I have a '99 4runner SR5 that had it's trans fluid slightly contaminated with coolant when I accidently during an oil change broke the trans fluid cooling line nipple at the radiator, which internally damaged it causing the 2 fluids to mix. I noticed it spraying out of the nipple right away once I started it so I shut it off but it was obviously too late. I changed the coolant and trans fluid replacing it with penzoil dexron mercon 3 by draining the trans pan several times in between short trips like I was told. However, when it's cold it doesn't like to downshift till about 3500 rpm even if I'm just coasting, but once it's warm it shifts perfectly. Does anyone have any advice like did I use the wrong fluid or should I have it flushed instead at jiffy lube or something? I don't know if this problem started right after the fluid mishap because I'm not the regular driver and she doesn't notice these things, but I know it wasn't like this when I bought it. Is there anything that could be causing this other than a junk transmission? Thanks any advice would be great!

 

I forgot to add that when I bought it it wasn't winter time so it wasn't nearly as cold when it was first started and driven. Could it be a characteristic that helps warm up the drive train faster in cold weather by keeping rpm's higher? Does anyone elses do this?

 

You must mean it doesn't upshift until 3500? Very common, all 3 of my 4runners did that once they got above 100K. My guess is the the tranny fluid just needs to warm up.

 

So you think it's normal well that's a relief, thanks alot!