2001 Lumina 92,000 miles

I use my lumina to deliver mail for the post office. Its worked fine for the last 15,000 miles that ive owned it but now its having some problems.

First off is the weird transmission jerking it gets sometimes. Its very weird because I can drive the car for weeks and it'll be fine but if the temperature outside gets over 85 degrees my transmission seems to start having problems under certain conditions (It usually happens after ive been idling in drive for a while). I can tell when it happens because the engine or transmission will start to have a higher pitched sound and the car will jerk everytime it shifts gears. The strangest thing is that if I turn the car off for about a minute and turn it back on it'll work fine. Ive had the transmission fluid and filter replaced since this has started. There hasnt been any check engine lights on since and the temp gauge never goes over half (just had a coolant flush too).

The next problem I think could be the master cylinder but Im not sure. This is another intermittent problem like the previous but completely unrelated. Usually when I first start my car up my brakes wont work, I will literally push the pedal to the floor but the car wont stop. If I pump the brakes the brake will usually catch on the second push. It will only do this for the first 20 minutes of driving the car, afterwords it will work perfectly. The brakes are all new and I just bled the lines yesterday.

Ill probably be taking the car into a mechanic to get it fixed but Id like to have a general idea of how serious the problem may be before I send it down there. Every day the car is at the mechanics I cant deliver mail so Id like to know as much as possible and tell him what to look for beforehand.

Thanks-

 

The problem that you mentioned when you are driving doesn't sound like the tranny. Try changing the fuel filter first and also a tune-up wouldn't hurt either. My car did the same thing n I just did that, now it runs smoother and does not hesitate when shifting gears. Now the brakes on the other hand sound like either the brake line or the cylinder...seems like the brake fluid isn't getting through correctly.