I posted this on a different forum, but I really would like to get some expertise on this so I'm posting this here as well. This is for my 1995 Buick Regal, with a 3800 Series 1, 4T60-E. The car has 213k miles and the transmission was rebuilt at 148k. If you know anything about these transmissions, any help would be very greatly appreciated.



It first started a while back; probably 3-4 months. I would start up the car, put it in reverse, and it would engage reverse perfectly fine. However, it would make a tapping vibrating noise that you could feel in the shifter, as if something was rubbing. The vibrating would increase the faster you went. This would be only in reverse, but Reverse would engage just fine.

Before I left for Chicago, I changed 1 gallon of the transmission fluid. I used a pump to suck out the old fluid through the dipstick tube, and did the same in reverse to get a gallon back in. As of now, after driving around for an hour, the level in park is about 1/4" above the full level.

My problem is now shifting in both drive and reverse, but moreso in reverse. If I move the shifter into reverse, it doesn't do anything. The torque converter engages, so you cannot free rev the engine anymore, but you can hit the throttle all you want and the car doesn't move. It feels as though the car is in park with the torque converter engaged. Once this happens, you can shift slowly down into Drive, and the exact same thing happens. The car doesn't move.

To fix this problem, I would run the shifter up and down from Park to 1 very quickly, then back into Drive, and the transmission would engage 1st gear no problem and I could drive off. I used to be able to do this same thing for reverse, but not anymore. Now, I can run the shifter up and down all I want, but reverse won't engage. I spent 15 minutes trying to figure out how to get my car to engage reverse, and this is the only method that now works:

I have to run the shifter up and down from P to 1 a few times very quickly, then while holding down the button on the shifter, I have to squeeze the shifter between Reverse and Neutral and hold it somewhere midway there. I have to play with the position a bit, and eventually I'll get the car to engage reverse. However, I have to hold it there, because the moment I let it slip back into reverse, the transmission locks up as if it was in park. If I'm moving fast enough, this will put a serious load on the engine and transmission mounts as it would be the equivalent of dropping your car into Park.

Any ideas? I have a feeling I soon won't be able to back the car out of a parking lot.

Aside from this, the car shifts perfectly fine, although it takes a couple of minutes every morning before TCC will engage while cruising on the highway. Not sure why that'* happening, but this problem is a bit more critical.





Trans was rebuilt at 148k. It currently has 213,005 miles as of now. Your reply doesn't help me at all. It shifts FINE once its in gear. It gets in gear fine, if you play with the shifter. The problem seems to be somewhere in the shifter position. I can repeatedly get it to shift into Reverse using the method I just described. It doesn't slip between shifts fall out of gear, have any other unusual symptoms.

Would dumping some seafoam in there and draining the transmission do anything?


I actually checked and the shifter cable is intact and its shifting the transmission **** properly. When you shift from park into drive, you hear the torque converter engage and you feel the RPMs drop for a second as you're no longer in neutral.

Honestly, it really sounds like the park transmission lock (or whatever its called) is not disengaging, rather than the gears not engaging, if that'* even possible. When you shift into any gear, you can hear the transmission engaging something, and for a second you can feel the car nudge in that direction. In layman'* terms, it feels exactly like your shifter is in Park, while its in gear.

Can any of this be caused by an overfilled transmission?

SQP358 is our trans gearhead. If he don't chime in soon, send him a PM. he should be able to answer any problems.

Thank you!

It has been suggested that my filter may be clogged and therefore is reducing pressure. Some have noted that when the engine is cold, that only worsens the situation as the pressure is further reduced, and this has only been happening recently. Coincidentally (or not?) the problems only started as the weather has cooled down here in northern IL.

During cold temps, the PCM will prevent your TCC from locking up until a certain eng/trans temp is achieved. This is normal for our cars.

The vibrating/tapping noise is a good indication that your reverse reaction drum is either not seated correctly, or is worn out.
The teeth on both ends of the drum can become worn. Though not very noticable on this picture.



If you ever experienced parking on an incline, and attempted to take it out of PARK, you would notice torque lock on the parking pawl. Once the shifter is out of PARK, the pawl no longer is in contact with the differential. Unless you had a failure in the linkage, then you would never get it out of park.

I don't see Seafoam doing anything here in your case. When was the last time the filter was changed? I suggest dropping your pan and inspecting the bottom of it including cutting open the filter. Something might have happened during the rebuild.

See, I thought at first that it could have been the reverse reaction drum, or something of that sort, but the very strange part is that the ticking or vibrating noise went away the moment I touched the shifter and moved it around. When the shifter is in the Reverse position, it has some wiggle room up and down before you have to push the button down to shift to another selection. If I move it up a bit without pushing the button down, that ticking noise would go away, which means it can't be the reverse reaction drum, because if it was, the noise wouldn't go away with me just repositioning the shifter.

I just went outside and tried moving it again. If I put it into neutral, I can kind of move the car a little bit. I can't really tell if Park is still engaged or not, but I was able to move it half a foot or so. The car wasn't on any incline, and left in Neutral, the car wouldn't move anywhere. I then dropped it into reverse, and the car moved back to the position from where I first pushed it, but then stopped as if it hit a wall or something. that'* one thing I noticed earlier testing the car in a parking lot. It felt as if the Park pawl would engage if you didn't hold the shifter in a specific position, the moment you tried to move in reverse.

Just now, I was able to get it into drive and move forward 2 feet from time to time, but it wouldn't always engage drive, and I couldn't figure out why it worked some times and why it wouldn't work other times.

In either case, you can tell a very noticeable difference while revving in neutral and revving in drive or park when it feels like the Park pawl is stuck. Still not sure what'* going on here. I'm replacing the filter some time this week.

This is getting weirder and weirder.

A video of this would be nice!! lol

I'm starting to wonder if its linkage related either at the shifter or in the trans. Anyway for you to inspect the shifter linkage in the center console? Though I'm sure its safe to say its connected in a simple manner and timing or adjustment is not possible.

Too give you an idea of what it looks like on the trans side...

802 is the detent lever that connects to shaft 807. These are keyed so assembly is idiot proof. I'm wondering if these two keyed items became un-timed and is allowing you to shift, but not take it physically out of park.
If those 2 pieces become untimed, not only taking it out of park becomes an issue, but selecting the right gear becomes a problem also.

I've been kind of watching this thread. I'm with Mike on the shifting linkage here. Here'* a picture of the inside of the trans, the linkage is near the top. I'm wondering if something is sloppy here.

I've already taken apart the center console. Everything looks ok there.

I hooked up my car with my ALDL usb cable and ran TunerPro, and the ECM registers each shifter selection properly. I ran from P to 1, one notch at a time, and the ECM knew exactly which position I was in every time.

I also had my fiance'* brother run through the shifter positions while I was under the hood and the shifter cable was intact and was moving the notch on top of the transmission as it should. No problems on the outside of the transmission as far as I can tell.

Also, it seems to be something else other than the shifter linkage inside the transmission, because I can shift into neutral just fine, and free rev, and then shift into Drive or Reverse and the car responds exactly as if you had the brake floored. The car won't move, but you'll hear the engine struggling and it won't free rev. You hear a gear engage in the transmission in either Drive or Reverse, but you can't go anywhere, exactly as if the parking pawl was constantly engaged.

I'll have to see if I can push the car a good distance in neutral when some of the ice in my driveway melts away, as I can't push it to save my life at this point.

There'* a linkage on the inside, #800 in the diagram. That goes to the parking pin. If this is sloppy, it would make sense that the computer will see the shifts correctly, because that'* from the outside of the trans. But the trans won't leave park.

THAT WAS WEIRD because when I made my last post, I was gonna ask if you had a scanner that could show what gear you are in. Good, that narrows it down further. But that only shows that the sensor on top of the trans is working. It won't really show what gear it really is in.

Dan has a better image than I do of that linkage assembly.

Only way to verify if it is the linkage is to visually inspect it. Which requires the side pan to come off. Only way to do that is to drop the trans. Or lift it up some to clear the frame rail. And the drive shaft has to come out too.

EDIT:
Pop the diff cover off. Then you can observe the action of the parking pawl.