1996 Tahoe, hard shifts

[m610]

Like I mentioned in the title, I've got a 96 Tahoe, four-door, 4WD, 315k miles, and in the hot Sacramento Valley summers I get a hard shift into 2nd after leaving a stop sign but only after an hour or so of highway driving. It does not happen in winter or during short around town trips. Possibilities I have been considering:

1. Is my transmission going out, bands slipping, etc.? I understand that generates extra heat.

2. The radiator has two ports on the passenger side that are plugged and appear to never have been used. I understand that side of the radiator is for a transmission cooler. Seems I should utilize it. Has anyone added that capability? Does it involve more that hooking up some hoses?

3. Is it time to drop the pan and replace the filter? Do you think that would help?

My main question is about the cause of the hard shifts and the remedy.

Thanks in advance.
Mike

 

[m610]

Here's a good discussion of the problem.

Link: https://www.tahoeyukonforum.com/threads/4l60-e-hard-shift-from-first-to-second-gear.20800/

Several people report the same symptoms as I am experiencing. No hard shift in winter or when driving short distances, but in summer after highway driving the hard shift returns. After parking for a few minutes the problem goes away but soon comes back again after driving a bit.

Likely causes are worn valve body, worn accumulator, defective pressure-control solenoid. A number of external problem's, such as fuel pressure and O2 sensors, were also identified but these situations did not seem to be related to temperature.

In a YouTube video one guy described solving his problem by replacing the thorttle position sensor.

Where to start?
Mike

 

[PNW NBS Z71]

With 315k miles and likely not knowing if the existing trans is original or not and when was the last filter and fluid service done? You can attempt the basic inexpensive service and see what happens.

The radiator ports may not be used but you may have a transmission cooler out with the radiator and a/c condenser. Is there a small cooler just behind the grill, in front of the a/c condenser and radiator?

 

[dunpomax]

Hope you have it fixed soon.

 

[PNW NBS Z71]

By doing what?

 

[m610]

I just replaced the radiator and in the process found the transmission cooler.

I've got a filter kit and the solenoid people say is the problem. Waiting for a good chance to install them.

 

[PNW NBS Z71]

Great. Pay close attention to was the bottom of the pan looks like when you drop it and drain the fluid out of it. You don't want to see fibrous chunks of material or metal chunks. A little bit of fine shavings is ok because that is the sharp edges of gears and baskets in there, rounding off and the sludge would be friction material from the friction plates. Take pics and post here. What solenoid and what brand is the solenoid?