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Thread: No Reverse? Fix it YOURSELF!

  1. #1
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    86 MR2, 91 MR2T

    No Reverse? Fix it YOURSELF!

    Hello,
    Reverse gone out on your BMW with ZF transmission? Maybe this write-up will help you!
    The particular car I am working on did not have any forward gears, but the failure was so similar to the normal no-reverse complaint that it should help. This is NOT for the casual do-it-yourself mechanic. You could very easily miss a small detail when tearing down or re-assembling the transmission and cost you all the labor and parts you put into it. If are going to have to install a used trans anyway, what can it hurt to attempt the repair yourself?
    Drain all the fluid you can from the vehicle, and remove the trans. This takes about 2 hours. Roll the trans onto its back on a table covered with heavy paper, and remove the pan. Remove the 2 bolts holding the filter, and remove the filter. Throw it away. If you have the classic no-reverse problem, you will probably find several dozen aluminum "teeth" bits that have broken off the center support drum. These allow the snap ring to move too far and the brake clutch pack "D" will not be able to engage.
    Pull the clip that holds the electrical connector and push the connector into the case. Remove the bolt holding the output speed sensor into the case and thread the bolt back into the case so you don't lose it! Unclip the 2 pin connector on the bottom of the valve body that leads to the input speed sensor. Unlike what I have shown in the picture, leave the wiring harness plugged into all the solenoids. It is easier to just bring it out with the harness attached.

  2. #2
    Join Date
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    Z3, 528i, M5, X5, Jetta
    Sounds incredibly interesting, however, since you are a new member, you're not able to show pics.
    1999 528i - Titanium Silver over Black Leather, Sport
    2000 Z3 2.3 -Topaz Blue over Sand Beige, Sport
    2003 M5 - Imola Red over Imola Red/Black, Sport
    2004 X5 4.8is - Estoril Blue/Black

  3. #3
    Join Date
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    2009 C350
    Also removing the trans without proper tools and a lift will take a lot longer than 2 hours for most people here. Still would be interested in seeing the pictures.

  4. #4
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    86 MR2, 91 MR2T


    I forgot to mention, the VERY first step of any transmission or hydraulic repair is to pour approximately 1/2 quart of ATF over your head. You will be getting very oily and dirty soon, so might as well start it off right.
    Now you can carefully remove the valve body! You will see lots of Torx screws... the VB is 3 pieces, and we want to remove it in one piece. Some of the screws hold the pieces together, while the largest screws hold the complete VB to the trans case. Remove all of these large screws and set them aside. Have a clean cardboard box or shop rag on a flat surface ready to set the VB on. Lift it out, and it should be free from the trans case, as long as you disconnected the wiring from the input speed sensor. Be advised that there is a piston in the VB that engages the shift arm coming through the side of the case. It should slide free of the shift arm as you lift it up. You can now remove the input speed sensor and set it aside, remembering to screw the bolt back into the case so you don't mix it up or lose it!



    Here is what you should have after removing the VB from the case. Note that I left the harness in the case and both speed sensor are still installed. I advise leaving the harness attached to the VB and removing it all as one unit. Look at the far left of the picture, you will see 2 plastic tubes with o-rings on them. These are the oil feed and pressure lines from the oil pump. One passes through the VB directly to the filter. This feeds oil from the bottom of the pan to the oil pump in the front of the transmission. The other is pressurized oil from the pump to the VB. These tubes need to be removed to allow you to remove the pump from the case. One tube will come out easily, and might even have stuck in the bottom of your VB. The other has a metal thingy in it, to remove it push it down slightly and turn it CCW, it should disengage some tabs and come out with a spring behind it. The tube itself is held into the pump by some tabs. To remove it, first take off the top o-ring so you don't damage it. Grab the tube firmly with some needle nose pliers and pull straight up firmly, rocking it around slightly in a circle to get the tabs to disengage. Even if you do everything right, you may break the tube. It is a replacement item, and it is not a bad idea to get both tubes new.



    Now it is time to remove the front pump cover and pump, and all the "guts" of the transmission. Remove all the bolts holding the pump in. You should have a flat, clean area of your workbench ready with some cardboard on it to place the parts on as they come off. Also, a jar of vaseline or trans assembly lube to "stick" bearings or races to the trans parts so you don't lose track of where they go.
    Using a combination technique of pulling on the nose of the pump cover casting, and pushing on the pump from the inside of the transmission, remove the pump from the case. It is 2 seperate pieces, but you want to keep the pump together, and "clocked" correctly. There are fluid passages that go between the 2 pieces, and if you rotate it when you bolt it back together it will not work. Due to the arrangement of the pump bolts, you should not be able to get it off, but better to keep it correct from the start! Carefully study all the pictures, and you can see where I split the gearset/clutches. If you just yank on the pump nose, it may not split where you want it to, so pull on the nose and push on the gearset in the middle of the large opening next to the input speed sensor to get it to come apart as shown. Pay close attention to any bearings/bearing races that may come out as you are taking the pump out. Immediately put them back on the shaft they came off of, holding them in place with a dab of Vaseline!



    This is what should be staring at you now.... The input shaft. Scared yet? You should be, but too bad! You are commited now!
    Last edited by cacrawfo; 02-03-2010 at 05:03 PM. Reason: Automerged Doublepost

  5. #5
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    2009 C350
    Wow this looks like it will be an EPIC DIY. Keep it going .

  6. #6
    Join Date
    Feb 2010
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    86 MR2, 91 MR2T
    This is what the pump assembly and first few clutch/brake pack sets should look like on the bench.



    Note the 2 pieces to the pump assembly, in between the pump inlet/outlet holes there is a bolt hole for a pump bolt. If you follow that up you can see where I made a mark on the inner pump casting with a white/silver Sharpie pen. Make a mark here for yourself in permanent pen or scratch a small mark with a sharp tool. This will help you line it up when you are installing it.

    Now you can take more internals out. Next pieces should be the main planetary gearset. Try to get it out in one piece, if it comes apart carefully put it back together before you forget how it came apart!


    You should now be at a point where you cannot get anything more out without removing the center support drum. You should also be able to see now why reverse will not work. In fact, some of the brake frictions and steels may be barfing out at you because the snap ring cannot retain them without the little ears that broke off. To remove the center drum, you have to remove the 3 large bolts from under the valve body. With these bolts out, you can slide the drum out. Try to leave the rearmost clutch packs and planetary set in the transmission, you do not need to take them out to replace the drum!



    Here are the 3 bolts that hold the drum in place. Note the 3 holes and 2 threaded holes. The threads are where the VB bolts on, but the 3 holes are for fluid to pass into the drum to activate servo pistons "D", "G" and a 3rd one. "D" is on only in reverse, while "G" is applied in P,R,N,1, and 2. In my car, "G" side of the drum had failed, so I got no forward or reverse! Also note the larger "window" in the case on the left side, between the drum and the park lock. Try to get the drum to separate from the rest of the trans there. Leave as much in the case as you can. I took out more than needed and this is what I got...



    By now you should have an impressive/depressive pile-o-parts that looks like this:



    Now you will have to forgive me, I was so oily at this point that I did not get a few critical pictures of disassembling the brake packs out of the broken drum and installing them into the new drum! I will try to describe it as best I can! Another option is to take the broken drum and packs with your new upgraded ZF drum to a trans shop and ask them to swap it all over for you.
    To remove the packs, pry the snap ring out with a small screwdriver. Turn the drum over and shake out all the frictions and steels, keeping them in order. Set them aside. Do the same for the other side of the drum. The two sides are different sizes, you cannot mix them up! You have one more step to do to get the drum down to its most basic form. You will need to compress the spring and remove a snap ring to be able to remove the large shaft in the center of the drum. I made a special tool to do this: a short length of 3" steel exhaust tubing with a small "window" cut into the side of it so you can have access to the snap ring to remove it. A small bench press will accomplish this, it only takes a few hundred pounds of pressure.



    When you are pressing it you need to support the center of the shaft opposite the side with the snap ring. There is a wave spring on the other side of the drum as well, and you can put unwanted stress on the drum with the press if you do not support the center shaft. This center shaft should now be able to be pulled free from the drum. This is where the one-way clutch (sprag clutch) is located. Be careful to keep the shaft in the sprag when you take the assembly out of the drum. What you should have now is the center support drum with both servo pistons in place. (in the bottom of the drum)

    Here is what my broken drum looked like. Keep in mind the typical no reverse problem is the other side of this drum!




    Now you need to remove and transfer the servo pistons from the broken drum to the new drum. Remember those 3 holes in the case I showed you? Here are where they go in the drum itself. The 3rd hole passes through to the center shaft you just removed to apply another clutch pack. These are the 2 we need to be concerned with. Using shop air, blow air into one of the holes to "pop" the servo piston out of the drum. Here is what you get! Do this on both sides to get the pistons out. See how they cause the brake packs to engage?


    You need to closely inspect both the inner and outer O-rings on the servo piston. On the side of the drum that failed, the piston can over-extend because the snap ring does not restrict the movement. This can cause the transmission fluid to eat away at the outer seal as the oil "squirts" around the o-ring. Here is the failed outer o-ring on my trans. It obviously got replaced when I re-assembled it.


    Using Vaseline, lube the o-rings, inner and outer bore of each side of the new drum. Gently press the servo pistons into the new drum. Re-install the center shaft, paying close attention not to damage the piston ring seals on the shaft. You must compress the spring again with the special tool and re-install the snap ring. Now you can re-install the brake pack frictions and steels, followed by the snap ring.
    Now you can put it all back together! It takes some twisting and turning of the clutch and brake packs to get them all to slide together. When you install the frictions, make sure you line all the inner tabs up so the next assembly will fully seat into them. You can turn the output flange of the trans to help it all mesh into place, or sometimes it is handy to lock it in park to turn something against it. you should never have to hammer or press HARD on anything! When it is lined up and meshed correctly, the center support drum will be the correct depth so you can re-install the 3 bolts. Don't ask me the torque, I looked up a standard value for that size thread.
    The rest of the planetary's and clutch/brake packs can now be installed, it helps to have a helper there to twist the input or output shaft to get things lined up. Don't get frustrated!!! Remember, you are saving $3,000+ doing it yourself! This part is tough, but what more can I say, go slow and make sure you don't lose a bearing or race when you are trying to get it all to mesh. Stick them to the shaft with Vaseline so they stay put. When it comes time to install the pump housing, pay careful attention that you get the front and rear pump housings lined up correctly! This is where that mark will come in handy, as you can see it from the bottom of the trans.... With it all back together, you can install and tighten the bolts that hold the pump to the case. Install the pump to valve body plastic tubes, and the spring and metal thingy into the pressure tube. The speed sensors can go back on, and the valve body can go back on as well, pay attention to the gear selector piston!!!!! Of course, the torque converter needs to be properly seated all the way into the pump housing!
    Install the new filter, and new pan gasket. Install transmission, and fill with fluid to the top plug level. Start the car for about 20 seconds, then shut it off and fill again. You should now be able to start the car and let it warm up for 10 minutes or so to get the fluid to a temp where you can check the level accurately. Run it through reverse, neutral, and drive a few times to let the fluid get to all the parts of the valve body and servos.

    Hopefully, (cross your finger and toes!) you have reverse and all the other gears as well! This is definitely a detail-oriented repair, but there is no magic to it if the no-reverse was indeed caused by the failed drum and there was no resulting damage.

    Here are the parts you have to have at minimum to do the repair:

    New upgraded center support "D" drum
    outer servo piston O-ring for "D"
    new pump fluid tubes with o-rings
    main pump housing o-ring (goes around pump)
    filter
    pan gasket
    fluid

    I only had the new drum, and the failed o-ring was a total surprise, so I had to stop and order it. It is best to do this repair quickly as your chances of getting it back together go down as the time increases! It took about 2 hours to remove the trans, 45 minutes to tear it down, and 1.5 hours to swap the new drum in and put it back together. 1.5 hours to get the trans back in.

    Not bad for someone who has never opened an auto trans before....
    Last edited by cacrawfo; 02-03-2010 at 06:12 PM. Reason: Automerged Doublepost

  7. #7
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    Wow, that is unreal. Did you have a Bentley manual or something to guide you with this? Or just a large quantity of beer?

    Either way, Bra-Vo.

  8. #8
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    Blown 530
    Curious myself about some of the torque values

  9. #9
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    Dude this is epic! If I had the time and a second car I would have definitely tried this! I had to have my Transmission rebuilt by ZF.

  10. #10
    Join Date
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    2002 540i Sport
    WOW!! Thanks for the writeup. i don't think i'd ever try this but was facinated with the knowledge you shared.

  11. #11
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    98 528i,06A6,11Ford Flex
    I might be crazy enough to try that, but only if I had a spare that I was sure would work. Love to take things apart, especially if I don't know what the hell I'm doing.

  12. #12
    Join Date
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    2003-525i BMW
    If I had a hat on --I'd take it off for you dude--what a DIY---how did it all turn out for ya

  13. #13
    Join Date
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    1997 540iA, '06 GSXR
    Wow, thats awesome. Nicely done. Maybe if I have some free time I can start fixing BMW transmissions for others.
    I've torn apart Ford and GM's, shouldn't be that much harder.

    When all else fails, just give up. But make sure you leave no sign of even trying. (oOO\(lll)(lll)/OOo)

  14. #14
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    00' M5 | 06' 330i 6 Spd
    I think Dan (544iA) and I may use your DIY to repair my tranny! Anyway that you could tell me where you got the parts from and how much you paid?

  15. #15
    Join Date
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    98' 740il
    your one hell of a "noob"

    btw great diy, but i has manual
    past cars 99' 328i, 01' 325xi, 97' m3/4/5, 00' 540i-6, 01' 325ci-5, 93' 325i-5, 00' ///M5, 95' 325i
    present 98' 740il,98' ///M3

  16. #16
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    Wow dude! And here I thought pulling my interior panels to fix a water leak was like complicated.

  17. #17
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    Nice DIY!All that for a broken clutch-pack snap-ring retaining lip.Not bad man.

  18. #18
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    86 MR2, 91 MR2T
    Yo,
    Thanks for all the props! I was very pleased with myself when it all went back together and actually worked! It was either going to work and I would brag about it, or it would blow up on startup and I would never speak of it again.....
    I got my parts from Transtar, they have local branches all over the USA. You can also try Cobra Transmission Parts, they have all you need for the ZF.

    I spend about $300 total with parts, filter kit, and fluid. (Maxxlife ATF)

    I just bought an 01' 740il with trans issues, hopefully I can pull it off again...

    Carl C

  19. #19
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    That is without a doubt the most awsome DIY Ive seen yet,You are the MAN!!!

  20. #20
    Join Date
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    E39 hamster/ruberbandPWR
    Absolutely amazing!
    Are you a mechanic by trade?
    How did you know how to do this?
    Did you use a book?
    I wonder if any of this would apply to the GM transmissions?

    Pictures of the 740iL?

    Thanks!
    Jason

  21. #21
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    '98 528i
    I shall be attempting this soon, I am SO HAPPY that you posted this DIY cacrawfo!!

    My 528i's auto tranny just recently started acting up. It can engage into reverse, but none of the drive gears work any more. It wasn't sudden, it happened over a few days getting worse over time. Hopefully I can restore my tranny to working order using your guide!!

    Living in Canada I'm unsure as to where to source out the required parts (not wanting to go to the stealership unless absolutely necessary). Any suggestions?

  22. #22
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    2003 530i Sport
    nice job
    but not for everybody ... looks like for professional mechanics only

  23. #23
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    Welcome to the forums

    Nice job Carl. I don't think I'll be tackling that anytime soon. Lol.

  24. #24
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    '98 540ia
    That is one hell of a DIY. Good post!

    Now if I can just find that thread about replacing the oil filter mounts.

  25. #25
    Join Date
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    02 530i
    Man this is awesome. I was scared to death of breaking the trans in this car when I got it. Now not so much Im not gonna worry bout it at all now, just enjoy manual sport mode more often

    For those interested ZF has a distributor locator on their site as well as lots of good reference info. Distributors

    ZF Friedrichshafen AG / Product Catalog

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