Carrera 3.2 G50 drivetrain slack

[RobFrost]

I have significant drivetrain slack in the Carrera 3.2 G50 - i.e. if I was to repeatedly accelerate/decelerate on the throttle it would feel like I might break something. My instant assumption was engine / gearbox mountings but I saw some chatter about this possibly being wear in some aspect of the G50. Is there a most common cause of this on a run in (150,000 miles) Carrera 3.2 G50, and a way to discriminate between the possible causes?

[911hillclimber]

Maybe first check the bolts for the CVs are tight?

[RobFrost]

Maybe first check the bolts for the CVs are tight?

I drove 200 miles in it so I hope they are! But will check.

[RobFrost]

Maybe first check the bolts for the CVs are tight?

CV joints are all done up tight. Both shafts leaving the diff have a little slack, say 3 degrees or 3mm movement. Not totally clear whether it's lateral or rotational. I wonder if this is normal on a G50?

[Nige]

If its the old style clutch with the rubber damper failing? Maybe?

http://forums.pelicanparts.com/porsche- ... -disc.html

Other than some chattering in first my 155k G50 still feels tights, so from what you explain it isn't normal for a G50.

I assume from what you have said you have changed the gearbox/engine mounts already?

[MikeB]

Other options

Check that you hub nuts are tight, what about play in a CV joint. Jack each rear wheel up at a time, put the car in gear and see if thee is the same play each side. Are the output shafts bolted up tight into the diff?

[RobFrost]

Other options

Check that you hub nuts are tight, what about play in a CV joint. Jack each rear wheel up at a time, put the car in gear and see if thee is the same play each side. Are the output shafts bolted up tight into the diff?

Right, I've done that. If I ignore around 0.75 degrees of play in the right hand cv joints, there's around 6.75 degrees of play in both wheels in first and reverse, 9 degrees in 3rd and 11.25 degrees in 5th, in both wheels. Seen here: https://photos.app.goo.gl/SRus76K2m7J5KxyTA

Turning the wheels feels smooth and is quiet and turning the engine using either wheel in 5th gear is smooth and quiet. Rocking the innermost cv joint possibly feels a bit more crunchy but it's hard to say what's normal.

Turning through the slack is free and without resistance - like moving a gear through clear space rather than stretching or compressing a degraded rubber bush. Then when it bites it's pretty firm with maybe an eighth of a degree of firmness before it locks.

Clearly, play after the gearbox would be equal in all gears whereas assuming I have standard 3.2 G50 ratios of 3.5 and 0.889 in first and fifth, play in the engine-rpm speed components of the transmission would yield play at the wheel in a ratio of around 4:1 between fifth and first. So given a bit of rudimentary comprehensive school O-level maths, the car either has:
-2 to 3 degrees play in the final drive and 9 to 10 degrees in the input shaft / clutch etc.
-some amount of play in some shaft or gear which first and fifth share in a ratio of around 2:1, and which reverse and third also use in proportion to gearing
-some combination of the above
-something else

[sladey]

My G50 box still feels tight after 320k miles.

My first thought was engine/gearbox mounts. I replaced my gearbox mounts with super pro ones and was surprised at the difference - the originals had got sloppy and I’d got used to it

[RobFrost]

My G50 box still feels tight after 320k miles.

My first thought was engine/gearbox mounts. I replaced my gearbox mounts with super pro ones and was surprised at the difference - the originals had got sloppy and I’d got used to it

Same here but upon jacking it up, it's definitely driveshaft rotation. Most of it seems to be pre-gearbox because there's more rotation in top gear so I guess somewhere in the vicinity of the clutch. I'm thinking clutch splines on the input shaft.

[Nige]

I don't have my car here at the mo, otherwise I could check for comparison.

[andytat]

It sounds like the rubber damper (part of the clutch friction lining) has failed.
When this happens there is a lot of drive train back lash and it feels like it's coming
from the gearbox. To properly identify the problem the engine box & need to come
out and the clutch pressure plate removed.
Hope this helps.

Andy

[911hillclimber]

I thought that rubber hub design has 'passed-out' of the system years ago?
If they rip would you get a lot of vibration too when driving?

[RobFrost]

It sounds like the rubber damper (part of the clutch friction lining) has failed.
When this happens there is a lot of drive train back lash and it feels like it's coming
from the gearbox. To properly identify the problem the engine box & need to come
out and the clutch pressure plate removed.
Hope this helps.

Andy

Thanks Andy. Fingers crossed it's that as the main input shaft would be a £1,500 part plus the work. I can't see how it could be anything other than something on the input drive when the slack is so much greater in top gear than first. Would you put the rubber bush back in or replace with the more modern solid type?

[Nige]

New G50 clutches don't have the rubber damper. Mine still has the rubber version fitted, though I have new style on the shelf ready for when the day arrives. I also have a good used rubber damper clutch plate version available.

See below for difference.

[Berny]

With the G50 box you can take it out without the engine!