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Transmission ZF 5HP24, ZF 5HP26 & ZF 6HP26 RepairWell my 99 xk8 went to the transmission shop. Made a right turn into the parking lot and the check engine light came on with a transmission fault and moved like a slug. Checked the code and found P1722. Yes I know! It was towed to the transmission shop. The car has 113,000mi on it and I had the transmission serviced at 107,000mi. For 6,000mi the transmission seemed to shift better after it was serviced. Found out that the B drum failed. What I find out was that the drum is in limited supply because the company went out of business and another has not taken over. I was also told that changing fluid and other maintenance procedures would not change the failure. This is a common problem with this unit.
I am not a transmission kind of guy and will ask additional questions when I get the car. I told him to do what was necessary. In the mean time I am trying to stay out of his way and not bother him. I want to verify the trans. model, the cause and the likelihood of another breakdown. When I got the car back I found out that Tom had to replace the B clutch hub, forward drum and the torque converter and of course the overhaul kit with filter and fluid. I have the B clutch and forward drum see the attached photos. The torque converter was changed for fear of metal parts from the B clutch hub that broke off and scored the forward drum and feared that the shavings would get into it and causing additional problems down the road. Now the best question is did I know it prior to it failing completely? Now that I look back I probably did. At times both my wife and would hear a slight roaring noise off and on from what appeared to be coming from the center to the rear of the car at speeds of 45mph – 50mph. I had the car put on a lift prior to the transmission failure looking for where the noise was coming from and I was unable to find it. I thought it was in the rear differential or the one set of universal joints I did not replace. I never thought of the transmission being the cause because it ran so well. I considered getting the reconditioned B clutch hub but when I mentioned it Tom told me that the replacement hob with the dimples are the best bet. The recondition as he said had several problems of its own and was not worth taking the risk. At this point I am pleased with the decision I made, the car runs great and I will move on to my next project. Had several questions about the valve body so I called tom and asked about the valve body and did it contribute to the B clutch hub failure and he told me this. The valve body on this transmission does not have a high failure rate but this is one of the areas that he checks. This one was OK! He also said if the valve body were worn or not it is not the primary reason that the B clutch hub fails. Just poor design or construction in the drums. The newer design has dimples on the one side of the B clutch hub. Also see the additional links for ZF5 HP24 & ZF6 HP26 – 28 on my http://jagrepair.com/jaguarxk8xkr1997_2006.htm under Drive Train & Suspension. ZF 5HP24 Automatic Transmission - Spare Parts Catalog Catolog-1, ZF 5HP24 1 Repair Manual, ZF5hp24 valve body TSB, ZF 5HP24 transmission parts manual For Transmission Control Information Use This Link This document is from a BMW technician training. Gives a overall perspective of the electrical controls of the transmission. Use This Link ZF Electronic Automatic Control System for BMW I found this to be a great resource; http://openpdf.com http://openpdf.com/ebook/zf-5hp-24-pdf.html Listed below are a few manuals I came across;
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