transmission help please

well here goes.
i was driving home late last night when i discovered a wierd feeling in my transmission. at around 45, at very light throttle, it seems to "kick" into another gear. when i try to accelerate, it stays for a second, then it "kicks" out, and the rpms rise about 1500 rpm.
to make sure it wasnt simply downshifting to second, i put it into 2, and the motor shifted to second. didnt hurt anything, but the motor was near the peak of its rpms at 50 in second.

the reason i say this is weird is because it feels like the car is shifting into overdrive, but last i checked my car has a TH350, and hence, no overdrive.

the only other thing i can think of is that the torque converter is un-locking up.

if this is the case, it might help explain my poor gas mileage i have been getting lately.
i seem to max out at 18 on the highway at ~60 mph which is pretty bad for a 3.8L V6 with a 3.08 rear end.

thanks for any help.



p.s.
just for shits and giggles, if anybody has pictures of how to identify the trans by the pan, it might be fun to make sure that i really do have a TH350 and not the 700r4, and that my adjusting the kickdown cable about 2000 miles ago wasnt actually the TV cable, which could be bad.

the only other thing i can think of is that the torque converter is un-locking up.

Bingo.

if this is the case, it might help explain my poor gas mileage i have been getting lately.
i seem to max out at 18 on the highway at ~60 mph which is pretty bad for a 3.8L V6 with a 3.08 rear end.

I'd say that's actually QUITE GOOD for such a setup, ESPECIALLY with no overdrive. The best economy to be had in one of these cars is via a 305 setup and a TH2004R, not a V6.

I used to have a 1975 Pontiac Grand Am (the GTO replacement) which I installed a Chevy 350/TH350 into back in 1994 thanks to my sister who blew the Poncho 400 (another story), and this car never got more than 10-12MPG (14 on the highway if you had a tailwind while driving downhill). The _very same_ engine is now in my Caprice and with the TH700R4 it gets about 20-22 on the highway.

http://www.silicon212.org/pan_id.jpg

Pan 1 is an aluminum Powerglide (for reference only)
Pan 2 is a TH200/C
Pan 3 is a TH250/350/375B
Pan 4 is a TH400/3L80/TH375
Pan 5 is a TH2004R
Pan 6 is a TH700R4/4L60/E
Pan 7 is a 4L80E

If you have one of either 5 or 6 (OD) your shift quadrant will be

P R N (D) D 2 1

-or-

P R N D 3 2 1

If you have 2 or 3 your quadrant will be marked

P R N D 2 1

if the TC is not locking up, then how do i fix it?
do i need a new solenoid or a new TC

btw, why wouldnt a v6 get better mileage behind a 200r4 than the 305?

What you are describing, the "shift", is the TCC coming in and out.

Because your V6 is underpowered in that big car. It will use more gas.

right, but what i am saying is that it only locks up within about 1 to 1.5 inches of pedal travel. any more and it wont lock up, meaning that at speeds greater than 55 or so, it is unlocked.

is there a way to reprogram it or do i need a new solenoid?

anybody???
it seems wrong that it only locks up at very light throttle. 1-1.5 inches max.
that translates into around 45 on level ground and 50 ish down hill, which is rather useless for highway driving.

You could be having a TCC solenoid issue as well.

I think what silicon is getting at is try replaing the TCC... it's not all that hard, but does involve dropping the pan I believe.

I think that somewhere here I saw detailed instructions with pictures that was very good. But not that bad to do. You can also temporarily unplug it until you get to it or have it done. The plug is at the driver's side of the transmission, towards the front of the case.

Bob

Bob, I heard that if you left the TCC unplugged for extended periods of time that it tends to put excessive wear and heat on the 4th gear bands. I could be dead wrong, but I dunno.

well i dont have a 4th gear band...
so should i replace the solenoid or is there a way to adjust it?
it seems like the solenoid is working, but needs adjustment

Bob, I heard that if you left the TCC unplugged for extended periods of time that it tends to put excessive wear and heat on the 4th gear bands. I could be dead wrong, but I dunno.

True, that's why I said "temporarily", as in taking the car to the shop or running locally to pick up parts.

Mine has been uplugged for at least 50k miles. I keep an eye on the fluid and add a little now and then. The transmission still works just fine. If I keep the car another few months, I just may crawl under it and change it.

Bob

well i dont have a 4th gear band...
so should i replace the solenoid or is there a way to adjust it?
it seems like the solenoid is working, but needs adjustment

As far as the TCC soleniod goes, there is no way to adjust it, just replace it. Get a price from a couple of transmission shops, I can't see it costing more than $100 or $150.

Bob

As far as the TCC soleniod goes, there is no way to adjust it, just replace it. Get a price from a couple of transmission shops, I can't see it costing more than $100 or $150.

Bob

I am not sure about the process for a TH350C, but I cannot see it being different from any of the overdrive units. One should be able to get the solenoid for less than $20 if one does it themself, plus the cost of a pan gasket and filter kit and about 3 - 5 quarts of fluid. Probably $40 total if one doesn't mind getting a little dirty. Don't forget the jackstands!

On a TH350C, the TCC is only there for CAFE reasons, it can be disconnected and left alone. Just remember that TCC converters have a higher stall speed and more slip than non TCC converters. This means more heat and less economy. Install an aftermarket cooler.

I had priced the solenoid once and it wasn't that bad. Check online at Auto Zone or Napa. I'll probably do mine soon, just add it to the growing list of things I gotta do on the car. Lots of nasty little things are breaking on it.

I have to be careful, I have a pretty new driveway and brickwork all over the place. It can probably be done on ramps too, I use the jack and jackstands are a must as you say. I use 1/2" plywood under them so they don't sink into the asphalt.

Bob

wait wait wait
if i unplug the tcc, does it mean that the tc will NOT lock up or that it will STAY locked up?

i WANT it to lock at speeds over 35, and if possible, i want it to be locked except at or near WOT.

if i replace it myself, which i would plan on doing, are there any special things i need to know to avoid hours of needless hassles?

If you disconnect it, it will stay in freewheel mode. The problem is most likely to be the TCC solenoid. Get a book on the transmission.

It shouldn't take a lot of time to do.

ok
thanks
thats what i wanted to hear

Another thing to check the the TPS voltage. If it is set too high, it will tend to drop the converter clutch too soon. The MAP/VAC sensor could also affect TCC operation.

Mine shifts fine unplugged, It shifts 1,2,3 and goes into overdrive. I should replace it so the transmission runs cooler. If I can find a link to a solenoid replacement tutorial, I'll post it here.

Bob

how would i go about checking the TPS voltage?
incedentally, i have had to make my own TPS rod thingy... it got ingested into the engine after a rushed carb rebuild.
i measured it with calipers and made my own from a nail, but there is a chance it is slightly off.
should it be longer or shorter to decrease the voltage?
its probably a bad idea, but is it possible that i could grind it down a bit and trick the computer into thinking the throttle is "less pressed" or whatever.

Get the engine to operating temperature and make sure the choke is fully opened and the idle screw is off the fast idle cam. Connect a voltmeter to the A and B terminals on the TPS (backprobe the TPS connector). That should be the blue and gray wires. Adjust the TPS position to obtain a reading of 0.48VDC at the closed throttle position AFTER all other adjustments.

The vacuum sensor on the firewall also needs to be connected to a good manifold vacuum source. Incorrect inputs from either of thee can cause the TCC to hunt.

The VAC sensor... if it's what I'm thinking of (the sensor on the wheel well that measures vehicle vacuum) then it could be the cause of your improper locking of the tc if theres a vacuum leak. I just realized now the vacuum line had melted on the exhaust manifold and may have explained the premature tc locking.

The VAC sensor... if it's what I'm thinking of (the sensor on the wheel well that measures vehicle vacuum) then it could be the cause of your improper locking of the tc if theres a vacuum leak. I just realized now the vacuum line had melted on the exhaust manifold and may have explained the premature tc locking.

Yes, this can definitely lead to the problem.

It's one of those hard plastic vacuum lines that connects the MAP sensor to the carb. These get brittle and eventually break, especially near where they get hot from the exhaust on the passenger side. I even had mine get plugged from engine crap once - I had to clean it out. On mine, the MAP sensor is on a bracket to the left of the distributor behind the carb. The line is about 6" long. The BARO sensor is placed on a bracket along with the ECS module on the passenger fender.

Adjusting the TPS on one of these E4ME jobs requires the removal of a lead or epoxy plug to get to the adjusting screw.

It's strange... I always could tell that I had a vacuum leak but could never find it until I pulled out the motor. Well now after I tear everything down I find the cause of all my problems. Oh well, such is life.