TRANSMISSION ISSUE ON THE HIGHWAY

I have a 2007 DCSB with A/T. At hwy speeds if I hit the gas I get a clean down shift into 4th to pass, but it doesnt want to up shift to 5th after letting off the gas. I literally have to take my foot all the way off the gas and then it makes a rough shift into 5th/overdrive after a little while. I am due for a transmission flush, but I am worried that this may cause an issue if there is a problem in the transmission...does the sicking sound like a major issue? All other shifiting and acceleration are smooth as silk, and no slipping or hard shifts at all at any other speeds. If anyone has had this issue and can shed some light please do. The truck has about 50k miles on it, and the trans fluid is very dark, but still red, and doesnt smell to badly burned.

 

With very dark fluid I would have the fluid changed.

 

Start by scanning the ecm and a road test with the scanner connected .
There are too many variables to guess at the problem . The scan will eliminate any computer control problems .
I have some information for you posted here
http://www.tacomaworld.com/forum/te...hift-kit-shift-recalibration-kit-2nd-gen.html
EDIT ...Thanks to KenLyns in the post below .I thought the OP had the 340 series trans .
I changed the my link to correspond with the OP,s correct transmission
.
.

 

The trans fluid gets dark pretty early. On its own, the dark color is not indicative of degraded fluid. How did you check the fluid condition? Did you open the drain plug a little and let some fluid seep out?

Go for a basic drain and fill if you are uncomfortable about flushing. The important thing is to have the right quantity of fluid in there. Your problem could be caused by fluid level too low or too high.

 

Edited my post with correct info . Thanks KenLyns !!!!

 

I removed one of the lines from the radiator and drained a little into a plastic bottle.

I will have to find the thread that has the steps to check fluid level and see if it is under...I assume if it is over then a ton of fluid will spew from the "check" plug once at the proper temp...

 

My truck did the same thing when I was do for a flush (55K miles). Had the flush, problem went away and my mpgs went up as well

 

I had an 08 that did the same thing. Took it to the dealer has it was under warranty and they did a computer reflash ? and it solved the issue.