I got my Bronco back from the exhaust shop and I've confirmed the transmission is leaking from what appears to be the front seal. It's not the clutch slave cylinder, it's definitely transmission fluid. After I drive it it's dripping pretty good.

It shifts nice, it buzzed a little on a quick shift from 1st to 2nd and later on another quick shift from 2nd to 3rd. It is loud in neutral, but I think that's normal. I filled it with new fluid back after I installed it for the "last time", before I moved. It was not leaking until I started driving it.

The transmission was a Craigslist find of unknown condition, so this isn't the worse case scenario.

Yes, I have a back up ZF5 I found cheap before I moved from Gunnison. It too is of unknown condition and has sat for years. It was actually full of more water than oil after sitting out through several winters. I drained everything, and poured some trans fluid in and sloshed it around before I moved. Recently, I opened up the PTO cover and shifter opening and everything still looks good, with little or no rust.

Hopefully someone with more ZF knowledge than me can help.

Option 1:
Let it leak and hope it finds a happy point where it's not leaking but still "full". Is this even a possibility or is it going to leak till it's empty/nearly empty?

Option 2:
Pull it and replace the front seal. How hard is it to swap the seal?

Option 3:
Pull it and swap in my back up and hope for the best.

Pulling the Atlas, shifters, and transmission doesn't sound like fun right now, and I'd rather spend the time testing the truck before the Rubicon trip.

I had a similar issue after my swap to a ZF-5 and trip to Moab, seemed like it leaked more when it warmed up. My leak was on the tail housing, it turns out the place I bought if from tried to weld a crack up. You could see where it had been welded and ground down. I ended up pulling it and got it warrantied. I finished that trip to Moab with the leak and pulled the ZF-5 and Atlas when I got back. With the time crunch to the Rubicon I would probably evaluate how bad the leak is and decide. To me the other issue is that there really is no easy way to fill the ZF-5, not sure I would want to be trying to fill it on the trail.

I vote fix the seal.

Not sure about your exact setup, but I can pull the Atlas and ZF-5 in around an hour if I lay the tools out beforehand and work fast.

From there, you just tip the trans on its tail and separate the case to get out the front seal. The case comes apart real easy.

I don't have any experience replacing that seal but if its easy to replace I would just go that route, better safe than sorry. Time wise Digger is right on, pulled my ZF-5 and Atlas in about the same time. Worst parts for me was bleeding it after and having to cut my exhaust and weld it back.

I'm leaning that way. I just have to remember what all is involved. The new exhaust was built in sections so the collectors to muffler can be pulled out without cutting it out.

I assume there is a seal (paper?) where the case splits. I don't see that seal on Rock Auto, except maybe with the seal and bearing kit.

If everything comes out, and it's not too much trouble, I may try the back up transmission first. Or if something goes haywire replacing the seal.

I was thinking it was the slave cylinder, or rear main, or rear of the intake. This wasn't on my radar. Sort of wish that was the slave cylinder at this point. All the same work, I just wouldn't have to crack open the transmission.

Of course, literally, as I'm considering all the options, the fridge starts leaking - pin hole in the water feed line, so I can add that to the pre-Rubicon prep list. And the exterior light that got bumped and the junction box cracked, leaving it hanging off the wall. Of course HD and Lowes are back ordered on 3.5" round j-boxes that fit. COVID back orders strike again. Had to go to Ebay and wait for shipping for a stupid j-box. LOL. Not to mention the emergency vet visit Saturday evening that prevented me from picking up the Bronco until Monday. Crazy.

Digger probably has some input on that other seal since it looks like he has gone through one. If its absolutely leaking trans fluid that should rule out the rear main and slave.

It's definitely the front trans seal. I could see it dripping from between the trans housing and slave cylinder.

Exhaust and Atlas are out. I wish I could say it only took an hour. Lol.

With no body lift and the Atlas notched into the frame it's a tight squeeze. The Atlas shifters weren't easy to get clear of the body either, especially the doubler shifter. I'm not exactly sure how I got it all in.

I picked up the input seal today. Maybe by tomorrow night I'll have the trans out and taken apart. I guess at that point I'll have a better idea of what it will take to seal it all back up. My goal is to be back on the road by this weekend. Them start fixing the minor stuff, wiring the winch, etc.

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I forgot you have the 4 speed Atlas! Good luck getting that all done!

There is no case seal. You have to buy an anaerobic gasket maker that meets Ford spec WSK-M2G348-A5

Here's a link to an online copy of the service manual
http://www.vaglinks.com/Docs/Catalogues ... anual_.pdf

Thanks

Looking through the manual there are several steps to separating the case on pages 21, 22- removing the shift interlock, detent springs, etc. (steps 7-13) are these steps necessary if I'm just replacing the front seal? Maybe this will become obvious as it comes apart. From your first post I was hoping it could be done by just pulling the rear bolts out and separating the case. I don't want to get in over my head and end up screwing something up.

I'll need to check my photos when I get home. I dont remember for sure, but I dont recall it taking long to disassemble. I remember thinking it was the easiest trans disassembly I've done.

The big ? in my mind was whether you need to replace expendable parts like the freeze plugs.

I think I tracked down what they are and have them coming tomorrow.

I found this page:
https://www.transmissionpartsdistributo ... 630361077/

and confirmed the size is roughly 3/8" from measuring my back up trans.

Hopefully they don't have to be "soft", and a steel freeze plug will work:
Dorman # 555-115
https://www.oreillyauto.com/detail/c/do ... ag0/555115

Had to buy 10 but they will be here tomorrow morning along with some anaerobic gasket maker. I'll have some "inventory" for future work, lol.

If these work Melling #MPC-222A should work.

Napa said they have part number 381-2185 that will work, but they wouldn't be here till next week.

That went pretty well. I realized there is a transmission to engine bolt that is right behind my passenger side collector. I either need to leave that bolt out or I'll have to pull the header off anytime I pull the transmission. Hmmmm.

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I found the reason for the leak. Sorry for the crappy pic.
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After some scotch-brite, 1000g and PB Blaster, there is clearly a bad seal surface. Fortunately there is a Speedi-Sleeve for this. I'll pick it up tomorrow.

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The shift rail retainer is cracked on one side. The magnet in the transmission was covered in a film of black sludge, I'm assuming pulverized shift rail retainer. Everything else looks pretty good. The piece has a little play, but I think that is normal. It's secured with 3 other bolts so I'm going to leave it as is.

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Yikes on that input shaft! Glad you can repair it.

Did you need to remove the freeze plugs? I couldnt fin any photos where I did that, but I remembered them.

Have just about everything together. It fought the whole way.

I just need to reinstall the clutch hose. Powers out so I took the rest of the evening off.

What's the best way to bleed the clutch? I didn't have any trouble when I installed everything. But I want to be prepared if I have problems. I've read about 10 different versions of how to do it.

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I would try to follow these instructions: I had about every issue known to man trying to bleed my system and could not get it to bleed until I finally decided to put a different slave cylinder on mine. Basically had a faulty/leaking slave right out of the box. When I put a different one on, it took about 10 minutes to bleed.

First things first, because it took me a while and lots of frustration to figure this out, REMOVE the rubber diaphragm in the MC (under the cap). Your master cylinder should come with a short bleeder hose that you insert into the MC where the hydraulic hose goes and loop the other end back into the reservoir. Fill the MC with fluid and have a helper pump the clutch pedal. Fluid (and a bunch of bubbles) will cycle through the hose, back into the reservoir. After several pumps, quickly remove the bleeder hose and stab in the hose going to the slave cylinder.

You’re half way there. Now you need to bleed the slave cylinder, find a wrench the fits the bleeder valve. The ford manual had the best instructions I found and they go something like this. With the bleeder CLOSED pump the pedal 10 times pausing for 1-2 seconds at the top and bottom. On the 10th pump, hold the pedal to the floor. Crack open the bleeder for a few seconds, some combination of air/bubbles/fluid will out, close the bleeder, then release the pedal. Repeat. It probably took me about 12-15 times to get a good pedal feel. Don’t forget to check the fluid level as you go, it’s a small reservoir! When done put the rubber diaphragm back in and cap it off.

If you follow these exact instructions it should only take about 20-30 minutes and minimal frustration. As a side note you can do this alone.

I seem to remember having to use a pry-bar on the slave to get mine to bleed enough.

I never updated this thread.

Everything went very well, everything is still sealed up. My rear main seal on the other hand did not like sitting 7 years and is leaking pretty bad.

One thing, the 3/8" freeze plugs weren't tight enough to stay in the case.

I found a socket that was slightly larger then the ID of the cup and kind of hammered the socket into the cup. This expanded the OD slightly and made them fit tight. I did add some red loc-tite for good measure.

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To install the Speedi-Sleeve, I found the installation "tool" fit very nicely inside 1.75x0.120 DOM. I cut off the closed end off the "tool" and slid it into a short section of DOM. A few taps with a hammer and it went on nice. The DOM would have probably worked fine, I just didn't want to risk distorting the sleeve.

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I have about 500 miles on things, mostly off road and it's doing well. If I shift too fast, especially with lower t-case gears engaged I'll get a buzz moving into the next gear. But otherwise it's doing great. I don't know if that means a rebuild is needed, but I'm confident this one can be rebuilt. I still will keep my "back up" ZF just in case. Plus they seem to be selling for close to $1000 lately. I think I got the one in my truck around $350 maybe, and my back up for $250.

Thanks for the share.

I'll give it a try. I think I have some adjustment available. I also built in a pedal stop to prevent over travel possibly damaging the slave cylinder so I know I can get more clutch engagement.

Thanks

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