Thread: 4T65E strange 4th gear shift

I have an '01 Impala with the 3800/4T65E trans, all stock with 244K miles on it. Trans seems OK for the most part. No clunks/slams when shifting from P. 1-2-3 shifts fine, TCC seems to operate like it should. Shifting into 4th is a little bit funky though. When it goes into 4th, you can feel the car pulsing or stuttering slightly, like it's trying to fully engage the clutch pack. The tach fluctuates by about 100-200 RPMs while this is happening. It takes about 2-3 seconds to stabilize, and then it does fine. If I lift the throttle for a second or two at the shift it will stabilize quicker. No codes present, cruise works fine, down-shift seems to be normal. I have not done a lot of troubleshooting on it at this point, but I do have a trans pressure gauge that I can hook up to see what it's doing. I am not a trans expert by a long shot, but I am hoping that it might be a solenoid problem. I've felt one of these transmissions strip the 4th clutch hub before, in a '00 Montana that we used to own. It hit 4th gear, shuddered for a second, and that was it. 4th gear departed the premises, not to be seen until the trans was rebuilt shortly after. The trans guy showed me the hub. Stripped smooth like it had been machined that way. This Impy is not doing that. I have not dropped the pan yet, but I have changed the fluid. Vacuum pump kept my hands clean, lol, but the fluid was a little darker than I like to see. Shift feel improved slightly, but nothing drastic. Any ideas?
Dave

Oh yeah... I do have a decent bi-directional scan tool. That's what I used to read the codes. I saw a post with ohm readings for the various solenoids somewhere, but I can't remember where I saw it.
Dave

OK, I remember seeing a wiring diagram and ohm values for the solenoids, but I can't seem to find it now. I've been doing more digging around and found a thread or two about TCC oscillation. That is probably as good or better description than what I posted. One suggestion from several people was to simply disconnect the battery and let it sit for a while to reset things. It's free, so I'll give that a shot before I go digging into anything else.

Sounds like the TCC is dying. Try this- when it starts bouncing around keep your foot steady on the gas and lightly tap the brake pedal with your other foot (enough to make the brake lights come on) and see if it quits bouncing. This unlocks the converter.

IMHO best bet would be to get a Trans-Go shift kit for it (I didn't install the whole kit, just the 1-2 and 2-3 accumulators), new filter and refill with whatever amount of fluid came out of the pan drop and see what you get. At that mileage it probably just getting worn. My 00 GP GT does this every now and then. Although it seems to do it more when the fluid gets a bit low so double check that too. It sounds like you have good knowledge but just in case check it with a fully hot trans on level ground with the car running in Park.

I will say the Trans-Go kit really helps. I also always turn off my traction control. Not sure if that is doable on an Imp. The other thing I do is always drive in "3" until I know I'm going to be above 45mph for a sustained amount of time. Keeps the trans from hunting in/out of OD all the time.

Check out https://tripleedgeperformance.com/ Dave has been a goto guy on these trans. for years. Should have the kit as well.

Thanks, Fordman. Triple edge is where I found the best explanation of the TCC oscillation. If the weather cooperates I'll take it for another spin and see how it reacts to a light touch of the brake pedal. I know that shifting manually from first through 3rd, and then to OD it doesn't do it as much. More to follow.

Thanks, Fordman. Triple edge is where I found the best explanation of the TCC oscillation. If the weather cooperates I'll take it for another spin and see how it reacts to a light touch of the brake pedal. I know that shifting manually from first through 3rd, and then to OD it doesn't do it as much. More to follow.

I disconnected the battery this morning, cleaned the terminals and let it sit while I was working on other things around the garage. I will reconnect the battery tomorrow and take it for a short drive to see how it behaves.

Looks like I'm still in moderator's new-guy probation here... At any rate, I hooked up my pressure gauge to check line pressures this morning. Cold out here, weather app on my phone says 28*F when I first fired it up. The crimped hose connection on my gauge is leaking, so I did not drive with it connected. Pressures read at cold start while engine is warming up.

Pressures at initial start up: 28*F, approx 1200 RPM
PRN - 140
D4,3,2 - 140
1 - 157

Pressures at approx 1000 RPM after a minute or so of run time:
PRN - 115
D4,3,2 - 80
1 - 157

Pressure in P did vary with engine speed. It would jump when I blipped the throttle.
Since the crimped connection was leaking, I shut it down, removed the gauge, and put the plug back in. I'll have to have another fitting crimped in before I hook it up again for another pressure reading. I connected my scanner (X-Tool D7) and took it for a short drive. It seemed to behave pretty much like it is supposed to do. Smooth shifts, no oscillation going into 4th. 4-3 downshift on acceleration felt pretty good. I thought I was recording data while I was driving, but I guess the scanner is smarter than I am. It looks like most of the recording data pids stopped changing about half way through the 3 mile drive when I went to replay the recording. I was able to watch the live data and see the gear change, TCC duty cycle, RPM slip, etc. I'll try data recording again later.

I have not had my pressure gauge repaired yet, so no updates on pressures. I have not driven it any more, either. I do have another question, though. Will the 4T65E from a '00 Montana work in this '01 Impy? I could probably get the van that I used to own back for a very good price if it will. When I had the van I had the trans rebuilt by a very well respected local shop. The guy is a wizard with these things. I don't think they put too many miles on it after they bought it from me. The van has the 3400 in it. That swap would be a last resort, though. I want to get the trans in the Impy diagnosed before I do anything else. With 244K on it, it's probably just worn throughout. Looking back through the Impy's previous owner service records, the trans was flushed at 106K, fluid & filter change at 163K, and I did a fluid change at 244K. I thought that I had changed it before then, but it must have been the '04 Impy with the blown engine.

Hey, I was wondering when you would show up! The Impy is in limbo right now. My daughter was driving this as a daily until the trans started acting funny. She bought a '10 Corolla to drive, so I let the tags expire on the Impy. I have it listed for sale on C-list, pretty cheap because of the funky 4th, but not much interest. I'm half-heartedly tracking down a recurring evap code, too. Once I get my line pressure gauge fixed I'll see where we stand with a warm trans. Driving this thing will be limited to the back road where I live. The ECM reset seems to have stopped the oscillation, for now anyway. With 244K on the clock it's probably just plain worn out.

Originally Posted by cozwurth

Hey, I was wondering when you would show up! The Impy is in limbo right now. My daughter was driving this as a daily until the trans started acting funny. She bought a '10 Corolla to drive, so I let the tags expire on the Impy. I have it listed for sale on C-list, pretty cheap because of the funky 4th, but not much interest. I'm half-heartedly tracking down a recurring evap code, too. Once I get my line pressure gauge fixed I'll see where we stand with a warm trans. Driving this thing will be limited to the back road where I live. The ECM reset seems to have stopped the oscillation, for now anyway. With 244K on the clock it's probably just plain worn out.

You can use your scan tool to check the trans shift times for each gear. I am not certain of the value but if it exceeds 300ms or so the tcm will command maximum pressure and the trans will slam into 4th. The tansgo shift kit might help but it sounds like your clutch packs are wearing out and it's slipping in 4th. If that's the original trans you certainly have done well with it. Good luck.

No updates on the car itself, but I've had no joy in getting the 1/8 swivel pipe fitting replaced. I went two local places, neither had fittings that small. Looks like I'll be heading to the hydraulic service place near where I work.

GXP, I did not look at shift timing when I had the scanner hooked up. I'll look for those next time I take it out for a spin.

Hydraulic Service to the rescue. They fixed up my gauge hose in just a couple of minutes and I was on my way. Tomorrow will be another drive with the gauge and scanner.

Shift timing...
I hooked up the scan tool again this morning and got my wife to drive while I looked at shift timing.
On the drive out, I had her stop a couple of times to make it shift through all of the gears again. The 4th shift time was only a 3-4 shift after slowing down a little, so no other times listed.
1-2-----1.07--1.00--1.00---------0.45
2-3-----0.78--0.97--0.95---------1.25
3-4-----0.40--0.32--0.28--0.40--0.45

On the way back I got her to be a little more aggressive on the acceleration on the last two runs.
1-2----0.50--0.50--0.97--0.42--0.42
2-3----1.27--1.30--0.60--0.30--0.25
3-4----0.45--0.42--0.35--0.55--0.40

Looks like this trans likes a bit more throttle on the 1-2 & 2-3 shifts, but a lighter throttle on the 3-4 shift.

Pressure at startup: (a bit warmer today than last time, engine settled into 900-1000 RPM pretty quick, and then dropped slowly as it warmed up)
PRN - 115-130
D32 - 85-95
1 - 160

I'm also getting a bunch of CANBUS error codes now, too. I probably disturbed something on the ABS module while installing the pressure gauge. I guess I'll have to look into that, too.

The CANBUS errors seem to have been related to the connector at the ABS module. I must have moved it a little while disconnection the pressure gauge. I unplugged it and plugged it back in and those errors went away. I don't think the lock/latch part of that connector is working right. Something else to look into. Wonderful. I'll take it for another spin in the next day or so and see what happens.

Not much to update, but the CANBUS issue was the connector at the ABS module. Once I got that plugged in securely those codes went away. I had someone come out to look at it a few days ago. They seemed very interested in it, so hopefully it will be sold. If not, I'll keep plugging away at it.

Well, I've been busy with other things for the last week or two. I've been trying to take care of a few little things on my '57 that have been bugging me so I have not messed with the Impala any. At this point I really don't need to. I've had it advertised for sale for a while, and I had someone come out to look at it tonight. They liked it well enough to buy it. Full disclosure on what I've been doing on it, and the transmission behaved well during the test drive. SOLD!