4l60e Slipping

[JPVortex]

Hello y'all, having this problem and wondering if anyone has any advice?

So I have a 1994 K1500 with the 4l60e. 2nd gear is slipping, but it's more complicated. When upshifting going into 2nd gear it shifts without slipping, it does shift a bit slow but it still shifts with no slipping.

I can go from a dead stop floor it in first and it shifts to second fine.

However here is the issue. If I'm im third and I need to downshift to second on a hill or something to gain some acceleration it totally slips on me. Most times it will rev like it's in neutral until I let off the gas and it goes back into third, sometimes it will catch though and accelerate.

Fluid is still red, doesn't really smell burnt at all.

Anyone know what the possible culprit could be?

Thanks!

 

[tayto]

was this trans rebuilt somewhat recently? has it always done this or just started? it sounds like shift timing if there is indeed no slipping on the 2nd shift.

 

[JPVortex]

was this trans rebuilt somewhat recently? has it always done this or just started? it sounds like shift timing if there is indeed no slipping on the 2nd shift.

The trans has never been rebuilt as far as I know. I just recently obtained this truck so I don't know much about it. Is there a way to adjust shift timing on a 4l60e?

 

[JPVortex]

Its just annoying having to go up hills so slow as it totally slips when downshifting to second, every other gear is fine and second is okay when upshifting.

Maybe its the 3-2 shift solenoid?

 

[tayto]

a lot happens on a 2-3 upshift or 3-2 downshift in a 4L60E. in the case of a 3-2 down shift you are releasing the 3-4 clutchpack and the 2-4 band is engaging. if one of those things happens to soon or to late you will get a flare or slip. I can tell you if a band or clutchpack slips once it is comprised.

As far as shift timing, this depends on 2-4 servo pin travel, 3-4 clutchpack clearance and orfice hole sizing. It could very well be the trans is just tired. Playing with the above stuff is not for the average DIY'er. The 3-2 solenoid is an overcomplicated way to exhaust fluid, I like to block it. it is a huge area for internal leaks.

how much milage?

 

[JPVortex]

a lot happens on a 2-3 upshift or 3-2 downshift in a 4L60E. in the case of a 3-2 down shift you are releasing the 3-4 clutchpack and the 2-4 band is engaging. if one of those things happens to soon or to late you will get a flare or slip. I can tell you if a band or clutchpack slips once it is comprised.

As far as shift timing, this depends on 2-4 servo pin travel, 3-4 clutchpack clearance and orfice hole sizing. It could very well be the trans is just tired. Playing with the above stuff is not for the average DIY'er. The 3-2 solenoid is an overcomplicated way to exhaust fluid, I like to block it. it is a huge area for internal leaks.

how much milage?

Yeah playing with all the internals of a transmission is not something I want to do, I'd rather throw a used trans in.

Is there a chance the 3-2 solenoid could be bad?
And the truck has 223k on the body, which I'm guessing the trans has aswell so it may be tired.

 

[tayto]

the 3-2 solenoid just changes the rate at which fluid is exhausted. solenoid on, softer 3-2. solenoid off, firmer 3-2. it doesn't actually control the shifting from 3rd to 2nd. Like I said, I block this valve so the shift feel can be dictated by orfice size in the separator plate. FWIW, GM deleted this solenoid from 2009 until end of 4L60E production.

it sounds like a shift timing thing to me. if you want to try something i would throw a corvette servo in and a longer servo pin. check the current servo travel to determine what pin you need but I suspect it will be .125" or more. I would get it to around .075" to .090". This can be done in situ but I am not sure how much room there is. I normally do this with trans out of vehicle and on the bench.

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[JPVortex]

Hey so an update here with more info I got.

Talked to the previous owner today, apparently the trans is not original and is a lower mileage unit, which makes me confused why it has no second gear once it warms up(2-4 band I'd think)

I also believe the truck has been sitting for 2 or 3 years. I found receipts from no later than 2021, and the previous registration expired 2021.

Is there a chance the issue could be caused by the fluid breaking down from it sitting? The fluid looks fine. I put 2 bottles of lucas stop slip to see if itd do anything which obviously it didnt lol

 

[RDF1]

What about manually shifting it from 3rd gear to 2nd gear? What does it do?

 

[JPVortex]

What about manually shifting it from 3rd gear to 2nd gear? What does it do?

When I'm manually in second it free revs, it has 2nd gear until the truck warms up, then it just revs high in 1st and drops into 3rd.