Rear Torsion tube Bushing replacement

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Heidi Frances
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Rear Torsion tube Bushing replacement

#1 Post by Heidi Frances »

Hi All,

This weekend had Eva (our '58 Cab) in stirrups for rear torsion tube rubber bushing replacements. I ordered the bushings from Stoddards and they look like they are good quality rubber. The bushings are conical meaning one end is larger diameter than the other. The bushing cups are likewise conical so it was easy to figure out how they go in. This is a photo before I started. You can see the rust where the tube has been riding up on the upper flange opening.

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I started by jacking up the car on both sided to get the rear up and level. The big issue here is to get the swing arms back on at the same angle when the whole assembly is un-sprung. After the wheels are off, the next thing to remove is the shock – only the bottom attachment need be removed. This will allow the axle to drop a bit further. This is where you want to throw on an angle meter and read the drooped angle of the swing plate. For me, it was 10deg. The actual number isn’t important just that you end up with the same angle when it all goes back together.

From here, just remove the three bolts holding the axle to the swing arm plate. I found it best to start at the rear and work forward. You will actually see four bolts, but the most forward one is actually an alignment stop. It has a big thick washer that should be riding up against the axle flange. It will be important on the reassembly to get the washer in the same place verifying the rear wheel alignment. Something to note about the swing bar and the axle flange it mounts to: they won’t be co-planer. As you remove the bolts attaching the two, the plate will start to twist relative to the axle flange. I had to think about this a bit, but the swing arm has to be rigid the vertical bending to carry the torsional force to the torque rod, but it also has to allow for the wheel to ride up and down on an arc so it has to bend horizontally and also twist a bit. This is important because as the attachment bolts start to loosen up, the plate will start to twist. If you start with the rear bolts, the separation isn’t as bad because the front bolt is still holding the plate a bit. With the rears off remove the bolt forward of the axle. The rubber extension stop is on a mounting plate that attaches to the bolts on each side of the axle. Just remember to put it back on when you finish. Just ask me why I know to mention this ;)

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Now remove the four bolts holding on the torsion tube cover plate. Be really careful here because they will be super rusty and breaking one off would be a big bummer. I have been emailing back and forth with Bruce Baker and he warned me that they will be trashed. I used several sprays of WD-40 to help lubricate them to get them off in one piece. Luckily for me they all came out with out incident, but they were a mess. It took a little lovin’ from the wire brush wheel to clean them up. The cover plate comes off easy enough and you get your first look at the old bushings. Originally they were assembled with graphite and mine had clumps of silver smutz all over them and the steel cover. Also, since the torsion tubes had been riding up on the cover plate opening, there was a gap of the rubber in the cup at the bottom letting in moisture. The bottom inside of the cup were also pretty rusted. I got those as clean and smooth as I could so the new rubber bushings wouldn’t be damaged.

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It seems like a simple thing from here to pull the plate out and off the torsion bar. Simple, but not easy… You see, the problem is that the big swing arm plate has to pull out like 8” or more and it collides with the axle mounts. The best thing to do to get it off is to use a strap to pull the axle rearward (hook to the bumper mount NOT the fender support!) and then move the axle upward to get the swing arm plate on the outside of the axle mount flange. It has to be outside or you can’t pull the torsion tube off the torsion bar splines. Here is where I had a bear of a time. The first one took me over an hour to get off but the second one only about 15min. It is tricky, but you can pull the plate and tube out while working the swing arm plate past the axle flange. The big problem is that the torsion rod will most likely pull out of the inner spline (center of the car) before it pulls out of the swing arm plate. If it gets off a spline notch, you will not be able to get your angle back and the car won’t sit straight. I have a sneaky suspicion that the splines on the inside are different than the ones on the outside of the torsion bar. That would allow for much finer adjustment without cutting finer splines. Anyway, if it does pull out of the center first, just be sure to get it back exactly how it came out. It should be all covered with grease to keep it from rusting and so you can pull the swing plate off the spline. Any of this make sense? One trick was to get the plate free of the torsion bar splines and then spin it upward to get it past the brake drum.

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After a bit of work you can get that swing plate out and the torsion bar in the torsion tube in the car oriented exactly how it was. Go ahead and throw a little grease on the end to make of the torsion rod splines to make it easy to re-assemble. With the swing arm off, clean it a bit because you will have to slip the new outer bushing covered with grease over the tube. Take a look at the inner bushing cup at the base of the torsion tube in the car and look for the same rust in the cup as on the outer plate. Clean that up as best you can and try to get it a bit smooth. For bushing grease I used silicone grease that I found at the local hardware store in the plumbing section. Bruce mentioned it and I think it will out live the graphite. First I lathered up the inner bushing and placed it in the inner cup on the car. Now the swing plate is ready to be reinstalled. Here we go again… the plate will start out outside the axle flange and then have to move to the other side as the plate moves into the torsion bar splines. It is super important that you get that same angle you measured when you started. I found that the only way to get it on the inside of the flange and at the correct angle was to pull the axle rearward and up as high as you can get it and the swing arm will just clear it of you rotate the axle CCW a bit.

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Once the swing plate is at the correct angle and on the inner side of the flange, add the trapezoidal torsion bar cover plate, sliding the gooey new rubber bushing over the torsion tube and then add and the four bolts. Mine has a washer on the bolt and also a washer between the cover and bosses the bolts screw into. I lubed up the bolts to help discourage rust and ran them in hand tight. Then I worked on the big 19mm bolts that hold the swing arm plate to the axle. I found the if you do the one forward of the axle first it is a lot easier to do the rear ward ones. Don’t forget the rubber stop! Also be careful that the flange rides up to the washer under the bolt you didn’t take off on the swing plate. That will insure alignment didn’t change. Make a final angle reading on the swing arm and then finally tighten the four cover plate bolts.

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After that, all that remained was re-attaching the shock bottom. I took a moment to adjust my shocks and also replace the heater tube, which I had damaged. Now is the time to take photos and look around in there. You can see lots and lots with the wheel off.

That is about it. The difference in the ride was amazing! Totally worth the hard work. If your torsion tubes are riding on the top of the flange opening and even a little rusty, you might want to look into replacing them. You’ll be so happy you did!

Franny

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Vic Skirmants
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#2 Post by Vic Skirmants »

Franny,
Great write-up! Sounded like you've been doing this your whole life.

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John Clarke
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Bushes

#3 Post by John Clarke »

Hi Franny,

As Vic says a Very Good Write Up, I shall Use This, Many Thanks.
This is one of those many Outstanding Jobs for the Winter Months!
We have the Heavy Duty Harder Shore Rubber Bushes from Mike Smith's PR Services here in the U.K. Should really Notice the Difference when Fitted.

Cheers

Jay

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Heidi Frances
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#4 Post by Heidi Frances »

Thanks guys,

Glad you enjoyed the read. I had lots of help from Bruce - several emails before I started. He is excellent about pointing out those little details that help make a project successful.

I enjoy working on the car so much, I kind of wish I had been doing it all my life ;)

Franny

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#5 Post by David Nicholls »

Franny.
That's a great story.
Dont forget to do a rear wheel camber check, after all the hard stuff is done.
The aim is to get the camber within specs, after the torsion bar and trailing arm adjustments, as per The Spec Book.
Regards,
David

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Tom McCoy
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#6 Post by Tom McCoy »

I suggest this good writeup should be posted on the Tech Section.
Great job!
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Mike Horton
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#7 Post by Mike Horton »

Excellent job, Franny, and now that you have grease under those finger nails, I'll warn you, it is addictive, and very rewarding. Bruce's tip on the Silicone Dielectric grease is key to the success here, as I have tried it with the graphite, and glycerin, called out in some manuals, and it is much more difficult. In aviation, we always used Moly grease on splines, to prevent wear, and in this case, any rust. I also marked a reference line on the car, from the angle of the spring plate, after it was off the lower stop, as a "return to original" reference for the torsion bar re-installation. Most of us do these one at a time, but know, those torsion bars are directional, and should stay on the side they were on. You are correct in that there are a different number of splines on the inner end from the outer end, to allow for fine adjustments. Thanks for taking the time to do the write up, and sharing it with us all. Again, congratulations on both the acquisition of your car, and a job very well done.
Mike (TX) :D

Alan Close
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Re: Rear Torsion tube Bushing replacement

#8 Post by Alan Close »

I have the torque value for the attachment to the axle but cannot find ths same fpr the bushong cover plate.

A C

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Martin Benade
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Re: Rear Torsion tube Bushing replacement

#9 Post by Martin Benade »

Very nice writeup. I'll add one useful general tip that I did not believe for years- "Blaster" is far superior to WD-40 for rusty bolts. It can make quite a difference.
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Tim Herman
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#10 Post by Tim Herman »

Tom McCoy wrote:I suggest this good writeup should be posted on the Tech Section.
Great job!

I will vote with Tom. Good job Franny and we need more like these
Tim Herman #2197
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Jorge Avila
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Squeaky front end on a 1964 356C

#11 Post by Jorge Avila »

Dear Franny, how about the front end squeaks on my C. I've replaced all the bushings on the anti sway bar. New shocks ( they weren't that old, but the car sat for 15 years). It still squeaks, any ideas? The noise is driving me nuts, lol. Thank you, Jorge

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Jim Clement
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Re: Rear Torsion tube Bushing replacement

#12 Post by Jim Clement »

I did mine a few years ago.. and darn, dispite many many blasts with different products, two of the bolts on the one side broke off, captured in the frame.. I had to get a guy to do the weld a nut on it from the inside with a lot of heat..then the finally came out buy that time I had the whole car apart.. so puting it bak together was easier when doing it in the easier sequence.

I also very much like the write up, with great pictues to see the steps in progress..
 

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Harlan Halsey
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Re: Rear Torsion tube Bushing replacement

#13 Post by Harlan Halsey »

Heidi, I have enjoyed your adventures for quite a while now. Thank you.
That job is one I would rather tackle with the car on a chassis lift. I might add that a vice grip pliers is an aid to clamping the spring plate to the axel casting so that you can more easily get the bolts out, and back in. Marking the chassis at the angle of the spring plate is a help to getting it back together. The workshop manual goes into some detail on adjusting the angle to spec, and to changing the camber angle if that is desired. Ideally you want to get the spring plate off the torsion bar without the bar coming out of the car. Rocking the plate while pulling back facilitates that. Kroil or some other penetrating oil usually works better than WD40 on rusty bolts. I use one of the versions of Never-Seize as assembly lube on Chassis bolts. There are several versions of the bushings out there, and not all of them will fit. I had to reject several last time I did this job so fitting the bushings to the spring plate and cover first can save a bit of frustration.
The spring plate torsion bar tube starts out in the middle of the opening in the cover plate with new bushings. Over several years the bushings allow the bar tube to move closer and closer to the metal cover. I usually think it is time to change the bushings when the clearance has been reduced to about 1/16". But I have seen a situation where the cover had worn a deep groove in the top of the tube due to lack of attention.
I look forward to your next project.

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Re: Rear Torsion tube Bushing replacement

#14 Post by Al Zim »

Mechanical areas that have not been addressed: A) Even if you VERY carefully mark the location of the axle to the trailing arm it will not be correct. In this case 52 years of driving will wear (move) things out. B) we have found that when the car sits with the suspension unloaded it will need to be driven for 50 or so miles for the suspension to return to a MORE NORMAL position. This will allow the first attempt at alignment. Now you are on another 30 to 50 mile drive to settle the car since the suspension is closer to factory settings. NOT THER YET! One more alignment and you should be there. C) Our experience indicates that you cannot align a car by using sting or wire. Take your new car in to align the cameras (This protects you from crashes) and you will see that it is ALL done electronically.
While you are fixing the rear take your grease gun and lubricate one side of the torsion bar the grease that comes out will be rust brown colored. This means the front end has not been greased at correct intervals. The grease is there to lubricate the the bearings. As it is pushed through the bearings it removes the grit that has accumulated. If you decide to complete your suspension restoration. You will have to remove the trailing arms and spindles, Take them to a shop that has the Porsche tool P69 and VW tools 256A and 259. Pictures of these tools are shown in the shop manual. If you are purchasing front trailing arms and spindle assemblies have them checked on the factory tools. A good bump into the curb will bend a trailing arm...most 356 Porsche's have bumped the curb.
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Re: Rear Torsion tube Bushing replacement

#15 Post by Brad Ripley »

Above, Jay mentions he installed the harder durometer bushings from PR Services. On Jay's car that would be the earlier completely round bushings, inner and outer. However, PR Services does not offer a harder bushing (the one with ribs on the OD) for later cars. But PR does offer a red Polyurethane version with the ribs. Does anyone have experience with such red ones? Or, are they for race cars, etc ?

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