TCC lockup problem

oldsmobile
catalytic-converters
transmissions
clutches
silhouette

#1

I’m fairly certain that my '00 Olds Silhouette is dropping in and out of TCC lockup in a herky jerky fashion - under steady throttle, very noticeable up over 45-50, it stammers with a characteristic 2-300 rpm change, and not smoothly. Its not misfiring - at least not so as my vacuum gauge would notice.



Other than that, the trans is fine and smooth with no strange shifting or slippage. The fluid level is correct and the fluid is pretty and red and smells just like it does fresh out of the bottle.



The van has about 136K on it, but the trans was replaced under GM warranty at 55K (long before I owned it) so the trans has about 80K on it. Unfortunately I don’t know if the torque converter was replaced then or not. Its been serviced twice - flushed (unfortunately) with about 38K on it before I owned it and then I did the pan & filter about 35K later. There was clutch mud and a very small amount of fine, powdery metal that I only found by cutting open the old filter.



This is the 4-speed 4T65E so it has no vacuum modulator or any vacuum controls at all. There is no way that I can see to disable the lock-up just to be sure (I hate that).



I am going to get it scanned on Friday, so there’s not much that can be said yet. But the hardest part for me is always talking to the shop. I’m always outmatched in terms of information and just want to be able to understand whatever it is they come back with. (I don’t have a trans shop that trust all that much).



What I have in mind as the list of possibilities are:



1) gee, wouldn’t it be nice if I had a squirrely connection in my brake light switch? (Ok - I’m not holding out for that, but it is a possibility isn’t it?)



2) electrically faulty TCC solenoid (not great but there are worse things)



3) TCC solenoid that can’t hold the pressure, either from bad o-rings or worn valve body or both. The former is less bad, but it probably matters little since I’d imagine transmission disassembly may have to take place to find out - ?



4) The torque converter itself? I doubt that b/c there are no other signs of an issue.



I crossed the TPS off the list b/c I tested it and it behaves itself even while driving.



What else would be on the list? (I don’t plan to give the shop my list - I’ll let them tell me what they think. Its just that knowing the possibilities helps me sort through whatever info they come back with).



Any help appreciated.


#2

It sounds like torque converter clutch shudder. You might give this a try. http://www.lubegard.com/C-230/Dr.+Tranny+Instant+Shudder+Fixx

Tester


#3

Thanks Tester. In fact, if the only option that comes out of it is a rebuild then the first thing I was going to do was track a tube of that stuff down and give it a whirl. I first saw it in another post of yours. If that’s what it comes to I’ll let you know if it does anything.

I should probably clarify a little tho I don’t know if it makes a difference, but the TCC does appear to lock in smoothly. But then it will kick out - then on - then out. Its like its toggling on and off. I don’t know if that’s like clutch shudder or not. Presumably a scanner will shed some light on it.

(And for the benefit of anyone who wants to say so, I do know that lubeguard isn’t not going to “fix” anything. But I’m not going to get the thing rebuilt so I’ll try whatever to keep my wife on the road long enough for me to get another van that isn’t a complete piece of crap).


#4


#5

So I think I may have screwed myself up with regards to the scan, and discovered another problem in the process.

I did have three stored codes:
P1107 - MAP sensor circuit intermittent low voltage
P1122 - TPS circuit intermittent low voltage
P1860 - TCC PWM solenoid circuit

The problem is that I recently tested both the MAP and TPS with a voltmeter. My Haynes says that the testing will set a DTC. Well, maybe it did and maybe it didn’t b/c apparently I also have a problem with the MIL circuit. The engine light has not come on at all - yet apparently it should have. (So another problem to troubleshoot).

So now I am stuck wondering whether or not the TPS and MAP codes are real or artifacts of my testing. Any thoughts on that? Would testing a TPS set an intermittent low voltage signal? I can’t see why - all I did was use a straight pin to back probe the connector. I checked it KOEO and then actually rigged a couple of long jumper wires & drove around with the meter on for a while. (I noted no anomalies in the signal).

The shop wanted to replace my TPS (at something like $180 on a guess - as I said I don’t have a place that I trust). One thing they never mentioned is that the TPS & MAP share the same 5V reference circuit from the PCM. I actually didn’t find that out until I got home and checked the diagrams. I don’t know yet if that means anything but I’m going to find out.

They basically said that they would clear up the TPS code before even looking at anything else - this is where I run dry on expertise to know what to ask about what else their scanning showed - though it does look like if the TCC issue isn’t from the TPS then it is at least an electrical issue with the solenoid. I’ll take that any day though it isn’t easy to replace.

Anyway, my next step is to check the wiring for all of this stuff. Any thoughts about any of it would be appreciated.


#6

So I got this thing back into the trans shop - the first day I had it in the actual real trans tech wasn’t even there.

He drove it, and pulled a P1811 code. This is confusing to me. I know of the P1811 problems and the symptoms aren’t TCC lock up problems (or at least that’s not the most common).

He thinks the converter clutch is coming apart.

In any case, he said that when he finds an 1811 he just orders a rebuilt unit from a company that he trusts with them. He said he’s done everything with these things from solenoid work to complete rebuilds and no matter what he does he often ends up with the same problems again.

This trans seems to be a rats nest of complications.

Anyway, maybe he’s right. At the moment I just can’t get how P1811 gives me TCC dropping in and out of lockup.

Any thoughts appreciated.

Those initial codes (TPS MAP) were just caused by me. I also must have caused the 1860 b/c I thought (wrong!) that I could temporarily pull the TCC fuse to disable the lockup. No so - it disables all shift solenoids. Anyway, they had cleared those codes and none were still there.


#7

You said that you crossed the TPS off because you tested it and tested it while driving. How did you test it?? If it was just with a DVOM you can forget it. The DVOM is fine for checking voltage and sweep but ineffective for checking for spiking. You need a high end scanner or scope to properly monitor a TPS. I commonly find TPS’s spiking both high and low and NOT setting codes. Your P-1122 is showing a intermittent low signal. Thats enough to cause a TCC to drop out. Are you positive you caused that?? That TPS could very well be your original problem. You really need to check that out with a high end scanner with scope and/or graphing capabilities.

transman


#8

Thanks transman. I first used a DVOM, then what I have is a laptop based scanner (OBDlink). It does actually sample down to 100ths of seconds, though I still don’t know if that’s good enough. But when I check out the output I can graph things like the TPS, MAF, rpms, load etc. next to each other. The drop in/out episodes are obvious - rpms and load readings for example fly up and down while the TPS just stays flat. I have more than once considered just throwing a TPS on there though. Its only $50 but I still hate “throwing parts” at things.

Unfortunately this scanner only does the generic OBD stuff so I can’t access the transmission commands myself. I also can’t even verify the P1811 code. When I asked why the 1811 wasn’t there the first time the guy just shrugged. He doesn’t care. Apparently he sees the code and quits there.