Transferred from the C4S Valuation Thread
----------------------------------------------
JColbourne
PCGB Member
.........Regarding the gearbox changes, there have been persistent symptons that have prevailed with the last 2 gearboxes that I'm still pursuing with the OPC and Porsche Technical to resolve.
In brief there are two gear changes that result in a snatched gearchange effect and a distinct "clunk". One is in 4th gear in Manual mode at around 1,200 RPM 26-28MPH with light acceleration. When I change down to 3rd their is a jolt in the car and a metallic "clunk". Same is true in Auto mode with reasonably hard though not excessive braking, when the gearbox changes from 3rd to 2nd their is a distinct jolt under those circumstances although this symptom is more intermittent. It could be dependent on the amount of bracke force applied. It is similar to the "kick down" effect when accelerating hard in Auto.
Also when accelerating and decelerating i.e. in slow-moving traffic, the "clunk" sound is present and feels like there is play in the transmission system as if something is not tightened up fully e.g. engine mountings although these have been given the OK. The OPC have had the car back several times since the 3rd gearbox was installed and still not got to the root cause of the symptoms and hence not identified a fix. The 2nd gearbox was replaced on the advice of Porsche Technical who diagnosed it as a Transer Box failure. As the symptoms have prevailed across 2 gearboxes, it could be assumed that it's not a gearbox failure. The front-to-rear prop shaft was changed at the time the 2nd gearbox was installed so I doubt it's that. Any clues/similar experiences anyone?
I might start a separate topic on this to get a wider view.
Rgds
John
==================================================================
Black80XSA
PCGB Member
Just a thought... what happens if you disconnect the drive to the front axle - do you still get the shunt ?
When putting C4S on rolling roads its common practice to disconnect the front transmission. so a short run on road with just RWD might be worth a try.
==================================================================
Richard Hamilton
Good call.
Also, did the gearbox come with a new torque converter?
Richard
==================================================================
JColbourne
PCGB Member
I'll mention that to the OPC and see if they've tried/could try that. Prior to the 3rd gearbox going in, there had been one instance of a very loud metallic sound "clanking" from the front nearside of the car (as if a front driveshaft was loose) when I was on a motorway slip road but this went away when the latest gearbox was installed.
Rgds
John
==================================================================
JColbourne
PCGB Member
Hi Richard,
I asked the OPC the question a few weeks back and was told that each gearbox comes complete with a torque converter.
Rgds
John
----------------------------------------------
JColbourne
PCGB Member
.........Regarding the gearbox changes, there have been persistent symptons that have prevailed with the last 2 gearboxes that I'm still pursuing with the OPC and Porsche Technical to resolve.
In brief there are two gear changes that result in a snatched gearchange effect and a distinct "clunk". One is in 4th gear in Manual mode at around 1,200 RPM 26-28MPH with light acceleration. When I change down to 3rd their is a jolt in the car and a metallic "clunk". Same is true in Auto mode with reasonably hard though not excessive braking, when the gearbox changes from 3rd to 2nd their is a distinct jolt under those circumstances although this symptom is more intermittent. It could be dependent on the amount of bracke force applied. It is similar to the "kick down" effect when accelerating hard in Auto.
Also when accelerating and decelerating i.e. in slow-moving traffic, the "clunk" sound is present and feels like there is play in the transmission system as if something is not tightened up fully e.g. engine mountings although these have been given the OK. The OPC have had the car back several times since the 3rd gearbox was installed and still not got to the root cause of the symptoms and hence not identified a fix. The 2nd gearbox was replaced on the advice of Porsche Technical who diagnosed it as a Transer Box failure. As the symptoms have prevailed across 2 gearboxes, it could be assumed that it's not a gearbox failure. The front-to-rear prop shaft was changed at the time the 2nd gearbox was installed so I doubt it's that. Any clues/similar experiences anyone?
I might start a separate topic on this to get a wider view.
Rgds
John
==================================================================
Black80XSA
PCGB Member
Just a thought... what happens if you disconnect the drive to the front axle - do you still get the shunt ?
When putting C4S on rolling roads its common practice to disconnect the front transmission. so a short run on road with just RWD might be worth a try.
==================================================================
Richard Hamilton
ORIGINAL: Black80XSA
Just a thought... what happens if you disconnect the drive to the front axle - do you still get the shunt ?
When putting C4S on rolling roads its common practice to disconnect the front transmission. so a short run on road with just RWD might be worth a try.
Good call.
Also, did the gearbox come with a new torque converter?
Richard
==================================================================
JColbourne
PCGB Member
ORIGINAL: Black80XSA
Just a thought... what happens if you disconnect the drive to the front axle - do you still get the shunt ?
When putting C4S on rolling roads its common practice to disconnect the front transmission. so a short run on road with just RWD might be worth a try.
I'll mention that to the OPC and see if they've tried/could try that. Prior to the 3rd gearbox going in, there had been one instance of a very loud metallic sound "clanking" from the front nearside of the car (as if a front driveshaft was loose) when I was on a motorway slip road but this went away when the latest gearbox was installed.
Rgds
John
==================================================================
JColbourne
PCGB Member
ORIGINAL: Richard Hamilton
Also, did the gearbox come with a new torque converter?
Hi Richard,
I asked the OPC the question a few weeks back and was told that each gearbox comes complete with a torque converter.
Rgds
John