Hi everyone. I changed the fluid and filter in my tranny. No leak at first, then 1000 miles later it started leaking from unfindable spot. The fluid would accumulate and drip from the pan. It leaked whenever the car was running… not just when driving.
I put in blacklight glow fluid and drove it on the highway. The blacklight revealed fluid splashed up onto the undercarriage tranny tunnel and rearward… also accumulated around the pan again. I found NO leaks at cooler lines.
I then put it in the shop and they cleaned the area and ran it for two hours but found no leaks. I then drove it 50 miles with no more leak and the shifting seems good.
I changes fluid as directed and didn’t overfill it in my opinion
My questions are as follows.
1. Is there somewhere fluid may leak from safely or by design if I overfilled the fluid, then stop when gets to correct level?… or is this (as I believe) indicating a definite breach in my system that needs to be addressed?
2. Since shifting behavior is good and leaking has stopped, is it safe to drive or am I likely risking tranny damage by driving?
I know I can refill the fluid to see if leaking returns but thought I’d look for advice before attempting. Thanks for your input! You guys have help me tremendously in the past & I am very grateful for knowledgeable guidance!

 

As long as there is still the correct amount of fluid in the transmission just count your lucky stars and move on to more pressing problems.

Z

 

It wasn't overfilled in your opinion? Do you have anything more substantial than that? From what you described, it sounds like it was "leaking" from the vent, which is in the top of the trans housing and could, conceivably, spit fluid onto the underside of the car, and would certainly cause drips to accumulate along the pan flange.

The level needs to be such that it trickles out of the fill hole when the fluid is between 30c and 40c. Any more and the trans is overfilled. If it's done when the trans is cold, it's overfilled.

As it's no longer dripping it may not matter, but I think I'd bring the trans up to the prescribed temp and double-check the fluid level. Just in case.

 

Another reason an oil leak can stop is when there is no more oil. Easy enough to check the level on a 4.0 XKR, not so easy on the cars with ZF gearboxes for reasons known only to the manufacturer - presumably there is no need to change the ATF or check the level on a sealed for life unit.

 

If it had lost 50% or more of its oil you get a nasty grunching noise from the pump......check or drive on

 

I'm not sure if this is relevant to your year of car but when I recently changed my transmission oil, I started to get a very small amount of oil appearing around various parts of the pan. The new gasket was rubberised material and I discovered that the initial torque settings on each screw had reduced. I re-torqued the fasteners and now it's completely dry. Maybe worth checking the fasteners again?

 

Check closely around the electrical connector. Did you change the connector for a new one when you serviced the box?

Richard

 

Thanks Zray. That’s what I’d like to do, but I fear damaging the tranny due to inaction. I’ll see what the consensus is before I take any chances. I appreciate your input!

 

Thanks Y2KJag. A double-check is good advice and likely what I’ll do.
I filled the fluid within the correct recommended temp zone until it trickled. I said “In my opinion” because I wonder if I didn’t let it trickle long enough before replacing drain plug. It waited for a tiny stream I define as a trickle, but it wasn’t quite a Drip yet.
I wasn’t aware of the ‘vent’, but hoped for such a possibility as alternative to problematic leak. So thanks a lot for that info! I’m glad you responded.

 

Dibbit I’d be more worried about the fluid level if shifting wasn’t perfect, but so far it acts completely normal. Mine is a 4.2 XK8. Checking level is a pain, but doable. I’ve seen a lot of opinions that sealed for life is a fable for a healthy life expectancy.. but opinions do vary! I chose to change as a preventative and was strongly advised against ‘flushing’ as it can lead to looseness in the internal gears/bearings. So a straight fluid change and new filter. Thanks for the comments!

 

Hi RichardS. I did NOT replace any electrical connectors. Is that something I should have done? I don’t remember any such recommendation before I changed fluid. Thanks and please let me know if you have more info on the ‘connector’ replacement.

 

I was just kidding about the "opinion" thing. You followed the procedure exactly, so no worries about overfill.

 

The ZF 5HP and 6HP gearboxes are both prone to leaking around the sleeve where the electrics plug into the rear end of the gearbox. It's usually referred to as the mechatronics sleeve. Sometimes a new sleeve is supplied with the gearbox oil and filter kit, especially with the 6 speed boxes. ZF have changed the design a couple of times to try and ensure a longer life so newer sleeves are usually sold as "latest design".

I believe that the sleeve/connector are actually above the level of the fluid in the gearbox but fluid seeps past when the car is moving and then runs down over the back of the box. If the gearbox were overfilled, the fluid would presumably leak out and drip under the car even when stationary until the level has dropped.

If you can see that the gearbox is wet with fluid around and below the connector, then you know that it is leaking. You can unplug the connector with the pan in place but you cannot change the sleeve (the cylinder which the plug twists into) without draining the fluid and removing the pan. It's an easy job once the pan is off.

Richard

 

"Lifetime" is really the length of the warranty. After that expires, the car manufacturer couldn't care less. ZF's literature pegs the service interval at around 60K miles, depending on the trans. Fluid/filter change is correct, however the 6 speed has its own set of issues. The main one is the mechatronic sleeves. They connect the mechatronics (valve body to us oldsters) to the trans housing. They're "rubber" and harden with age and begin to leak. Symptoms are usually weird shifting issues. So, it's a good idea to change them during fluid/filter changes, although it's a bit of a PITA because the mechatronics has to come out in order to replace the sleeves.

 

Just a point of clarification. The "sleeves" kit includes both the portion of the electrical connector that you're referring to, and five "rubbery" pieces that fit between the mechatronics and the trans housing. They should all be replaced at the same time. The mechatronics needs to be removed in order to replace those 5 pieces, hence the need to remove the electrical connection from the trans housing. As that electrical connector piece is sealed by a couple of o-rings, it's good practice to replace it, along with the other pieces.

 

I agree with your description, although I have always done it the other way around and replaced just the leaking connector sleeve, which does not require the mechatronics system to be removed and can be replaced easily once the pan is off. I've never had any problem leaving the five internal sleeves in place as they have always been fine as the gearbox is working properly.

Certainly, here in the UK, you often find that the connector sleeve is included in the refurb kit but I've never seen the full set of sleeves included so that perhaps suggests where the priority is thought to be?

Richard

 

I can't speak for the UK, but here when you order the kit from ZF you get all the pieces. The hardening of those sleeves is a known problem, although it does not seem to happen at consistent mileage or age. Of course, most of my experience is with BMWs in California, which do get driven substantially more than a Jag with the equivalent transmission might, so that is probably a factor as well.

With the cost of trans fluid around $15/liter here, I like to err on the side of caution and spend the extra $30 on the kit and ensure I won't be back into the trans any time soon. If one has already removed the pan, filter, and electrical connector, sleeve replacement doesn't add significantly more time to the job.

 

The leaking sleeve came first. Then as the years went by the bridge seals became another problem. Both require the pan to be removed so it's just common sense to combine the two repairs.

I agree with Richard as I have never seen a 6 speed ZF that did NOT have the sealing sleeve at least weeping. Some will leak much more. The plug is up above the pan on the rear of the transmission and is not easy to see or get at.

Circled in red. The white plastic part with the arrow is how you release the sleeve. Pull down - Remove and replace sleeve - push lock back up into transmission to lock the sleeve in place. Now I have had to fiddle a bit with this as getting the sleeve in has to be right and it has a groove and notch that must be lined up or it won't go in. Of course all this is hard to see if you have not worked on that before.




It's real easy with the transmission out and sitting on the bench as in this picture!

If left unrepaired the fluid can and will start to travel up the wires inside the insulation. This will lead to transmission and/or TCM errors. It just depends on how long it's been leaking and how bad.
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Looks like you received most of the key information already. The one thing not mentioned is that there are instances where the some form of overflow occurs, and manifest with a leak from the dust plug at the bottom of the bell housing. That plastic plug does not seal very well and allows fluid to escape. Might be worth checking.

Best of luck, keep us posted.

 

Not tightened oil pan probably