all i know is that the rpms are not increasing smoothly from 1st to 2nd and at overdrive 42-55mph. When you take off and hold the accelerator at a steady position the car hesitates for a second a bucking feeling and then shifts. WHen it shifts it feels very subtle, not like you popped the clutch or anything like that and it will shift at an appropriate speed. This bucking feeling was first interprited by me as a slipping of the tranny and really it could be, it's just hard to tell the difference. at low overdive/med highway speed, (42-55mph) the car bucks forward and back, and the rpms move about 200-300 from normal. It could be something different but it just happened when i changed the fluid. What really makes me wonder though is that the transmission shifts very smoothly. I'm sorry if I don't know exactlly what your talking about, i'm just 16 with limited knowledge of a transmission.

 

Let me first state that I'm not arguing by no means with any previous members posts. For clarification: As stated earlier mine does what I think yours is doing. A few years back I was backing up and my reverse gear went completely out as the tranny had been slipping in reverse already. I had the tranny rebuilt by a professional and a new filter put on. Ever since the blazer "lunges" or "bucks" and is very noticeable as you can see the tachometer jumps at an increment of 500-1200 rpms at 42-55 mph. I had the dealer look at it, I had the warranty company look at it (not that they know anything ), and I hook a OBD II scanner to the car. All said it was the secondary air flow (Po410). It seems that moisture gets in it easily. Mine definitely isn't a traditional slip and I never looked into it any further as I have greater problems at the moment to deal with. I do know the warranty company wouldn't cover it at the time (probably because it was up in 3 months). Also, the fuel mileage seems to be lower (2-3 mpg). With that said maybe we'll both get an answer. And If its is a slip I do know the pressure and changing the viscosity of the transmission fluid (dirty and clean) can make a big difference, whether it be bad or good. I hope this helps and clarifies the previous posts.

 

thank you everyone for all your help in trying to diagnose this problem. I'm going to take it to a garage soon and see if they can help.