904 Backup light Question

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wes beem

wes beem

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the transmission in my Duster finally took a poop on me, and i have another 904 thats been totally rebuilt with shift kit ext that im wanting to swap in.

I didnt however notice until now, the neutral safety switch plug on the new trans i want to use only has ONE plug instead of 3. Am i able to just screw the 1 wire one out and swap in my other one to have working backup lights?

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Altho I've not done it myself, apparently going 1 wire to 3 wire or vise versa requires changing the "comb" inside. They are matched so to speak.
 
What year is your rebuilt transmission? The very early 904s ('66 & older or '67 & older - I forget the years) had a smaller crank register for the converter snout to fit into and the input splines are different so converters won't interchange. Driveshaft yoke might have different splines too.
 
thats a good question, the numbers are wore completely off of it so im not totally sure, but if i remember correctly it is no older than a 68
 
wes beem said:
I didnt however notice until now, the neutral safety switch plug on the new trans i want to use only has ONE plug instead of 3. Am i able to just screw the 1 wire one out and swap in my other one to have working backup lights
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1 wire and 3 wire switches are not interchangable.

If your wiring requires the 3 wire your kind of out of luck without trans surgery
 
No they are not interchangeable. 1 wire switch uses the pic in the middle with no plastic on the comb. 3 wire switch uses the comb with the plastic on it. The switches themselves will screw into the case. If u use the 3 wire where the single wire was your back up lights will be on in drive. Kim. In the above pic number 1 is for up to 65. Middle is 66/67/68. 3 rd is 69 up.
 
Ok, so i need to take the Comb and the switch from my old one and swap them into the new one, Thanks!!!
 
Sometimes it’s not quite that simple. The comb isn’t the only thing different. I know Sonnax makes the plastic but not sure if it will fit on your older comb. That may be your best option. U have to check where the stop hits the valve body. Kim
 
my car is set up for the 3 Pin and thats what makes my back up lights work correctly or i would just change it
 
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