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Discussion Starter · #1 ·
I have an 86 w/ 94,000 miles with automatic transmisson with OD. When engine and transmission are warmed up and coming to a stop, the transmission starts jerking and kills the engine before stopping. I put the car in neutral, it starts right up and I then put into D and drive on. The transmission seems to shift thru all three gears. I now am concerned about driving in heavy traffic as I don't want to continue doing the restart. I now hold my foot on the brake and increase the idle when a dead stop. I have not taken this to GM or a transmission shop, but want to resolve this. Someone has suggested the torque convertor may be locking up on the de acceleration although it does ok when accelerating. Any suggestions on what may be happening and would a Chevy dealer be better than a speality transmission shop like Amaco? Nick
 

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Sounds like the lock-up solenoid to me. I'm not sure how to fix the problem, but you can unplug the wires on the drivers side of trans as a temporary fix( 4 prong plug).
At least this might confirm the problem.

Tim
 

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x2 on the lockup switch. They are around $60 and take 1/2 hr to an hr from start to finish, it involves removing the transmission pan so you will also need new ATF and pan gasket. It's also a good time to replace the filter in the transmission.
 

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sounds like a shorted pressure switch or bad lock up solenoid as mentioned above.check with tranny mike for sure. i would say its the solenoid because the brake interupt should disengage it.try disconnecting the wires from the brake light switch as it could be bad doing the same thing. dont disconnect the orange and white wire plug thats your brake lights .the one on the end of the brake lights switch. the brake light switch has two plugs one for brake lights and one for converter interupt
 

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It's the TCC solenoid.

You can verify by unplugging the connector on the driver's side of the trans. when the powertrain is cold. The problem will be absent when warmed up due to no lock-up of the converter clutch.

Fairly easy to drop the pan, replace it and replace the 4th gear pressure switch for good measure.
 

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Discussion Starter · #7 ·
Thanks guys for the excellent advice. Not sure how all this happened, but I'll take a look. Should I decide NOT to do this work myself, is it wise to go to Amoco or Chevy Dealer?? Nick
 

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i personally would stay away from amco this is a very easy fix what ever it turns out to be .no adjusting anything just plug and play parts .if you can change the fluid you can change the solenoid.its only 2 bolts and 2 wires once you have the pan and filter off,its right in the open and accesable. i would try the dicconnecting it first to make sure its not a control issue first. i would unplug the brake switch first then move to the trans 4 wire plug if disconnecting these one at a time doesnt stop the problem then change the solenoid and pressure switch.talk to trany mike he owns a tranny shop and wont steer you wrong
 

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Discussion Starter · #9 ·
Yes, I am capable of changing parts as suggested, know nothing about making adjustments to transmissions, etc. I'll get it up on jack stands, drain the fluid, pull the pan and take a peak. FIRST, do the preliminary check by uplugging to determine if I am on the right track. Thanks for the words of encouragement. Nick
 

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I need to replace mine it's leaking from the switch but I can't find the part number for my 87 305 with OD. Does anybody have it from rock or auto zone sure would help me.:dontknow::beer:
Robert
 

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Discussion Starter · #11 ·
Tranny Mike are you out there? Getting comments that U R the go to guy on resolving the shuttering transmission when slowing down. 169CCC says to change the solenoid, so what say U? I am willing to do the preliminary check as suggested, do the pan removal and all he's suggested. Nick
 

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Discussion Starter · #12 ·
Transmission Jerky/shuttering when downshifting

Ok, unplugged the cable on the driver's side of the transmission (easy to do) and the transmission shifts during acceleration and de-acceleration without shuttering, even in OD. So, this must then confirm the solenoid is bad? What's the purpose =dumb question?= if it's working without? The transmission pan has a new gasket & fluid 3.500 miles ago, but I can still drain it, replace the filter, install another new gasket and replace this solenoid?? Will all of this be available from Advanced Autoparts or OReilly? Thanks, Nick
 

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no if it is fine now its a control issue. either you have a shorted pressure switch or bad brake switch or possibly a bad ecm. if you had unplugged it and it was the same then would have been the solenoid.at this point you will need to do some more work.did you unplug the brake switch?
 

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Ok, unplugged the cable on the driver's side of the transmission (easy to do) and the transmission shifts during acceleration and de-acceleration without shuttering, even in OD. So, this must then confirm the solenoid is bad? What's the purpose =dumb question?= if it's working without? The transmission pan has a new gasket & fluid 3.500 miles ago, but I can still drain it, replace the filter, install another new gasket and replace this solenoid?? Will all of this be available from Advanced Autoparts or OReilly? Thanks, Nick
Yeah, you need a lock-up solenoid. Advance has them for $35. With the unplugged cable, you have no converter lock-up.
 

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the solenoid is fine, he said it was fine when unplugged.unplugging a bad solenoid would not change anything. a bad pressure switch or bad brake switch will cause this problem
 

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the solenoid is fine, he said it was fine when unplugged.unplugging a bad solenoid would not change anything. a bad pressure switch or bad brake switch will cause this problem

Yes it would. Instead of being jerky and seeming to stall when slowing, the trans shifted smoothly after unplugging said lock-up solenoid. That's because the lock-up solenoid is on it's way out.
 

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sorry something is turning the solenoid on when not supposed to.unplugging it stops all control of the solenoid .you clearly dont understand how the system functions. when therer is no power the solenoid is off and the converter unlocked.when you have power to the solenoid it opens and locks up the converter.if he unplugged it and the shudder went away it cant be the solenoid. there are 5 posible causes for this condition.! # 1 shorted harness giveing false signal to the ecm.#2 shortted pressure switch giveing the ecm false signals.#3 a bad brake switch not overrideing the converter lock up.#4 a bad or shorted map sensor or circuit.#5 a bad ecm.if the solenoid was bad unplugging it would do nothing to change the condition it would still shudder
 

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Discussion Starter · #18 ·
Bought the Solenoid, fluid, filter, gasket, but not the Brake Switch or ECM (what's this?). Where are these located & easy to install also? I can take back the solenoid along with filter I bought at Advance Auto Parts if that's not the problem. Thanks to all contributing to helping me solve this problem. N
 

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ECM is the computer that controls the carb, distributor and is how your engines emissions, timing, and I believe fuel mixture and idle control. All them wires and sensors under the hood connect to it. The main harness for it runs down the passenger side fender and under the heater box into the interior. The computer itself is behind the passenger side kick panel.
 

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sorry something is turning the solenoid on when not supposed to.unplugging it stops all control of the solenoid .you clearly dont understand how the system functions. when therer is no power the solenoid is off and the converter unlocked.when you have power to the solenoid it opens and locks up the converter.if he unplugged it and the shudder went away it cant be the solenoid. there are 5 posible causes for this condition.! # 1 shorted harness giveing false signal to the ecm.#2 shortted pressure switch giveing the ecm false signals.#3 a bad brake switch not overrideing the converter lock up.#4 a bad or shorted map sensor or circuit.#5 a bad ecm.if the solenoid was bad unplugging it would do nothing to change the condition it would still shudder
Having put many miles on a few 200-4Rs in multiple vehicles and owning several of the 1980s factory service manuals, even reading them at times and having changed out TCC solenoids of my own vehicles and customers, I'll keep it short for you.

It's not #1.
It's not #2.
It's not #3.
It's not #4.
It's not #5.

The ECM, wiring and related switch can be 100% functional. What happens is the TCC solenoid fails to disengage, which holds the TCC locked until the trans. downshifts to 1st gear, which hydraulically disiables the TCC circuit.

You're welcome and good night.
 
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