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Old 01-18-2011, 05:21 PM
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X5 4.4i trans rebuild/repair accomplished (long post)

I’m posting the results of my researching and ultimately solving a transmission problem with my 2002 X5 (4.4i). After researching a little bit, I ended up removing, disassembling, and rebuilding both the transmission itself and the valvebody. Although I generally don't have the time to read forums (or otherwise participate) I did make use of information within various forums, and felt the right thing to do is take time to share what I did, and the results therefrom. Again, I'm talking about the 5 speed auto (ZF 5HP24, also known as A5S 440Z).

I'd had my X5 for a couple of years and was well aware that transmission problems pop up with some regularity. In my case, it began as slipping and jerking under certain stop & go traffic situations. Sometimes would end up in 5th gear and in trans failsafe. Car had about 95K miles on it at the time. It seemed to worsen over a few months, so taking the initial easy approach, I dropped the pan, changed the filter, and changed over to Mobil's multivehicle synthetic. I was going to use the called-for Esso stuff, but after looking at an Esso bottle, I noticed it was made by Mobil. Since Mobil says their multiveh stuff is compatible with the BMW spec, why not? The old fluid was dirty and somewhat "black" but did not have an unusual or burned smell. There were no metal parts, chips, or other possible evidence in the pan. Well, as may have been expected, no change. None. As summer progressed, I started to notice that if it was cool out, or on initial start up it would work fine, but would start slipping and jumping up the gears very shortly thereafter. Always ended up in 5th gear failsafe. I downloaded and reviewed a powerflow diagram, and it seemed to me the "A" clutch wasn't holding (that clutch assy is used in 1st through 4th), and the slipping was triggering the faults based on the computer detecting the slip via the input and output speed sensors.

I did have to go through the 5 stages of grief to reach acceptance, and parked it whilst I pondered my options. Finally, I concluded that since there was clearly a transmission problem (not a computer problem), I probably would not be any worse off if I pulled it apart myself and took a look-see. Now, before I head down the whys and wherefores of my pulling the transmission out and apart, I do need to point out a few things. First, I have a well stocked garage, and I am a metal working hobbyist besides. Thus, I find stuff like this interesting as opposed to "a chore". Also, removing this tranny was not my first rodeo, so to speak (although I did think I was long since finished with finding myself horizontal under a car). This is not my main car, or even my second alternate car, so it could stay down for the count as long as necessary.

In researching this, I found that parts for this tranny are readily available and, in my opinion, very reasonably priced. Doing this was starting to become a no-brainer. I ordered a rebuild kit (clutches and seals, etc.) as well as a valve body kit, and the ZF transmission manual. All told maybe $660 or so + fluids. I do have a Bentley manual. While I reviewed its procedures, if you've ever pulled a tranny, then this is straightforward; nothing unusual as far as I was concerned. It took a couple of hours to remove. NOTE - I put the car up on platforms (maybe 14" tall?) and left it on the wheels. The reason is that since I have to do the refill procedure with the car running, I did not know what the Electronic Height Control computer would make of an apparent "airborne" BMW while running during the fill process, so I wanted it to be at regular right height and on its wheels. Well, guess what. You have to pull a front wheel off to remove the sway bar on an X5 (and you won't get out of not removing the bar), so that's a consideration I had to deal with. As mentioned, I have a wide selection of tools, and knew already this one would use somewhat atypical size wrenches, like skinny 18mm (sway bar), 16mm here and there, etc. I supported the trans on a tranny jack, lowered the cross-member slightly to gain access to the transfer case bolts, and removed first the cross-member (one bolt), and then the transfer case. Then I lowered the transmission ever so slightly and carefully to gain access to the bell-housing bolts. I should point out that before lowering, I did unfasten the fan shroud under the hood so that as the engine rocked back, the fan wouldn’t bind. I also kept tabs on the clearance and any lines, cables, etc so nothing would pull or tear. It went well. I sat indian style with my head where the transfer case used to be, and fed the appropriate socket up along the tranny to each bell-housing bolt, and backed it off. I'm not a fan of those star-headed Torx head style bolts, but things went well enough. NOTICE: the 2 uppermost bolts are a different (smaller) head size than the others, and that little piece of info is less than obvious from the viewpoint you have with yer head in the trans tunnel. I have air ratchets, so once I broke the bolts loose by hand, I could just trigger it to back them out. Also, 2 of the bolts hold the starter as well, and the 2 bolts opposite the starter are actually a nut & bolt combo. Then just remove the trans in normal fashion (and don't drop the converter out the front in the process). I’d taken pictures of how the various wiring harnesses were routed over and around the transmission. Several are “clipped” to the fins on the upper part of the housing. Once you’ve lowered the back slightly, you can see how things are run.

Skipping most of the removal as straightforward, my only other suggestion is if working alone as I did, have a handful of jack stands around to support the exhaust assy as you remove it - it's all welded as a large "chunk" to come out. I replaced all exhaust nuts since they were off, and such hardware is cheap.

Transmission disassembly was straightforward as well. Unlike the Bentley manual which I consider somewhat optional in this case (assuming you have worked under a car/truck before), I consider the transmission manual essential. The transmission really only comes apart and goes together one way, but there's a wealth of little odds and ends in the manual which decreases the stress of the unknown. I bought a couple of bus-boy tubs at the local restaurant supply place - these are invaluable containers to hold stuff, catch oil, whatever. And they stack inside each other when not in use.

Ok, so pulling this apart was no big deal, but you will need "special tools" in a manner necessary to compress, I dunno, I call them "cone springs. I did all but one of them using PVC adapters from the local hardware store. Maybe $12 total here. I have no way to describe it, but essentially you use a hole saw to make a hole in the side of the PVC adapter so you can compress the spring with the adapter, and reach in with a little magnet, or little needle-nose pliers, and remove the clip that retains the spring. These springs/clips are for the application pistons for each clutch unit. I did take numerous pictures, so I included a few. One of the tools needed to compress the spring could not find in a ready-made size, so I made my own tool out of some steel (remember, I'm a metal working hobby dude, so cutting and welding to achieve what I needed was no big deal).

Reassembly was straightforward, albeit tricky in spots. Some of the assemblies are heavy enough that you can't really just hold the oily end of a shaft to maneuver it and not risk slipping and dropping the assembly on the floor, with the resulting weeping and gnashing of teeth that'll likely occur. The ZF book shows a "special tool" which appears to just be a clamp arrangement on the end of the tower I shaft, so I made a similar item using a thick pad of rubber (protect the shaft), and clamped it to the shaft. Then I recruited a neighbor to help steady the trans case, and to help maneuver. If you are considering this DIY approach an option, consider buying the manual first (roughly $65 or so?) before ordering kits, and from that perhaps you will be able to decide if it's for you. Big clue - the manual discusses removing, say, a snap ring from an assembly, then has a picture of a dude in coveralls with a screwdriver prying out a snap ring. Seriously.

Ok, let me get to the point - what was going on? Slipping, jerking into gear, and launching into trans failsafe when the computer detected that slipping. What were my findings? All the clutches looked great except the "A" clutch, as suspected from the slipping symptoms. It was black whereas the other fiber disks were still brown (orig color). I replaced all of them anyway (duh). Seals and o-rings were not too bad, but it was obvious some o-rings had seen better days and seemed a bit brittle. Maybe heat? All were included in the kits I bought and therefore replaced. And the reason for all of this? An axial bearing between the nested "A" and "B" clutches was shot, the rollers being held together basically by its bearing races. It was obvious as soon as I saw it - and had I not parked it may have come apart at some point, turning the rest of the trans into a boat anchor. The axial bearing, while not load bearing specifically, allowed the input shaft and A/B clutches to move about - not a lot, but enough to cause a loss of clamping pressure due to bleed off of oil pressure. As the trans got warmer, the oil would thin some (my take on this), and lose whatever ability to clamp it may have started out with. And of course by slipping, the fiber plates for that clutch were clearly overheated at one point. Part cost was $35 from the same outfit I got the rebuild kits from. Except for the clutch that was slipping due to lack of clamping pressure, all other plates and wear surfaces looked excellent.

After reassy (and still using the Mobil's multiveh trans fluid), the car has been brilliant. Probably have about 2,500 miles on it since reassy, and I simply love the results. It’s been on at least 2 300 & 400 mile trips at 80+ Will it last another 100,000? Shrug. Who knows? I figure I'm way ahead of "Hey dealer, lemme pay retail for another tranny, will ya?" I also replaced all seals and springs in the valve body (although I didn't see anything amiss whilst in there.

How long did this take? Well, I removed the trans on a Saturday morning, and by that Sunday evening (and not working all hours) I had disassembled, cleaned, and reassembled the transmission to the point at which I then needed the new bearing in order to continue. Once the bearing arrived, reassembly and reinstallation was under one day – I started on a Saturday morning and I was tooling around town trying it out late that afternoon.

So, there was really nothing to this - read up and understand how an auto trans works to begin with, and if you have adequate space and are not intimidated with the prospect of taking it apart methodically and analytically, then here's some food for thought.

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Old 01-18-2011, 07:52 PM
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Nice! Thanks for writing that up. I'm not going to attempt it, but it was interesting to read about it and see the pics.

You might make a few bux if you rented out those "special tools" to others who have trans problems!
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Old 01-18-2011, 08:02 PM
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This is a fantastic post.

It's clear this isn't the first time you've gotten your hands dirty on a job such as this, and the way you decribe it gives me confidence that an experienced DIY'er who appreciates the complexity of the job at hand can in fact make a success of a rebuild.

I too have the 4.4 with the 5HP24 trans. It doesn't need rebuilding at the moment as it's performing well after 110k miles. However if ever it should start to give trouble I would intend to perform a rebuild myself, and I've no doubt your post will be valuable. I'm going to save it locally so I don't loose it.

So thanks again, and wll done.
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Old 01-18-2011, 08:39 PM
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Great post. Good job.

For the reassembly process and the clutches that have specifications, I believe there are various thicknesses of snap rings available. Did you find that all were in spec? I ask because you didn't mention waiting for special snap rings, or does the overhaul kit contain an assortment of different thicknesses?

Congratulations, and nice to give back to the forum by telling the story.
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Old 01-18-2011, 08:50 PM
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This is the kind of post that is very dangerous for me. Makes me think things are easy, and I will just run down to the hardware store and get some PVC and pull my tranny. I prefer the posts where someone spends all day cussing at the OSV and finally gives up. Somehow that makes me feel better about myself.

BTW, great job and thank you for posting pictures and directions.
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Old 01-18-2011, 11:25 PM
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Wow! Planetary gears and clutch packs. Hey it's an automatic transmission. Great work! I can't believe you have not been flamed for using the so called wrong fluid. Nice to see the case cracked, no more difficult than any other auto trans. The rebuilds just cost for the BMW name.
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Old 01-19-2011, 10:14 AM
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Well, to answer the last 2 posts, the rebuild kit did not come with snap rings. - I'll confess to looking at how the manual showed and described compressing the clutch packs and taking various measurements, and decided not to worry about the specific clutch packs in that regard. I do have the tools to do so, but not the fancy jig they used to compress (preload) the clutch disks for measurement. I did mic the old plates and new plates for comparison. I expected an obvious difference in thickness, but aside from the pack that had been slipping, the thicknesses of individual plates was VERY close. So, I cheated on the clutch pack measurements, and apparently I got away with that. For those not specifically familiar with what we are discussing, the clutches "float" in their spaces. When fluid pressure is so directed, the fluid slides a "piston" (best term I can think of) against the clutch pack and by compressing it, locks up one part of the planetary gear sets. 2 of the clutches, "D" and "E" are actually keyed to the trans housing by the assemblies they fit into, and thus don't turn, but when engaged act as a brake for parts of the planetary sets. See attachment powerflow diagram. The cone springs to be removed in order to remove the pistons do not serve to compress the clutches, they are to disengage and pull the piston back when fluid pressure is removed. If you think about it, if you have a chamber full of pressurized fluid spinning at tranny speed, removing the pressure source is only part of the disengagement. Without the retract springs, the fluid's centrifugal (sp?) force in that chamber would prevent it's bleed off through the center shaft orifices and cause that pack to "drag." The clutch pack clearances referred to are to ensure the clearance is close enough to engage within spec, but loose enough so the released clutch doesn't have drag. Kinda like disk brake pads - close enough to apply and brake normally, but not so tight they drag on the disk when not braking.

One area I did NOT cheat on was end-play measurements with a dial indicator. Although I could not check certain end play measurements until the replacement part arrived, I did not want to bolt down the oil pump/bell housing assy and find later that clearance was below spec and risk binding when parts expanded, or even binding right off the bat. The spec is tight, but I was right in the middle on end play.

As far as the fluid goes, just telling folks what I did. I probably would have used the called for Esso stuff if was going to leave the tranny buttoned up for another 95K or whatever. Shrug. I'll point out that unlike the pretty green sticker advocating lifetime fill, the actual ZF trans manual does not take that position. This car is kind of a hobby/toy. I got it cheap because the dealer couldn't move it when gas prices were up, everything works, and it's fun. But I'm not going to put a lot of dough into it.
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Old 01-19-2011, 07:34 PM
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Congrats as I am having the same problems and thought of selling till I read your post. GJ
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Old 01-20-2011, 09:25 AM
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Great job on the write-up! I'm definitely dumping this out to a document for my folder of (how to fix shit) that I keep in my shed. Hopefully for my sake it won't be needed, but I'd rather have it and not need it than need it and not have it! By any chance, was your trans ever displaying the symptom of hard shift into lower gears during stop and go traffic? I swear, when I'm in heavy traffic and make the transition from brakes to a little bit of gas it feels like I'm getting rear-ended!

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Old 01-20-2011, 12:42 PM
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Very impressive. Thank you taking the time to write this up.
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