I’ve not long got my car back from having the t56 rebuilt and are now experiencing some issues with reverse when parked up.

it all seems to be working fine when the engine is running but when I park up and put it in reverse for the column to lock the car doesn’t recognise it.
I’ve read that it could be the reverse switch so today I got under there and saw there’s 2. Just in case they were plugged in the wrong way round (if that’s a thing) I reversed the plugs.
now I’m getting a service column lock message and the car reverse is locked out completely and won’t let me engage it when ignition is off. Again with ignition on it engages and drives fine.

what could the issue be (should I change out both reverse switches) and why has the issue changed when I reversed the plugs in the sensors?

 

Being that this a 2005 M6 car (the only one that makes you put the trans into reverse to allow the car to go into sleep mode).

Disconnect the battery, put the car in to reverse, then test both the back up and the reverse light sensors to make sure they have continuity through them with multimeter.
If not, then make sure that washer was not installed on the sensor that is not allowing it to be threaded in deep enough for trans linkage to depress the ball, and if no washers installed on it, then remove sensor, push the ball in on it, and make sure your getting continuity through the sensor while in hand.
If yes, can get continuity through sensor, then either when sensor was installed, it was wrong on that is too short, or when trans was rebuilt, did not get the internal shift linkage set correctly (or part was worn out), to press the ball in when the trans in in reverse.

If you do have continuity through both switches (reverse and b/u lights) with trans in reverse (correct parts used to rebuild the trans and the correct working switches), then problem is not at the trans, but the connector and wires back up line off the reverse switch.

https://www.corvetteforum.com/forums...tch-issue.html

 

Thanks for the reply.

could you talk me through exactly how I go about check for continuity please?

 

I too have a MN6 2005 which needs to be in reverse when parked. Mine goes in reverse very easy IF the engine is still running. Occasionally I forget and shut the engine off first. Then, much more effort is required to shift to reverse. Just my findings.

 

Not really trying to thread jump but I do have a T56 issue if you guys have any ideas. I recently rebuilt a 1994 Trans Am LT1. Installed the engine only to find out the T56 had bad synchros. I picked up a used T56 locally and installed in the car as a replacement and everything works great except reverse! The reverse lockout is installed but not connected, I can shift into the reverse gate fine! When the engine is running it will not engage the reverse gears! it won't even get to the gears.....no grinding or anything. Its like I am hitting a wall. If I shut down the engine I can shift into reverse and start the car.....reverse works fine. I have already changed the plastic cup the ball sits in, I am getting plenty of disengagement with the clutch. I am at a complete loss with this one. The only thing I can think of is idle RPMs. Currently my idle RPM is 1000, do you guys think it could be idling slightly high and that is what's keeping it from going?

 

t-56 uses brass reverse gear,


https://i.ebayimg.com/images/g/a6UAA...qv/s-l1600.jpg

And its not so much the pointy teeth the problem, but either the back slots that will peen over time, that allows the gear pointy teeth to over rotate against each other, allow mating pointy teeth sets to over rotate to be tip to tip or slightly past, and brass gear can not be blipped back rotated on pressure to allow engagement.
The other one, the bearing surfaces that is designed to stop the gear on the shaft during engagement is worn, and not allowing the steel gear to be stopped fast enough instead (will get gear grinding if this is the problem)..

Simply put,when rebuilding a T56, always replace the brass reverse gear. Again, it not the pointy teeth so much (that can get peen), but the back U slots that peen over time, that allows it pointy teeth to over rotate on steel gear pointy teeth to now allow engagement on pressure, and what locks up the trans from going into reverse.

 

Based on your post, you're saying the brass reverse gear is worn and not allowing engagement while engine is spinning transmission? If that is truly the issue I can live with it until I need a rebuild. Thanks for the reply and I will look into this more.