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1989 Buick Skyhawk Lockup


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07-08-03, 07:55 AM   #1  
1989 Buick Skyhawk Lockup

89 buick Skyhawk Wagon / Turbohydromatic / 130,000 miles
I changed fluid and filter to stop pan gasket leak. Now after 5 mile warm up, when stopping trans acts like a stick shift without a clutch as it jumps and dies when stopping forward and reverse. I changed filter and fluid again to make sure, still happens. I just rebuilt engine (emmission reasons)although problem was happening before rebuild, runs great, no codes. This is a hobby car so time doesn't matter. Always does good until it warms up. Even does it running on jack stands after 5 miles of 45mph.

 
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07-08-03, 07:57 AM   #2  
Joe_F
You have a wasted TCC solenoid. There is a square two or four wire plug on the top of the tranny. Disconnect it. Bet you don't have the problem now.

You can leave it disconnected, won't really affect much except the gas mileage a bit.

 
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07-08-03, 12:05 PM   #3  
Thanks for confirming that. I really want to fix it. The trans is a THM 125C/3T40. Got any idea on the cost of a new solenoid and best place to find it. Yes I like using GM parts, but I can't stand the fact of the 100% mark up for a walk in at our local GM dealers.

 
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07-08-03, 12:12 PM   #4  
Joe_F
It's not really worth fixing the solenoid....

The solenoid's about 60 bucks and the side cover of the tranny has to come off. But that's not all---GM has had numerous TSB's on other valve body problems and lock up, so the solenoid may not cure it.

Disconnect it and leave it alone. Drive the car till it pukes and then pitch it for something else . Money better spent elsewhere, frankly.

(It's disconnected on my 89 Cavalier with 27k original on it)

 
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07-09-03, 05:53 AM   #5  
I unplugged the solenoid last night and it works now. I read another article saying because of slippage with unit unplugged at speeds over 45, extra heat is generated. What is yor thought on that?
Thanks for the help!!

 
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07-09-03, 09:34 AM   #6  
Joe_F
Perhaps. But by the time the tranny fries the car will be very old, dead and buried .

Change the fluid every 25k with the filter and it should be good to go.

My vote: Leave it disconnected.

 
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MO

07-09-03, 10:29 AM   #7  
The solenoid is not 'wasted'. The fact that it is locking up means the coil is still good. It's pulling in. It just doesn't release, probably because it's gummed up with dirty fluid and other junk floating around. I had the same problem, changed the fluid & filter. After a 100 miles, the problem cleared up. A year later, the problem comes back, I changed fluid & filter, the problem goes away again. A new solenoid would probably help. Either a lot of work or a lot of money.
The Haynes books on transmissions caution that leaving the solenoid disconnected will cause overheating. How soon the damage occurs, they don't say. If you go on long highway trips, it will die sooner than city driving. How long do you want to keep the car/tranny without paying more big bucks?

 
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07-09-03, 11:43 AM   #8  
Joe_F
The solenoid IS likely wasted. . Once they are contaminated, they are likely finished for good.

All you are doing by leaving the solenoid unplugged is preventing lockup. I have yet to waste a tranny by doing this. Been disconnected in my Cavalier for well over 6 months, no issue.

Think about a THM350. There's a 350C and a 350 without lockup (open converter). Why doesn't a THM350 without lockup burn up the tranny?

GM has had NUMEROUS bulletins on uncontrolled Lockup on the THM125C. Many involve spill over into the valve body and involve modification/drilling of the valve body and internal tranny service. Not DIY repair.

Check alldata.com and you'll see there are numerous THM125C bulletins.

The bulletin is 8 pages long, I know I have it printed when it happened on my car .

You can try the various tranny additives to "flush" it out, but solenoid replacement/investigation of the uncontrolled lockup is needed to correctly solve the problem.

The solenoid can be bought at any auto parts store or Delco distributor, no need to buy it from the GM dealer.

 
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07-10-03, 08:03 PM   #9  
unless you have a temp guage in the trans fluid, you have no idea how hot it's getting!! most new style electronic transmissions will lock the torque converter in 2nd, 3rd and 4th gears if it senses the fluid is getting too hot. the torque converter makes 99.9% of all the heat in the fluid, and an unlocked one makes heat. it seems 4speed automatics are more prone to overheating from a nonlocking converter as there is more physical mass to turn and less mechanical advantage on the input shaft when in OD(4th) at highway speed. i have seen in particular a dodge van with a code "no rpm drop seen after t/c lockup" part of the test had me flow check the cooler, i ran some out of the cooler line into an antifreeze jug and the fluid was so hot, the jug got very soft and i couldn't hold it anymore(after a three mile test drive)



if the guy is capable of rebuilding his own engine(as it sounds like HE did), how is he not capable of replacing a solenoid inside the trans pan??? or even drilling the valve body if necessary??? most shift kits require this too, does B&M discourage people from buying their kits because you have to drill the separater plate??? at the very least it would restore it to when it was new when it did work correctly, these solonoids are notorious for failing like this, i know i'd much rather replace a solenoid than a burn't up trans!!

to the original poster: check out this website, even though the trans is different, it is still gm and they use the same technology across the board with all their products, especially read the description part of it stalling at stops, it sound all too familiar to your problem
http://www.montecarloss.com/TCC_Solenoid.html


my vote: i wouldn't drive with a lock-up solenoid unplugged, especially if the trans cooler is sized to work with a non heat producing locked up t/c

 
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07-11-03, 06:45 AM   #10  
Joe_F
Because it's very involved. Original posters choice. The tranny has 130k on it now, no telling what it's like inside.

There are up to 5 bulletins that may cause this problem. The solenoid MAY NOT be the problem. In one case I remember a new valve body being one of the "fixes".

This is a simple simon 3 speed that has been used forever in the GM line.

At minimum I'd suggest a GM shop manual if you are going to attempt this yourself.

Think about it: GM Turbo 350s were open converter forever. They didn't burn out. Lockup torque converters are mostly done for efficiency, that's why GM made them THM350C types after about 1980 to conicide with emission and fuel regulations .

You'll lose probably a few MPG leaving it disconnected if you want a "quick fix". It's disconnected on my Cavalier----no noticeable difference.

(And I drive it 50 miles a day).

 
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08-05-03, 09:23 AM   #11  
Well as I stated in the start of this, time was not a factor and I like to putz. I got a new solenoid from Advance Auto for about $20, pulled the wheel, side cover. Instructions were great in the package and so far it shifts fine. The job only took an hour. After seeing this problem, I think I am going to listen for people going to junk these cars as they think they have a bad engine or trans. The job is complete on time as the 16 year old son is taking the written test for his driving learners permit this week. No way he going to drive my Durango. Thanks to all, this site is great.

 
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08-05-03, 09:48 AM   #12  
Joe_F
Good for you, you got lucky . Not all the time is it the solenoid, but glad to hear it was the case for you .

 
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