TOPIC: Forward Shifter Ball Cup Replacement

My forward shifter ball cup joint came loose during a test drive a couple of weeks ago. It wasn’t a fun feeling. I went after replacing the cup insert. I couldn’t find any posts on this on our site so I thought that it might be useful to document what I found and did. Perhaps there will be a discussion about this very necessary, but not easy job, at least for me. Judging by the posts that I found, it was not an easy job for many people.

I found that there were two major tasks, developing clearance above the torque tube ball, and seating the cup assembly onto the ball. However, a beginning minor task is to get the cup assembly off of the rod. I was reminded by Hans SerVaas that it’s much easier to take the old cup assembly off the rod if you disconnect the rod from the shifter inside the car. You can pull the cup assembly down (I pulled it to the driver’s side ), grab the rod with something ( I used channel locks), loosen the lock nut, and then unscrew the cup assembly.





New Insert






No Room to Rotate Cup Assembly

1. Developing clearance above the torque tube (TT) ball

The Rennlist posts are all over the map about how hard it is to get the refurbished cup (assumes the cup has been properly cleaned with all remnants of the old insert removed and that the new insert has been completely seated into the cup) assembly up over the TT ball. My car is a ’79. I found that there was not enough clearance between the TT ball and the top of the TT tunnel to rotate the cup assembly onto the top of the ball. I also found that it’s virtually impossible to seat the cup assembly if the cup is not on top of the ball. There’s even a post by Greg Brown that states that the 78/79 models have less clearance than the later years so there may be legitimate reasons why this might be harder for the earlier models.
rennlist.com/forums/928-forum/956028-78-...t-cup-any-ideas.html

The clearance is also a function of the state of the motor mounts. Older motor mounts should allow the TT to sit a little lower relative to the top of the tunnel. For whatever reason, not enough clearance between the ball and the cup assembly to get the assembly directly on top of the ball appears to be a fairly common problem. However, plenty of people clearly have no problem with repositioning the cup assembly. I simply couldn’t do it with the clearance available. What I ended up doing (after consulting with Roger and Hans) was to lower the transaxle just a few inches to create the clearance needed to get the cup assembly into position. There are 6 bolts holding the Rear Axle Cross Member to the car. I supported the cross member with a jack and safety stands and then removed the two interior bolts and two of the exterior bolts, leaving one exterior bolt on each side almost completely backed out, and then lowered the jack. This created plenty of clearance above the ball to be able to rotate the cup assembly. I have to admit that I was a little apprehensive about lowering the transaxle because I had never done it before, but it turned out to be an easy thing to do. I’d be remiss not to note that there are other options, particularly if you are doing other work, e.g., changing the clutch, changing the motor mounts, or changing the TT bearings.
928motorsports.com/installpdf/shifter-ball-cup-install.pdf


For later reference:
The outer bolt torque spec is: WSM Vol 4, pg. 42-02 “Transverse member to body”, M10,…Torque: 46 Nm.
The inner M12 bolts torque spec is: WSM Vol 3, pg. 37-123, “…tighten transmission mounts/cross member bolts with 85 Nm”.

2. Pulling the cup assembly down

Once I had enough clearance, I still had to get the cup assembly seated down onto the TT ball. I found this to be a major PITA task. There are some posting that report this to be a 30 min. job. I’m certain if you have the right jigs and equipment, this could be a quick job. However, be aware that the postings are full of reports of many hours and attempts to get cup down over the ball. It took me 2 – half day sessions trying to accomplish this task, which included trips to the hardware and auto parts stores. I tried 3 methods: 1) ratcheting strap with a bottle jack; 2) ratcheting strap by itself; and 3) a metal band clamp. On the initial attempts, methods 1 and 2 would both start pulling the cup down, but #1 was hard to keep in line and both methods would reach a point where the cup would slide to the side. I didn’t have a large enough band clamp until second day, so I can’t say what it would have done with a brand new cup. I will observe, though, that it appeared that the cup would go down further on each attempt. I think that what was happening was that the nylon cup material was both stretching and relaxing. On the second day, I was able to get the cup on the ball almost fully on using method #2. I did let it sit there for a while. It was a small ratchet and just didn’t have enough leverage to complete the pull. However, I observed that it looked like the cup was actually slowly creeping down at the max ratcheting position, but again the cup slid to the side when I tried to force it to the next position. My first attempt with the metal band clamp also got the cup pretty far down, but I ran out of travel. I tried one more time with the metal band, but with a pry bar at the bottom and it seated! I had grease inside the cup, which squirted out with a splat sound. Trapped air and grease could also be working against seating. Anyway, now I’m wondering if the many attempts reported before success may be facilitating the stretching and relaxing of the cup material until it’s finally ready to seat. Many people apparently put the cup in the freezer to shrink it before trying to pull it on. I didn’t try freezing the cup, it would be nice to have a comparison to know if freezing facilitates the installation. I will note, though, that I did this in the middle of winter and that my garage was pretty cold and although the cup material will shrink with cold, it will also get stiffer.







Metal Band Clamp






Success!

I'm limited on the number of links that I can have. Just do a google search on "Porsche 928 front shifter cup"

Good write-up, but I thought the general consensus was not to lubricate the new ball joint as it can lead to it popping out during enthusiastic shifting?

nluk100 wrote:
That's interesting. Do you, by chance, have a reference? It would be good to read it. I wished that my search would have turned this up! I'll try not to be too enthusiastic!
Honestly, I did it because it made some sense to me to minimize the wear of the cup material. Also, given how hard it is to get the cup to get over the ball (and presumably how hard it would be to get it off) and after seeing all of the bits of insert that are left in the cup and how one had to carefully clean the cup lip to get the new cup insert to completely seat in the lip, I was wondering if many premature cup failures could be due largely to inadequate cup preparation and seating?


I think that this points to another opportunity. I know that the 928OC.org is going through some changes. What I find unique to the OC is that it provides the structure for an organized archive of knowledge that FB or even Rennlist does not. For people like me, who are probably doing these tasks for the first time, it can be a long and tortuous path to find the answers that we are looking for. And I never know if I had found all of relevant and the "best" information. It would be great if the technical section of the OC could be expanded to a finer gradation of tasks, e.g, replacing the forward shifter ball cup. Maybe the relevant Rennlist posts could be linked, plus knowledge like yours, e.g., the consensus to not lubricate the ball, could be added, etc., plus a "crowd source" voting mechanism to help searchers see ratings of the comments? It would be wonderful to have a one location stop for information. Another example that I just went through would be that of getting the rubber boot back over the rear shifter coupler. Everyone complains about it. I just did it in the middle of winter here and just happen to find that taking a heat gun and warming up the front of the boot made pulling it over the coupler almost easy. I bet that I'm not the first person to discover this, but if it's posted somewhere, it's probably buried deep. It's just a thought. I do think that the OC is uniquely positioned to be a "one stop shop" for 928 info!

Thanks for the additional info!

I've just replaced my front cup, but I managed to get a complete unit at a reasonable price to save any potential issues getting the a new cup to seat correctly whilst the car was on the ramp. I would imagine it would be almost impossible to do job this on axle stands, but no doubt someone out there has managed it! It needed some heat on the threaded insert part to get the old one to release.

I got the advice not to lubricate from a UK 928 specialist who has done hundreds of these over the years. I'm guessing that if the original one lasted 20+ years then so should the 2nd one.

I have also passed your comments onto the 928oc board for further comment.

nluk100 wrote:
Yep, I just read a post somewhere in which someone replaced the cup insert, in-situ, using "long screwdrivers". That must have been hard!
Blessed are the 928 knowledge keepers!
Thanks for passing my comments on!
All the best to the UK!