Faulty front differential. Anyone else had similiar issue?
05-01-2017, 04:55 AM
#16
Racer
Thread Starter
There has to be "play" in the gearbox. The gears are not interference fit parts.
My opinion is if the transmission/diff is not making any noises like howling groaning, shifts ok, stays in the gear you put it in, and is not manifesting any real signs of any problems, and is not showing any leaks, the transmissin is fine.
For the clonking noise this can be sometimes a self-inflicted problem. Every car's drivetrain has "play". The trick to avoiding hearing this play in the form of clonks is to be easy on and off the gas especially at low speeds in low gear.
Unless the front diff is manifesting more in the noise department than the clonking and it is leak free and especially if you change your driving technique to try to avoid using the car in such a way that produces the clonking noise I'd hazard an opinion the front diff is ok, too.
But obviously I have not been at the car have not heard the noise. So a second opinion as you indicated you are doing is I think a very good idea.
My opinion is if the transmission/diff is not making any noises like howling groaning, shifts ok, stays in the gear you put it in, and is not manifesting any real signs of any problems, and is not showing any leaks, the transmissin is fine.
For the clonking noise this can be sometimes a self-inflicted problem. Every car's drivetrain has "play". The trick to avoiding hearing this play in the form of clonks is to be easy on and off the gas especially at low speeds in low gear.
Unless the front diff is manifesting more in the noise department than the clonking and it is leak free and especially if you change your driving technique to try to avoid using the car in such a way that produces the clonking noise I'd hazard an opinion the front diff is ok, too.
But obviously I have not been at the car have not heard the noise. So a second opinion as you indicated you are doing is I think a very good idea.
05-01-2017, 12:00 PM
#17
Race Director
BTW, while this seems to be the recommended "fix" for everything I think in this case it is applicable to in order to give you every chance to be smoother with the car and to minimize the clonking -- assuming the 2nd shop's opinion doesn't agree with the 1st shop's opinion -- consider doing an E-gas calibration.
This can help with low speed/low RPM engine control.
The steps to do this should be in your owners manual but I think the steps are the same for your car as for my 2003 Turbo and 2002 Boxster.
With the key off and your foot off the gas pedal through the entire procedure turn the key to the on position and leave on for at least 60 seconds. Then turn the key off for at least 10 seconds. The next time you start the engine the calbration is complete.
05-02-2017, 04:14 PM
#18
Racer
Thread Starter
Be sure to report back.
BTW, while this seems to be the recommended "fix" for everything I think in this case it is applicable to in order to give you every chance to be smoother with the car and to minimize the clonking -- assuming the 2nd shop's opinion doesn't agree with the 1st shop's opinion -- consider doing an E-gas calibration.
This can help with low speed/low RPM engine control.
The steps to do this should be in your owners manual but I think the steps are the same for your car as for my 2003 Turbo and 2002 Boxster.
With the key off and your foot off the gas pedal through the entire procedure turn the key to the on position and leave on for at least 60 seconds. Then turn the key off for at least 10 seconds. The next time you start the engine the calbration is complete.
BTW, while this seems to be the recommended "fix" for everything I think in this case it is applicable to in order to give you every chance to be smoother with the car and to minimize the clonking -- assuming the 2nd shop's opinion doesn't agree with the 1st shop's opinion -- consider doing an E-gas calibration.
This can help with low speed/low RPM engine control.
The steps to do this should be in your owners manual but I think the steps are the same for your car as for my 2003 Turbo and 2002 Boxster.
With the key off and your foot off the gas pedal through the entire procedure turn the key to the on position and leave on for at least 60 seconds. Then turn the key off for at least 10 seconds. The next time you start the engine the calbration is complete.
Haven't heard from the second tech yet. Will post when I get the verdict.
10-04-2017, 03:51 AM
#19
Racer
Thread Starter
Cross-post to my other thread:
Some update on this long standing issue. The "clonking" sound got progressively worse after switching to semi-stiff transmounts and RS engine mounts. Had the car in for inspection at my regular indy who isolated the issue to the front diff: it was possible to manually wiggle the diff and when the front drive shaft was mechanically discoupled the sound went away during driving. The verdict was that the front diff was faulty and needed to be replaced or removed.
I went ahead and asked for a second-opinion at another well-renowned shop. Their assessment was that it's nothing wrong with the diff itself. They came to this conclusion by electronically disabling the diff but found that the issue was still there. So they think that it's most problably something wrong with the mounting mechanism of the diff. They also found a crack in the flex disc for the cardan drive shaft ("the doughnut") but didn't think that could be the cause.
Since the sound was there BEFORE i switched to stiffer transmounts and engine mounts (but got more pronounced) I'm thinking that the problem is with the mounting of the front diff (the cardan shaft front carrier?? http://www.design911.co.uk/fu/prod135481/99737593400/) The next logical step should be to replace both the flex disc and the front carrier and see what happens. Would love to hear the thoughts of more experienced people on this. Are there any other components in the mounting of the diff/front cardan that could be adressed? Anyone had issues with the front diff/cardan shaft after changing to stiffer engine and trans mounts??
Some update on this long standing issue. The "clonking" sound got progressively worse after switching to semi-stiff transmounts and RS engine mounts. Had the car in for inspection at my regular indy who isolated the issue to the front diff: it was possible to manually wiggle the diff and when the front drive shaft was mechanically discoupled the sound went away during driving. The verdict was that the front diff was faulty and needed to be replaced or removed.
I went ahead and asked for a second-opinion at another well-renowned shop. Their assessment was that it's nothing wrong with the diff itself. They came to this conclusion by electronically disabling the diff but found that the issue was still there. So they think that it's most problably something wrong with the mounting mechanism of the diff. They also found a crack in the flex disc for the cardan drive shaft ("the doughnut") but didn't think that could be the cause.
Since the sound was there BEFORE i switched to stiffer transmounts and engine mounts (but got more pronounced) I'm thinking that the problem is with the mounting of the front diff (the cardan shaft front carrier?? http://www.design911.co.uk/fu/prod135481/99737593400/) The next logical step should be to replace both the flex disc and the front carrier and see what happens. Would love to hear the thoughts of more experienced people on this. Are there any other components in the mounting of the diff/front cardan that could be adressed? Anyone had issues with the front diff/cardan shaft after changing to stiffer engine and trans mounts??
10-12-2017, 11:10 AM
#21
Racer
Thread Starter
No, I have not and I don't think the previous owner had either since it's not part of the regular service until pretty high up in the milage. I'm acutally planning on changing oil in the front diff and gear box when it's in for the other stuff that I mentioned, just in case. Do you think that could improve the noise issue?
10-13-2017, 09:35 PM
#23
Racer
Thread Starter
10-14-2017, 04:33 AM
#24
Rennlist Member
Normally wear due to misalignment, likely from toe being too far out.
12-08-2017, 12:36 PM
#25
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After reading your post, I think my issue is similar, but maybe not so severe? The noise is definitely audible if you're paying attention, but really not that loud. I will get it checked out soon and let you know if it's something similar. Think the front diff. is covered under my warranty (hopefully) 
