Early sign of transmission failure?

[DocBrown]

Twice over the past week I had a strange thing happen. Within 5 minutes of a cold start driving down the road and getting to about 40/45mph the transmission shifted up and down several times between 3rd and 4th gear like it was hunting or couldn't quite hang on to OD. Let my foot off the gas a few seconds and then back up to 45 then it was fine. Doesn't do it again once I've driven for bit. 150k miles and I'm due for a fluid change. I'm not convinced that will "fix" it, but maybe? I don't really mind having to have the trans rebuilt, its far cheaper than a new truck. I just don't want to get stranded while towing on a vacation. Thoughts?

 

[AtlWrk]

My first thought is a damaged separator plate. The steel check balls in the valve body pound the heck out of the plate and "losing 4th" can be caused by one of the balls blasting all the way through. The good news is that if that is your problem it's a cheap and relatively easy (albeit messy) fix.

Now the obligatory: how's the fluid level? condition? when was it last changed?

 

[DocBrown]

Good question. I haven't checked the fluid level. There are no leaks, but I'm going to look. Last change was at 109k.

 

[DocBrown]

Gotta love GMTNation! You're suggestion about the separator plate got me trying a search and I think I found everything I need. Just reading about the symptoms of sluggishness too makes think this is the way to go because I'm experiencing all those symptoms too. I know if I take it to a trans shop they are just going to tell me I need a rebuild. $170 to do this is far cheaper!

http://gmtnation.com/f93/how-remove-4l60e-valve-body-replace-plastic-accumulator-pistons-4972/

http://gmtnation.com/f24/built-4l60e-replacement-4894/

 

[gmcman]

How many miles on the trans? I replaced my plate at 165K and since then I have over 20K on the fix and it drives great. I wish I had replaced it at around 120K.

This is what I would do if I were you.....

Replace the separator plate
Replace the 1-2 & 3-4 accumulator pistons
Install a vette servo
Replace both shift solenoids
Swap the PWM TCC valve with a Trans-go PWM eliminator kit which removes the soft, subtle converter lockup into a positive off/on style lock up, feels like another gear and is a great mod for towing.

I did all this, less than $200 and it made my trans shift and work better than new.

 

[DocBrown]

How many miles on the trans? I replaced my plate at 165K and since then I have over 20K on the fix and it drives great. I wish I had replaced it at around 120K.

This is what I would do if I were you.....

Replace the separator plate
Replace the 1-2 & 3-4 accumulator pistons
Install a vette servo
Replace both shift solenoids
Swap the PWM TCC valve with a Trans-go PWM eliminator kit which removes the soft, subtle converter lockup into a positive off/on style lock up, feels like another gear and is a great mod for towing.

I did all this, less than $200 and it made my trans shift and work better than new.

I appreciate you telling me this. 150k and I'm due for a fluid change. So I thought as long as I have the pan off I'd do pretty much everything you listed. On Friday I ordered all the parts. First I have to fix the leaking trans line that rusted by the radiator.