Any car mechanics here?

GarageSmoker · Jun 26, 2002

A problem has come up with my Chevy S-10 since I arrived here in Florida. It is a 4300 V6, 4 speed automatic.

The daily commute is 35 miles with 4 traffic lights going and 3 coming home. The trip is 9 miles of 50 - 60 and then 20 of 75 - 80 (trucks force you to do that on the interstate) then the last 6 back to 50 - 60. I don't notice this as much in the morning as in the afternoon, but is has happened on both legs. It just seems that it is on every trip home.

After exiting the interstate the truck upshifts very hard. Hard enough that it chirps the tires from D1 to D2. No chirp on 2 to 3 but still a quick shift and less so into OD if I get up to that speed. To add to the mystery (or solve it) if I stop the truck and shut it down for a short period, like today getting gas, it doesn't do it anymore. And in the morning when I leave for work, no problem either.

I expect they will have a hard time duplicating the problem at the shop since I doubt they will be taking it on a 35 minute test run so is there some hint I can give them other than describing the problem? Will the computer see this one if it is OK when I drive it in? (dealer is close)

Any thoughts?

GS

JerryG · Jun 26, 2002

GarageSmoker,
Start by changing the transmission oil and filter. Most people never change those and that is one of the major reasons of transmission failure.

cp1969 · Jun 26, 2002

Temperature. Hot ambient plus hard driving equals hot transmission.

Maybe the radiator needs cleaned out?

GarageSmoker · Jun 26, 2002

Actually I think they just serviced the transmission before I left which doesn't mean anything other than they may have screwed it up or charged me w/o doing it.

And as to running hot it doesn't seem that way on temp gage and would it cool off enough at a quick gas stop?

GS

Youare · Jun 26, 2002

I don't know if it is true on your transmission but earlier automatic transmisions have a vacuum operated modulating valve that controls the shift from D1 to D2. I once had a car where the vacuum line came disconnected and it would not shift from one gear range to the next.

Maybe you have a sticky valve that makes the transmission shift abruptly. Do you notice if the same action happens when you accelerate slowly? Does it seem like the engine RPM is higher when the transmission shifts hard?

I'm sure ther is an answer out there some where. /w3tcompact/icons/smile.gif

Randy

GarageSmoker · Jun 26, 2002

If there is a slow moving car ahead of me pulling away it does seem to shift even harder. I think it is somethink vacuum related as well but the part about it self correcting after a short shut down (and overnight) has me baffled. And I am afraid it will have them as well, causing a bunch of try this and try that repair visits.

GS

CSAW · Jun 26, 2002

GarageSmoker

General motors uses a throttle pressure cable instead of a modulator on some transmissions. This is a cable that is hooked to the throttle body opposite of the throttle cable. When you push the throttle it pulls the throttle pressure cable that goes into the trans. This tells the transmission how much throttle is being applied. The more pressure (the longer pull) the harder and later the shift.

Check to make sure the cable going from the throttle body down to the trans is not stuck in the out possition or binding. To adjust this you hold the throttle wide open (engine off) and adjust the cable to the fully extended possition. There should be a push button spring lock of sorts on it. A little confusing at first but simple once you figure it out.

One other thing is if it is a late model the torque converter has an electronic lock up. Sometimes the solenoid that controls this will stick. That will usually cause the vehichle to stall when you come to a stop, just like stopping a standard shift car in gear.

I make no claims to being a transmission man but have played one on occassion.

I think a transmission shop would know right off what is wrong. Good Luck

Jeff396 · Jun 26, 2002

I had a '95 Ford E150 that had almost that identical problem. It would intermittantly shift hard from first to second. Everything else worked fine. I don't think mine ever chirped the tires but that may have had a lot to do with the fact that the truck was a pig on power. Anyway, the dealership wanted to remove it and replace everything that had to do with first and second gear.....$1100.00....Yikes! So, I took it to a great mom and pop outfit and let them have a look see. It turns out that my problem was caused by a $3.00 spring that had broken. I was told that it held tension on the plunger which controlled how hard the shift was. I was fortunate that the broken spring had not galled up the cylinder it rode in so I was just out the money for the spring and a fluid change. One of the few time I came out ahead.

Jeff

bgott · Jun 27, 2002

The first thing I would do is change the TPS if you have the 4L60E transmission. The throttle position sensor is what controls the shift points. There are diagnostic routines for checking the sensor but two thirds of the time it will check out good and be bad anyway. You can always carry a can of refrigerant and a tap and freeze the sensor when it is acting up and see what happens. Wait until you hit a good sized puddle with it, it'll really shift funny then. I'll bet you lived in a low humidity area before, didn't you? I'd just go ahead and stick it on, if you have a lot of miles it's due for one anyway. Be sure and get a Delco, every time I've used an aftermarket computer control part I've regretted it. I've fixed quite a few of these changing the sensor. What year is this thing, anyway?

rdln · Jun 27, 2002

<font color=red>Hard enough that it chirps the tires from D1 to D2.</font color=red>

after dropping a bigger engine into my jeep pickup this started to happen...and I loved it.

Frank_Mulligan · Jun 27, 2002

I knew someone who had a Ford Diesel truck that would cut out after about 45 miles of driving. Proving this to a mechanic was a little tough.

Sounds like something's getting hot. I used to have a 3 speed Gremlin/w3tcompact/icons/tongue.gif where the starter would get hot. If I stalled out or turned off the engine I'd have to wait awhile for it to cool down before I could start again. Popped the clutch many-a-time.

bgott · Jun 28, 2002

"I knew someone who had a Ford Diesel truck that would cut out after about 45 miles of driving. Proving this to a mechanic was a little tough."

I hate intermittents! I've driven customers cars for two week trying to find intermittent problems just to have it come and go when I wasn't paying attention or I was stuck in traffic and couldn't concentrate on the problem. It's a little hard to charge someone for driving their car for hours to find a problem. If that Ford diesel was computer controlled it probably was a cam sensor.

Rowski · Jun 29, 2002

What model year and what is the 8th digit in the VIN?

JohnMiller3 · Jun 29, 2002

<font color=blue>...what is the 8th digit in the VIN?...</font color=blue>

Derek... do you mean the 10th place...? (may be digit or alpha)

Rowski · Jun 29, 2002

Well, your right, I forget I'm not at work (you know the work place lingo... everyone knows what you mean not what you said/w3tcompact/icons/tongue.gif). "th" place. It can be alph or digit. The 10th would give me the year. The 8th gives me the engine code. GM had two types of 4.3l engine configurations.

GarageSmoker · Jun 30, 2002

Maybe some of these digits don't count. Our GM uses a code like the Cuban cigars manufactures. The truck is a 97.

1GCCS19X8V8178910

GS

Gary_in_Indiana · Jun 30, 2002

Almost all if not every vehicle ID in the last 30 plus years has seventeen characters. The last six are sequential (only differentiating one vehicle from the next). Of the first eleven, ten have distinct meanings and one (the ninth) is what is called a "check digit" so that bad or incorrect VID numbers can be more easily caught if mistakenly entered in computer programs which recognize how the check digit works (most now do as it's an incredibly simple subroutine).

The ten characters which have meanings tell everything from country of manufacture (the first character) to the model year (as discussed above) and the engine. I can look at a VID number on a Chevy pickup, for example, and tell you if it's a 350 or 305, etc.

Sadly, there's not a whole lot of call for that skill, but it does save me lifting a hood once in a while. /w3tcompact/icons/smile.gif