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Mark944na86's Avatar
 
Join Date: Mar 2005
Location: Brisbane, Australia (Formerly: Sunnyvale, CA)
Posts: 190
Report on Rennbay kit ball-joint rebuild

I thought I’d report on my recent ball-joint rebuild using the Rennbay “uber deluxe” kit. (Where's that umlaut key when you want it...)

I was originally planning to do this at my place. Rob (“Rob in Oz” on Rennlist) volunteered to come over on the day, to assist and observe. After he observed my facilities, he suggested going over to his place to do the rebuild as his workshop is a little better equipped. That, of course, is a gross understatement... his workshop is a huge purpose-built shed on his acreage property in Barrelin Point, full of high quality tools and equipment. On the other hand, my "workshop" is my double garage with the Honda kicked out onto the street. And not nearly so many nice tools.

Anyway, Rob’s suggestion that the job might go more quickly and easily at his place was a good call, because as it was it took us the best part of the day. It was an interesting job, that went not quite according to the Rennbay kit instructions, requiring a little improvisation around the edges, but all-in-all went well resulting with a satisfactory repair.

It was quite interesting to see the innards of a worn ball joint... the plastic insert bushes (I think of it as "cartilage") were quite distorted and (on one) broken up, but the sound design meant they were still doing their job. Indeed, when we first got the control arms removed, but before we opened up the joints, the joints still felt pretty solid, and I wondered whether the whole exercise was necessary at all.

But actually seeing what was going on inside the joints clarified matters. See pic below:



As this picture shows, the only really critical parts that were worn were the upper bushings; these cups were very distorted and worn, and as can be seen, one was split into two halves, only one half of which is in the picture above. The lower bushings, and all the other internal components for that matter, were in relatively good shape.

I can understand now why the 1mm movement rule is used as a rule of thumb for the rebuild; at 1mm they are definitely very worn, but there is still enough bushing material left to prevent metal-to-metal contact.

I should mention that the bits we got in the kit weren’t entirely consistent with the web-based instructions on the Rennbay site.There were three parts for each ball-joint that we had some problem with; these are shown below:



The metal spiral clip was a bit of a mystery. At first we assumed this to be a replacement snap-ring to hold the new zerk fitting equipped base-plate in place, but we couldn’t get it to do this. We ended up just reusing the original snap-ring, which worked fine.

The orange plastic washer also had us scratching our heads. We hypothesised, experimented, discussed our results, and finally just left them out. Travis at Rennbay obviously went to some trouble to get these into the kit, since they were custom-made parts with “Rennbay” cast into the plastic. Yeah, I’m sure it was OK to leave them out! No mention in the web-page instructions of what to do with these guys, either.

The last part we had a problem with is the new black plastic boot which came with the kit, which was a replacement for the original rubber boots which are often split or are damaged while disassembling the joint. We could not get these to stay in place while putting the ball pin back in place – they kept slipping off the top of the ball joint because of the angle the pins went in while there was no weight on the wheel.

Maybe they would have reseated themselves once the wheels were back on the ground and there was some weight on the suspension – don’t know, and again the instructions fell short in the enlightenment department. At any rate, we ended up just reusing the original rubber boots, as these were still OK, although one had what looked to be the beginnings of a split.

So, apart from some mild frustrations from the less-than-perfect instructions, I think it was worthwhile to do this job when we did, and rebuilding this way is definitely a good option if the joints haven't been ridden past their use-by date.

BTW, Travis at Rennbay is a very cool guy, very helpful, and when I phoned up originally to order the kit, he spent quite a bit of time on the phone as we discussed which kit would be the most suitable for my particular application. I’m sure if he spent as much time on the phone for every sale he’d never make a living! I would have given him a call to enquire about the unexplained bits of the kit but because of time zone differences, it would have been very early Sunday morning (by that I mean the middle of the night, basically) in the US, and I don’t really expect there to be a Rennbay emergency response team available 24/7. It was Sunday afternoon in my time zone, the car was on jack stands, and we wanted to wrap things up.

As an epilogue, I took the car to get the alignment redone the following Tuesday, and the guy who owned the tyre place turned out to be an ex-944 owner. He was quite the enthusiast, and even got the photos out to show me what had been his pride and joy! He even let me borrow his shop’s tools to retension the bolts for the ball joint pins while it was up on the lift and things were easy to access, to save me the trouble getting under there again once I got home. He finally even knocked a bit off the quoted price for the alignment, just for the hell of it, as far as I could gather.

Such is the power of the invisible bonds of 944 ownership. When you buy a 944, you don’t just buy a car, you join a brotherhood! And for life, it seems...

-Mark
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Currently 1990 944 S2, Black on Linen, 17" Turbo Twists

Last edited by Mark944na86; 04-08-2005 at 04:39 AM..
Old 04-08-2005, 12:50 AM
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I did this a while ago. The kit has changed since I did it. The washer is to go under the base of the spring. My origional take apart had one. The boot stays on when you put the arm back on the car and shove the pin back into the Strut. Not the best design but it works. Glad you had sucsess!
-Greg
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Old 04-08-2005, 02:28 AM
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How many miles on those ball joints?
Old 04-08-2005, 02:36 PM
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7K? I think. I only did one because the other is non rebuildable, it is one that someone pressed in a sealed joint. They are drilled out to do so and are toast once the joint wears out. So far the rennbay one worked fine. The only touble i had is that it actually fell out on me because the c-clip wasn't seated and copious amounts of epoxy diddnt hold. That was before he included bottom plates so i had to make my own. Otherwise im quite happy with it.
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'88 944 240,100 miles -race car
'05 Boxster 110,000 - Daily Driver
'74 911 Targa - long term project
Old 04-08-2005, 02:44 PM
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My ball joints had about 146K kms (~87K miles) on them. I was surprised they needed rebuilding at this stage, because many owners seemed to be going much longer before they needed doing. But the proof that they did is the photo above.

I'm not sure if the heavier suspension components (bigger sways, etc.) on the S2 contributed to this -- just speculation.

-Mark
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Currently 1990 944 S2, Black on Linen, 17" Turbo Twists
Old 04-09-2005, 06:13 AM
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