Original issue: 1-2 fine, 2-3 neutral, no 4
pulled that trans to rebuild. Had a spare that I wasn’t sure the status of and put it in.

spare has 1-2 fine, but never leaves 2 to go to 3 or 4.

suspect original trans has burnt 3-4 clutches and spare trans has a stuck valve?

thoughts?

 

The biggest failure in a 4L60E is the 3-4 clutch. The shift solenoids change state between on and off for the 1-2 & 2-3 shift. If you you have an actual transition between the gears that tell me that the solenoids are working.
On the second unit It is very likely that it is not getting the command for 3rd gear. If that is true then you would need to look at other things.
step 1) check for a 3rd. gear command with a scan tool. most inexpensive scan tools will not be able to do this. It requires a Bi-directional scan tool and with one of those you can shift it yourself.
Step 2) check the internal pressure switch commands for proper switch function. I have had these fail and cause some malfunctions.

 

Almost every 4l60 i've taken apart had the 3-4 clutches fried. trans that are still being driven with fried 3-4 clutches end up burning up the band that rides on the reverse input drum causing neutral issues. worst case scenario the input drum could have grooved lugs and even a loose shaft in the drum making it unusable. no mater i change every part in the input drum. to have lasting 3-4 clutches i do all the updates that sonnax has for the front pump assy. and make sure the pump rotor assembly is replaced with one with the most vanes. of course a complete overhaul needs to be done with a complete disassembly and cleaning of the valve body. since 2008 i have overhauled too many to count 700r4/4l60/4l60e with i'm happy to say no comebacks. there are many other parts i normally change on these units that are too numerous to list here and other procedures i perform during the rebuilding process that leads to reliable units.

 

I did watch with a tech2 and everything looks correct. It is commanding all the gears correctly, which is why I thought it would be a stuck valve on the loaner trans.

im pretty set on the 3-4 clutch being bad on the original trans due to the neutraling on the 3 shift, and that it was slipping in third when I got on it a little more than normal driving.

im going to swap all the electronics over and check the valves for movement, maybe even swap the entire valve body.

original is getting rebuilt I was just hoping to have a functional spare while I was rebuilding.

 

Disconnecting the electronics should default it into third gear but if a valve is stuck it’ll probably stay stuck in second?

 

Had a 4L60E that wouldnt shift out of first once. You could watch the command for second & 3rd come on, it just wouldn't shift. The 1-2 shift valve was stuck and I never found where the chunk of metal came from..

 

3-4 clutch definitely burnt up completely on the first trans, took it apart last night. Going to rebuild that and reinstall it and then I'll break apart the loaner.
I did notice that the loaner trans has the same 3-4 slip when its cold, but after it warms up for about 5 mins, it only shifts 1-2 then stays in 2, so I suspect its 3-4 clutch is shot but also has a stuck valve. I swapped the shift solenoids and nothing changed.

 

any slippage cannot be cured swapping electronics. lack of lubrication, low pressure, high mileage, stuck or worn servos/pistons not applying correctly burns up units in short order. once the frictions, bands , drums etc are glazed or starting to show burn marks from slipping you're done. you need to pay close attention to any aluminum servos and accumulators. as the seals on these wear or become brittle the servo or accumulator come in contact with the bore in the case causing major damage. there are case savers made for some of these bores. if not worn to bad i use 80 grit emery cloth with trans fluid to smooth out the damage then finish it off with red scotch bright. otherwise the case is junk. before reassembly i will also use the 80 grit to remove the glaze on any pressure plates i am reusing. i use the scotch bright dry to remove the glaze on all aluminum bores in the case. i hope some of this helps. i could go on further but this thread would get to long.

 

TIP. Make sure the pressure plates are flat if possible. Start with 120 to 150 grit and work your way to 1,000 and then 2,500 grit when done. The smoother the pressure plate (or any clutch steel) will give more surface area (holding power), and transfer heat faster. A mirror finish has the most surface area. This is a little time consuming. However, according to Borg Warner and Raybestos, this works the best in terms of holding power and long clutch/band life.