, prayers have been mostly answered but it is still leaking ever so slightly from the same banjo bolt.
**advice on which way to go with this appreciated. the three options I see are: 1) don't worry about it as the leak is very slight 2)loosen line partially and let it drain, clean it with carberator cleaner, apply some silicon, retighten and let dry 3) order new set of washers, r&r existing washers knowing from experience that this bolt can be a pain in the a$$ to get back in.

An observation/question. My friend who helped me with the job and provided the space and tools to do it insisted I remove every fourth spring from the back of the pump when resealing it ( 4 in total) saying he was taught this by a transmission specialist from the dealership he used to work at. He told me why he was doing it but i forgot what he said- something about less resistence allowing the pump to work better.Has anyone heard of this or done this before?

Some screw ups. One of the cross memeber bolts gets stuck and needs to be grinded out. I find a new bolt clip and reattach-no problem. detaching/attaching the transmission dipstick got the better of me on both ends. bent on the way out taking it off too late and breaking the line just above the banjo bolt that runs out the back of the turbo by putting it back in too soon (i'd say it should be one of the first things to come off and the last to be reattached). I have a spare line thankfully and ran the car home by connecting the line to the bolt with some vacum hose. This seemed to work out OK in a pinch.

My major screw up, which i think I fixed, was messing with something I shouldn't have been bothering with in the first place. I had a spare modulator pin and wanted to get the modulator off to check on the pin (only because this had given me problems on my other wagon). Allen bolts look rusted on. On the first one I try a little too hard to remove and don't pay heed to that soft slow way it starts to move instead of that breaking feeling and before I know it I am looking with horror at a broken Allen Bolt with the head in my hand and the body still in the Modulator. I quit there messing with the modulator, drill the bolt out to a point where I can run a tap in there a decent way and get another allen bolt with an extra washer and lock washer added to sung it up. Any one else experienced this dilema/screwup before? My question here is what happens if you drill down further than the bolt extends? do you end up in the body of the transmission? I didn't want to find out the hard way.

All in all another major learing experience. I no longer hold the same fear and resistence i once did with transmissions. I also have to publicly say that i was completely inspired by nickydubs, a member from Chicago who had broken down earlier in the week, who i assisted with an extra set of hands and a hydraulic jack only as he pulled out his tranny, replaced the pump, and put it back in without having ever done the job before in less than 24 hours, on the side of the street in uptown New Orleans. and he made it back home without incident. mighty impressive.

good luck to all in your endevors

Good going - glad to hear you jumped in and did it. If it only lasts a while, you're still ahead because next time will be easier - and you'll be able to replace that pump bushing, loosen that broken screw, etc. It is a bummer when you initially do the R&R and you have the same problem, no? BTDT and recently! You are now one of the few, the proud, the soaked in ATF!