I have a 2006 MC LS (3500). The trans will shift hard and then i'll park the car and when i come back after a while or whatever and it will sometimes still shift hard and sometimes it will shift as if it was brand new. It also shifts hard through all the gears. Now that it's turning into spring here in milwaukee it seems to do it more often. I had a thought that it might be overheating but im now towing anything or driving hard. It seems to be one thing after another and im frusterated as hell and don't know what to do.

 

If your tranny fluid has about 30k ish miles, I would flush it. The shop around here flushes it and they give it a warranty. I would check your local shops.My car does the same thing and I'll be having it flushed. As long as you dont gun it, and use second gear for steep hills and side streets, you should be fine.

 

Have your Monte scanned to see if there are any diagnostic trouble codes stored in the engine control module or the transmission control module. Many transmission related DTC's will not turn on the check engine light but will cause the tranmission control module to enter a default mode which increases transmission oil pressure resulting in harsh shifts.

 

I had the fluid completley flushed earlier this year but im going to check to see if there was a warrinty to see if i could have it flushed again perhaps there is some stuff in there that has come free since the last flush.

 

I will examine this also I am thinking that I might just buy a diagnostic tool and seein what the hell is up. But it has to go back to the mechanic anyway because i have a fuel trim prob i gess.

 

Be careful about flushing it too much. I would get it scanned first.

 

A fuel trim related DTC will also cause the transmission to go into default mode. You possibly do not have a transmission issue at all.

 

hey man, keep your head up and dont give up...i always say that when **** breaks or goes wrong, theres always a way to fix it or get it done, and i dont think i can help you here, but many of the other knowledgeable members on MCF can help.

 

I'm not sure how hard its shifting obviously, but, my 06 LT 3.5L has always since the day I bought it shifted somewhat hard...Nothing to be concerned about, but you feel the shift, it just feels like its slightly performance tuned or something...

Like I said, I don't know how hard your is shifting, but I do know that a firm shift is normal for our cars.

If your still under warrently, I would have it checked out..

Also, when you had it flushed, are you 100% sure that the place you had do the work flushed your tranny with Dexron VI? ALL 2006 and newer GM cars and trucks REQUIRE the use of Dexron VI transmission fluid. If the flush shop did not use the correct fluid, and used Dexron III fluid, this could be your problem. The new fluid has a lighter viscocity than the old stuff, and is a semi synthetic fluid with new friction additives. Personally, I change my own tranny fluid, and I know Dexron VI is not the easiest fluid to find, so I would be suspicious that the tranny place you had flush the fluid, used the older Dexron III.

Anyway, just a thought...Good Luck

 

Is there a way test the fluid i have to make shure its the right type.