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1986 ElCamino 305ci.
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Discussion Starter · #1 · (Edited)
200-R4 Trans ...The Overdrive Lock Up goes On & Off while Driving...."SOLVED"....Found TPS Defective...Replaced and Adjusted the TPS....Overdrive Locks Up Normal.. also note that it Locks Up in 3rd & 4th Gear on a 200-R4...and I Installed a Toggle Switch on my Dash to Turn the Overdrive Lock Up On & Off if I Choose.....It still Shifts All 4 Speeds with the Switch Off...
 

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1987 GMC Caballero, 400 HP 350, Holley Sniper EFI, 200-4R
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Thanks for posting this. I have 300 miles on my Caballero and am sure my TV cable is not properly adjusted. I've gone from one extreme to another but haven't found the happy place, yet.
 

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1986 ElCamino 305ci.
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Discussion Starter · #3 ·
Try Setting the TPS to .4 - .5 Volts if you have a Electronic Carb....Mine Works Very Well....
 

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1986 ElCamino 305ci.
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Discussion Starter · #4 ·
Oh .......I see you have a Holley Carb....No TPS......
 

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It probably has something to do with improper setup of the carb linkage . I have a 2004R but I am using the Quad. so can't help you on setup
 

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I am having difficulty understanding if you are explaining how you resolved the problems, or if you still have a problem with unpredictability of the TCC lockup.
"The Overdrive Lock Up goes On & Off while Driving.. "

You have a modified set up for the torque converter clutch lockup.
1) There should be a switch adjacent or shared with the brake pedal light switch. This should be activated with the lever that pivots with the brake pedal. This sends a signal to tell the TCC to unlock when you press the brake. If it does not release the lockup, it would cause the El Camino to lurch as you tried to slow from higher speed, like going from 55 to 10 MPH. You may have a switch adjustment problem, loose connection. or losing the signal in the wiring.
2) There should also be a solenoid inside the transmission that accepts that signal along with another signal inside the trans. Called the 4th gear solenoid it sends the fluid to engage the torque converter clutch to lock up. There may also be a 3rd gear solenoid. I am not sure if it can be setup with just one to do 3rd and 4th gear TCC lockup. These solenoids or the wiring to them can fail.
3) Sometimes (not as frequent) there may also include another solenoid that is driven based on vacuum. If vacuum drops because the accelerator is pressed enough that the engine load changes enough to reduce vacuum to a level that has been set, then a signal is sent to cause the signals to turn off TCC lockup. This disengages the TCC clutch, allowing the torque converter to use fluid dynamics to let the engine rev higher into the engines torque band increasing the rate of acceleration. Once the foot pressure on the accelerator is reduced, the load on the engine reduces and the vacuum level should rise allowing the TCC to once again lockup.
4) The 1986 likely came standard with the TCC lockup signal coming from the EMC (computer).
5) It seems like yours has an added switch (toggle or push button). This usually gets wired in to either brake the ability to go into TCC lockup or allow it depending on which way this binary switch is current set.
6) This can occur if the driver has a bad "two foot" habit. In this case, one foot is on the accelerator and the other is on the brake pedal. We have all been behind annoying "two footers" as they accelerate, yet the have enough pressure on the brake to keep the brakes lights lit up. Basically this causes the difficulties in 1) above and varies based on the amount of pressure on the brake pedal.

The most likely problem is that the wiring to add 5) has a difficulty.
The second most likely is 1) needs adjustment in brake pedal switch or wiring.
 

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1986 ElCamino 305ci.
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Discussion Starter · #7 ·
No ....I don't have a problem with the Overdrive anymore ....I was just saying how I fixed the problem with the TPS and how installing the Toggle Switch that I can control the lock up if I want it...
 

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Thanks for posting this. I have 300 miles on my Caballero and am sure my TV cable is not properly adjusted. I've gone from one extreme to another but haven't found the happy place, yet.
Cab.. Get that adjusted buddy. I smoked my 4L60 and had to put another in. Found out that it did not have the Holley adapter for the right geometry and brackets running it like that for about 6 months after buying the car. Lotsa Vids on how to do it.
 
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I have found that owners I have told about getting the carb to tranny linkage correct just blow me off as a crackpot.Its either going to be correct or else !
 

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1986 ElCamino 305ci.
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Discussion Starter · #10 ·
I have found that owners I have told about getting the carb to tranny linkage correct just blow me off as a crackpot.Its either going to be correct or else !
I Adjust the carb to tranny linkage to get a Firm Shift to my Liking....
 

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Is a lockup t c. Overdrive? Or is overdrive a actual extra gear?
Overdrive is a gear that is numerically lower than 1.0 :1.
Example TH700R4 3rd gear is 1.0 :1 so it is not overdrive. Yet the 4th gear is 0.70 :1 so it is overdrive.
Example TH2004R 3rd gear is 1.0: 1 so it is not overdrive. Yet the 4th gear is 0.67 :1 so it is overdrive.

Torque convertors provide the fluid dynamics that allow for the smoothness in automatic transmissions.
Some Torque Converters come with clutches that can engage to temporarily replace the fluid smoothness with a direct drive (like letting up on a clutch on a manual trans fully engage).
When the clutches in the Torque Converter Clutches (TCC) are engaged that is called TCC lockup. It does not mean any thing is broken. It can provide better fuel mileage and a slightly lower RPM for the same speed vs when just in fluid drive.
When TCC locked up, it can be difficult to slow down quickly, so you want them to disengage (come out of lockup) when slowing, or the car will jerk when slowing.
It would be similar to slowing with a manual trans without stepping on the clutch.
 

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87 elcamino v6 4.3 t.b.i.
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Overdrive is a gear that is numerically lower than 1.0 :1.
Example TH700R4 3rd gear is 1.0 :1 so it is not overdrive. Yet the 4th gear is 0.70 :1 so it is overdrive.
Example TH2004R 3rd gear is 1.0: 1 so it is not overdrive. Yet the 4th gear is 0.67 :1 so it is overdrive.

Torque convertors provide the fluid dynamics that allow for the smoothness in automatic transmissions.
Some Torque Converters come with clutches that can engage to temporarily replace the fluid smoothness with a direct drive (like letting up on a clutch on a manual trans fully engage).
When the clutches in the Torque Converter Clutches (TCC) are engaged that is called TCC lockup. It does not mean any thing is broken. It can provide better fuel mileage and a slightly lower RPM for the same speed vs when just in fluid drive.
When TCC locked up, it can be difficult to slow down quickly, so you want them to disengage (come out of lockup) when slowing, or the car will jerk when slowing.
It would be similar to slowing with a manual trans without stepping on the clutch.
Thanks Great explanation. Totally understand since you broke it down to gear ratios. Totally get why it's called overdrive now! So how do u know if you have a lockup? By the model trans? Or does same model come with a normal converter,and a lockup? Also,..I'm trying to identify my trans. Thought it was a 200r. Now I'm doubtful,cause I Climbed under car today and trans says METRIC, real big on pan.
 

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From GM, the year and trans should normally help determine if it has lockup.

Some transmissions have aftermarket torque converters that can be ordered that do not have lockups. An example would be California Performance Transmissions (the Real Art Carr) make a TH2004R with a Torque Converter without lockup for racing.

You will need to check with the 1987 folks on that Metric trans to see what it really is and has.
@87next2last1 Steve may know more about that 1987 Metric transmission.
 

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[/QUOTE]
Thanks Great explanation. Totally understand since you broke it down to gear ratios. Totally get why it's called overdrive now! So how do u know if you have a lockup? By the model trans? Or does same model come with a normal converter,and a lockup? Also,..I'm trying to identify my trans. Thought it was a 200r. Now I'm doubtful,cause I Climbed under car today and trans says METRIC, real big on pan.
with metric that will be the TH200C which is a 3 speed with lockup
the TH200C is the worst tranny GM made, they are just weak from the factory
I have that same tranny in mine & had it rebuilt with stronger parts & I'm over 100,000 miles with it
If you have an overdrive you will have this shifter plate with the square D for overdrive (4 speeds)
If you don't have the square D then it's just the 3 speed
I posted the pics of the tranny pans & tell you what tranny you have on another thread you did

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87 elcamino v6 4.3 t.b.i.
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with metric that will be the TH200C which is a 3 speed with lockup
the TH200C is the worst tranny GM made, they are just weak from the factory
I have that same tranny in mine & had it rebuilt with stronger parts & I'm over 100,000 miles with it
If you have an overdrive you will have this shifter plate with the square D for overdrive (4 speeds)
If you don't have the square D then it's just the 3 speed
I posted the pics of the tranny pans & tell you what tranny you have on another thread you did

View attachment 141103
[/QUOTE]
Jeez Louise ...that's worrisome. Worst trans they made huh? Others with same year &trans tell me all of them leak like a water fountain, especially from gear selector shaft. (Wich mine does), ive learned after warming engine,before leaving to go thru gears R, pause one sec, D, pause,2,pause,1 pause back to D ,and leave. I'm assuming I'm lubricating the o ring on selector shaft,cause otherwise it leaves about a four-six inch drip mark. And that gets old real quick on your driveway. Other then being wet looking and leaky gear selector shaft,trans runs nice,shifts smooth,downshifts correct ,etc. Guess I will brace myself for the day it stops .at least I wont be shellshocked. Figuires i get the only g.m. trans with bad rep.lol. your word is golden when it comes to the 87. Thanks.
 

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87 elcamino v6 4.3 t.b.i.
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Thats totally int pic of gear selector! Crazy how they cover the o.d. if u don't have. I remember reading a thread where you explained that.
 
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