Hello, I haven't posted to the forum in some time. I hope everyone is doing well. My torque converter is once again giving some stuck in lockup mode trouble again. To give the history, if you recall I replaced my tranny with a used 1998 tranny that only had 29K miles; a Sunday driver that ended up getting salvaged due to a wreck that damaged the frame of the car. I replaced all the solenoids on the valve body before installing. I also replaced the input shaft because it had some slight damage; had intended to put one of the hardened input shafts but the price scared me away from that as I was getting low on funds. I wish I hadn't done that as I had to remove the valve body, replacing the gaskets etc. I had a six month warranty but let it elapsed because I thought the torque converter lockup issue was just some trash that would flush out; that it was just due to the trans sitting so long. I also used the torque converter original to the transmission. The fluid that I saw in the pan when I got the tranny was nice and pink and clean looking. I put seafoam trans medic in the fluid and drove the car and the torque lockup issue disappeared for several months and then returned. I added a second can of seafoam transmedic to the fluid and the torque converter lockup issue disappeared completely in a year of driving. Recently the torque converter lockup issue has returned. It us my understanding that there are both a solenoid and a valve that controls the lockup. At this point I am getting ready to do a fluid and filter change; not a flush but just a fluid change. I have ordered seven quarts of the new Dexron VI synthetic fluid. Should I do a flush or just drop the pan and do a change of fluid along with the filter? The car isn't driven daily; mostly once a week but sometimes a few extra days in the month.

Now for another issue that I have noticed. This issue tends to happen mostly on a good climb after the car has been driven for a bit, like 20 miles or so. I don't think I have really noticed it on a cold engine. On climbing a grade at around 50 to 60 miles per hour; although I think I saw it once when at 45 on a climb, the RPMs of the engine will climb and fall, climb and fall, climb and fall, it climbs around 400 to 500 RPMs for a short period, drops back down, and repeats. Is this torque converter or downshift related? I can't really tell if the car is downshifting and it would be nice if someone with more transmission experience was driving the car when it happens. I have been on climbs where I had to open the throttle to the point the trans downshifts and I can feel that. I don't really feel like a downshift occurs during the RPM thing.

Based on the amount of driving, the mileage on the current transmission (assuming it is still under 50,000 miles), and the fact that you've already changed out just about all of the fluid, I'd say a pan-drop/filter swap would be just fine.

For this one, if you can catch it:

1. You are driving up a grade like you describe.
2. The RPMs climb 400-500 like you describe.
3. Quick! Pop it into 3rd gear with the selector before it goes back to "normal".
4. Did this quick gear selection change the RPMs from the not-normal 400-500 more than before?

. . . and/or . . .

1. You are driving up a grade like you describe.
2. The RPMs climb 400-500 like you describe, then return to "normal". Remember what RPM the 400-500-higher RPM is.
3. Pop it into 3rd gear with the selector.
4. Is this about the same RPM as when it did this on its own?

What part of the world are you in?

Less throttle equals less severity of downshift. Based on your description I don't know what gears you are downshifting from and to when you open the throttle to cause one. 400-500RPM is about right at normal highway speeds for a 4-3 downshift in this car. If you were opening the throttle enough to shift from 4th to 2nd then that would be more severe. If you were going slower than the 50-60 we are discussing and you got it to shift to 1st, that'* always a severe downshift with this transmission.

Currently, for the 50-60MPH that we are discussing, I suspect that you are seeing a downshift from 4th to 3rd then back to 4th. 4th is a little too tall for the work being done while 3rd is a little too short: I can't quite hold this speed at 60.0MPH, I can't quite hold this speed at 59.5MPH, I can't quite hold this speed at 59.0MPH, I can't quite hold this speed at 58.5MPH, okay shift to 3rd, I can gain speed back to 60.0MPH, I can back off the throttle, now at this throttle opening my mapping tells me that I can shift to 4th. Repeat.

Exacerbated by altitude as well.

Since we're looking at this through the Internet, we'd also like to know:

What altitude are you starting to climb from?

How much weight is in the car with you in the form of other people and cargo?

Are we talking about 50-60MPH uphill with cruise control on?

Air conditioning on?

Headwinds?

Hello, I am located in the east/mid-atlantic; rolling hills at an elevation above sea level of 830 ft (253 m). The issue with the up and down RPM was under a fairly steep climb guessing a 20% grade (I am not good at guessing grades), no other passengers or cargo, cruise off (it isn't working), ac off (it isn't working either; a leak somewhere that hasn't been located) the engine was up to operating temperature; trans was hot; I had driven the car approximately 23 miles. Trans was in overdrive. It is hard to say how open the throttle was on the climb; the throttle position sensor has not been changed, the IAC was changed (throwing parts at an idle issue; yes, stupid) and the MAF sensor has been changed; that was a needed repair as the MAF was defective. The speed on the start of the climb was around 55; speed limit was 55 on that road. As I got fairly into the climb is when I noticed the rapid; maybe an interval of 3 seconds, it was up and down rapidly, change in RPMs. It scared me a bit as I was into an approximately 55 mile journey. I was holding the accelerator constant. RPMs were around 1600 and would shoot up to around 2000+; the gauge on the LeSabre is marked in 500 RPMs increments so no precise data. I would think that if a downshift was needed the trans would have stayed down longer; as I have noticed in climbs before, not the rapid fluctuation I witness. Unless something is faulty and the trans was getting confused signals; which is why I am posting here. I have read where the '98 computers had a history of failure; am I correct in that the computer is both the engine computer and the trans computer in one? I decided the other day to remove the computer and carefully clean the pins with some electrical non-conductive cleaner in case a signal was not getting through properly. I drove the car today, did not notice any issues; although now I am getting jumpy driving the car.

If I see it happen again, I will try the shift to third and see what happens; although the idea of shifting while driving makes me nervous.

One more thing. I read somewhere that on the 98 4T65E there was an issue with the valve body that had a recall for changes. Is there a way I can check to see if that is the case and check through the VIN if that happened with this transmission? I had the VIN of the car that donated the tranny somewhere; it was provided to me so that I could check the claim that the tranny only had 29K miles on it at the time I purchase it.

1,600RPM in 4th would be about 2,300RPM in 3rd if it shifts down. That makes sense.

Remember, this car isn't as intelligent as a lot of the newer cars are today. If it gets above a certain point of throttle opening versus speed it will downshift. If it gets below a certain throttle opening versus speed it will upshift. If you were alarmed by the sudden rise in RPMs and instinctively backed off the throttle a bit then it will upshift.

I haven't heard this.

Yes.

If you're not comfortable doing this, practice first. Last thing you need is to accidentally pop it into 1st. If you do it, it is simple, one click down. Look at the PRNDL after you do it to make sure it is on 3.

I have a 1997 LeSabre with more miles than yours and with the original transmission and engine and this shift you are describing sounds normal.

I hadn't heard of this recall for 1998, but I know there was a recall for valve body issues on the 1997. Either way, take the VIN number to the service department at a GM dealership and have them look it up.

OK, thanks for answering. I am feeling better about the car now. My fluid is on its way so will get the fluid changed and post when I do.

Sounds good!