Does synthetic ATF cause shudders in automatic tra

Thanks,
Matt

1. Is the engine running up to par? Ludwig's post may sound a little wild but it can very well be a problem. The shift is controlled by the computer "torque management" which is very soft on modern Rocks. If the criteria is met to shift into OD and then the engine bogs slightly under the extra load the trans can shudder rather then make a crisp shift.

2. Your computer is the learn type. It shifts and does everything else to some degree based on the driving style of the previous owner. You may be on the other end of the driver spectrum. When you buy a used vehicle or one that develops a computer related glitch, do a computer relearn. Disconnect the battery(s) to kill all power to the computer for 20-30 minutes. That will erase the data in the learn memory and it will relearn matching your driving style.

I am not saying this is definitely your problem, but try the simple things first then go for the $$$ fix.

The other thing to consider, unless the trans was a new trans filled with synthetic, or a Ford AOD tranny, you would not be able to drain all the fluid from it. Emptying the pan gets you 3 to 5 quarts, while the tranny can hold upward of 12 qts, depending on what it is. You can never change it all unless you can drain the converter, and most transmissions don't have provisions for this.

Charles

Use Mobil1 and have noticed smoother and more complete shifting, shifting earlier (lower rpm's) and when very cold it now smoothly shifts into 4th (OD) whereas before, with paraffin oil only, it wouldn't go into OD for several miles at highway speed.

I suck out and put in new 2 qts every time I change the engine oil.

txblu