Subframe help please

[Maverick76]

Hi everyone, glad to have found you, hope someone can help.

I bought a Porsche 944 S2 cabriolet back in 2002. It was my everyday car for 6 years until the clutch packed up.

Doing things on the cheap, I decided to replace the clutch with the help of a friend (who is a mechanic) on my driveway off of axle stands.

The clutch part went fine I'm happy to say, the part that went wrong was me trying to change parts on the rear sub frame.
A few months before the clutch broke I had some knocking noises and I was told it could be spring plates, so while we had the gearbox out I thought it was a good time for me to change them before we put it all back together the following day.

Unfortunately, I just unbolted the spring plates without marking their positions, so when we put everything back together and lowered it off the axle stands my tires were up in the wheel arches and the back end of the car was nearly on the floor.
Seeing as it needed a lot of rust work to be done, as well as taking the gearbox and everything else back out to adjust again, it was put into the garage until I could save up for the bodywork.

Here we are 12 years later, and I am able to get things going again.
The car had a battery connected a month ago and after fitting a £25 fuel pump from eBay, fired up straight away and is ticking over.
I have managed to get one second hand front wing (without any rust) and some new side sills and rear quarter panels to put in.

The next thing to do is tackle the 2008 mistake and correct the ride height at the rear end, but before I dismantle the back end again to get the subframe out I have questions.
Once I have the subframe off and laid on the floor, is there a factory setting measurement to set up the spring plates onto the torsion bar?
I really don't want to put it back, then find it needs further adjustment and have to take everything out again and blindly hope I get it right.

If you know of any information on this subject or any manual that I can purchase to make this job any easier to get done, I would seriously appreciate it.

 

[bmnelsc]

Clark's garage had an article on the how to along with a clever device you can make to perform measurements. For the S2 and all post 85 944s, torsion bar set up and initial ride height adustment is performed with the whole suspension removed so it can be leveled as a starting point (level across the top of the mounting plate I believe). Then the spring plates are installed at an angle of 23.5 degrees and a spring compressor used to raise the spring plate so you can install the suspension stop under the spring plate before removing the spring compressor. This will create the proper pre-load on the torsion bars so that when the rear assembly is re-installed the car body doesn't sit down on the tires and you actually have some suspension travel. This is where you went wrong the first time based on your description.
This describes the basic procedure but DO NOT TAKE THE 23.5 DEGREES AS CORRECT. This initial starting point varies from year and from Turbo to S2 to S to regular. The internet giveth and the internet taketh away...I found all this once complete with pictures - and I'm quite sure it was a Porsche document however I can't seem to find it in my electronic copy of the Porsche Workshop Manual volume 3 Chassis where most people would expect to find this. Hopefully someone recalls where this secret information is stored and can share it.
Anyway - hope I got you thinking about the procedure...now just need some details

 

[Maverick76]

Thanks for your reply to me, I have done some searching this morning and found this, would it be the article you were talking about?
http://www.clarks-garage.com/pdf-manual/susp-06.pdf

 

[bmnelsc]

Hello - yes that is the article however this procedure is based on a current correct starting point which you don't have. The factory method assumes you are starting from a collection of parts (because you are starting from an un-indexed base - you are here). But you don't really need to disassemble everything...I've read a procedure where you fully support the vehicle on jack stands or appropriate - remove everything back to the torsion bars (wheels, brakes, trailing arms, etc). Using a level on the chassis at the door opening - make sure the body is level for-to-aft...both sides and I would think level left to right would be ideal also. Then you can start by positioning the spring plate at 23 degrees (see previous message for disclaimer here) - use spring compressor (or jack under the spring plate? must be very careful here not to dislodge the car from what ever you have it raised up on - not sure this will work) to raise it up enough to install the stops and so on.
The procedure of starting with the spring plates at a specified angle is how the factory assembled this suspension during manufacture so we know the procedure is sound...we just need to confirm the initial angle of the spring plate. You do know that torsion bars have a different number of splines on each end so by rotating forward and backward you can get to quite a fine adjustment of angle. This also I have seen on the mystery web which included calculations on the rotation needed on each end of the torsion bar to achieve a variance of a degree or two as well as the effect of rotation to ride height (i.d. x degrees of rotation = 1 inch difference in ride height).
Sorry I can't provide a link to these documents at this time but this info is out there somewhere...perhaps another forum member can help.

***SAFETY WARNING*** - once you start pre-loading the torsion bars things get dangerous...once loaded if you let them slip of whatever compressor you are using they will return to their starting position with great force (broken bones very likely if you are in the way).

 

[Maverick76]

Thanks you so much for your help, hopefully it will finally be put back to correct height, then it can go off to the body shop to sort a lot of rust out.