Carl Fausett

Been there, Done that.

...and when I found something close and bought it, found that the poly bushing material does not drill clean (if you need to make the hole bigger) and does not turn or cut clean (if you need to reduce the OD. The finished product was not good enough to sell to anybody.

Polyurethane needs to be cast to size and shape. Its resiliant by design. It resists turning, drilling, and reshaping. (although it does bandsaw well)

WallyP

If you have a polyurethane sample of anything handy, try freezing it, and drilling or turning while frozen...

longleader

Can I do this on ramps in the driveway or do i need to lift the car? Anything I need to know before doing this?
Thanks for the help,
Larry

Rob Edwards

Ramps will be fine. There are many options for solid bushings now, made either of delrin or aluminum, one piece or split, I would advise perusing the threads in which they are discussed.

longleader

Thanks Rob
I have a 1983, auto with 93500 miles on it and mine look like they have seen better days. I was going to replace them with aluminum or do you think I should stay with OEM.

toofast928

Replace with aluminum. I did mine with the engine removed and it was pain. You may have to remove the rack or use puller of sorts.

Speedtoys

On that last photo Carl...you -have- to remove the engine first to make it easy?

Is that a missing step?


*just having fun*

Rob Edwards

Definitely upgrade to the solid rack mounts. I have one set of aluminum and one set of delrin on my two cars. Honestly I can't tell the difference between them. (But you could put a pea under my driver's seat and I wouldn't feel it, I'm not a very sensitive driver...)

It will be a medium sized PITA to do the R&R on your back but it can be done on ramps. I would drop the rack cover, undo the rack mounts, and lower the rack, leaving it attached to the tie rods, the steering U-Joint, and the PS hoses. You can use two sockets and a large C-clamp to push out the old rubber centers of the factory bushings, then use a BFH and a cold chisel to collapse the remaining metal donut rings of the old bushing. Once you've raised two edges of each ring, sometimes you can move things along by crushing the ring with channel lock pliers. Then just install the new ones and wrestle the rack back up into place.

Speedtoys

Ya..carls note says that the rack bolts are captive.


They...are not.

A 6mm allen head (the short side) can be used to wedge in 'tween the bolt flat face and the rack edge.

Carl Fausett

They are captive in the early crossmembers, 1978-1982.

They are not captive from 1983-1995.

We make two models of 3-piece crossmembers for this reason, and of course, the change from early to late motor mounts.

GregBBRD

The downside to a metal bushing is obvious...all of the chassis harmonics are going to be transfered into the rack and the rack wasn't designed to be mounted solid. The little "ears" that mount the rack are not designed for all that vibration and harmonics. I'd expect them to crack, over time. I'd also expect pre-mature seal wear, inside the rack, from all the harmonics.

There's a reason why Porsche mounted the rack in rubber and not in cast iron or aluminum. Note in applications where Porsche needed more support on pieces of aluminum, they did switch from rubber to Delrin....not to aluminum or cast iron....the front transmisison mount on the 993 models when used in high performance applications, is an excellent example.

The other obvious problem is that if you install a "push fit" metal bushing into another piece of metal (the rack) and it is not a proper "press fit", there is obviously going to be wear between those two surfaces....especially once any vibration is added. Two metal pieces with a loose fit are going to vibrate and wear the crap out of each other....pretty much a given. I'd guess that if we were to go and look at your (Rob Edward's) aluminum mounted rack, there would be a grey thick gummy powder around the junction between the rack and the mount. Obviously, the bushing can be re-replaced when it wears....not too sure what you do with a worn steering rack bushing hole. (Sounds like it might be time to start collecting steering racks, if people are going to ruin them.)

Again, using the transmission mount on the 993 as an example, aftermarket people decided that they could make mounts out of aluminum cheaper than buying the factory Delrin mounts and that making Delrin mounts was "too close" to what Porsche did. The result was aluminum slip fit bushings that wore the crap out of the transmisison and the mounts, ruining both. I've fixed many. The repair was easy. Expensive, but easy. Buy a new front transmisison nose section and put in the correct mount.

I've tried everyone's Delrin steering rack bushings. I'm not sure who copied whom, but all of the delrin bushings that I got all of the suppliers fit very poorly. The OD of the bushings was way too small and the hole for the bolt was also small. The result was Delrin bushings that "fell" into the bore of the rack, but then had a tough time getting over the bolts. Took two people and 4 hands to keep the darn things from falling out of the rack, when trying to install the hardware. Because they fit too loose in the steering rack, they wore like mad.

I simply correctly measured the bores and made bushings that actually fit....not a very novel concept. They do not wear....because they are not "flopping around" inside the hole. The Delrin front transmision mount in the 993 model is, again, the perfect example. This is a very high load position. The entire mass of the engine and transmission is handled by this mount under braking. Huge loads. The stock Delrin bushings work great, here...becasue they fit correctly, in the first place. I'm sure that if one were to machine a bushing that "fell" into the hole and wasn't the correct fit....the resulting slop would wear out that bushing, also.

It's all about precision. Aftermarket pieces have to be well thought out and then well engineered, if you are going to build a successful part. Improper fit or the improper material is going to "kill" parts.

928 International sells my design rack bushings. I've given a sample to Roger to look at and I'm going to send him an entire set to install in a car. Hopefully he will carry the correct fitting piece in the future.....

Rob, get those aluminum things out of your rack, before the rack is ruined. Stop by and I'll give you a set of bushings that fit and work. As you said, there are many choices for rack busings. Not all are good choices, but there are many of them.

Carl Fausett

Thanks for the offer of sending me a set of yours, but I have no need.

I do not make or sell Delrin steering rack bushings, and never have. The first ones I made for my own car for testing were Delrin (as I have posted before) and they wore out quickly, mirroring your comments above. They never made it to market.

The ones I manufacture and sell are made from 6061 aluminum, tapered to start the installation, and then a proper press fit (our instructions show you how to cover them with a socket and tap them into place with a hammer).

I have been thru 3 iterations now on this product over the years, and I have to say the design we are making now is the best we have ever had. The best fit, zero returns, zero complaints. I'm sticking with it.

GregBBRD

And there is a major portion of my brain which is thrilled that you are!

No point in everyone doing it the same way, right?

Time brings everything into better clarity.

What seems good today, might not be as good tomorrow.

I see that you mention that this is your third iteration......

ROG100

Hi Greg,
Interesting that we measured the OD of your bushing against ours and they are the same. I have sent it off to my machinist to have it double checked. I will let you know what they say.
In coming up with the measurements for the delrin/aluminium bushes we checked a number of steering racks from early to late and found that the tolerance on the mounting hole varied a lot. Probably why Porsche used a split bushing. We designed the bushes to be able to fit all rack iterations. Having fitted many sets myself and watched plenty more being fitted the fit was always tight but not always an interference fit because of the tolerance on the mounting holes. How you ensure one size fits all perfectly is a good question.
The single piece design was changed about two to three years ago for the much better two piece. This ensures no vertical movement of the rack and emulates the peened factory design.
Thanks for your kind hospitality.
Roger

GregBBRD

Roger:

Really enjoyed your visit. You are an amazing guy, with an amazing wife. Thanks so much for spending time with us.

I'm glad my bushing compares favorably with yours....could be I just got a couiple sets that were slightly off.

I am glad that you are using the proper material and are using the two piece design. Much better than other ways, in my humble mind.

I sent you a PM to further talk about this.