Auto Tranny Characteristics

[bl87xj]

'88 Auto. 4.0

Once I reach a steady cruising speed (35-45) The tranny seems real sensitive to upshifting/downshifting. Almost feels like it is hunting in and out of an overdrive???

Not sure if this a sign of trouble or is a normal characteristic of these rigs.

Recently had a cat, flowmaster and tail pipe done, not sure, but I may notice it more since then. Could just be that I can hear a bit more with the muffler. I wonder if having less backpressure would contribute.

Don't notice it at freeway speeds. Seems to shift at the right time and smoothly when accelerating through the gears. And seems less noticable if I leave the tranny switch in the Power mode.

 

[Ecomike]

'88 Auto. 4.0

Once I reach a steady cruising speed (35-45) The tranny seems real sensitive to upshifting/downshifting. Almost feels like it is hunting in and out of an overdrive???

Not sure if this a sign of trouble or is a normal characteristic of these rigs.

Recently had a cat, flowmaster and tail pipe done, not sure, but I may notice it more since then. Could just be that I can hear a bit more with the muffler. I wonder if having less backpressure would contribute.

Don't notice it at freeway speeds. Seems to shift at the right time and smoothly when accelerating through the gears. And seems less noticable if I leave the tranny switch in the Power mode.

Try a new Throttle Position Sensor, TPS, on the throttle body, right side.

 

[bl87xj]

TPS is brand new from dealer by previous owner. I have the receipt.

 

[Ecomike]

OK, then I would take a real close look at the ground wires, and harness connectors, especially the TPS to TCU sensor ground wire. I had to run a new ground wire on mine. Should be less than 1 ohm from that ground wire to the battery negative post and to the engine, and to the firewall body ground all with the igniton power OFF.

If over 1 ohm, remove and clean both sides of the ground connection. See "ReniX Files" thread for lots of discussion on this. Mine is 87, Renix. A bad ground connection can change the TCU perceived volatge (and perceived throttle position) when the wire moves as the engine moves.

 

[jeeperjohn]

My '92 has an adjustment for the transmission kickdown cable. It's on the valve cover next to the throttle and cruise cables. It has a button in the center that if you push down on it releases the sheath of the cable and allows you to move it in or out. Moving it to the left makes the tranny downshift sooner, the opposite for moving it to the right.