Trans. experts: 4th gear switch bad?
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From: Elverson PA
Trans. experts: 4th gear switch bad?
I have been struggling with my torque converter lock up for the last year. 
Today I finally got around to really checking it out as per the fsm. When I went through the diagnostics, I came to the last steps where I found there to be 12.5 volts at the fourth gear switch (light blue wire @ terminal B on trans harness). The manual describes this condition as a grounded switch or wire, or the switch not opening.
I suppose this means I need a new switch. So what do you think? Is this hard to repair? Thank you very much if you can help.
Dave
Today I finally got around to really checking it out as per the fsm. When I went through the diagnostics, I came to the last steps where I found there to be 12.5 volts at the fourth gear switch (light blue wire @ terminal B on trans harness). The manual describes this condition as a grounded switch or wire, or the switch not opening. I suppose this means I need a new switch. So what do you think? Is this hard to repair? Thank you very much if you can help.
Dave
Last edited by black85; Apr 20, 2008 at 05:06 PM.
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From: Elverson PA
Also, you don't think I messed up my new trans driving like this do you? I hear it makes extra heat when the torque converter is slipping. I haven't driven too far at all. No more than 1/2 hour at a time since this condition started. Also, the Amsoil fluid looks brand new still.
Here is the diagnostic procedure I followed. The pencil checks indicate my results:
I just don't understand how they are saying the fourth gear switch is bad when you are testing the harness for voltage while it is unplugged from the trans. and switch. How would a different switch in the trans effect the voltage from the wire harness when it isn't even hooked up? I am clearly confused about this.
Also, just noticed that I had the trans connector unplugged, then turned on the ignition, then checked the voltage. Hopefully that didn't skew any results.
Here is the diagnostic procedure I followed. The pencil checks indicate my results:
I just don't understand how they are saying the fourth gear switch is bad when you are testing the harness for voltage while it is unplugged from the trans. and switch. How would a different switch in the trans effect the voltage from the wire harness when it isn't even hooked up? I am clearly confused about this.
Also, just noticed that I had the trans connector unplugged, then turned on the ignition, then checked the voltage. Hopefully that didn't skew any results.
Last edited by black85; Apr 20, 2008 at 11:00 PM. Reason: flow chart
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From: The Top of Utah
Originally Posted by black85
I just don't understand how they are saying the fourth gear switch is bad when you are testing the harness for voltage while it is unplugged from the trans. and switch. How would a different switch in the trans effect the voltage from the wire harness when it isn't even hooked up? I am clearly confused about this.
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From: Elverson PA
I guess this is the right switch:
http://www.murphysautomotive.com/Mer...ode=SSGM700-R4
Guess that is it aside from a few quarts of Amsoil and a new gasket.
http://www.murphysautomotive.com/Mer...ode=SSGM700-R4
Guess that is it aside from a few quarts of Amsoil and a new gasket.
Last edited by black85; Apr 21, 2008 at 03:23 PM.
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From: Elverson PA
My FSM specifies a 3-4 switch that does not appear to be in my transmission! I see the hole where it should be, but it isn't there. The diagram does cover a few different models aside from "Y" body, but WTF.
Would my trans guy take it out? I just had it rebuilt 2 yrs (3000 miles) ago. He knew I was drag racing, and said he rebuilt it with that in mind. Can anyone help?
Note: The guy who rebuilt it was very reputable, but he since retired. I never spoke w/ him or met him. My mechanic sent my trans to his guy, b/c he was having some trouble changing out a seal. In the end, I said rebuild it while it was in the guys shop. Sooooo.......I have no clue what he did. He did put a new lock up solenoid in it, so he wasn't trying to disable the lockup converter.
Would my trans guy take it out? I just had it rebuilt 2 yrs (3000 miles) ago. He knew I was drag racing, and said he rebuilt it with that in mind. Can anyone help?
Note: The guy who rebuilt it was very reputable, but he since retired. I never spoke w/ him or met him. My mechanic sent my trans to his guy, b/c he was having some trouble changing out a seal. In the end, I said rebuild it while it was in the guys shop. Sooooo.......I have no clue what he did. He did put a new lock up solenoid in it, so he wasn't trying to disable the lockup converter.
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From: The Top of Utah
Originally Posted by black85
My FSM specifies a 3-4 switch that does not appear to be in my transmission!The diagram does cover a few different models aside from "Y" body, but WTF.
Originally Posted by black85
Would my trans guy take it out? I just had it rebuilt 2 yrs (3000 miles) ago. He knew I was drag racing, and said he rebuilt it with that in mind. Can anyone help?
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My FSM specifies a 3-4 switch that does not appear to be in my transmission! I see the hole where it should be, but it isn't there. The diagram does cover a few different models aside from "Y" body, but WTF.
Would my trans guy take it out? I just had it rebuilt 2 yrs (3000 miles) ago. He knew I was drag racing, and said he rebuilt it with that in mind. Can anyone help?
Note: The guy who rebuilt it was very reputable, but he since retired. I never spoke w/ him or met him. My mechanic sent my trans to his guy, b/c he was having some trouble changing out a seal. In the end, I said rebuild it while it was in the guys shop. Sooooo.......I have no clue what he did. He did put a new lock up solenoid in it, so he wasn't trying to disable the lockup converter.
Would my trans guy take it out? I just had it rebuilt 2 yrs (3000 miles) ago. He knew I was drag racing, and said he rebuilt it with that in mind. Can anyone help?
Note: The guy who rebuilt it was very reputable, but he since retired. I never spoke w/ him or met him. My mechanic sent my trans to his guy, b/c he was having some trouble changing out a seal. In the end, I said rebuild it while it was in the guys shop. Sooooo.......I have no clue what he did. He did put a new lock up solenoid in it, so he wasn't trying to disable the lockup converter.
Granted, I have only done 6 or 7 1985 vette transmissions, but that has been my experience.
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From: Elverson PA
Quote from Pete K.
OH I AM HAVING SO MUCH TROUBLE!!!! I bought the 4th gear switch at the Chevy dealer. I changed it out. I still have no lock up converter. I ran through the whole chart from the 1985 Corvette FSM, and came up w/ the same results.
CFI-EFI- I know you are trying to help, but I am reallly sure I got my trans back. The manual shaft still leaked. Also, my fsm is a real corvette fsm. I will post the page I am refering to. There are 12 different setups in the fsm. Here are two. One is supposed to be for the 85 vette, but looks a little different than mine. I only have the 1 pressure switch (labeled 4th clutch switch), but wires for two.
In my trans, the blue connector goes to a single pole switch, as per the fsm was the forth gear pressure switch. There is another couple wires that are neatly wire tied together that look like they could have been for another switch in another application. I guess I may have to give up. I really hate to take it anywhere. Are you guys sure it is so bad to drive w/o lock up? Also, can I just go to a manual switch somehow?
Thanks guys
I have never seen a stock 85 vette A4 use a 4th gear switch.
Granted, I have only done 6 or 7 1985 vette transmissions, but that has been my experience
Granted, I have only done 6 or 7 1985 vette transmissions, but that has been my experience
OH I AM HAVING SO MUCH TROUBLE!!!! I bought the 4th gear switch at the Chevy dealer. I changed it out. I still have no lock up converter. I ran through the whole chart from the 1985 Corvette FSM, and came up w/ the same results.
CFI-EFI- I know you are trying to help, but I am reallly sure I got my trans back. The manual shaft still leaked. Also, my fsm is a real corvette fsm. I will post the page I am refering to. There are 12 different setups in the fsm. Here are two. One is supposed to be for the 85 vette, but looks a little different than mine. I only have the 1 pressure switch (labeled 4th clutch switch), but wires for two.
In my trans, the blue connector goes to a single pole switch, as per the fsm was the forth gear pressure switch. There is another couple wires that are neatly wire tied together that look like they could have been for another switch in another application. I guess I may have to give up. I really hate to take it anywhere. Are you guys sure it is so bad to drive w/o lock up? Also, can I just go to a manual switch somehow?
Thanks guys
Last edited by black85; Apr 26, 2008 at 03:16 PM.
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From: Elverson PA
I should have put another tcc solenoid in there while I had the pan down. That is probably it. It is my understanding that the computer grounds the solenoid, therefore activating it. Can I just test that? Seems like you could just put in a toggle switch. Then I would know for sure if that solenoid is bad. Right?
Sooo.....That would mean there should always be 12 volts to terminal A (figure 22 above). Just tested, and I do have that
PS- I just did a lot of research, and the '85 did have the fourth gear switch. It is the blue wire from ecm terminal C8 to trans connector B. It is ckt 446. What I am thinking of doing is grounding the tan/blk wire (ckt 422) from ecm terminal A7 to trans connector. That should enable manual lock up right?
Sooo.....That would mean there should always be 12 volts to terminal A (figure 22 above). Just tested, and I do have that
PS- I just did a lot of research, and the '85 did have the fourth gear switch. It is the blue wire from ecm terminal C8 to trans connector B. It is ckt 446. What I am thinking of doing is grounding the tan/blk wire (ckt 422) from ecm terminal A7 to trans connector. That should enable manual lock up right?
Last edited by black85; Apr 26, 2008 at 04:44 PM.
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Ohm test the solenoid. 20-25 ohms is typical.
If you wish to have 4th gear only lock up (my preference), Put a normally open pressure switch in the 4th port, and run the wire from the switch to the ground side of the solenoid. When the trans shifts to 4th, the switch will force lock up only in 4th gear.
If you wish to have 4th gear only lock up (my preference), Put a normally open pressure switch in the 4th port, and run the wire from the switch to the ground side of the solenoid. When the trans shifts to 4th, the switch will force lock up only in 4th gear.
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From: Elverson PA
Yesterday 03:58 PM
Pete K Ohm test the solenoid. 20-25 ohms is typical.
If you wish to have 4th gear only lock up (my preference), Put a normally open pressure switch in the 4th port, and run the wire from the switch to the ground side of the solenoid. When the trans shifts to 4th, the switch will force lock up only in 4th gear.
Pete K Ohm test the solenoid. 20-25 ohms is typical.
If you wish to have 4th gear only lock up (my preference), Put a normally open pressure switch in the 4th port, and run the wire from the switch to the ground side of the solenoid. When the trans shifts to 4th, the switch will force lock up only in 4th gear.
I guess there isn't really an easy way to do this. I wish I had an extra trans harness to dangle the wires down. To even get my arm up there I'll have to pull the header y pipe. I thought of checking the resistance at the computer, but will probably get a false reading unless I unplug the ecm. fun fun....
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Finally tested the solenoid. It ohms out at 23.5 ohms. I have no idea what to do now. All I can think of is that there is something wrong with the actual hardware inside the trans. I am beyond frustrated with it.
Are you sure it is bad for the car to drive w/o the lock-up converter? What years is it bad? I know many cars don't come w/ lock-up. I really am beside myself.
Maybe I can just ground out the one wire and try that. This has been going on soooo long.
Where would I even take this problem? I don't want to go to the stealer. They charged me $600 to install a wheel hub when I first got the car and didn't know better. Now I know you can get them for about $75, and install in about 1/2 hour. I felt raped. I'm not spending $1000 fixing a $5000 cars lock up. I'd rather just buy a good converter w/o the stall option.
I feel like a trans shop would have no clue, and mess up my interior and everything getting to the ecm and all. Also, I'm sure they would not use Amsoil even if I supplied it. That would probably go home with the mechanic. They might just say it needs rebuilt even though it only has about 1000 miles on it and drives perfect except for this...<end rant>.
Know what else? Sometimes I'll be driving along, and presto.....the tcc locks up every now and then. Like once a month. AAAAGGHHHH. Something so simple is driving me over the edge.
Are you sure it is bad for the car to drive w/o the lock-up converter? What years is it bad? I know many cars don't come w/ lock-up. I really am beside myself.
Maybe I can just ground out the one wire and try that. This has been going on soooo long.
Where would I even take this problem? I don't want to go to the stealer. They charged me $600 to install a wheel hub when I first got the car and didn't know better. Now I know you can get them for about $75, and install in about 1/2 hour. I felt raped. I'm not spending $1000 fixing a $5000 cars lock up. I'd rather just buy a good converter w/o the stall option.
I feel like a trans shop would have no clue, and mess up my interior and everything getting to the ecm and all. Also, I'm sure they would not use Amsoil even if I supplied it. That would probably go home with the mechanic. They might just say it needs rebuilt even though it only has about 1000 miles on it and drives perfect except for this...<end rant>.
Know what else? Sometimes I'll be driving along, and presto.....the tcc locks up every now and then. Like once a month. AAAAGGHHHH. Something so simple is driving me over the edge.
