Pelican Parts Forums - Time to replace 30 year old suspension

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- - Time to replace 30 year old suspension - little help please? (http://forums.pelicanparts.com/porsche-911-technical-forum/324765-time-replace-30-year-old-suspension-little-help-please.html)

[QUOTE=randywebb;3115073]Pål - Without the rubber between the steering wheel and the road, every bump is going to be transmitted to your hands. You will fatigue quickly. If you want as much feel as you can possibly get, you don't want any absorption and you will be racing the car. If you want to run in an endurance race, then you will have some compromise such as Porsche used on their race cars. If you want a street car - as he does - then you will want to be further out on that spectrum - a bit more absorption by having some rubber in the suspension.

QUOTE]

Randy, I wouldn't normally disagree with the wisdom and knowledge you contribute on this board, but I think you are massively overstating the increase in harshness from monoball top mounts. If there is any increase at all, it is tiny IMHO. There are a whole lot of us in the UK who have in the last couple of years gone to ER P-B bushes, monoball top mounts and turbo tie rods and we are unanimous that it is a great improvement - for the road as well as the track and I am pretty sure our roads are worse than the US. The top mounts take friction/stiction out of the steering to an extent that none of us imagined giving a lighter steering feel. The harshness you talk about would be primarily transmitted thru the tie-rods to the rack and steering not thru the suspension mounts and I have yet to hear anyone suggest that turbo tie rods are unsuitable for road cars.

We don't drive as far as you guys do in the US but I am yet to feel the fatigue you talk about.

RB

[Note: This post was too long (sorry), so I had to split it into three parts. Please continue to the next posts for pictures referred to in this post]

While I was waiting on the arrival of some parts to finish a few sub-projects on the front half of the car (non-A/C ventilation, battery relo, fuel lines), I decided to resume some actual suspension related work on the back half. Besides, I needed to get the back up on jacks to get to the fuel and brake lines for that sub-project.

The first challenge was actually just getting the back half of the car up in the air. I thought this may be a problem and was prepared. Consider the fact that the front of the car is basically nothing but a shell at this point with the following removed:

- Suspension (Wheels, control arms, struts, belly pan, etc.)
- Crossmember
- Steering rack
- Calipers
- Battery
- Spare Tire
- Gas tank
- Fuel pump

So, given that the engine & transmission are still in the car, there is now a HUGE weight bias in the back. I lifted the rear of the car from the engine mounting crossmember and placed jack stands at the aft-most spot shown in the jacking points diagram. I lowered the car until it just touched the rear stands and checked everything - which looked good. I then continued to lower the back VERY slowly, and quickly realized that the rear end just kept going down. I stopped and checked up front - sure enough, the front was lifting off the front stands. I jacked the car back up, and removed the rear wheels to reduce some of the weight. Believe it or not, that was enough to stop the front from lifting off the front stands. I left the jack in place about an inch below the engine and went up front to see how much weight was holding it down. I could actually lift the front of the car with one hand - not good. So I put the car back up and moved the rear jack stands to the torsion tube. Even though it was only a few inches further back, I could no longer lift the front of the car at all. I decided to proceed but to leave the floor jack in place under the engine as a safe-guard until I removed more weight from the back. Hmmm, jacking the back half was supposed to be the easy part - hopefully the rest will go smoother. Actually I’m probably lucky because if I had put the car up on 4 stands at the beginning of the project with the rear stands ahead of the torsion tube, it could have been ugly when I removed that one item up front which finally upset the balance :eek:.

Next came removal of the spring plates. After all the reading I've done on this, it seems there are basically two different methods being used. I discovered that, at least in my case, while both will work, the second method described below (which requires one extra step) is better than the first. I used a different method on each side and will show the difference.

Both methods, of course, require that you remove the torsion bar access cover in the quarter panel. I won’t go into details here, but for 74+ cars, you need to remove the lower rocker panel first to access the cover (remove end caps, peel out rubber strip, remove screws top & bottom). It’s probably best to do this first after the car is up, and get it out of the way.

Method 1 (not preferred)

0. Detach/remove rear sway bar by unbolting bracket(s) (photo #0).

1. Since even in their fully extended position, the rear shocks are still under load from the torsion bar, you must relax the load on the shock to remove the large bolt at the bottom of the shock where it attaches to the trailing arm (photo #1). If the car is still resting on the rear wheels, you can simply remove the rear bolt before raising the car. Otherwise, place a floor jack under the trailing arm (not on the bottom of the shock) and raise the trailing arm just slightly – enough to transfer the force pushing down on the trailing arm from the shock to the jack – about a cm or two should do.

2. Remove the bolt at the bottom of the shock. This bolt took quite a bit of force to break loose with a breaker bar and extension (a concern with the weight balance issue) – an impact wrench may be a better option. Once the bolt broke free, I could back it out with my fingers and looked like new after it came out. Note: if the bolt is not backing out easily, there is probably still a load on the shock – stop.

3. Remove the lower spring plate cover bolt and spacer (photo #2). Some instructions say to remove all 4 cover bolts at this point – I didn’t like this idea as the spring plate is still under considerable load from the torsion bar. Note that only the bottom cover bolt has a removable spacer behind it (you’ll see why in a minute). On the other three cover bolts, the spacer is welded to the chassis as a boss.

3. Lower the jack and let the trailing arm all the way down. None of the info I read mentioned this, but I discovered that even with the shock disconnected and the bottom cover spacer removed, the trailing arm was still under load from the torsion bar when lowered down without support. The only thing I could think that would prevent the trailing arm from lowering further would be the sway bar – that is its job after all since the other arm was higher. I didn’t want to unbolt the sway bar under load, so moved to the other side and removed the on that side shock bolt as well to get the two arms at nearly the same height. Unbolting the sway bar as the first step may be better so I inserted this as Step 0.

4. If not done above, detach or remove the rear sway bar. Since I am replacing the sway bar anyway, I simply removed it. This did allow the trailing arm to drop a little further, and it was now bottoming out on the bracket where it attaches to the torsion tube. I thought I was good at this point and all load on the trailing arm from the torsion bar had been removed (maybe this would be the case with a lowered car, but I discovered that on my US spec height car this was not true – read on).

5. Remove the two main bolts holding the spring plate to the trailing arm, and the two alignment bolts (photo #3). Note that you may want to trace the position of the spring plate against the trailing arm before you unbolt it to help with alignment when reassembling. It was at this point I discovered that the trailing arm was still under a small load, as when I removed the last bolt, the spring plate shot down about 5mm – if you notice tension on the bolts – stop. This is why I do not recommend this method.

At this point the two methods converge. Skip to step 8 of Method 2 below (next post).

[Post 2 of 3 - too many images to fit in this post - images continued on next post]

Method 2 (preferred).

0. Same as Method 1/Step 0 above

1. Same as Method 1/Step 1 above

2. Same as Method 1/Step 2 above

3. Lower the jack and let the trailing arm rest on the bottom bolt spacer of the spring plate cover (photo #4). This now transfers the torsion bar load to the spacer, thus removing the load on the trailing arm completely.

4. Place a jack under the trailing arm again and raise it until it just touches the trailing arm (don’t raise the TA). The goal here is to support the trailing arm so that when it is separated from the spring plate it won’t put stress on the fasteners and then fall.

5. Remove the 4 bolts holding the spring plate to the trailing arm as in step 5 in Method 1. Once unbolted, the spring plate will move away a bit from the trailing arm (which is good for the next step). Lower the jack supporting the trailing arm. Photo #5 shows how far the spring plate separates from the trailing arm.

6. This next step is a bit tricky. The goal is to now remove the load from the lower spring plate cover bolt so that the cover can be removed. To do this, place a jack under the spring plate itself near the end (photo #6). The reason I say it is tricky is because the spring plate is only about a cm away from the trailing arm at this point, and it is also on an angle. You may have better luck jacking from the middle of the spring plate. Either way, lift the spring plate just until you see it rise off the cover bolt spacer.

7. Remove the bottom spring plate cover bottom bolt and spacer (Photo #2) and lower the jack completely. All the load is now finally off the spring plate. You can see how much further the spring plate comes down in the picture below (photo #7) shot through the torsion bar access cover hole. Again, this will differ based on ride height settings.

8. Using an angle finder tool, measure the angle of the spring plate at rest which you will need to set your ride height later (photo #8).

9. Remove the three remaining spring plate cover bolts.

10. Remove the spring plate cover. Some people posted problems removing the cover. I guess I was lucky and mine slipped right off. Btw, I should mention what started me on this whole adventure was the spring plate bushings being so worn/compressed that the spring plate torsion bar tubes were hitting at the top of the hole in the spring plate covers, making a racket over every bump.

11. Now comes the fun part – removing the spring plate from the chassis and torsion bar. At first I thought my spring plate was frozen to the torsion bar, and the torsion bar was also frozen to the torsion tube because I could not get the spring plate to budge. It turns out it was not the torsion bar at all that was keeping it in, but the rubber bushing pressed into the chassis, so spray plenty of lubricant or Blaster around the bushing first. I then found the following technique which worked beautifully on both sides to remove the spring plates with little effort. Using a pry bar pivoting on top cover boss, pry with constant outward pressure on the top of the spring plate. While applying pressure with one hand, simply tap up on the bottom of the spring plate at the end of the tube using a hammer with your other hand (a rubber mallet also works). In my case, each hit caused the spring plate to move outward about 1mm. This is hard to explain, but see photo #9 for what I mean.

12. If you’re lucky (as I was both times), the spring plate will come off and the torsion bar will stay seated in the car (photo #10). If you’re not so lucky and the torsion bar comes out still attached to the spring plate, then you have some more work ahead of you. Search on Pelican and you can find many threads devoted to resolving this issue, but first you may want to drill a hole in the end of the spring plate end cap and squirt some Blaster in there to break things up.

13. I was very lucky and the inside of the torsion tubes were rust free and the torsion bars look like new (over 30 years old!). Even still, I had to use generous amounts of Blaster and wiggling over several days to get the first bar out. Once the first bar was out, getting the second one out was easy. Find a bar smaller in diameter than the inboard end of the rear torsion bar, and use it to hammer the bar out from the other side. For me, the perfect bar for this job was one of the front torsion bars - these bars were going in the trash anyway. It only took a few hits and the second bar easily broke free. Whew – I read so many horror threads about rear torsion bar removal, I was dreading this part.

That’s it for now. Take a look at photo #11 – I think it’s safe to say this bushing is shot! Next I move on to the trailing arm monoballs – but I decided to take a little detour along the way and drop the motor to make things a little easier.

Frank

Photo #0
http://forums.pelicanparts.com/uploa...1201066043.jpg

Photo #1
http://forums.pelicanparts.com/uploa...1201065490.jpg

Photo #2
http://forums.pelicanparts.com/uploa...1201065732.jpg

Photo #3
http://forums.pelicanparts.com/uploa...1201066143.jpg

Photo #4
http://forums.pelicanparts.com/uploa...1201066469.jpg

Photo #5
http://forums.pelicanparts.com/uploa...1201066640.jpg

Photo #6
http://forums.pelicanparts.com/uploa...1201066701.jpg

Photo #7
http://forums.pelicanparts.com/uploa...1201066823.jpg

Randy,

The only rubber/plastic in my suspension, front and rear is the tires.(17 inch 40/45 series) This includes the lack of the rubber isolater between the steering shaft and the steering rack. (mine has a special U-joint instead) Depsite the theory, there is next to no vibration or extra fatigue passed to the driver because of it.

This is on a complete monoball mounted, heim jointed suspension and steering.

Now the noise from the motor is another story when it comes to inducing fatigue... :)

Cheers

Thanks to both of you for those observations. Individuals do differ in their sensitivity to NVH - some of it is age (I'm 55 now) and some may be gender related, plus road surface conditions.

I've driven "tight street" (22/28 torsion bars) and nearly stock cars side by side to test them on some of our windy & bumpy roads nearby. Neither had metal joints (monoballs or purely metal Heims). I drove them back to back and it takes only about 7 minutes to get to that road from my house. I found that the softer suspended car was not only more comfy, it was also _faster_ on this road. My leased Boxster S was much much faster than either.

So the above is my basic comparison I use when thinking about what I want to do on my suspension. I don't race or even do DE's anymore.

Nice photo's and discussion, will use as reference when I attend to my suspension this spring.

Very nice work, thank you for the great write up. I need to go through my suspension in the up coming months.

Quote:

Originally Posted by RWebb (Post 3722225)

Thanks to both of you for those observations. Individuals do differ in their sensitivity to NVH - some of it is age (I'm 55 now) and some may be gender related, plus road surface conditions.

..... I found that the softer suspended car was not only more comfy, it was also _faster_ on this road. My leased Boxster S was much much faster than either.

Randy,

Great observation. I tend to think that a more compliant (read soft) suspension is better on "real world roads". If the road is like a race track (i.e. smooth), the suspension does not need to soak up hte bumps, just ensure tire contact. After all, if the suspension does not soak up the bumps, the people in the car do. If you are not being bumped about, you can put your effort into being sure you are getting to where you need to be.

Stuff to read up on.

an update on how this all worked out would be great...

Thx, Bob

Believe me, I would love to provide an update on this project, but as I stated in my last post I took a little detour once I dropped the motor and decided to replace all brake and fuel lines, do some painting, and basically unbolt everything from the bottom of the chassis and refresh/replace it. Classic "while you're in there" syndrome. Oh, and retrofit an non-A/C ventilation system, convert the ignition over to an Electromotive setup as well.

Unfortunately, progress on these side tasks has been slow. Around the time of my last post, things at work really started getting busy (I work on wireless 4G LTE radios), so I did not have a lot of weekend time for my hobbies. Now that the first gen of LTE is deployed, things are a little more sane at work, but I have Ironman Canada coming up in August, so I am going be short on weekend time up until then (not to mention the normal family stuff, Lacrosse coaching, etc.). I know, I have too many hobbies.

Anyway, I hope to get the fenders back on the car in the next few weeks, and finish up some paint work after that so I can actually start putting this car back together. My kids forgot what it looks like :).

[wow - I just looked and it's been 4 years since my last post on this thread. That is scary. I guess I need to change '30 year old' in the title to '35 year old' :(]

Get it on the road already!

I am in the process of rebuilding the front suspension of my 69T. I am installing Koni's with SC calipers. Well scope creep got the best of me, all new bushings, turbo tie rods, ball joints etc.

I was stuck on a few items and found this thread. Thank you for the excellent write up. All of my questions were answered here.

Finally, an update!

After Ironman Canada I was able to resume work on the 911 project in earnest starting in September. I had many boxes of parts that I removed from the car since I started the suspension and various side projects, and I wanted to have them all re-plated. Unfortunately, the plating shop I used several years ago now only accepts commercial jobs. It took me a while, but I finally found a shop that would take the parts about 45 minutes away, but it's conveniently just down the street from the restoration shop that is working on my fenders. The down side is that they fit these types of jobs in when they can, between their commercial jobs - so no guarantee on when they will be ready (usually 2-3 weeks). Fortunately, the owner is a "car guy", so he enjoys doing this for people like me.

I also wanted to have the zinc plated parts clear powder coated afterwards, and the powder coat shop is 45 minutes in a different direction. The powder coating shop also does media/soda blasting. So the process was; take the parts to be blasted (1 to 2 weeks), take the parts to be plated (2-3 weeks), take the parts back to be powder coated (1-2 weeks). Once you throw the holidays in there, and some re-work at the plating shop, it took several months to get all this work completed, but I just recieved most of it back yesterday.

With parts finally in hand, this weekend I began the "downhill" side of this project by re-assembling the trailing arms (TAs). FYI, I decided to pick up a used set of 78+ style trailing arms with the boss instead of the ball for the sway bar mount, since I also picked up an OEM '87 rear sway bar (thicker). The used arms came with hubs, but no parking brake components or stub axles. I removed the stub axles from my old arms, and was able to find used parking brake pieces on Pelican for a good price, so I decided to leave the parking brakes intact on my old arms, thinking they may be easier to sell that way (plus I was able to use the old arms as a reference when installing the parking brake parts on the new arms).

Like everything else, the TA parts were re-plated and/or powder coated. And, of course, I had to install new rear wheel bearings in the "new" TAs after removing the hubs (I'm pretty sure they were shot anyway).

Tomorrow I'll work on getting the pedal cluster back together, and maybe the steering rack.

The long pole now is going to be getting the paint work done on the chassis. I want to have the area under the fenders, under the quarter panels, and the engine compartment painted. Unfortunately the restoration shop cannot take on this work for 3-4 months. And then there are the logistics of getting a non-roller to the shop. My options are:

1) Paint these areas myself. This was my original plan, but once I started looking into everything I would need to purchase to do this, I decided to just let a pro do it. But I really don't want to wait another 3-4 months (I'm targeting an event in early May to have the car ready).

2) Build a dolly and flat-bed the chassis to the body shop when they are ready

3) Attach front & rear suspension to car to make it a "roller", and then flat-bet to body shop. Upon arrival, remove suspension pieces to allow the underside to be painted.

I have not provided details of the trailing arm re-assembly here because that work is already covered in the many rear wheel bearing threads here on Pelican (which are what got me through it).

Here are some pictures of the finished TAs. I still need to install the monoballs (which I will document) before the TAs are ready to install in the car.

Left trailing arm with hub and stub axle ready to be installed
http://forums.pelicanparts.com/uploa...1358747792.jpg

Right trailing arm - old vs. "new"
http://forums.pelicanparts.com/uploa...1358747829.jpg

Oh, one thing I forgot to mention is that I was thrown another curve on this project back in December. Since I had the engine and transmission out and separated, and I was waiting on parts being plated, I decided to replace all the gearbox seals (fortunately). When I removed the right output flange seal, I discovered that the seal had failed and allowed moisture to enter and damage the differential carrier bearing.

This kicked off a whole new saga (and thread), and I am now fabricating a tool to measure the ring gear backlash so I know if replacing the bearings cause the backlash and/or preload to be out-of-spec. If so, then the gearbox is off to the mechanic to have the backlash/preload dialed in - something I don't have the tools or skill to do. Sigh.

Here's the thread if you are interested:

http://forums.pelicanparts.com/porsche-911-technical-forum/721155-differential-carrier-bearing-race-corrosion-replace.html