My gf just got a 00 Monte 3.4l that she loves and I want it to be a great car and run forever(I'm all about maintaining all my rides) and I'm just now starting to address the few little problems but don't know all about the 3.4s.

1st problem. On a cold start when the cars been sitting for hours. Start it put it in drive it just wants to rev up for about a minute or two then will go as if normal. When it does this I haven't tried to hammer the gas or anything but I have gotten it to 2500rpm and still nothing. Doesn't have any hard shifts, it does whine a little bit that I think could be the tranny... What's going on? Where do I start? Looks like a newer tranny and fluid looks pretty good.

Also the temp gauge started to not show it getting warm....when she first got it. It was good and would read right below middle....if it idles at a stop for awhile it moves up maybe a quarter....simple t_stat?

 

Change trannt filter and fluid

 

You think thats it? Or possibly internal issues

 

Also what's the best fluid and filter to put back in it, and should I put any Lucas tranny stuff in with it

 

I agree, change the trans fluid and filter. I've heard of a case like this that the fluid was just crap until it got warm.

No need for additives, just get a fluid/filter change. I've used Valvoline brand trans fluid in the past. Any major name fluid should be fine. I also recommend the molded trans pan gaster vs the "freebie" flimsie one that comes with most filters. It appears based on some discussion the OEM trans pan gasket is meant to be re-usable, but if you are changing fluid at 100K or more miles, IMO, change the gasket. Re-usable or not, it's a rubber coated gasket, the rubber has been crushed/seated for over 100K and through lots of hot/cold temps. Trans fluid/filter changes are not often, why tempt fate for a gasket leak IMO.

As for the temp, when you turn on the heaters, is it warm/hot? If it is always warm/hot, I doubt it's a tstat. The clusters are known for the stepper motors that operate the gauges to fail. Next thing to do IMO is if you can get a scan tool that can read sensor data from the ODB-II port under the dash, see what the PCM reports the temp being. If it reports it as normal and the gauge is reporting nothing, I vote stepper motor failure.