Anyone have a surefire way? The new to me truck (4l60e 2wd) shifts hard in 1-2 and 2-3. Like chirp tires hard. Seller claims it has a shift kit. Id like to figure out if it actually does when I have the pan down to change fluid and filter.
I had initially reported that it shifts hard in 1-2 only, but more miles has me feeling 2-3 as well. Just not as hard as 1-2
So, how do we tell? Or is there something wrong?
See if valve body or filter look aftermarket valve body or filter. Does it look like pan has been off?
Also I'm leaning to bad trans, but that's because people lie.
Looks like pan has been off, but not like trans has been out.
And, ive only ever experienced slipping as a sign of a bad trans. So, hard shifts can be as well? Even though 3-4 is normal?
Hard shifts can be a sign of a hurt transmission. But I was always under the impression that the 4L60E was prone to mush shifts and slipping when dying.
4L60E... could be either problem.
Fortunately, if it's a bad trans, it is most likely in the valve body. The pistons in the shift valves get galled frequently. They are supposed to move gradually as pressure is applied, but they stick and then move all of a sudden causing the wham shift. The other common issue with 4L60s is the separator plate. There are a few of the round holes that get peened by the check ball constantly whacking into it. Eventually the ball gets stuck in the hole causing slipping, but eventually pushes through and can't do it's job at all making hard shifts. The fix in both cases is pretty simple. Pull the valve body. If it's a check ball/separator plate you'll see it. If not, pull the pistons out of the valves and assess the condition of the bores. If they're bad, there is a hone/sleeve kit to fix it.
It could also be an incorrect separator plate. GM used about 8 different plates depending on the application. The kit would have come with 6 or 8 different plates and the installer would have to make sure they used the right one. They're all marked with a stamped letter code in one corner, like AB or AC. If they grabbed the wrong one, it can make all kinds of weird things happen.
A shift kit could also be installed and making the problem worse, or if it was poorly installed it could just be defaulted to the max shift pressure.
4l60e's have a line pressure solenoid inside the pan and when it fails you get full line pressure and harsh engagement and upshifts. Symptoms would probably be exacerbated by a shift kit. Might be something to look at.
In reply to Vigo (Forum Supporter) :
How do I inspect that?
Im not versed in automatic transmissions. Until soon, all ive ever done has been fluids, filters, and replacement.
All of those seem like good potential candidates; I'll just add one tidbit. Usually if a 4L60 is on its way out in the slippery way, shifting into drive or reverse when you first get in and everything is cold will usually feel really aggressive, and the first few shifts of the day will be really harsh and eventually smooth out. Even if it never ends up slipping, this all usually means the trans is near the end of its life as these issues are caused by the computer seeing that the transmission is not meeting expected shift times and trying to compensate with line pressure and such, in a rather sluggish '90s way of transmission copmuter learning.
Long delays going between reverse and drive are also a bad sign. A good 4L60 will shuttle between forward and reverse pretty darn quick, as I found out trying to get my truck un-stuck a few times.
Dusterbd13-michael (Forum Supporter) said:truck (4l60e 2wd) shifts hard in 1-2 and 2-3. Like chirp tires hard.
Use more throttle?
You could buy a reman valve body, swap it in and see if it changes anything.
Most shift kits only change things in the valve body.
Vigo (Forum Supporter) said:4l60e's have a line pressure solenoid inside the pan and when it fails you get full line pressure and harsh engagement and upshifts. Symptoms would probably be exacerbated by a shift kit. Might be something to look at.
True, but defaulting that to max pressure wouldn't cause tire-chirp shifts. The 4L60E in the Impala SS that I sold had that solenoid defaulted to max and it only modestly affected shift quality. 4L60Es are also programmed in the ECM to default to full pressure at WOT, and they still shift pretty lazy. As far as I know, that solenoid basically takes the pressure from wimpy at low load to a little less wimpy at high load, so if it goes bad, you just get slightly less wimpy all the time, but not tire chirp.
Michael, does it happen at any load? Just hard accel? Just light accel? Is it just a really firm shift, or does it make you soil your trousers and feels like you just go rear ended at 20mph? If it's the latter (soiled trousers) I would look at the pistons in the valve body first, but of course if you're doing that you can just check for a shift kit or other malfunction at the same time.
A good real-time scan tool should let you compare the signal to the pressure solenoid and the actual line pressures, but my guess is that you would have a CEL and an appropriate P17xx or P18xx code.
Suffice it to say... if you're getting hard shifts in a 4L60E, it's most likely something in the valve body. The spinny parts of the trans are pretty straight forward, so if you had a deeper internal problem, it would likely show up as slippage.
I also thought of another thing. Find a scan tool that will show you trans temp. The temp sensor is a resistance wire that is part of the internal wiring harness. If it fails, the temp will read something like -273C. If that is the case, it is trying to open up everything it can to let the molasses flow and I have seen that failure cause funky symptoms. Since it is also still providing the ECM with a value, it doesn't usually trip a CEL. The range is set for something like 0v to 5v with zero being absolute zero (-273C) and 5v being something like +200C. If they had instead programmed the range to be 0.1v to 5v, then it would read 0v as being a fault, but they didn't.
If you're inside a higher-mileage 4L60E, replacing the internal wiring harness isn't a bad idea anyway. The hydrocarbons and heat eventually break down the insulation of the wires and since the stuff dissolved in tranny fluid is mildly conductive, it makes gremlins. IIRC, they're about $64.
Ok, so i think I need to put more miles on the truck to really get a feel for the shift quality. From what i can tell so far, light throttle gets a jarring shift, but no discernible shift. Think tapped in the bumper at 10mph. Full throttle 1-2 is laying a patch of rubber off one of the tires. 2-3 is firm, and by god you know it shifted, but not like 1-2. 3-4 is normal. They are quick shifts compared to my other 95 with a 4l60e.
I have the pan drained already for a filter and fluid, as well as getting rid of the aftermarket trans cooler that was added and putting the radiator cooler amd factory towing cooler in its place.
I had picked up the parts to rebuild the 1-2 accumulator when i was mistaken and thinking it was only 1-2 shift. Thankfully dad noticed 3-4 on the steering linkage test drive. I hadn't paid it much attention before that.
Not sure what truck you are working on, but I know I had put a Transgo kit. My main issue was a code for torque converter slip, and I used the version of this kit they offered 10 years ago:
I replaced the separator plate, installed the stiffest springs in the kit, and it was firmer than stock, but not harsh.
Checking the solenoid would mostly be checking the resistance of it and maybe jumping power and ground to it and seeing if you get a click out of it. If you had a scantool i think you could command it to do things and then see if they happen, but that's dependent on the scantool. Normally you wouldn't get tire chirping out of it but if the shift kit made things firm even when it was working it may make the failure mode a lot more harsh as well. Just a theory, though.
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