Porsche 911 UK Enthusiasts Online Community Discussion Forum GB

Welcome to the @Porsche911UK website. Register a free account today to become a member! Sign up is quick and easy, then you can view, participate in topics and posts across the site that covers all things Porsche.

Already registered and looking to recovery your account, select 'login in' and then the 'forget your password' option.

Porsche Targa, Roof Drive Gear Observation

KampFreddie

New member
Joined
19 Feb 2024
Messages
2
Well my targa roof had always struggled to make the final closure, I'd put it down to an old battery, or a cable system with too much resistance, turns out it was something else altogether and something that was possibly built into my car all those years ago ,(2003).

Anyway just recently my roof had 100% siezed, new battery, engine runing, no difference. I dreaded that I was looking at a roof out job and some big money to resolve. Mechanically moving the roof with the 4mm Allen keys made no difference and I wrecked the heads, if I'd have read the instructions more deeply you need to press and then turn, when you open up the drive motor gearbox it becomes clear why.

I removed one of the rear drive motors (to keep the cables in sync, you only remove one motor at a time), and then I removed the pressed steel gearbox plate, low and behold you see a worm drive, (you can't drive a worm gear backwards, those lego days had paid off, thanks Dad!) with two plastic reduction gears. The final gear drives the main cable sprocket via a spring loaded dog clutch. That dog clutch as a small thimble made from cast aluminium, both of mine had split and had lost and shreaded a number of (very fine) drive teeth, mainly through my ham fisted believe that I was working against siezed cables, I was not!

What struck me odd was that final drive gear runs on a spigot held within the pressed steel gearbox cover plate. On both my gearbox that spigot was a press fit, which to mind it should never have been. I measured both spigot and hole and to my surprise the spigot measured 20.2mm dia, the pressed steel hole 20.1mm. I could barely move the gear once installed on the plate with my fingers, it was mega stiff.

I worked the hole out with three grades of wet and dry, 80, 180 and 400 grade, I worked the spigot a little with 400 grade and boy what a difference!

Basically each motor that pulls no more than 10amps, (120 Watts of power each) was lossing a lion share of that power just trying to drive the reduction gearbox, talk about transmission loss!

I had to revert to Aralditing (epoxy) and pining the mashed clutch pinions to the gear which means I've lost the clutch and manual drive option, I'll fix that by some other method later on.

So my car sat for the whole of three years not being roof cycled, I feared the cables would have been siezed, turns out those are just fine, my gearboxes though were never right and that was the problem.

My guess is either the tooling that Webasto? Used to press the gearbox plates was worn out, or the plating process was not being controlled too closely, either way my roof closes sooo much better than its ever been.

So if like me you had to help the final roof closure by hand and fear sieving cables, I'd suggest taking one drive unit out, remove its cover plate and try and spin that final gear, if it was like mine then try the above and it may just resolve your problem.
 

Attachments

  • 20240223_183544.jpg
    20240223_183544.jpg
    1.2 MB · Views: 12
  • 20240224_125147.jpg
    20240224_125147.jpg
    1.8 MB · Views: 12
  • 20240224_152136.jpg
    20240224_152136.jpg
    1.9 MB · Views: 12
Excellent right up
A problem, Targa roof owners have certainly experienced @infrasilver and it all comes down to those tiny little gears
 
Thank you for the feed back, I've learnt a lot from other people's write ups, so i hope my learning is helpful to others.
 

New Threads

Forum statistics

Threads
124,594
Messages
1,441,910
Members
49,025
Latest member
StephCafe
Back
Top