The Rear Suspension

VW rear suspensions sometimes sag as the car ages, especially if it has carried a few large loads. Rob's 1970 1500cc Beetle has carried more than it's fair share of loads (perhaps even overloaded a few times!). Rob reports that he has only had to adjust the rear suspension in this car twice in the 29 years he's owned it.

This procedure is written for a swing axle model, but the principle is the same for the IRS - double joint - rear axle, there is just a bit more hardware to remove/install.

In this article, the word "rear" means rear-of-car. "Front" means front-of-car.

Description of Parts:

• Torsion bars - Round bars which twist under load providing the "spring" for your suspension. Mounted crosswise and horizontal forward of the axles, just under the back seat area of the floor pan.
• Cover plates - These cover the outer ends of the torsion bars, and hold the torsion bars in place using large rubber bushings.
• Spring plates - These large flat spring steel plates connect the axles to the torsion bars. On the newer IRS models, these plates simply move up and down, but on the older swing axle models, the swinging motion makes the spring plate twist as they work up and down.
• Axle assembly - This is where the spring plates bolt to the axle, and they also hold the brake assembly in place.

You'll need a good trolley jack (this job can be done with a hydraulic bottle jack or screw jack, but it will take more time), axle stands (preferrably 4 of them for front and rear), box wrenches (ring spanners), a file or cold chisel, two extra large screw drivers or a set of tyre levers, and a lazy afternoon.

Raise the whole car off the ground (measurements are easier with the car level, and you need some working room under the rear). Make sure it's well supported - you need to do some pushing and pulling at the back. Axle stands under the front and rear torsion bar tubes work best.

Procedure:

1. Remove the rear road wheels.
2. Examine the spring plate ends where they meet the fitting on the axle end. The spring plates have elongated holes so you can set the rear suspension toe-in. You might even find an alignment mark on top of the axle fitting (mine has one). Make a mark across the axle fitting and top of spring plate so you can line it all up again on re-assembly. If you use a cold chisel or a file you'll have a permanent mark, for next time (in about 10 years) when you have to do it again!
3. Check to see if your car has had adjustable spring plates (after-market item) fitted. These have an adjusting bolt and an 'additional' short plate nearer the torsion bar end of the spring plate - front of car end). If you don't have these additional fittings, you have the original non-adjustable type, which must be rotated. (No garrantee the adjustable type would give you enough adjustment anyway, it's really a 'trimming' device to even up the two sides).
4. Remove the three bolts holding the spring plate to the axle assembly. These are large bolts and have a lot of torque on them, and not a lot of room around the bolt heads. You need good box wrenches (ring spanners), rather than the open-end type, or you risk rounding the bolt heads. The spring plate is 'twisted' as the suspension moves through an arc (swing axle models), so you'll see it 'untwist' as you undo these bolts. This keeps the bolts under some tension - they don't just come loose and spin off. There is probably a rubber bump-stop attached to one of these too - take note of how it's mounted so it can be replaced the same way. 67-70 manual transmission swing axle models also have an anti sway bar linkage attached to the axle with these bolts too - remove this mounting. You should then be able to manouver the whole axle towards the rear of the car, free of the spring plate, without loosening any of the brake lines etc. You might need to tie it back clear of the spring plate. If it won't move back far enough, you may have to loosen the hand-brake cables. Do this from inside the car - pull up the rubber boot over the hand brake, and remove the horizontal balance bar between the two cables. Now the axles can be pulled back and the cables will pull out of their sheaths slightly as they follow the axle.
5. Now look at the front of the spring plate. There is a cover plate with four bolts. Remove these, and pull off the cover. There is a large rubber bushing underneath, and you should now be able to see the splined outer end of the torsion bar.
6. Now comes the interesting part. The spring plate is still under considerable tension, and will be sitting on a stop-lip - a lip just to the rear of the torsion bar. If you try to lever the spring plate outwards it will fly downwards with a big thump (breaking any arm or leg in it's way), so it's better to ease it down. Place the trolley jack (or a bottle jack will do) under the axle end of the spring plate and jack up the spring plate just enough so it is just free of the stop-lip.
7. Now carefully lever the spring plate outwards about 1/2 inch, using very large screw drivers or tyre levers top and bottom, working at the torsion bar end. Once clear of the stop-lip, you can then lower the jack and the spring plate will drop a lot lower, past the stop-lip (this is why you need the car up off the ground).
8. Leave that side and attack the other side now, so you get both spring plates hanging free on their torsion bars.
9. Measure the distance between the ground and the axle ends of the spring plates, so you can judge the effect of the adjustments. VW recommend an inclinometer here, with different angles for different models, but you can get it pretty good just by taking note of the height from the floor to the rear end of the spring plate. The torsion bar has 40 splines on it's inner end, and 44 on it's outer end. VW designed it this way so you can make fine adjustments to the angle of the spring plate (ride height of the rear end of the car).
10. Now, working on one side or the car at a time, you pull out the spring plate WITH the torsion bar, until it is free to rotate (about 1 inch or so). Might be a bit fiddly, as the assembly might stick a bit on the inner rubber bushing around the torsion bar end. Then rotate the whole spring plate AND torsion bar downwards by one (inner) spline, and push it back in. This increases the spring plate angle by 9 degrees, which is too much, so you now pull the spring plate off again, but this time push the torsion bar in (you can see the end of it remember), so ONLY the spring plate comes loose. Now rotate the spring plate alone upwards one (outer) spline. This decreases the spring plate angle by 8.1 degrees, for a total angle increase of 0.9 degrees. The axle end of the spring plate should now be a little closer to the ground (which of course raises the car on it's wheels).
11. Do the other side similarly. You'll have to judge how many times to do this rotation trick, But usually one "rotation" is enough. Two rotations might be needed for a really sagging rear end. If your spring plates were hanging at similar heights before you started (point 7 above) it is easier, as you simply match the rotations side for side. If they were at different heights, you'll have to decide which setting you like on one side, and then match the other side to it. It is ESSENTIAL to get the sides matched fairly closely in height, otherwise the car will 'squat' on one side. (Adjustable spring plates are usefull here, as it is then easy to fine-tune the angle of each side).

Note: The spring plate angle should be about 20-21 degrees, but this does vary from model to model.

12. When you are happy with the settings, bolt the coverplates back over the torsion bar ends (pulling it in evenly with the bolts so the rubber bushing is not distorted). Be careful here, as you need to pull the spring plate up just snug against the stop-lip, then jack up the axle end until the plate is higher than the stop-lip, then tighten the cover plate fully, so the spring plate will rest on the stop-lip when you release the jack. DON'T try to jack the spring plate up before you start fastening the torsion bar cover plate - the plate must be partly secure BEFORE the spring plate is raised, or you'll never be able to start the bolts in the cover plate.
13. Then remount the axle assembly at the rear end - being careful to line up the toe-in marks you made previously. Don't forget the bump-stop, and any other attachments at the axle end.

Note: Don't forget that the spring plate will be 'twisted' again as you do the bolts up (swing axle models) - I found it easier to install one bolt (where the spring plate and axle assembly are closest - bottom bolt I think) first and tighten it up to start the 'twist' and you'll then be able to spin on the other bolts on a little easier. Lining up the toe-in marks might require some hefty wacks on the brake drum nut with a rubber mallet or block of wood (DON'T use a metal hammer please), as snugging the bolts up twists the spring plate and makes it quite a tight fit, even before you tighten the bolts completely. Don't forget to reattach your hand brake fittings inside the car, and adjust the horizontal balance bar between the two cables so the hand brake pulls evenly up 3 to 4 clicks.

14. Once the car is back on it's wheels, you have to roll it back and forwards (or drive it a few yards) for the swing axles/wheels to move into their 'natural' position, and you can then check the height of the rear end. The axles should be close to parallel viewed from behind - perhaps just a slight wheel-end-down angle (slight positive camber), with the running boards parallel to the ground (assuming that the front suspension has not been altered).

There is the possibility that you will need to do it all again if the suspension angle is still not right.