Switch Part Numbers

Ken Bak

Member
Joined
May 20, 2017
I'm changing my TCC solenoid and figured I should change the other two switches while I'm at it. My 200-4R has a pressure switch (No 6) and a 4th clutch switch (No 8) as shown in the attached picture. I purchased (2) ACDelco 8683502 switches, and then someone told me the two switches should not be the same ... they should have different pressure settings. I've done some research, but I can't find anything concerning pressures, or if the switches should be the same or not. Does anyone know if there are different switch part numbers for these two switches? IMG_0344.JPG
 
Thanks pacecarta.

Does anyone know what the pressure switch (No 6) is for? I got the picture from my Buick service manual I purchased from the dealership when I purchased my car in 1986. It's the same one the dealership used. I'm surprised about the lack of information about this switch.
 
(6) is third gear for the ecu flag which was only used in 87 on the turbo 3.8l BRF so that it could engage lockup in 3rd gear (above 47mph) and also signals the ecm to change the timing and boost solenoid duty allowing higher boost in 1st and 2nd ..being ecm controlled it also allows disconnecting lockup at WOT ..other trans configurations didnt have ecu control of lockup and only used a 4th gear switch that controlled the lockup internally and wouldnt lock unless it was in 4th and stayed locked at WOT
 
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heres how other 87 trans were wired , notice only the BRF has 3rd gear switch
and also an elec diagram how the 87 BRF functions internally
 

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Thanks again. Lots of information for a guy who doesn't know how all this works. It's nice to talk to someone who does.

I pulled my trans pan and gave it a couple days to drip dry, so to speak. So last night I took a picture of the wires and switches inside and compared with my service manual, so I confirmed that my transmission matches the diagram ( 1986 MODEL BY ) which I attached to my first post.

Today I looked at my electrical section of my service manual, and I found the diagram for both the 3rd and 4th gear pressure switches, but no information on the switches.

When you say "(6) is third gear for the ecu flag which was only used in 87 on the turbo 3.8l BRF", I'm not sure what you mean. My 86 clearly has the 3rd gear switch. Does my 86 use the 3rd gear switch differently than the 87?

The guy who told me the switches are different works for Performance Automatic Transmission Center. He said the reason they're different is because you don't want 3rd and 4th gear to lockup at the same time. He said it's better to have 3rd lockup around 40 mph and 4th lockup around 50 mph. I don't remember the exact word he used, but he said lockup at the same time will cause "chugging" or something similar to that.
 
i mean in 1987 the brf was the only one wired with two switches ,, goes without saying was same for 86 turbo also for 89 TTA trans
 
also no suh thing as 3rd lockup one speed and 4th different locks on speed 3rd or 4th
 
Found the description in my service manual. I never heard of it before.
 

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So what you're saying is the 3rd switch opens at one speed, and the 4th switch opens at a faster speed? I'm just trying to understand your description.
 
3rd opens when you get to third gear and the ecm can see this and with a scanner you an see the 3rd gear flag active .. the third switch stays open even into 4th gear and then when in 4th 4th swicth opens too ,, and the ecm see that too and 3rd and 4th flags will be active
lockup occurs at 47mph and disconnects below 45 .. you have a manual its all there under tcc operation
 
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