96 4L60E Too Flush or Not

[Caman96]

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Ok 96 K1500 just hit 50,000. At 46k I dropped pan/new filter and replaced what came out. Fluid looks clean! When cold it sometimes has a hard shift into second but otherwise shifts smooth. Any thoughts on whether to do anything like fluid exchange through cooling lines, transmission flush/fill(at transmission shop) or just leave it be? I’d say aside from fluid I replaced, the rest is 25 year old OE fluid.
Btw-I did just add auxiliary cooler!

 

[Frank Enstein]

I would leave the return line off at the transmission and flush a few quarts of new stuff through. If you get the fancy TCI or B&M fluids they aren't red (Green and Blue is I remember correctly) so it's easy to see when the new stuff comes out.

I do not recommend any sort of "Flush" products. Only flush with the correct fluid. Cheap insurance.

 

[0xDEADBEEF]

Since you already did the pan drop and filter, this is another use for the mighty vac. Stick it down the dipstick and suck out what you can and then replace with the exact same amount of fluid. Make sure the fluid is approximately the same temp to account for thermal expansion. (Don't replace hot fluid with an equal amount of cold fluid.)

 

[Schurkey]

I'd expect that the service manual has a flowchart for hard-shifting issues.

I don't know how detailed it might be. It'd be worth looking at.

I "fixed" my 250K mile 2003 Trailblazer 4L60E. Wouldn't engage reverse when cold. 3-seasons, no problem. Winter? No reverse until the trans warms up some. Putting the lever in "R" was no different than "N". As it warmed-up, it would "bump" reverse now and then, but not move the vehicle. Once warmed, reverse worked fine. All forward gears worked fine no matter what the temperature. This has been a problem for ten--twelve years.

Dropped pan, replaced filter, flushed fluid via the trans cooler tube. 14 quarts of fluid--trans works perfectly now.

 

[alpinecrick]

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Ok 96 K1500 just hit 50,000. At 46k I dropped pan/new filter and replaced what came out. Fluid looks clean! When cold it sometimes has a hard shift into second but otherwise shifts smooth. Any thoughts on whether to do anything like fluid exchange through cooling lines, transmission flush/fill(at transmission shop) or just leave it be? I’d say aside from fluid I replaced, the rest is 25 year old OE fluid.
Btw-I did just add auxiliary cooler!

Buy a deep pan with a drain plug in it. Every other oil change pull the plug, drain what's in the pan, replace with fresh ATF. That is the first recipe for a longer lived 4l60. You've already did the other with the cooler install.

https://www.cfrperformance.com/CHEVY_GM_700R4_4L60E_4L65E_STEEL_TRANSMISSION_PAN_p/hz-7599-pbk.htm

 

[Caman96]

Buy a deep pan with a drain plug in it. Every other oil change pull the plug, drain what's in the pan, replace with fresh ATF. That is the first recipe for a longer lived 4l60. You've already did the other with the cooler install.

https://www.cfrperformance.com/CHEVY_GM_700R4_4L60E_4L65E_STEEL_TRANSMISSION_PAN_p/hz-7599-pbk.htm

That’s a great price too! What about using synthetic atf as I weave in new?

 

[alpinecrick]

That’s a great price too! What about using synthetic atf as I weave in new?

My trans rebuilder says synthetic ATF is of minor improvement, but it doesn't hurt, either. I just pulled the plugs on my 02 Savana and 01 Sierra and refilled with Walmart Valvoline synthetic. When I buy ATF at Walmart I usually buy 3-4 gallons--a gallon or two of Super Tech and a gallon or two of Valvoline synthetic. I use them interchangeably.

 

[alpinecrick]

You may want to read through this thread for a bit of extra info:

https://www.gmt400.com/threads/time-to-get-serious-with-4l60e-4l65e-cooling.50138/page-6

 

[alpinecrick]

That’s a great price too! What about using synthetic atf as I weave in new?

The one I linked is the stock capacity, here's the one I meant to show. Sorry about the price increase....

https://www.cfrperformance.com/CHEVY_GM_700R4_4L60E_4L65E_STEEL_TRANSMISSION_PAN_p/hz-9712-pbk.htm

 

[Schurkey]

Make sure the deep pan doesn't hang so low that it gets whacked by road debris.

I wouldn't bother. Changing fluid piecemeal requires wasting a heap of usable fluid.