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back up lights on in reverse and drive positions

  
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back up lights on in reverse and drive positions

 
716brooks54 716brooks54
New User | Posts: 1 | Joined: 08/10
Posted: 08/13/10
08:33 AM

I have restored a 1970 roadrunner.   727 auto transmission had a neutral safety switch with single post .  I replaced with 3 prong switch for backup lights.  now backup lights come on in reverse and also in drive.  I have determined that the transmission is possibly a 1968 or earlier because it had just the single post switch.  Is there something that needs to be changed in transmission or wiring to correct this problem.  

GTX73SPRBRD GTX73SPRBRD
User | Posts: 179 | Joined: 11/08
Posted: 08/18/10
01:01 PM

UUMMMMM,.,....... Replace the neutral safety switch with the correct one for the car ?  

agw70Charger agw70Charger
New User | Posts: 1 | Joined: 09/10
Posted: 09/03/10
08:01 AM

I'm having the same problem with my 70 Charger, did you resolve this issue and if so, which switch did you use?  

68440Barry 68440Barry
User | Posts: 91 | Joined: 04/09
Posted: 09/03/10
12:15 PM

Your trans is a 68 or older & just changing switch won't do it. Been there. Quite frankly, I don't remember what I did, but I'll take a look at my truck & let you know, assuming I made them work. It's a 74 D100 with a 68 440 and it only gets driven to the dragstrip and not very often anymore.  
RACE CARS - NOT GREYHOUNDS

waynep7122 waynep7122
Enthusiast | Posts: 643 | Joined: 08/09
Posted: 09/03/10
07:53 PM

there is a difference in how the later 3 wire switch is activated... verses the single pin version..

Nsswitches




below is the proper rooster comb for the 3 terminal switch.. the other two will NOT WORK...

Switchnshoe



thanks to root 66 for the great pictures...  

drmzcometrue drmzcometrue
New User | Posts: 2 | Joined: 09/10
Posted: 09/11/10
06:42 PM

can someone pleaseeeeeeeeee tell me what the solution to this problem is... i am having the same exact problem... 727 tranny 1967 installed in my 73 dodge challenger and the reverse lights stay on in drive! thanks a million  Grin  

waynep7122 waynep7122
Enthusiast | Posts: 643 | Joined: 08/09
Posted: 09/15/10
07:41 PM

so... you car takes the 3 wire switch... with the right of the 3 shift detents..

but you have installed the 3 wire switch into a car that has one of the left 2 detent plates...  

mb70Coronet mb70Coronet
New User | Posts: 5 | Joined: 09/10
Posted: 09/22/10
07:02 AM

Hey guys...new to the site...I've got a similar setup to brooks but with a different issue.  My 70 Coronet has a 68 727.  I purchased the car already restored.  My reverse lights do not work in any gear.  I checked the neutral safety switch...it's a 3 wire (which would be correct for the car but possibly not for the tranny).  The car will not start in gear so the switch seems to be working as far as that is concerned.  Does that mean the 3 wire switch is working and the lights problem is elsewhere?  

marcohotrod340 marcohotrod340
Enthusiast | Posts: 459 | Joined: 09/08
Posted: 09/22/10
02:18 PM

u all need to pop the pan and change the shift arms unit to match the switch that matches vehicle year.  

waynep7122 waynep7122
Enthusiast | Posts: 643 | Joined: 08/09
Posted: 09/23/10
07:21 AM

the 66 to 68 torqueflites use a single wire switch for the neutral safety control only...

when the manual lever is in park or neutral the tabs push on the center contact of the switch depressing the button and causing the contacts inside to close...  this grounds the terminal to ground...   the other end of this wire is attached to the starter switch....  

the 66 to 68 transmissions were designed to use a back up light switch mounted to the shifter inside the car... or to the steering column ,,,,


the 69 and newer transmissions  use the 3 pin neutral safety and back up light switch....

the detent cam on the  manual lever is totally different...  as the switch plunger is held at the half way... so its not totally depressed .. and not totally extended...

when the 69 and newer  manual position lever is in the park or neutral position..  the detent cam depresses the plunger into the switch body and closes the neutral safety switch center contact... the center is now grounded to the shell of the switch so the starter relay on the firewall will now work...

when the 69 and newer manual position lever and cam are moved into the reverse position...  the plunger is allowed to extend more as its normal half way position is dropped into the lower area on the cam..   this closes the contacts between the outer two terminals in the switch...      these terminals are isolated from ground....


putting a 3 terminal switch into a 66 to 68 transmission with the earlier valve body will result in the back up lights staying on all the time.... as the cam does not maintain the switch plungers half way position... is just not going to work...

i am still looking for information if a 69 and up valve body can be installed into the earlier case.. or if the detent plate can be swapped onto the earlier valve body..       but it looks like it was answered above...  

mb70Coronet mb70Coronet
New User | Posts: 5 | Joined: 09/10
Posted: 09/23/10
07:45 AM

Thanks, Wayne!  Great info.  I have read in a couple of places that Chrysler changed to the 3 wire NSS on 5/15/68.  So if I am reading your post right, the fact that the reverse lights are not on at all (in either reverse or drive) and that the car will not start in gear may mean that the 3 wire switch is correct for the tranny and that either the switch is bad and/or there is a short somewhere else for the backup lights.  Would that be a good assumption?  

mb70Coronet mb70Coronet
New User | Posts: 5 | Joined: 09/10
Posted: 09/24/10
11:07 AM

We're working on some transmission leaks today (lunch right now).  Once we took off the pan we saw that it was the wrong rooster-comb for the switch.  We're going to try to change it to the correct one and see what happens.  Thank you all for the help and great information.  

waynep7122 waynep7122
Enthusiast | Posts: 643 | Joined: 08/09
Posted: 09/24/10
10:17 PM

take some photos.... if you can... of the rooster comb in park.. in reverse.. in neutral .. in drive..  this is in relation to the back up light switch...  post them....

i don't have any torqueflites laying around to photograph...  

mb70Coronet mb70Coronet
New User | Posts: 5 | Joined: 09/10
Posted: 09/29/10
12:40 PM

Well, we were not able to change to the correct rooster-comb for the car because of trans build differences ('70 car/'68 trans).  We will have to stick with the comb that is in the tranny.  I did discover why the backup lights do not come on in any gear (which I keep reading they should with the 3 prong NSS)...no bulbs! DUH!  I will have to figure out a way to "rig" a switch for the lights to come on only in reverse.  More later...  

mb70Coronet mb70Coronet
New User | Posts: 5 | Joined: 09/10
Posted: 09/29/10
12:43 PM

Wayne, we were not able to get any photos but if you look at the photos of the different rooster-combs earlier in this thread, my trans has the one in the middle.  The one on the right is the one we tried (which is correct for the 3 prong NSS).  

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