Any car mechanics here?

[GarageSmoker]

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]

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]

Temperature. Hot ambient plus hard driving equals hot transmission.

Maybe the radiator needs cleaned out?

 

[GarageSmoker]

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]

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]

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]

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]

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]

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]

<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.