I need help, My 2000 monte ss with 84000 kilometers, is starting to shift hard after 20 minutes of driving. It starts out fine but as soon as my temperature gauge reads a little over a quarter to half my transmission starts to shift with a hard pop! also my check engine light came on and the code read thermostat. My tranny is cooled from my coolant system right? if the sytem is not cooling properly could this be part of my problem? please any information will be much appreciated..

 

If the code reads thermostat, change it out. Its cheap and it can cause a lot of problems.

 

I will be changing the thermostat this weekend, and flush the coolant. your right it is inexpensive and needs to be done right away. But what about the effect on my tranny? any thoughts?

 

Usually when this happens you are already too late. You can do a trans filter and pan drop, but don't do a full flush.

 

When it starts shifting hard does it stop after you pull over, turn the engine off wait for a few seconds and restart?

 

it doesnt always hard shift, I have tried everything, including stopping and restarting and sometimes it seems to be ok, I changed the thermostat and it did not help.

 

my 04 ls does the same and i'm going to partially flush the tranny oil and change the filter. the oil level was low for a long time so I would make sure the level is normal. i will do this tonight and hopefully can post some results

 

Its weird How so many People have this hard Shifting problem I have the same thing ive had it since i pritty much ownd the car. Mine has 97 500KMS Someone told me It could be the CAT soo i change that to a Offroad stainless. SOUNDS BETTER did not fix the problem.. Then just befor winter storage a Code came Up I think 1811 or something along those lines.. Im Also Going to try oil and change filter Also Heard that doesnt WORK either and Could be the solinods Inside the tranny witch youll have to PULL tranny Out...

Other Words Good LUCK KEEP us posted and I think i might just trade in my Monte Befor I hear the Tranny GO BOOOOOOOOOOOOOOOM. I feel sorry for the next sucker . I already have a buddie that wants to trade his 2006 chevy 5.3 for my monte I might just have to take that offer...

 

the hard shift was fixed by simply replacing the fluid to dexron VI. it was expensive but i think worth it every cent. i also replaced the fluid filter as well. it takes 14 quarts and it is sort of easy to do. pepboys charges 135 for the labor and parts which is not bad. I paid about 75 dolars for the fluid and 15 for the filter which is just around 90. I'd recommend just go have it done at pepboys.

 

^^x2

also, ik this sounds kind of basic, but check your tranny fluid level. This simple step sometimes gets overlooked and we get caught up in the moment and think something is seriously wrong.

Check it after you drive around, then leave the car in park on a level surface with the motor on (still running), and check the trans dipstick. If you're low put in a half quart of drexon VI and repeat until fluid level met. It's crazy how such negative side affects can be created by something as simple as low trans fluid.