From
No Forward Cold
One of the most common problems I have found after the milege gets over roughly 60K miles. The scenario.... You are driving in traffic for a while OR your car has sat for a while and is a cold startup. You put the car in Drive range and it wont move, or if driving you come up to a stop light and in heavy traffic and the light turns green and SUPRISE!!! You are holding up traffic with a car that wont go anywhere. The most common cause of this problem is a worn out inner surface of the Input clutch piston. I will post pics soon so you can better understand why it IS a real problem. Once the inner sealing area wears it can prevent the inner lip seal for the piston from sealing properly. You may find that revving th engine up will finally get the car to move and it will BANG into gear. This is because the pump in the transmission is working harder and moving more fluid thus allowing the added fluid to overcome the leak which prevented the clutch from either initially applying or staying applied. From the factory the rubber lip seals that are used on the inner and outer sections of the input cluch apply piston are a Short design seal. The transmission repair service field has found that a Long style lip seal greatly helps against this problem and is what is included in aftermarket gasket and seal kits and is also what we use in our rebuilds. New seals from GM are still the short design and offer no benifit over the originals. Another area of concern that causes this is a boost valve in the valve body, not near as common but it can cause this problem on a lessor scale. If a fluid/filter service has not been performed in a very long time then a very dirty or plugged up filter can add to problems as it because a major restriction. IF the filter is found to be very dirty on the inside, which can be verified by cutting open the filter, then there are other problems inside the transmission anyways and an overhaul is the only correct way to fix the problem. Sometimes servicing a transmission with this condition will make the problem worse, so dont feel that you need to rush out to have a transmission fluid service done to make the transmission work like new again because it isnt going to.
