hi, i replaced my thermostat and coolant sensor and coolant sensor connector on my 05 Monte carlo 3.4 LS because my temperature gauge periodically stoped working which would also knock out my air condtiioning and cause my cooling fans to run. anyway, after replacing these things i put it all back toether and now my car shifts hard when i reach speeds around 40 to 50 mph. i looked for vacume leaks, replaced TPS sensor, cleaned throttle body spray cleaned the MAF sensor. i just had the car looked at by a mechanic and he could'nt find anything wrong only that the car seemed to have transmission problems. it never had tranmsission problems till after i replaced the T-Stat and Coolant sensor and connector. could i have fried something when i clipped the wire harness to the coolant sensor and replaced it with a new one? i might not have disconnected the battery when i did that. could the Thermostat be wrong? i bought a Duralst from autozone and i'm not sure what temperature it is? the box does'nt say? It did visually match up with the one i removed thou. but i'm not even sure what temperature i my car needs or if it even makes a difference? I would very much appreciate any help because it's givving me heasdaches worrying.

 

Bump!!

 

bump or blob?? that post= big blob

 

Sounds to me like this is coincidental. The T-stat has no relation to trans shifting.
- When was the last time the fluid and filter were changed for the trans?
- Is there enough trans fluid in it?

 

filter and fluid were changed last year and fluid looks bright red. this is what i recently figured out..... when i have my climate control set to "HOT" is when it shifts hard. when it is turned to "COLD" it shifts good. could the heater core be cooling the engine coolant too much thus causing the the coolant temp sensor to read a slightly lower temp and adjusting shift timing? because i read that any slight variation in temp messes with these newer cars computers. i changed the ATF and bled the air real well weeks ago. i recently bled (burped) it some more with the Lisle funnel made for this purpose. heat in the cabin has always been close to instantaneous. it's wierd i know. i think i may purchase a new radiator cap today and see if it's a pressure related thing. it could'nt hurt?

 

Little mixture of both, bump going up, blob coming down? Fair enough?

When my MC was having heating problems, the temp would rise and my tranny would start shifting real hard going into 2nd and 3rd gear. I basically have had 75% of my cooling system replaced in the last 3 months (THANK GOD FOR MY EXTENDED WARRANTY!!!!!) but my trans fluid was flushed out along with the rest of my system because whoever owned the care before me, let it sit up for a good while. I bought it with 49kmiles, now has 66k over 2 years of my ownership but I got it from the Nissan dealer and of course they cut every corner they could to make it sell able. They put that sealant crap in the engine and basically gunked EVERYTHING up. After 2 different mechanics and countless trips to the shop, we're stable but still sometimes if I just on the gas say on the highway and have to come to a stop for say 3 minutes at a long light, the temp will rise a little and the a/c will drop out for a little while. I'm in Florida...we need our A/C! So I just bought the 180 degree thermostat and going to buy a few more upgrades to see if we can eliminate this completely.

 

AH, and now that I think of it, the trans fluid is cooled by flowing through part of the radiator. If your coolant temps were overheating, you could have also cooked the trans fluid.
It's best to pan drop and change fluid and filter. NEVER flush. A flush sounds nice, but most people to have trans problems with a fluid change are those who flush. If your trans filter has NOT been changed, I would recommend trying a pan drop fluid and filter change. If you had bad fluid before, you may have a dirty filter in there.

 

Yep everything was cooked basically. They dropped and replaced all fluids and filters, replaced sensors, radiator, water pump, LIM twice, housings, thermostat and the list continues. I got a few things I want to get to increase the cooling and a little performance. Basically this car was bought new, driven rarely and sat up for a WHILE. Have hard water stains on the windows that won't come out for nothing. But we're getting there, been a great car besides user created errors, ~$5,000 worth lol

 

yeah, i'm planning on doing a pan drop transmission fluid change and change the filter and o-ring aswell. it still shifts great when i have my cabin climate control set to "COLD". the second i flip the sliders to "HOT" it starts to shift hard and slip. regardeless of weather the cabin climate control fan is on or not. despite having plenty of heat in the vehicles cabin..... do you think that the heater core could be partially plugged or perhaps the line leading out from the core is clogged? i read one time from a mechanic on google that installing a thermostat that is too cool for your newer computerized vehicle will cause the car to shift hard in upper gears. i recently took out the duralast thermostat and installed an AC DELCO from the chevy dealership down the street. it did'nt help any but perhaps the heater core is cooling the antifreeze more. i did flush it with a garden hose but i may buy that prestone T-Splice kit and try back flushing it with a bit more power behind it. also, my radiator cap may not be holding pressure like it once did. thanks guys, i feel we are finally zeroing in on something. :-)

 

oh yeah! My Temp Gauge after warm up is always steady at slightly under the middle line. so i don't believe it is overheating any.