I recently replaced my 700r4. I hooked up my autoxray scanner to check on another problem but I noticed that the scanner says that 4th gear is engaged constantly. It doesn't matter what gear the car is in. What could be causing this? I replaced the 4th gear switch, which didn't help. Would this damage my tranny in any way? Does this affect my computer? PLEASE help!

 

What year and application is this tranny.

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82 z28 350cid, vortec heads, comp 262h cam, Holley 600cfm carb, 2in twice pipes, MSD ignition, turbo 350 trans, 3.73 posi, manly b&m megashifter

 

I have a 86 Firebird 2.8

 

Did you check the wiring from the pressure switch to the computer. The worst that can happen is that th tcc could lockup in gears other than 4th. I doubt that will be much of a problem due to the other inputs the computer uses for tcc lockup. In most of those conditions you will be in 4th anyway.

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82 z28 350cid, vortec heads, comp 262h cam, Holley 600cfm carb, 2in twice pipes, MSD ignition, turbo 350 trans, 3.73 posi, manly b&m megashifter

 

I'm having a similar problem, sorta opposite, though. When in 4th, my scanner doesn't always show "4th engaged". It sometimes jumps back and forth from engaged to disengaged. It seems to eventually settle down as everything warms up, though.

I discovered this because my converter wasn't locking up like it should. I have my PROM programmed to not engage the TCC in lower gears until 64mph. I have 4th engagement set at 53mph. The converter was sometimes not locking until the 64mph mark, which made me suspect the fourth gear signal. The scanner confirmed my suspicions.

What is the likely culprit? Is the pressure switch inside the tranny going bad? Does that ever happen? Or is there a bad connection somewhere? Perhaps at the tranny connector?

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'87 IROC 5.7l TPI - original owner!

 

Just thought I'd run this back up for some input before unnecessarily tearing into the transmission...

To check it, I unplugged the ECM harness and measured the resistance between the connector there and the tranny case. If the switch is closed, it should read close to zero ohms. Mine reads 1.1 ohms. This suggests a less-than-great connection somewhere.

So, I unplugged the harness at the tranny and measured the resistance between there and the ECM and found none. This tells me that the added resistance is in either:[list=a][*]The external tranny connector,[*]The connector to the pressure switch inside, or[*]Within the switch itself.[/list=a]

Is 1.1 ohms enough to confuse the ECM so that it's not sure if it's closed or not?

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'87 IROC 5.7l TPI - original owner!

[This message has been edited by P J Moran (edited July 23, 2001).]