A-4 downshift lunge
I would be absolutely shocked if it was a big transmission problem. The car is showroom condition, highway cruising car. As far as I know, a 50 some year old lady owned it for the first 25k. It's had its fair share of WOT runs while going onto an entrance ramp etc and even fewer burnouts. I hate paying for tires. In fact the tires from 1998 just got replaced this year....
I have never heard the idle theory before. I am still on the stock tune. 20k miles and its never changed. Its never gotten worse, felt different, and outside of maybe 1 full day has it gone away. Does it on every stop unless i slow down in an extremely slow manner. Even then i can feel it just a little bit
I have never heard the idle theory before. I am still on the stock tune. 20k miles and its never changed. Its never gotten worse, felt different, and outside of maybe 1 full day has it gone away. Does it on every stop unless i slow down in an extremely slow manner. Even then i can feel it just a little bit
I think it's normal and you need to get used to it, or more like accept it.
One thing I've noticed about these cars is the programming keeps the fluid pressure high at 0% TPS. It's not like that on trucks.
Certain things I do in my f bodies will result in a slamming backout shift when coasting in lower gears, probably because I keep the Force motor table stock and modify the transmission and other areas to increase shift pressure. It rarely does it because I've learned to drive around this little issue. (meaning adjust my driving to prevent it)
Thats my answer, it's normal. Without having the car here and driving it, thats all I have and thats all anyone else has. A guess, you might get a thousand wrong guesses and a thousand suggestions to check this and that. All that all gets you nowhere, but they keep you busy with wasting time and money.
Like I said before, not in these exact words, have someone look at it. Preferably someone familiar with f bodies.
One thing I've noticed about these cars is the programming keeps the fluid pressure high at 0% TPS. It's not like that on trucks.
Certain things I do in my f bodies will result in a slamming backout shift when coasting in lower gears, probably because I keep the Force motor table stock and modify the transmission and other areas to increase shift pressure. It rarely does it because I've learned to drive around this little issue. (meaning adjust my driving to prevent it)
Thats my answer, it's normal. Without having the car here and driving it, thats all I have and thats all anyone else has. A guess, you might get a thousand wrong guesses and a thousand suggestions to check this and that. All that all gets you nowhere, but they keep you busy with wasting time and money.
Like I said before, not in these exact words, have someone look at it. Preferably someone familiar with f bodies.
That's a fair answer I suppose. I've seen a couple posts similar to this, a long time ago. There were 2 or 3 guys that said it happened to them since brand new. So i guess to an extent it is normal. I still am not fully on board with the comment about time and money, along with checking things. Isnt that part of the reason this forum is here? For troubleshooting? I mean I, again, have no issue trying everything I can, before letting a professional look at it. Or in this case, I will probably just leave it alone.
. I still am not fully on board with the comment about time and money, along with checking things. Isnt that part of the reason this forum is here? For troubleshooting? I mean I, again, have no issue trying everything I can, before letting a professional look at it.
The most direct route to solve the problem (that I would take) is tune it out.
It's programmed to downshift 2-1 at 10 mph at 0% tps, and coincidentally that's when it switches from the idle tables to the rolling idle table. At least on a 2001 and 2002.
That's just one of many things that can be tweaked for driveability with tuning.
Or is it mechanical.... how many things could it be. Motor mounts, I'm guessing you checked them.
Rear lower control arm bushings, rare to fail.
One thing I can think of to try is put your foot on the gas when you're going to come to a stop, an amount that will make it hold 1000 to 1200 rpm when fully stopped. Then let it off when stopped. If it is an internal transmission problem you'll still feel it, maybe even more.
Make a video. Since it would be so much easier for people to diagnose it with the car present, make the car present as much as possible.
TECH Junkie
Joined: Jun 2008
Posts: 3,197
Likes: 1,383
From: Nitro Alley
TECH Junkie
Joined: Jun 2008
Posts: 3,197
Likes: 1,383
From: Nitro Alley
Is this low roller problem going to happen at 46,000 miles? I don't think so, unless the car has been neutral dropped a few times. I've had that problem with a th350 that I rebuilt for a guy I worked with several years ago. The low roller broke.
I had at least 50 low rollers in buckets because a transmission hard parts supplier needed his building emptied out and let me take whatever I wanted. I looked at every one of those low rollers and they all looked as good as new, was trying to figure out why the one broke. Later I found out the guy had been neutral dropping it.
So this car and all of its major parts have 46,000 miles? If that's true there's more to this story. I have an '02 SS with 54,000 miles.....with a '99 4L60E built from a core that had 250,000 on it because I once converted the car to a six speed and went back to an automatic. It has no problems.
If I had to make a wild guess with what's going on I'd look at the idle on this car. The way it's described put this problem right where the idle transitions happen in the tuning.
I can't go out and drive either of my two because they have high stall converters (which change the feel of coming to as stop) and all the little quirks have long been tuned out, like way back when they were stock.
So what kind of life has this car seen in it's 46,000 miles? I doubt that will be answered. Maybe the transmission needs to be pulled, because now there's a direction to go (although I thinks it's the wrong one).
I had at least 50 low rollers in buckets because a transmission hard parts supplier needed his building emptied out and let me take whatever I wanted. I looked at every one of those low rollers and they all looked as good as new, was trying to figure out why the one broke. Later I found out the guy had been neutral dropping it.
So this car and all of its major parts have 46,000 miles? If that's true there's more to this story. I have an '02 SS with 54,000 miles.....with a '99 4L60E built from a core that had 250,000 on it because I once converted the car to a six speed and went back to an automatic. It has no problems.
If I had to make a wild guess with what's going on I'd look at the idle on this car. The way it's described put this problem right where the idle transitions happen in the tuning.
I can't go out and drive either of my two because they have high stall converters (which change the feel of coming to as stop) and all the little quirks have long been tuned out, like way back when they were stock.
So what kind of life has this car seen in it's 46,000 miles? I doubt that will be answered. Maybe the transmission needs to be pulled, because now there's a direction to go (although I thinks it's the wrong one).
Does it idle higher than 550 rpm?
It used to be common for the pcv hoses to rot way back behind the intake manifold where you can't see them or even access them without taking the manifold off.
A vacuum leak may cause weird problems, if it's small enough the idle air control will make up for it but cause weird transitions when returning to idle.
It used to be common for the pcv hoses to rot way back behind the intake manifold where you can't see them or even access them without taking the manifold off.
A vacuum leak may cause weird problems, if it's small enough the idle air control will make up for it but cause weird transitions when returning to idle.
Does it idle higher than 550 rpm?
It used to be common for the pcv hoses to rot way back behind the intake manifold where you can't see them or even access them without taking the manifold off.
A vacuum leak may cause weird problems, if it's small enough the idle air control will make up for it but cause weird transitions when returning to idle.
It used to be common for the pcv hoses to rot way back behind the intake manifold where you can't see them or even access them without taking the manifold off.
A vacuum leak may cause weird problems, if it's small enough the idle air control will make up for it but cause weird transitions when returning to idle.
Digged into stock idle rpms. Sounds like every 98 auto is 150 off on the gauge. Which then makes it 650 in gear and 750 in park. I obviously should hook a scan tool up for real world numbers.
Joined: Nov 2003
Posts: 6,216
Likes: 236
From: Wichita KS / Rancho San Diego
There has been some excellent discussion in this thread. But I must admit, I fail to understand what the problem really is. The car "jerking forward" on a 2-1 downshift? To me that sounds exactly like what would typically happen when a lower gear is engaged. A noise? I get clinks and clunks through my driveshaft all the time; I think the 2-3 upshift is the worst.
So basically, I'm befuddled as to what exactly is being discussed. What am I missing?