Gearbox problem Auto
01-29-2016 | 11:08 AM
#1
Thread Starter
Racer
Joined: Feb 2009
Posts: 258
Likes: 0
From: Kuala Belait, Brunei
Gearbox problem Auto
Hello,
I might be having a gearbox problem. My car is a 92 GTS 928.
On Thursday- I bring my car to the workshop to get the intake manifold gasket change due to leak. The car idles erratically & car seems to be less power. Before the intake manifold change. The gearbox would be a bit slow in changing speed. Usually the first gear.
After the intake manifold change- The car starts beautifully & idles much better than before & the car seems to responds good but the problem is
1) The car will jerk at first gear. You can feel it jerks.
I did post this problem at 928 Facebook page. One advice to check the vacuum hose. They did that already with the gauge. No vacuum leaks.
2) Change gearbox fluid. The fluid is really dirty & at the old filter the mechanic said there is some metal shavings.
After changing the fluid. The car still jerks at first gear.
The mechanic said my gearbox is going kaput? I find it strange an intake manifold change can lead to gearbox problem? One theory is that maybe the car idles good & more power from the engine- The gearbox cannot cope?
Advice.
I might be having a gearbox problem. My car is a 92 GTS 928.
On Thursday- I bring my car to the workshop to get the intake manifold gasket change due to leak. The car idles erratically & car seems to be less power. Before the intake manifold change. The gearbox would be a bit slow in changing speed. Usually the first gear.
After the intake manifold change- The car starts beautifully & idles much better than before & the car seems to responds good but the problem is
1) The car will jerk at first gear. You can feel it jerks.
I did post this problem at 928 Facebook page. One advice to check the vacuum hose. They did that already with the gauge. No vacuum leaks.
2) Change gearbox fluid. The fluid is really dirty & at the old filter the mechanic said there is some metal shavings.
After changing the fluid. The car still jerks at first gear.
The mechanic said my gearbox is going kaput? I find it strange an intake manifold change can lead to gearbox problem? One theory is that maybe the car idles good & more power from the engine- The gearbox cannot cope?
Advice.
01-29-2016 | 11:38 AM
#2
Rennlist Member
Joined: Jun 2005
Posts: 10,005
Likes: 804
From: Oman
Your engine will not over power that gearbox.
Dirty ATF with metal shavings in the filter is doubtless an indication of trauma in the box. Once such damage has occurred changing the ATF is not going to cure damage that has occurred - it may reduce the symptoms a little but sounds as though that is just not the case here.
There should be no linkage between an inlet manifold problem and this issue. If the vacuum connection to the gearbox modulator was lost the change will be harsh but should not damage the gearbox unless you ran like this for a very long time I would suggest.
Perhaps you can expand on your description of the symptom a bit more specifically to give those who understand gearbox problems a bit more to work with.
Whether or not there is anyone in your neck of the woods who can work on these transmissions remains to be seen- just remember it is basically a very solid Mercedes Benz transmission that can be repaired by someone who knows what they are doing. The viability of a repair obviously depends on the extent of the damage- should such exist.
Must say I am a bit surprised to hear this given your GTS had covered no distance worth talking about last time we heard from you.
Rgds
Fred
Dirty ATF with metal shavings in the filter is doubtless an indication of trauma in the box. Once such damage has occurred changing the ATF is not going to cure damage that has occurred - it may reduce the symptoms a little but sounds as though that is just not the case here.
There should be no linkage between an inlet manifold problem and this issue. If the vacuum connection to the gearbox modulator was lost the change will be harsh but should not damage the gearbox unless you ran like this for a very long time I would suggest.
Perhaps you can expand on your description of the symptom a bit more specifically to give those who understand gearbox problems a bit more to work with.
Whether or not there is anyone in your neck of the woods who can work on these transmissions remains to be seen- just remember it is basically a very solid Mercedes Benz transmission that can be repaired by someone who knows what they are doing. The viability of a repair obviously depends on the extent of the damage- should such exist.
Must say I am a bit surprised to hear this given your GTS had covered no distance worth talking about last time we heard from you.
Rgds
Fred
01-29-2016 | 01:55 PM
#3
Rennlist Member
Joined: May 2002
Posts: 8,295
Likes: 898
From: Roswell, GA
Perhaps in the past somebody compensated for the lack of vacuum at the transmission by dialing up the shift modulator. Have your shop test the modulator pressure and re-adjust the modulator.
01-30-2016 | 03:17 PM
#6
Nordschleife Master
Joined: Jul 2011
Posts: 5,663
Likes: 23
From: North Country
Glad to hear the symptom has been remedied (at this point) by exchanging ATF and filter. The metal found in the fluid is disconcerting though, and may herald future problems. Begin to consider who can deal with this MB 722 transmission in your area. You have a definite warning sign here, and planning ahead would be wise.
Another thing from your original post regarding your perceiving shift change issue after manifold was removed would be if the cable 'quad' was removed (likely) and the 'bowden cable' (transmission's control pressure control cable) had its tension foiled with. This cable, tied into your throttling, controls the timing of your gear changes. If altered, will give a definite perceived difference in how your car feels under your foot. An old adage on the 928 is to look to the last place worked on when a 'new' problem arises.
Another thing from your original post regarding your perceiving shift change issue after manifold was removed would be if the cable 'quad' was removed (likely) and the 'bowden cable' (transmission's control pressure control cable) had its tension foiled with. This cable, tied into your throttling, controls the timing of your gear changes. If altered, will give a definite perceived difference in how your car feels under your foot. An old adage on the 928 is to look to the last place worked on when a 'new' problem arises.