rear diagonal brace removal question
 

I am about to change the tiptronic fluid in the 04 boxster S and all the manuals and write-ups talk about supporting the car on jackstands and then removing the diagonal supports for access to the transmission pan. I have a drive on lift which gives me good access underneath and do not need to put it on jackstands. My question is whether there will be any difference if it is supported from the jack points as on stands or sitting normally on the wheels when I remove and replace the diagonal braces? I want to be sure nothing gets out of alignment during the process. I have a jack system on the lift that will lift one end of the car, but if I support the rear end with that then it will not be level for the refill and check process. I am hoping that nothing should move when I remove the bracing with it sitting on all 4 wheels. Any insight would be appreciatd.

It's my understanding that things do move and some have used ratcheting tie down straps to realign the holes.

I am wondering if there is any significant difference in possible movement with the weight on the suspension as opposed to the suspension just hanging. I suppose it doesn't matter as long as you realign it to match up the holes during reassembly. I would hate to get the chassis all racked out of alignment.

There is a thread going about this over on Boxsterregister.org, I believe somebody talked with someone at Porsche and got the following guidelines:
=============
Removal of these parts [The big diamond shaped plate] can affect your suspension alignment. Porsche recommends the following steps be followed to preserve the alignment during this procedure.

• All wheels must be lifted and freely suspended without weight on them
• The vehicle must be supported as flat as possible using the recommended jacking points

Suspension re-alignment is not necessary if the support plate and diagonal braces are removed and installed under these conditions.
=============

At least one of the threads was for 987. I believe registration is required but here are the threads:

PCA Boxster Register

PCA Boxster Register

I just looked in the Boxster Service manual for the 986 Boxster in the section "Removing and installing the sheetmetal brace" and it has those same steps listed. It also seems to suggest that if these steps are not followed, the rear alignment may change such that the steering wheel position may be different than before when driving straight ahead.

Also remember that when you are filling the transmission with ATF you will need to have the car running, the transmission at about 100 degrees F, and you need to run it through the gears and recheck the fill level several times. Much easier and safer if the wheels are free.

Thanks Steve. I will try to follow this procedure.

I just removed mine, piece of cake. ...message me with a number and we can talk

If the brace doesn't go in and out easily you can support the right and left axle a little bit - best near the brakes. But just a little bit.

Don't forget to remove the rear wheels before unmounting the brace.

got it done. As you said, no problem, just a little time and aligning the holes. The transmission fluid was pretty nasty. Not burnt, but very black and a bit og sludge in the bottom of the pan. No metal particles at all but really needed changing. Got about 4 liters drained out and replaced. No roadtest yet, but will do that tomorrow.

Not sure where your drain plug is on a Tip, but on my 6-speed, I took a hole saw and just drilled a 2" dia hole in the stupid plate - something the Porsche engineers overlooked. Works like a charm and I can drain and refill the trans in 30 minutes, without removing 2 dozen fasteners.

Porsche purists would be horrified, but as Stefan Wilkinson wrote in The Gold-Plated Porsche - purists are a pain in the ass, hahaha.

The "stupid" Porsche engineers didn't drill a hole in the brace plate, because the stability of this brace plate is realy important. It stabilizes the rear axle. And because it is made of alumiunium the material can get weak over years if you harm the structure by a 2" hole.

Maybe you should install something like this now:
http://www.rennline.com/Cayman_Boxster-Tie-Downs-Stabilizer-Bar/products/1067/

Or as an alternative:
http://986forum.com/forums/99433-post29.html
http://986forum.com/forums/99785-post32.html
Complete thread: http://986forum.com/forums/general-discussions/10817-driving-impressions-lower-stress-bar-2.html

Or another option: http://pedrosgarage.com/Site_2/TechnoBrace.html

BTW: how can i link to a position in a thread?

We put 2" holes in a lot of these plates, and have done for years without any issues, as have many other shops.