Transmission Diagnosis and solutions. Probs at higher gears
 

1998 Lexus GS 300 172,000 miles.

Shifting from Park, Reverse, Neutral, Drive are all ok. There are no check engine or Ect warning lights on the dash. I use Toyota ATF 4 and change out 2 quarts w/ every oil change at 4,000 intervals.

I can up and down shift the lower gears w/o issue.

The problem is when driving in the higher gears at 40 mph or higher. I'll let off of the gas and when I return to step on the gas pedal again, the engine will rev but I won't get a response from the transmission. I'll have to let off and rev a few times and the transmission seems to slip/drop clumsily back into gear. Heat is a factor as this happens more frequently on 105 degree days (Las Vegas)

I can't be convinced that this is normal behavior. It never did it before and now it is doing it more and more frequently.

1. What is causing this?

2. How hard is it to change out a transmission entirely? I know the cost is $3500 for the rebuilt transmission but I see them commonly at $1500 or less on eBay?

3. Tonight or tomorrow I will look at the Transmission pan. Is there anything special I should inspect once I have that opened up?

Thanks all:)

expect to find metal shavings.... a magnet should be there too. Mine does this, but only in exaggerated situations. I don't like this behavior either, but wifey doesn't drive like me...

I'd flush the fluid, do about 2-3 changes and get most of the fluid out. Recheck.

Extreme Heat can cause alot of things to act weird.

Same thing keep happening with mine last year. I have 191k mi and i know I have to start with the fluid. Did a complete tranny flush at toyota service (its way cheaper than lexus) and never had that issue again.

I'm disappointed at the lack of help here. Is there another board I could try?

If you're dissapointed in our responses where we actually tried to help you out only knowing that your tranny is acting weird to you under the situations that you posted then I suggest you take your car to a licensed and certified mechanic, a transmission specialist or the lexus dealership.

If you need more help there are plenty of other forums that you can join. This is a free forum open to everyone, we are not experts but in your post there are 3 people who tried to help you out. Saying that you're dissapointed in the lack of help is ridic.

If you want more help; here it is. Replace your transmission and your diff and driveshafts with brand new oem parts. Report back.

Recommendations?

There are multiple Lexus engineers that frequent Club Lexus and post
advice for ****s sake! I didn't even say you should necessarily
follow their advice, just take a look and come to your own
conclusions. You will find many people who have the EXACT same car as
you. When you begin to get advice from dozens of folks who have the
exact same year model, you can usually begin to see patterns that will
lead you in the direction of valuable information.

Apparently this hasn't been the case for me. The only advice I got was "change the fluid." which I've already done. The next advice was replace transmission and diff.

haha good luck getting a response now.

Like I had any shot of a meaningful response before.

I think we can rule out that the tranny fluid is the problem.

I'm thinking it's the torque converter.

http://files.sharenator.com/11596d12...-76449-580.jpg

very classy response...funny picture.

Not sure if the 98 has "E-shift" (steering wheel mounted up and down buttons) but either way, manually put the car in 3rd instead of drive and see if it exhibits the same problem.
When you let off normally above 40mph does the car have any engine braking (let off the gas and judge the "drag" on the car and then pop it in neutral and see if there is a difference).
I am not too familiar with the A650 valve body but it sounds like a sticking solenoid in the transmission. Are you using T-IV fluid?
My car sees its share of 100+ degree days with hard driving but I am also running an external B&M trans cooler.

In 3 I don't have any issue.. but ofcourse I can't drive very fast.

In 4 or "D" I get the -bad- behavior. No dragging... just won't respond to gas pedal.

I'm told a bad solenoid would prompt a check engine light.

I've spoken w/ 2 different mechanics and they tell me that the heat causes the fluid to thin out and for the seals to weaken causing my issue. They've also told me not to drop the transmission pan as the sludge in there is holding the tranny together on a hi mileage vehicle.

I'll put in the cooler and hopefully it won't happen as frequently and I can squeeze out another year or so out of the car. Fact is it's an old car and as much as I would like to keep it forever, I will eventually have to upgrade.