Partial engine Drop For Trailing arm Bushings

[Mike O'Meara]

I want to change the trailing arm bushes on my '72. As per numerous threads here, a partial engine drop will give enough clearance to remove the "wrong way" bolts close to the trans. I I've done a complete engine removal before, but never a partial. What do I need to/need not remove in order to give enough clearance to remove those bolts? Shift linkage, for sure, but what else? Axles, radius arms, brake lines and sway bar are already off. Trying to decide whether to go all the way or do a partial drop and avoid exposure to "whileyou'reinthereitis" Thanks

[Zeke]

People have R&R'd trannys before with the motor in. It's a matter of the angle of the engine/trans. If I had a lift, I'd probably do it that way. On stands, I'd pull the motor.

[930chef]

i had to replace both trailing arms a couple of weeks ago, and my bolts were situated like yours. i was able to remove the nut and tap the bolt inboard to expose the shank just below the head of the bolt. i then carefully used a sawzall with fine tooth metal blade and cut the head off. i was then able to work the bolt out without dropping the drivetrain. hope it goes well for you............kevin

[Mike O'Meara]

930chef - That'd be my favored solution. How did you protect the fuel lines and brake cables that pass right by on the driver side? And how were you able to work the bolt out? How tight is the bolt in there, and does the movement of the control arm help work it out? Thanks

[BlueWing]

I'm planning on engine/tranny removal in the near future. Is it worth swapping the direction of the bolts for future bushing replacement at that time?

Terry

[arrivederci]

I've done the partial drop (on my '72) as well as the sawzall method (on my '81, bolts were in backwards even though the t-bar tube is notched).

The sawzall method was easiest for me, although with the sawzall, I also had my car on a lift. Take the nut off, tap the end of the bolt so the head sticks out more. I simply pushed the fuel lines, etc to one side and used a short, fine toothed blade.

[Mike O'Meara]

Thanks, Josh and Kevin. I was just about to upload my photos of the bolt loosened and ready for the sawzall, when I saw your identical pics, Josh. But for the correct metal blades, the bolts would be cut and out by now. This really beats pulling the motor and trans, and leaves all those "while you're in there" items for a later date and I can concentrate on the suspension for now. Great! Thanks again.

[Mike O'Meara]

Got it done, but had to use a 9" blade on the sawzall due to the throttle linkage in the way on the driver's side. Haven't tried to install new bolts from the outside in yet, I'm hoping there is clearance - can I dent the torsion tube if necessary? New bushings, bearings, shocks, factory adjustable radius arms and bushings, clean everything and paint, then on to the front for the same and then alignment and corner balance. The shocks appear to be original, I can compress them with very little effort.

[arrivederci]

You'll need to either dent the torsion tube -or- buy something like this solution that WEVO offers.

Welcome to Windrush Evolutions - WEVO - Porsche Products

[burgermeister]

Replacing a 14mm bolt with what appears to be a 10mm bolt threaded into a 14mm sleeve is not a great idea. Much of the clamp load the 10mm bolt is capable of supplying will go to deforming the ears on the torsion tube to close the assembly gap to the bushing sleeve, leaving insufficient force available to clamp the bushing sleeve to the ears.

Looking at the chassis and comparing fastener sizes to typical US car sizes, it does not seem that Porsche went oversize for any of its fasteners. That joint will easily see 10+ kN loads during cornering, which ideally would use 100kN of clamp load (0.1 is a conservative friction coefficient for metal-metal clamped joint).

An M14 is good for 70 - 110kN depending on grade, an M10 is good for about 40% of that.

YMMV.

[Mike O'Meara]

I appreciate your thoughts, Burgermeister, but I'couldn't get past the cost of the part ($100) to begin with. I see your point, too. That is one hefty bolt, IIRC, the largest I've come across on my car, and at $2 or $3 apiece, I'll go that route and dent the torsion tube enough (as long as that's safely possible) to install it from the outside. Thanks all for your help.