I searched and couldn't quite find an answer to my question so I figured I would post and hope someone can shed some light on this. From what I searched & read apparently the ecos are notorious for timing chain fails so here is my question.

At times and it isn't often but at times when I go to accelerate my rpms will become sporadic between 1-3k just before or after going into 2nd or 3rd then my Speedo will twitch then struggle to keep reading accurately only to ultimately hit zero. During this no lights flicker and no dash lights appear aside from the Trac off and check engine(code p0507) which are always on, the car will lag or feel like it is being bogged down but if I hit the throttle enough eventually it will catch up and then car just takes off and hits 60 in a few seconds. I avoid doing this as I don't want to damage anything so I usually go with the other fix which is turning the car off for five seconds then turning back on.

Now I have noticed that sometimes when going from park to reverse, reverse to drive or simply park to drive that it takes like 3 seconds for the gear to set in place even after the knob is locked in drive or what not. Like it seems like the transmission is behind the shifter as if I was shooting a gun on cod only for the gun to fire 3 seconds after I emptied the clip. I know on my 97 I can go from park to drive and the gears are immediate, for my 04 I have to wait until I feel the gear set which gives a small nudge feeling. Is this the timing chain or torque converter or could my dog bone be the cause of this? On my 97 due to my old dog bone being @!#$e when I would go from park to drive the engine would ram itself into the firewall but it never caused a driving issue like this. It is a 4T40e by the way so what do you guys think this could be? It has never had a transmission filter or fluid change so that could be why but equally could not be. The car has only 124,158 miles on it compared to my 97 which has a ridiculous amount of miles. I changed the spark plugs and will be performing a fluid and filter change for both oil and tranny but would like to know if this might be a precursor to a much larger problem a simple fluid/filter change wouldn't solve.

I'm no transmission expert but sounds like a electrical problems for Speedo if it was timing chain which it's not it will rattle and make noise,or simply jump tooth causing misfire or engine damage. Maybe I missed it is this a automatic or standard transmission if automatic again electrical issues. Engine light should show issues but I've had problems with are self diagnostic systems.