IRS rebuild

[rsb]

I am getting ready to rebuild the IRS suspension on my 74 super beetle. I have read the Bentley procedure and several other versions but I still have a few unanswered questions...

So you make alignment marks on the trailing arm and diagonal arm (where they meet) before taking it apart. How do you mark the torsion bar position relative to the chassis, and relative to the trailing arm? Do you need to?

When you are checking/ adjusting the spring plate angle, is it off of the lower stop?

Thanks,

Brian

[FJCamper]

Hi RSB,

Mark the IRS spring plate to diagonal arm positions, at two places, top and bottom, as the diag arm not only slides back for toe, but can be slightly lifted or depressed in relation to the spring plate for camber.

Take the four bolts out of the torsion bar cap cover, and go through the usual safety precautions as you pry the spring plate off the ledge and lower it.

With the spring plate down, your next mark is to either measure the droop with an angle finder, or physically etch the position relative to the body with a square ... again, at more than one spot.

Then, remove the torsion bar cover extension, and be advised the cover will probably try to pull the torsion bar out with it. I've know some mechanics to actually drill small holes in the cover before going through this operation and squirting in WD-40 or penetrating oil a day ahead of disassembly to make the cover removal easier. You can drill a hole in the center of the cover cap and stick a punch in it, and tap the torsion bar back in place as you remove the cover.

If you are lucky enough to wiggle and tap the cover off the torsion bar and did not move the bar, clean it and paint mark it's place. Precisely. No broad strokes.

If you do pull the torsion bar out of its inner splines, don't panic. You can cuss, but don't panic. When the cars were being built on the assembly line, they didn't take the time to futz around with fit-and-guess. They slipped in the bar without concern about spline counts, and fitted a spring plate over the exposed end of the bar with a jig to get the droop angle right.

When the spring plate was raised and slid into place on the ledge, it was right.

Just slide your bar back in and do the same (once the inner and outer bushings are replaced) by getting the droop angle correct.

Take a look at this thread, which is on a swing axle, but illustrates the droop angle very clearly.

http://www.shoptalkforums.com/viewtopic ... e#p1080473

FJC

[Ol'fogasaurus]

viewtopic.php?t=110857&postdays=0&postorder=asc&start=0 Two pages of posts on this URL. Some of it might help.

Lee

[rsb]

Thanks for the great info guys!

Measuring the droop angle definitely seems to be the way to go. That way if I pull the torsion bars to inspect for rust I can slide everything back together at something close to the correct angle and adjust as necessary by rotating the splines. Luckily I have a magnetic protractor from when I rebuilt the front suspension and steering.

Any tips on how to remove and install a diagonal arm bushing? It sounds complicated and calls for tools I don't have.

Time to start tearing into this project, I'll keep you guys posted.

-Brian

[Ol'fogasaurus]

Don't forget to put a drop of lube on the splines.

As far as the bushing goes and I have been looking into it recently myself and I was told that it is pressed in and out job; I can’t guarantee it but that is what I have been told. I did cut one out and it is a most of lunch period project. I forget just how long but it did take a while.

Lee

[FJCamper]

Hi RSB,

If you don't have a press, take the diagonal arms to a shop that does, and have them press out the old bushings and press in the new ones.

For street use, the stock rubber with steel center bolt guide is enough. The fancy racing urethane ones are more precise in pivot and geometry, but can squeak.

Getting the big bolt out of the bushing can be a bear if the bolt has rusted inside the steel guide tube. A rusty bolt and disentergrating rubber bushing kept me busy once for a couple of days. Use penetrating oil.

FJC

[rsb]

Looks like I'll be taking the diagonal arms to a shop to get the bushing changed. I think they wanted $500 to completely rebuild both arms, but they have been very reasonable with misc. press work in the past. I am planning to redo the rear bearings myself while I have everything torn apart. Is it better to tackle the bearings on the car, or take the diagonal arms off and do them in a vise like Bentley shows?

When rebuilding the trailing arm / torsion bar assembly is it best to do one side completely before tearing apart the other side? It seems that it would be easier to match the droop angle on the two sides while they are both off the stops and can be measured.

I am working on collecting my miscellaneous hardware before I take the trailing arms apart. I picked up 5' of 1/4" chain. I couldn't find a tall headed bolt for the body mount (M10 x 1.5 (30mm)), so I bought a 40mm and added a nut. I also got oversize bolts for the torsion bar covers they are M10 X 1.5, measured them on the car it looked about an inch long, something like 25mm. I picked up a pair of 30mm and 40mm to find a size that will work. My car has the single spring plate, so you guys with apx. 68' - 71' double spring plates would have a different length.

http://www.shoptalkforums.com/viewtopic ... 1&t=135466

[rsb]

So I have got the spring plate angles adjusted where I want them, new polyurethane bushings installed in the torsion bar housing, new polyurethane diagonal arm bushings installed as well. In the drivers side everything is fitting back together pretty good. Passenger side is a different case... the spring plate and mounting flange on the diagonal arm are not parallel.



I am wondering if this is normal and it just needs to work in a little, or if this is a problem? Anyone else ever see this sort of thing? Someone else had had this side apart at some point, and left one of the big ol' washers out when they reattached the diagonal arm to the chassis. Hopefully I don't have something bent.

[Steve Arndt]

I changed IRS pivot bushings with basic hand tools. I do have a press, but it wasn't necessary to use it. A hammer and drift/punch was all that I needed to drive each bushing half out.

[Ol'fogasaurus]

I had to cut the one I had into several sections in order to get it out. They can be stinkers if/when they want to.