rocky5

iTrader: (2)

So lately I've been experiencing some tranny slippage from the 1-2 & 2-3 upshift that typically occurs around 1500 -2200 rpm's. Now, I understand my fluid is dark brown and not cherry red and I've no clue when, if ever, the fluids have been replaced. The odd thing about it is that it DOES NOT SLIP on cold morning starts. It tends to slip only after I've been driving the car for over 25-30 mins. More so, if I shut the car off after it started to slip, say I'm at a red light, I shut it off, light turns green and I restart it and drive off, it does not slip, even if I take off aggressively, it won't slip!

Now, I've read about the shift solenoids going bad and also read about the maf sensor being a possible culprit. I just don't understand how is there any relation between a slipping transmission and the maf. I'm hoping and praying it is just the maf but I can't understand the relation. See link

http://my.is/forums/f87/auto-transmi...my-fix-384874/

Has anyone here experienced something similar?

mveale

iTrader: (5)

Start with a simple transmission service. Flush it, new fluid, and install a new filter.

I don't know much about the shift solenoids, but I assume they're inside the transmission. If they are, I would read up on the issue and consider fixing or replacing the solenoids while you've got the pan off.

MattyG

"... I understand my fluid is dark brown and not cherry red and I've no clue when, if ever, the fluids have been replaced..."

You've answered your question in your second sentence. Anytime your transmission fluid looks like that and you've been driving around for awhile, it's going to be a problem.

Are you running a stock setup or modded? Bigger wheels, wider tires? Either way as mveale says, you have to start with the basics. Change fluid, clean the filter, rear differential fluid/condition/change.

A cold transmission is dealing with thicker fluid. A warm transmission shifts with hotter thinned out fluid. But if you take off aggressively there is more torque and pressure being put on the converter and the computer signals the transmission to shift that way.

rocky5

iTrader: (2)

MattyG, this is my 2nd gs400. I purchased this one 2 weeks ago, the car was fine and the slipping only began after I cleaned the maf with crc maf cleaner. I understand the viscosity when cold as opposed when being hot. But as I previously mentioned, even after shutting the car after a prolonged drive, and re start it immediately, the slip is non existent, and the fluid is obviously still hot (thinner viscosity)

Also, i'd have to disagree with your torque pressure theory, although I'd agree in any other circumstance because once it starts slipping, I can't drive "aggressively" because it just slips, but if I shut it off / restart it immediately, I can redline with absolutely zero slip

deepdish

I recommend a trans fluid drain and fill, not a flush (which I've heard is kinda dangerous for higher mileage engines). Then a few months later, do another trans fluid drain and fill.

I had slippage all the time on cold mornings from Park into 1st gear a few years ago. Then when I did a drain and fill it solved the problem immediately.

MattyG

A simple maf sensor cleaning should not be triggering this severe an issue. Did you unplug stuff? Something else going on here. Loose wires? Go look under the hood again.

bruceb58

Do a flush:

1) Drain pan
2) Refill
3) Remove return line from tranny and run into a pail where you can tell when 2 qts come out
4) Run engine until 2 qts come out and turn off engine
5) Refill with 2 qts
7 Repeat steps 4 and 5 until you get clean fluid out

This is not a power flush so it will not harm your transmission
Only use Toyota ATF.

If the solenoids are bad, you will get codes. I change my transmission fluid every 50K miles. I have 185K on my 2005.

gsean400

Dude before you go draining everything.. Unplug your battery and let the computer reset itself. I had bad slipping problems 2 times with my lexus and after leaving the battery disconnected it cleared itself up. The computer adjust to your driving style so sometimes it will get confused. My old gs400 had bad tranny soleniods and i got codes and the tranny wouldnt shift at all into gear. Worth a try before you go spend money on draining the fluid

rocky5

iTrader: (2)

Was the first thing I did. I Unplugged both terminals, car sat for 24hrs, connected terminals next day and drove fine for the first 2 hours then symptoms reappeared