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+--- Thread: Post trans swap reverse light issue (/showthread.php?tid=6061)
Post trans swap reverse light issue - dieselsmoke300d - 12-15-2014
Hello all. Just replaced the transmission in my '85 300SD from the 722.315 to the spare 722.303 that came with the car. Shifts great now! Unfortunately now the reverse lights aren't working... (not 100% sure they were working in the first place) Checked the switch, that's all good. checked the harness, that's all good. Checked the fuses and bulbs, they specifically test good. I have not checked much else yet. Kinda wishing I had my wiring charts right now... One weird thing though. The "new" tranny came with an identical harness, so I just used the one that was in the car to hook it up. Then I uncovered the car's stock plug which is an 8 pin with 7 pins in it... I tested it and it's all the same pins for park and reverse. But I don't know what the 7th pin is for. Could be part of the issue idk.
Any ideas?
RE: Post trans swap reverse light issue - w123love - 12-15-2014
I'm interested as well. I haven't be able to resolve a reverse light issue on my sister's 1985 300D for years. It may be the NSS switch being dirty, or not connecting properly. I will likely be ordering a replacement NSS in the near future.
RE: Post trans swap reverse light issue - dieselsmoke300d - 12-15-2014
It's gotta be in the harness somewhere. I'm not sure.
RE: Post trans swap reverse light issue - capflya - 12-18-2014
You could swap the nss from the old trans. Make sure you have it aligned properly or that could be the issue. There's that little arm that fits into the metal shift lever on the trans and that could be the issue.
RE: Post trans swap reverse light issue - dieselsmoke300d - 12-19-2014
We did some poking around tonight and someone physically unscrewed the power lead to the kickdown solenoid and the reverse lights from the bottom of the fuse box... Solved the problem. But there could be some other gremlins that aren't visible yet. The lack of the kickdown solenoid might've been what screwed up the original transmission too.
RE: Post trans swap reverse light issue - dieselsmoke300d - 12-20-2014
Ugh... Now for some weird reason the reverse light etc fuse blows whenever the car is turned on... And what's even weirder is that the glow plug idiot light and relay will not click on until after the fuse is blown... There's something freaky going on here... Probly a bad ground.
RE: Post trans swap reverse light issue - dieselsmoke300d - 01-06-2015
Alright just to keep everyone up to date, I solved the problem! Turns out that all of this was caused by the transmission's shifter position switch. It was shorting internally and causing near all of the problems! All I had to do was swap it with the other one! And I'm pretty certain that was the cause of the original transmission failing in the first place (when I swapped the tranny I used the car's original switch on the new tranny and unknowingly carried the problem over). With that switch shorting everything else out on that circuit, it prevented the overload protection from working along with the reverse lights and most of all, the kickdown solenoid which caused the transmission to never downshift on its own during acceleration and then caused it to burn the bands out from straining them. Gotta love how these things work huh? lol
And thank you guys for suggesting swapping the switch! I probably would have been dumb enough to never think of it myself otherwise. lol