Hi, I have a 94 c4 with the 4L60 trans in it. The PO had the trans rebuilt a few years ago and it only has 8k on the rebuild. It was done in another state so the warrantee for me is no good. When I bought the car several moths ago I drove it 5 hours home and it shifted perfectly. Since, I have only driven it a couple of miles as I haven't registered it yet and I've been doing other work on it.
Today, I went to put some gas in it. It drove fine for about a mile and then the check engine light came on and the trans started slipping. It seems like first is OK then it slips in 2nd and then its OK in 3rd. Not sure about OD. As soon as you hit the gas pedal it kicks down and starts slipping. It also seems to hang in first gear before it slips in second. All of this just happened in like 1 mile of driving. I live in the country and I did hit some bad bumps so I'm wondering if maybe a ground came loose in the pcm. I read that their was a bullitin about this and a kit to jumper the ground for the trans on the pcm. I would absolutely love it if that were the case.
Has anyone had any experience like this? I havent pulled the code yet but I have eehack and will do so soon. I've also had other ground issues with this car. Particularly a TPS sensor that floats around and wont stay at 0 at idle. Anyway, any help would be appreciated.
Thanks.. Bill

 

Giving us the code is the first step.

 

Apparently unrelated. It was H63 which is right bank o2 sensor. It is bad, I had just forgotten about it.

 

Did you check the trans fluid level?

 

sure did..

 

Describe what you mean by "slips in second". Second gear on these trans is a bit hard to explain. There is no clutch pack that engages to drive a different drum/hub. It is a band that locks the rear sun gear, forcing the planetary carrier to walk around the sun. This in turn alters the ratio in the front ring/carrier/sun. If the band slips, it will certainly heat and eventually burn but there is no point in time that the output shaft loses total drive. If the band is slipping, you will have a gear ratio anywhere between 3.06 and 1.62. Pretty hard to say anything definitively with this information. Does the oil look/smell burnt?

 

H63..but which module? 1? 4? 9?

Still probably unrelated to your trans slipping but still a good idea to be aware of.

 

What its doing is holding first gear and not shifting. Then it eventually goes into second and completely disengages. You can rev the engine and the car doesnt move. Then if you feather the gas pedal it will go into 3rd and be normal. As soon as you hit the gas again it tries to kick down and then just revs the engine. I'm not sure about od yet because as I said, when you try and bring the car up to speed it downshifts and then it just revs the engine. I dont really want to keep driving it as I dont want to burn anything up.
The fluid was slightly discolored but still mostly red. The trans only has 8k on it since rebuild. I figured the slight discolor was probably because the may not have cleaned the lines or completely cleaned drained the torque converter during the rebuild. But this problem just happened suddenly. No warning at all.

 

Hey Nomake!
I thought about that right after I cleared the code. So I drove it some more and the code did not reappear. I'm pretty sure it is the O2 tho. I'm going to put the computer on it today and see if I can discern anything.

edit: Do you know if their is anything on eehack that can diagnose the trans. When I open the trans section on an old file it shows no data. Is their any way to activate the data?

 

Yep! By default EEHack only reads the 'Main' datastream. If you want to look at transmission data, then before clicking connect, first go to the 'Main' tab and click the 'stream' button on the right to deselect it. Then go to the 'Trans' tab and click the same 'stream' button to select it. Then press connect. This will then log transmission parameters instead of engine parameters.

While it's possible to log both at once, it's not recommended--the serial bus on these cars isn't the fastest.

 

This is just a quick ride up the street. Lots of slipping in 2nd. I cant really make much of this log except the tps seems out of range. Of course it is..lol..
I'm not really a transmission guy.

 

Okay, so with a look at the data here, I'm not quite seeing the slipping you're reporting. At least, the transmission isn't reporting it. There's a jump in absolute slip of about +800 RPM right when the transmission selects 2nd due to you slamming the throttle to the floor while in 4th, but it only lasts 0.3 seconds before the transmission completes the shift. Additionally it looks like you did this logging with the car ice cold. The coolant was only 44C and your transmission was only 33.5C when you performed that little maneuver. At the very end of the log, the transmission gets to 46C, and the actual-VS-desired shift time for the 1-2 shift drops to 0.23s (from the start of the log where it was a whopping 6s). My '94 is also a little clunky when cold. So if you're only complaining about a cold temperature issue, I'd say let the transmission warm up.

Also, the temperature readings and TPS fluctuate pretty wildly. You likely still have an electrical problem. As I believe I've mentioned to you before, these readings should not be fluctuating. They should be rock solid and vary smoothly as their inputs change. Especially the TPS, which is directly related to transmission control (among many other things).

I'm not a transmission master, and my '94 auto doesn't have any transmission issues I've had to diagnose yet, so there could be something in the data I'm not seeing. But from where I'm looking, I just see the same old electrical issues, and a very cold car being asked to perform on command before it's had a chance to warm up.

EDIT: Again, probably totally unrelated to your transmission, but interesting that at 54 seconds into the log, your left O2 reports ready for closed loop. But it takes until 280 seconds before your right O2 reports the same. Again I have to wonder if you just have some serious electrical issues that are the cause of all your engine and transmission issues.

 

Thanks for the reply Nomake. The tps issue was never solved. Originally if you recall, I was working in that direction to fix a high idle and fluctuating idle. After numerous tests and talking with you, I was still never able to solve that issue. I tested everything, voltages, ohms replaced iac tps etc.. Just not solvable for me. However, none of that seemed to effect the operation of the transmission. It always shifted smooth. As for the o2, I replaced the left bank o2 and stripped out/broke the right bank. I 'm aware of that and I dont believe it would even run in closed loop anymore.( I need to take it to and exhaust shop and have them torch it out) But again, I wouldn't think that would effect the trans but I could be wrong. When I drove it to the store I hit some pretty severe bumps and I think that might have started it. Not sure.
The reason I started it and drove it cold is because I have no idea if I am doing major damage to the trans driving it like this. When it first happened I drove it some more, (a mile or two) and the car was up to temp, (fans were on), and the slipping got worse. I wasn't sure the car would make it home it was slipping so bad. It actually slips less when its cold. But as soon as you hit the gas it just slips right out and its like in neutral. I hit the gas to show that. Then it gradually catches and then shifts into third and is OK until you give it more gas and it downshifts and slips again. Its bad..
I was just hoping maybe a shift solinoid went out or something easy. The PO spent $2100. getting it completely rebuilt 8 k miles ago.

 

Okay, I had another look at the data, this time using some graphing rather than going by the transmission's self-reported slip and time-to-shift values. While the drive was very short and most of the time was spent in either 1st or 4th, there were a few seconds' worth of time in 2nd to look at. Two specific points--one very early on in the drive, probably the first time it shifted to 2nd; and one when you mashed the throttle--showed what appears to be excessive slip. Namely that the RPM shot up, but vehicle speed did not seem to respond accordingly. With the way gearing works, one would expect that the RPM curve for 2nd gear would be lower than 1st gear for a given vehicle speed, but that's not what's shown at those two points. I'm not sure why that wasn't counted as slip by the transmission's control routine.

If a solenoid 'went out' it would be reported by the PCM, as that's an electronic fault. No such fault appears to exist. If however the piston the solenoid actuates or its bore have failed, that won't be reported as it's a mechanical issue. All the log can tell you is that the correct commands are being sent, and what sensors are providing feedback on those commands.

Do you have the receipt for the rebuild? Did it come with any warranty? Does the company who performed the rebuild have any sort of reputation for rebuilding turbo hydramatic transmissions?

Here's a pretty awesome diagnostic flowchart for "every gear except 2nd works on a 4L60E" in case you want a peek: https://atracom.blob.core.windows.ne...3/2013-038.pdf

 

Thanks... The PO had the trans rebuilt in another state. The warrantee is non transferable. Do you know or does anyone know if the 2-4 servo can be replaced with the trans still in the car? Its a vert so I know their is a cross beam in the way but not sure of what else. Also, I drove it again and used the diag feature this time. Its shows a tcc valve fault. I would think that only has to do with converter lockup but maybe something else? I dont know.
Check it out.

 

I don't recommend using the 'diag' feature; it's not actually terribly useful and will report tons of "errors" that do not actually exist. For example, reporting that the circuit for the transmission performance LED is open. Well yeah...because a Corvette doesn't have one. Same with the 1-4 shift light on an automatic, or oil life on a Corvette (since on a Corvette that's controlled by the CCM, whereas on a B-Body it's controlled by the PCM). In this case, the reason why you are seeing "TCC CONTROL SOLENOID OPEN FAILURE" is because you own a 94, not a 95. This solenoid is the PWM control solenoid that was added to the 4L60E in 95, which is why it's throwing an error on your 94 that is leading you astray.

The 2-4 servo can technically be replaced in the car if you have a lift or other sufficiently safe way to raise the car enough to drop the exhaust (if you want more access room on the sides), convertible crossmember, etc.

 

40 PSI would definitely cause some issues. I agree that a gauge would be the first move. I see by your italicized "slipping" that you realize there really is no such thing as a slipping second gear. The band may slip but by itself does not cause any free wheeling. A slipping band only means you remain in 1st gear.(or really, somewhere in between because the rear sun is being slowed but not completely stopped) The OP stated that it is if he is in neutral. The only thing that would cause that is if the forward clutch were slipping or falling out completely. This is certainly possible under such low pressure. I don't think it is a leaking servo because he said it is OK in 3rd. The second gear servo pressure remains active in 3rd.

 

Good info guys. I guess the first thing is to get a pressure reading on it. I guess first thing would be to drop the pan and check/change the filter to make sure its able to suck in fluid and their are no obstructions. The fluid is slightly discolored anyway so I'll change it. Then check the pressure. Watched a couple of videos on that. It doesnt seem too hard I just have to get the gauge. When I drove it last time, I tried manually shifting it to 2nd and it totally slips out like its in neutral. You can downshift it back to first or get it to go into 3rd but 2nd just isnt having it. But I dont think 4th was working correctly either because getting it up to 55 mph or so it didnt seem to want to stay in OD. It was like it was losing pressure and dropping down to 3rd. Hard to explain because as I said, I didn't want to drive it much in this condition. When these things go, do they just go out in an instant like this did? It was fine and then it wasn't.

 

That's what I've tried to explain twice now. There is no such thing as a slipping 2nd. gear! To repeat, I also don't think there is a problem with the servo. If the servo were leaking enough to cause a forward clutch dropout, then it would also not allow the 3rd clutch to hold. OP says 3rd. is fine.

My money is on a problem with the 1st. gear circuit/clutch pressure.(or possibly line pressure) Here is my reasoning. In first gear, the gear ratio is high which allows the forward clutch to get the car moving relatively easy. When 2nd band applies, this creates a great increase in the holding torque required from the forward clutches and slipping may now occur. No different from a manual trans. When 3rd gear applies, the load is now shared between the forward clutch and the 3rd clutch. When 4th band applies, the forward clutch now carries 0 load. However, these are just educated hypotheses. Pressure checks is what is needed.

 

I drove it again. I'll be as specific as I can. Reverse seems fine . I held the brake, increased rpms and no slippage. I also did the same in drive, (first gear), no slippage.
Starting out in drive at normal driving speed the car starts out normal. Then it seems it just doesnt want to upshift. It holds first and then around 2100 rpms or so it just starts slipping badly. If you let the gas off it seems to go into 3rd. I got it up to about 60 and it seemed 3rd and 4th were OK and I think even the TC locked up. Its hard to tell exactly because I'm on rough roads and I'm driving a corvette. lol. Also, I dont want to drive it that much because of its condition.
So, from a stop manually shifting gears. It will hold 1st fine. Manually shifting to second it just goes into full slip. Shifting it into 3rd seems OK.
From the link that Numake posted could it be a broken band or a short/worn servo pin? I know you guys know much more than I do about the 4l60e and I appreciate the comments. I'm really hoping this isnt destined for a complete overhaul. I dont have a lift. I have a gravel driveway.lol..