Hoping you guys can help me figure out what's wrong with my 99 GS400. I took it to the mechanic, thinking I had transmission problems. He said that wasn't the case and I just needed new motor/tranny mounts. That helped the problem, but did not fix it.

Symptoms: While already driving, if I let off the gas and then press on it again the car bangs forward. However, if I'm already on the gas and accelerate further(even hard) it is very smooth. The only way to avoid this is to VERY tenderly press down the gas until the RPM's go up at least 500 and then I can push down further and it will not bang(hard to pinpoint the origin of noise and bang feeling).

From my research on TC's, I've heard symptoms include vibration at lower speeds and I believe I have that, but at this point I could be imagining things or even thinking old quirks are new quirks.

Also, when I put it into reverse and move back a few feet and then hit the break, there is a bit of a cracking noise. That could possible be a caliper I have had a little trouble with.

For no real reason(bc I have no real knowledge of mechanics, besides my attempts at research) I feel like this problems could be attributed to a transfer case, if not the torque converter? I only say that because of when/why it bangs and the way I avoid it. However, I couldn't find much on failing transfer cases and this is purely hypothetical...plus a guess from someone who doesn't know what they're talking about.

AFTER THAT LONG A** POST....

Can you help me? =\

I will be taking it back in about 2 weeks regardless, but wanted to ask you guys for opinions.

EDIT: I FORGOT TO MENTION, while using cruise control, the car now sometimes bangs forward several times while it rev's forward. The speed/RPM's barely change, but bc of the banging it's very noticeable. I think this is unrelated to the banging, and only a speed senor, but figured the more info the better.....

 

I wonder if that feeling could be the differential how does the car shift while accelerating hard?

 

It accelerates smooth as long as I've already been pressing the gas(i.e. maintaining speed), hard or soft acceleration is HARD if I am not already on the pedal. I haven't tried to accelerate VERY hard though. Would you suggest this as a way of further diagnosing the problem? Don't wanna literally break whatever it is and end up in wrose trouble though lol.

 

same thing is happening to me when its cold my tranny slips but after 5 to 10mins of driving my GS drives fine