99 Aurora with bad lockup clutch...solonoid?

JP

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#1
99 Aurora with 8 cyl. Northstar engine, 99K miles, in good shape

Lockup clutch on trans not engaging.

Dealership and other mechanic quoted between $1500 and $2K to fix. Car not driven frequently at freeway speeds, so lockup clutch doesn't affect gas mileage significantly. Car is driven about 3-4K miles a year.

I understand that fixing it involves dropping the engine cradle to just get at the transmission to check the lockout solonoid, and yeah, that doesn't seem like a shadetree job.

Any problems with not fixing it? Blue book is about $3K, I can't see spending a little over 50% of the value of the vehicle to fix it if leaving it unfixed is not going to lead to any sort of catastrophic trans failure.

What sayest thou?
 
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#2
Disclaimer: I do not really know.

But I drove a GM car without it locking up for years with no problem.

Some will say the trans will overheat. Well, of course there will be slightly more heat generated with the converter working than when it is not, but I feel (don't know) that the cooling design should be well able to handle it.

And I most certainly agree with you that putting 50% of the value into a car repair probably does not make sense.

That's my $.02. Hope someone that really knows jumps in here.
 

jasonn20

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If full lock-up between the engine and trans is not engaged then the fluid will deteroirate quicker because it will generate more heat especially if driven on the highway for extended amounts of time. It will cause premature trans failure.
 
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#4
Is the lockup solenoid really defective? Did anyone get as close to that solenoid with a 12V supply as possible and state its definitely the solenoid that is opened? Or are they just guessing? I never ran into a bad solenoid, its just like the fuel pump, a hell of a lot of stuff between the battery and these devices. Have fuses, ignition switch, PCM connector, that could have a bad driving transistor or a badly soldered one, connectors with corroded pins, dirty contacts in the neutral safety switch, I know they don't call it that anymore, a brake switch with dirty contacts, has to be closed with the brake in the normal position, and more contacts to the transmission.

Just like a fuel pump, wires, switches, connectors running all over the damned vehicle, that is were I find the problem or problems. Torque converter lockup is the last thing in the string, could even be the Vss skipping pulses at higher speeds and the rest of the transmission will shift okay, has to be in overdrive first before locking up.

I would want to be damned sure its the solenoid before laying out 2,000 bucks, and one way to know for sure is to check it out myself. Like guys that go through the effort of replacing a perfectly good fuel pump, to later learn it has a bad ground under the drivers' seat.

GM is also noted for not using the best connectors or switch contacts, ignition switches are typically five pole switches, other four can be operable, just saying, know exactly what the problem is.
 
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#5
I wanted to avoid this problem... BUT when I saw NickD with the exact same thought I want to add -

Are you certain it is the solenoid?
 
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#6
His REAL question is, "can I drive it this way". My answer is still , Yes. We drove automatic transmissions for years that did not have lock up converters and I drove one with a inoperative lockup for years also. So, I still am of the opinion that he can drive it for the 3-4 K miles per year and do noting, if he wishes.

On the other hand, all the suggestions of checking to make sure it is not something simple or different could be very helpful to him.
 
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#7
For most vehicles, lockup doesn't occur until you hit 38-45 mph, ha, just drive below those speeds. Really the major problems start when that lockup doesn't release, there is no ha, when this occurs.
 

billr

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#8
Yep, I concur with JackC; check for simpler stuff, of course, but with the low yearly mileage and infrequent highway use it will probably be fine. Even if the trans fluid does heat up more than normal and shorten trans life, what's to lose? It already is "beyond economical repair" if the trans has to come out...
 

mhamilton

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#9
This is very common on Northstar Cadillacs... this and the shift solenoids in the 4T60 are its weak points. There are two main problems, one that the TCC solenoid has gone bad (a $15 part burried deep in the upper part of the trans), or it is also common for the seal between the apply hydraulic circuit and the torque converter to have started leaking (internally). Either way, when you replace one you do the other and you need to replace the torque converter itself (if the Olds has the viscous converter as do Cadillacs, it will not tolerate a partial engagement condition).

That said, many people have ignored the P0741 for ages and had nothing bad happen. It will heat up your trans fluid more on the highway, and MPG will decrease slightly. And you won't pass inspection (if that's required) with the CEL on.

By the way, you can easily tell whether you have a TCC seal issue or a solenoid issue by which codes are present. P0741 the solenoid is fine but the hydraulic circuit is leaking. If you get 741 and a P1xxx electrical code, then your solenoid is open.
 
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#10
Torque converter lockup came out in the 80's as a means to increase CAFE ratings to please the EPA. But that's driving at a nice 55 mph on a clear interstate road. Doesn't do a damn thing when driving insanely in congested city areas where 90% of the people drive. In particular slamming on the gas pedal only to slam on the brakes for the next traffic light or stop sign. That is when an AT really overheats, not when cruising at 55 mph on an interstate.

That open solenoid code, well not sure about your Cadillac if they are running a separate wire directly to that solenoid for testing, can be anywhere between the PCM and the solenoid as mentioned previously. Another common problem is if the brake pedal is returning to the home position. Besides the torque converter switch, has the cruise control release switch and the brake light switch.

Can't think of a single AT installation that wouldn't benefit from an external cooler, that six inch long tube in the lower radiator housing is nothing short of a joke. And not sure if it actually heats or cools the fluid, feel the former is true since they are using the ECT for fan control. Damn radiator is ready to blow its cork before the radiator fan comes on.
 

mhamilton

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#11
NickD said:
Torque converter lockup came out in the 80's as a means to increase CAFE ratings to please the EPA. But that's driving at a nice 55 mph on a clear interstate road. Doesn't do a damn thing when driving insanely in congested city areas where 90% of the people drive. In particular slamming on the gas pedal only to slam on the brakes for the next traffic light or stop sign. That is when an AT really overheats, not when cruising at 55 mph on an interstate.
That is true. Especially with the N* setup going into lockup exactly at 41 mph. More than a few N* owners drive around town in 3rd to keep from going in and out of OD and lockup annoyingly often.

That open solenoid code, well not sure about your Cadillac if they are running a separate wire directly to that solenoid for testing, can be anywhere between the PCM and the solenoid as mentioned previously. Another common problem is if the brake pedal is returning to the home position. Besides the torque converter switch, has the cruise control release switch and the brake light switch.
The PCM is most certainly in control of the TCC solenoid on this drivetrain setup. The codes stored will tell you exactly what the problem is. If the PCM is setting a P0741 then it knows the brake switch is not interrupting the TCC circuit. P0741 means the PCM has requested TCC lockup, the solenoid circuit is complete, yet the trans senses slippage between engine and driveshaft. If the brake switch is stuck on, the PCM will set a B---- code. Likewise it will set a different code if it requests TCC and doesn't see a voltage drop across the solenoid. It's actually a very useful diagnostic system. Thousands of codes associated with the N* drivetrain for almost everything in the vehicles.
 

JP

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#12
I'll recheck the code that was set; as I recall, it was P0741. Either way, it sounds like this is a sell-it-to-someone-else-and-let-them-deal-with-it situation, when dad gets ready to sell the car. 99% of the 3-4K miles per year are done within a 20 mile radius, although when he drives on the highway, it is for a 2.5 hour trip both ways.

P0741 is an internal hydrolic leak, right? He would see no leaks in the driveway?

Bottom line is that it sounds like "benign neglect" is a very prudent option here.
 

mhamilton

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#13
JP said:
P0741 is an internal hydrolic leak, right? He would see no leaks in the driveway?

Bottom line is that it sounds like "benign neglect" is a very prudent option here.
Yes, P0741 by itself means the hydraulic circuit is leaking inside the converter shaft (nothing outside the car). GM has a TSB for this problem, involves replacing the TC bushing and orings, also replacing the TC itself.

If you see a P1860 code for the TCC Solenoid Circuit along with the P0741, then that solenoid is what has failed. But again, a cradle drop to get at a $15 part.

http://www.cadillacforums.com/forums/northstar-performance-technical-discussion/149834-information-p0741-p1860-1998-a.html
 
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#14
The only way the PCM can determine if that solenoid is opened or shorted is to run a separate wire to it bypassing that long string of switches, And that is only if that wire is good and making good connections. Have yet to see a PCM with a crystal ball installed, maybe your Caddy does have that wire, but don't see it on lesser vehicles.

And gum can cause that solenoid valve to stick and not fully close. Let's quit the speculation and do some real testing.

A ohmmeter is nothing more than a controlled current source, and a very small current at that, that flows through a resistance and displays a proportional voltage drop. Not very accurate as resistance through contacts changes drastically with current. So I test with a digital output power supply that can output as much as 30 amps with a current limit knob, as low as almost zero amps, and just read the resultant voltage on the meter. Expect to see less than 0.1V at the rate current of that junction. Then I know for sure what the problem is.

In like manner, if you can tell if the brilliance of a test lamp under various ambient light conditions is at 70% or 100% you are better than me. Can do that with a side by side comparison, but not when I am standing on my head under a vehicle. That 30% difference can mean the difference whether that device is working or not.

Know what the problem is.