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Pete, Pontiac Technician
Category: Pontiac
Satisfied Customers: 24142
Experience:  17 Years Pontiac Technician and training.
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2003 Pontiac Bonneville: shift would smooth out

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I have a 2003 Pontiac Bonneville,3.6. The transmission would shift hard every now and then but if I shut the car off and then back on it would smooth out. I recently changed the fluid and filter and now it shifts hard after just a few starts and stops in traffic. It will reset when I shut the car off but does it again sooner now. I have 133,000 miles on it.What has gone bad?
Hello,I will be glad to try and assist you with this,Welcome to Just Answer.


The first step that should be done here is the fault codes should be checked using a code reader or scan tool.There may be fault codes in the computer that will aid in diagnosing or pinpointing this problem here.This can be done at just about any shop or GM dealer and I have heard of parts stores checking codes free of charge in most places.

There are a couple of bulletins out on hard shifts like this and the fault being either debris in the transmission valve body or a mechanical fault in the transmission valve body.Usually if this is the case then the vehicle wouldn't rest the hard shifting when the key is switched off then back on.

What you may have at fault here is the transmission pressure control solenoid may be sticking in the valve body.This is an electrical solenoid that controls fluid pressure through the transmission valve body,if it sticks it can cause this problem.This can be fairly common for this solenoid to fail and cause this as I have had to replace quite a few of these before.

The solenoid can cost around $100 and about 5.5 hours labor to have it replaced as the transmission has to be lowered to gain access to replace it.It is located on the drivers side of the transmission under the side transmission pan.

If you wanted to you can have the transmission flushed by a flush machine to see if this corrects the fault in case it is debris build up in the transmission,this would be the cheapest step to have done first.

Let me know if you need anything else,click accept if you feel satisfied with your answer as this is how I get credited for my time,Thanks Pete!
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