Hey all,

I am hoping some of you can guide me in the right direction of where to look/fix my issue.
Car is a 2000 Trans Am - 5.7 WS-6 - Automatic, with about 112,000 miles. (wifes car)
- no real mods done (to my knowledge)... just SLP lid/KN filter (that I put in),
We bought it used, guy said he never moded it or raced it... Said it took it to a drag strip once for a couple of runs to see what it could do.
I think it does have an aluminum drive shaft tho.

No Check engine lights coming on.

Conditions are hard to describe but ill do my best.
Several years ago, on the highway on way to work, my wife noticed that after coasting (foot off pedal) she went to accelerate, and the car didnt want to go. It made a muted accelerating sound, and maybe she could only do about 50. At work, a coworker checked the trans fluid. It was a little low, so they added some. And the problem went away for a least a year. (no CEL or anything came on)

It happened again about a year later. I check the trans fluid, it was fine. not burn, not low, not overfilled, just normal. I had my wife bring it to a transmission place to check out. But they could not duplicate the problem, and since there was no CEL, they said they could find anything.
Aa couple weeks later, happened again, brought it to a different transmission place... they looked it over, couldnt find anything.

Things got busy, it was our 3rd car, so the problem was never resolved, car was used on occasion. sometimes working fine, sometimes acting up.
Some where along in this time, the RPM gauge would not move, stay around 1000 RPM... did some research, replaced a (what I recall being) speed sensor on the transmission the RPMs worked again.

This summer, we started having to drive it more and more and the symptom happened more frequently. Brought it to another transmission shop at beginning of summer, they couldnt duplicate, although it happened to me on my drive home from the place. I went back a few days later, and drove the Tech around. The car slightly acted up, but not the full on symptom. That transmission tech said it felt like a clogged cat. So I had their shop engine guy look at it... couldnt find anything.

I had one of their other guys drive it, and he said he experienced some brief symptoms, and thought a trans flush might help since at one time the fluid was low.
I was doubtful that a trans flush would solve anything, So i told them to drop the pan and also flush it. I was hoping there was debris in the pan that would point to a trans failure of some sort.... but they stated their was nothing out of the ordinary in the pan.

Now symptoms seem to be getting worse...just about every time we drive it, and now at slower speeds.
Just wanted to layout the whole backstory, to give as much info as possible.

So as a brief recap of conditions now, as best as I can describe.

At almost any speed, in 4th gear, while coasting (usually down small hill, or behind someone going slow), when you go to accurate, the Car doesnt seem to hook back into gear. The car sounds different, like a the exhaust is muted. The RPS will slowly raise when pushing the pedal, but NOT like revving and engine in neutral... Just seems like normal RPM activity.
From what I researched, sounds kida of like car going into Limp Mode. But every shop has dismissed this as there is no CEL
No CEL comes on.
Now does this going as slow as 30 mph
When you come to a stop, and then start to accelerate car acts normal, until you have to coast again.

I think I recently discovered that when it doesnt want to go... , if I apply the brake a little (does not have to come to a complete stop), then try to accelerate, it is fine, until I start to coast again.

Any ideas on where I should look? and how to do some diagnostic tests to pin point the cause?
I have thought about dropping in a new transmission, but dont want to spend the money if that doesnt solve the issue...

other random things (incase its linked)
never had any transmission fluid leaks (nothing noticeable on the ground)
do have a slow/small engine oil leak, when parked there will like 4-5 drops on the ground (after being parked for a few days).... just enough to notice on the garage floor.
tires/wheels are larger than stock. I want to say their 18" ( never Tuned to new tire size)

I was thinking about pulling the cover of the rear differential, to see if the gears in there were worn ?

Not sure where I should be looking, any help or suggestions would be appreciated.
thank you

 

Could you have a dragging brake? Pull over and see if one of the wheels is excessively hot shortly after this problem occurs. You could have an anti locking brake problem, old rusty brake fluid causing a problem, collapsed flexible brake line to the caliper or a sticking piston in a brake caliper.

My two cents . . . .

Rick

 

Thanks for the suggestion, it is a new idea I haven't considered looking at.
I'll have to take a look at the brakes this weekend.

But kinda odd that the symptom occurs when coasting. And by applying the brakes corrects it. I would think that if a brake was dragging, applying brakes would not correct the symptom. But I will check them out!

 

I've had brakes stick before. Hitting them sometimes frees them up. If you've never done them, I would take the wheels off and lube the slides and pins anyway.. ~2 hours and a jar of permatex. Might be time to just do it anyway. Inspect some stuff in there.

I'm not in the car so its tough to tell. Judging by the amount of transmission talk, it doesnt sound like you feel like the problem could be air/fuel related. Is it sluggish accelerating? What happens when you hit the gas exactly, do the RPMs go flying, does nothing happen, or does it bog?

 

Maybe the Torque Converter Clutch is staying engaged. When you hit the brake it is releasing it. Any chance you can get your hands on a decent scanner?
The Data would tell you if that's happening or not. It's got to be better than a standard OBD2 code reader if you want to see trans data.
Joe

 

Usually when you hear that funky intake sound and the car doesn't want to go it's running real lean. I've had that happen many times in my career as a tech.

I've had it from a clogged cat before too but catalytic converters don't come and go, once they are coming apart and clogged the problem will be there at all times. So I would go for the fuel pump and fuel filter if I were gonna take a stab at it.

I don't want to get too caught up in your description about how it happens and when because when I do I often find what I find as a tech is quite a bit different than what the customer feels the issue is.

The best thing you could do is take it to a really good tech. He will be able to tell you if it's drive line related or engine performance related. Trans guys know transmissions. I would stop taking it to only trans guys and have a very experienced tech look at it and do a fuel pressure AND volume test on it. Check the fuel filter. Check TPS sensor operation, stop light switch operation, TCC activity and trans slip rate.

Pulling the rear cover and inspecting the gears and changing the fluid is never a bad idea. Go ahead and do it just because maintenance is always a good plan.

 

My money is on torque converter. My 2000 needed one, same as my 2000 gmc sierra...apparently gm couldn't get a good converter in anything that year.

Get on the highway and at 40 give it some more gas than normal. It will go to lock up and see if weird stuff happens. Then on the highway lean into it while doing 60 or so, mine would hold until power came then it would fall on it's face and free rev.

 

That tells me torque converter too btw. Exactly what my car did. I put a cheap converter in it from advance for under $200, now I have a fti in it since the trans turned out to be fine. "Rpms flying" is exactly what mine did, it'll get bad enough you'll be able to recreate it, lock up clutches just need more abuse.

 

thanks for all the suggestions, I have some additional info.

So the other day when the car was driving fine, I lightly applied the brake while also accelerating. and the car acted/sounded the same way it does when my issue happens. So i thought for sure must be a brake issue. but on another day after the problem occured for a while, I pulled over and none of the wheels were hotter than others.

Tonight I jacked up the car, and I looked at all the brakes none of them were worn more than normal. (i would think if they were sticking the pads would be worn pretty bad, and or rotors worn, but everything looked fine.
So then I was thinking its got to be gears/teeth not aligning up, so I pulled the rear differential cover off tonight, expecting it to be trashed inside, but the inside looked good. The diff. looked greasy/damp, so fluid has been seeping out. but a decent amount of fluid came out. ( I forgot to check the fluid level before taking the cover off... so I dont know if the fluid was low (or if that would even cause a problem if it were low.) It also looks damp around Differential pinion seal, so fluid has been seeping. But I dont think this would cause my issues would it?... but it is something I will have to address.

When I pulled my tires off, and remembered that I had put on wheel spacers in the rear. ( I have Miro 111 18X19.5 w/25 mm bolt on metal spacers on the rear ( my wife want the car to have a wider stance in the back)... if I remember correctly)
The rotors spun freely for the most part but at 1 point something did kind of bind up, making it a little harder to spin and it made a little bit of a low grinding/ crunching noise.... Im thinking wheel bearings? But I stupidly spun the rotor in reverse and freed it up, before I could completely diagnose where it was binding up. but I am pretty sure it was coming from where the bearing would be.

So IF it is the rear wheel bearings that are occasionally grinding, binding up... I would imagine that would cause similiar symptoms...?
So tomorrow /this weekend I think I am going to try and change out the bearings.... And maybe the pinion seal, that kinda of makes a high pitch squealing when turning the wheels. I ran out of time today to do any more diagnostics.
I wish my garage was bigger! or I had a flat driveway to work on. the car is currently jacked up, in my garage. 1 side should be ok to get the axle out, but no way I can get to the other side.... so got to do 1 side and put it all back together to move it over, jack it up and take the other side off.

Oh, 1 more question.
the rear end squeaks, when bouncing the back up and down. While under the car, I discovered it was the drivers side bushing on the anti sway bar. I unbolted that bushing. The rubber/plastic like bushing was not cracked, brittle or soft. The metal on anti sway bar was bright metal when the bushing was. I plan on buying new bushings, but, do I need to apply grease where the bushing wraps around the anti sway bar?

Even though I am currently leaning towards the bearings being the issue. ( I dont know for sure) although, I am thinking that with the wheels on the ground and the weight of the car, maybe it puts more pressure on the bearings causing them to bind more... especially after just researching a little on wheel spacers!... but I had to trim the lugs on axle, so that they didnt stick out beyond the spacer ( and not allow the wheel to be flush).. so If I take the axle out to replace the bearings... maybe Ill put new full length lugs in, and not put the spacers on.

I do like the idea of getting a good scanner to test the torque converter... because that is what I was originally thinking transmission/torque converter issue, and I havent really ruled that out in my mind.
Although, I have previously taken the car to 3 different transmission/mechanic shops ( 2 of the place did both engine work as well as transmission work), as well as 2 other places that strictly did engine work. And most of them confirmed they would/did hook it up to the computer. they all said they couldnt find any codes.
So my question is, if the torque converter is bad, would that throw any codes, or do you have to look in at the scanner interpret the data. I dont know what I would be looking for if I had a decent scanner.
Can anyone recommend a decent one?

I appreciate any more comments or thoughts.
Thank you

 

This kind of got out of my wheelhouse... but I do you have any updates?

 

This is exactly what I thought after reading through the story and symptoms. It sounds a lot like the converter isn't unlocking when you slow down and then reengage the throttle. Sounds like a perfect time to get a stall done. I thought maybe dragging brakes like others have said, but you stated that it happens when letting off the throttle and coasting. Hopefully you have access to someone with a good scanner so that you can have them ride with you and watch the trans data while you are driving.

 

I could be wrong, but I don't think the converter would necessarily throw codes if it were having issues. I don't know everything though. Maybe someone more knowledgeable can answer that one.