How do trailing arms differ?
 

I am restoring a 74, and I am updating many parts. How do trailing arms differ from 74-89 or are they all the same.

In 78 the connection point for the sway bar drop link changed from a ball post attached to the TA (how the post is attached seems to be a bit of a mystery), to a standard bolt fastener. This only matters if you want to use an OEM style sway bar because most others appear to mount the drop link at the spring plate.

btw, let me know if you are looking for a set of 74-77 style Trailing Arms.

Are they all aluminum?

Post 74 all are Aluminum.

I thought the '74 was a one year only and the sway bar mount changed in '75?

not sure when that mount changed

the Al arms are lighter, stiffer, and IIRC stronger than the old steel ones

at some point, P AG put bigger rear wheel bearings into the Al arms, so the wt. went back up a bit

If anyone is looking: I've got a nice pair of aluminum arms off of a 1976, complete with new Elephant Racing monballs installed. Send a PM if interested.

74 to 89 are all Al.

There is no reason for you to update if you have good 74 Al arms. If for some reason you do use a later year than 74, make sure you keep the stub axles in the arms as they are 69-74, having 4 bolts and 2 pins to match to the CV joint.

There is some more info here about the sway bar mount for 74-77 vs. 78+ trailing arms:

http://forums.pelicanparts.com/porsche-911-technical-forum/550663-1974-1977-sway-bar-question.html
http://forums.pelicanparts.com/porsche-911-technical-forum/381841-77s-sc-drop-link-conversion-questions.html
http://forums.pelicanparts.com/porsche-911-technical-forum/301988-911sc-rear-suspension-swaybar.html

And many more links if you search for " trailing arm drop link ball"

great everyone, thank you for the time. This place continues to amaze me.