Tranny problem HELP!!

[xjndmud]

i have a 92 4.0, auto tranny,so what tranny i have no idea, but here's the problem, usally i can go at 75mph with no problem, but now for some reason 70 is about it in 4th gear if i want to go faster it shifts down into 3rd, why wont it stay in 4th like it use to at highway speeds?

 

[Marc]

Sounds like the kickdown cable needs adjustment.

 

[Ghost]

Zig......

That would be the AW-4 tranny. When was the last time you changed the fluid? Did you do it after she went swimming? Get a FSM and bring over I'll help you figure it out. But how would the kickdown cable affect that?

 

[GSequoia]

There is no actual kickdown cable in the AW4. There's a TV Cable (Throttle Valve I believe), that's easily adjusted (even haynes/Chiltons has this prodedure, sorry, I don't remember it offhand) and the TPS (Throttle Position Sensor), the TPS is where the signal to kick down. Check it's adjustment, if you can't get it in range replace it.

TPS Adjustment:
NOTE: A digital voltmeter is required to successfully complete the adjustment of the TPS. The DRB II or an equivalent scan tool can also be used to adjust the TPS. Refer to the scan tools' manual for adjustment procedure.
CAUTION: Do not disconnect the TPS electrical connector; instead, insert the voltmeter test leads into the back-side of the electrical connector. When inserting the test leads, make sure that the wires and harnesses remain undamaged.

Turn the ignition switch to the ON position.
Find the Four-way TPS connector and insert the black lead of the voltmeter into the back side of terminal (D). Insert the red lead of the voltmeter into the back side of terminal (A). Make sure that the throttle plate is completely closed against the throttle stop. Note the voltage reading of the voltmeter as it is connected across these two terminals, this reading is the input voltage.
Remove the red lead of the voltmeter from the back side of terminal (A) and reinstall it into the back side of terminal (B). Make sure that the throttle plate is completely closed against the throttle stop. Note the voltage reading of the voltmeter as it is connected across terminals (B) and (D), this reading is the output voltage.
Divide the output voltage reading by the input voltage reading. The ratio should be between .825 and .835 (.830 optimum).
If the voltage ratio is not within this range, adjustments can be made using the two mounting screws. To make large adjustments, loosen the bottom mounting screw and pivot the sensor. To make small adjustments, loosen the top mounting screw and pivot the sensor.
Disconnect the voltmeter, and tighten the mounting screws securely.

 

[xjndmud]

FSM? whats that, the tps is about to go anyway, would that have this kind of effect on the tranny?

 

[Ghost]

Facrory Service Manual

 

[PaulJ]

The TPS is one of the input signals used to determine when to shift the tranny. I think lots of folks like to assume they have a bad TPS without testing it. How did you decide that your's was about to go?

 

[xjndmud]

i decided my tps was bad, cause of the jumping rpms at idle speeds, and then some time when i push the gas, it dose nothing for a few seconds then i back off of it then a few seconds later it will go

 

[PaulJ]

There may be a flaw in you diagnosis so just to be sure, manipulate the TPS with your finger while the engine is idling and see if you get the same symptom. On my Renix 4.0, it doesn't really seem to care much.

 

[xjndmud]

where's the tps at?

 

[xjndmud]

is it true that if u never changed your tranny fluid not to?

 

[GSequoia]

Um, if you've never changed yoru tranny fluid do it now! I'd even go the extra mile, pull the transmission pan and replace & examine the filter (it's just a metal screen). I'd do this, also do a Berryman's B-12 chemtool flush on the trans (I know somebody here has that procedure memorized...), fill it up with some good ATF (non-synthetic, just regular), and then adjust that TPS.

The TPS is on the throttle body at the front. YOu will notice that it moves when you open your throttle up, that's it. (it's basically a rheostat). Before replacing it check it. Hook it up to the voltmeter like it says to up there and slowly turn your throttle from closed to full open (do this with the engine off but key on please!). Anyway, you should get a smooth change in voltage. If it spikes around then it's bad.

If it tests bad replace it, then do the adjustment procedure in my previous post.
If it tests good just adjust it, if you can't get it to adjust into spec replace it.

Do those things and I'll be your tranny will be most happy. The AW4 really is a very difficult transmission to kill!

Sequoia