Speedo no shift issue
Thread Starter
Staging Lane
Joined: Mar 2009
Posts: 60
Likes: 0
From: Devils Lake, ND
Speedo no shift issue Having an issue with my drag car. Issue does not occur every pass but more often than not. When i roll into the burnout box all is fine. I do my burnout, speedo working fine at this point, and roll out of the water. As i slowly roll forward to stage, the speedo quits working and reads 0 or nearly 0. Upon launch I have apparently lost vss signal and the trans will not shift. Sometimes I do not lose vss signal until I'm on the 2 step. Same result. After I lift a few seconds later the signal comes back, speedo works car shifts fine. I have changed vss and swapped out pigtail. No help. I have separated vss signal lead so it is nowhere near any other wires so as to avoid any interference. No help. I have also found that if it does work and shift I show 1-3 mph on my log while on brake and on the 2 step. I have found a completely unacceptable workaround and that is if I unplug my vss plug from the sensor and then re plug it back in between rounds, It works flawlessly. E38 ecu, t42 tcm 416ci ls3 with an RPM trans 4L60E with Rossler trans brake. PSI custom harness. Due to stupid covid **** I only got out 1 time this year but all worked perfect in 2019. Possible TCM issue, ECU issue, still some kind of feedback issue, mech issue or ??? Any thoughts would be appreciated. Log and tune attached
Teching In
Joined: Nov 2020
Posts: 39
Likes: 2
I had the same thing happening to me on my truck I swapped, the VSS is in the transfer case in my truck, one day I pulled it out and there was alot of metal shaving on it, I cleaned it off and re installed it and it has worked fine ever since.
with the amount of metal that was on it I have ordered parts to rebuild the transfer case but they havent all showed up yet.
I would remove your sensor and take a look at it
with the amount of metal that was on it I have ordered parts to rebuild the transfer case but they havent all showed up yet.
I would remove your sensor and take a look at it
Teching In
Joined: Nov 2020
Posts: 39
Likes: 2
intermitent wire issues suck, if unplugging it and than re plugging it temporarly fixes it than maybe something with the plug is faulty, or a broken wire somewhere, I dont know much about the tuning aspect of these motors/computers but it seems tunes usually work or they dont, I would be leaning tword a broken wire or mechanical issue.
Thread Starter
Staging Lane
Joined: Mar 2009
Posts: 60
Likes: 0
From: Devils Lake, ND
Thanks again for the reply. Will not discount either of your thoughts. So I made 5 passes on Friday. Pass 1 and 2 it lost signal so those runs it didnt shift. For the 3rd pass i replaced vss and pigtail and obviously removed harness wires. Worked perfect. Pass no 4 failed. Figured out the "cure". Pass 5 was perfect. Made 5 more passes on saturday each time removing sensor wires and had no issues. I'm not really thinking mechanical but still wondering about feedback. Possibly a ground. I do not have a ground specifically to the trans. Have plenty to engine, body and frame.
Thread Starter
Staging Lane
Joined: Mar 2009
Posts: 60
Likes: 0
From: Devils Lake, ND
They are not. They were not on my new harness but I have just ordered some twisted pair shielded wire to run from tcm direct to vss. I may also get a new tcm coming also. Not sure what else it could be
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Of course, the 4L60 looks at both mph and rpm to shift. No mph, won’t shift. I’ve honestly found it a crap shoot to get dialed correctly.
I have a C5 Corvette that I drag race.
So I’ve wondered often if an aftermarket controller would do a better job?
Ron
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Staging Lane
Joined: Mar 2009
Posts: 60
Likes: 0
From: Devils Lake, ND
It took me a long time to dial in the shifting the way I wanted it. It is a bit fussy but it had been working great. I have plenty of electronics located in the car that I am sure can and do cause feedback. Delay box, 2 step, timing controller, nitrous controller, ecm, tcm. All potential problem areas. Going to go through it all.
Thread Starter
Staging Lane
Joined: Mar 2009
Posts: 60
Likes: 0
From: Devils Lake, ND
It's a Lingenfelter 2000 combo rev limiter/ timing controller. Not wired into tcm just into the coil packs. I do have the lingenfelter diodes wired into all required ( i believe) circuits.
Thread Starter
Staging Lane
Joined: Mar 2009
Posts: 60
Likes: 0
From: Devils Lake, ND
You got me thinking. I'm going to have to recheck that. When I separated my vss wires, I went through my trans tunnel not very far away from my trans brake trigger wires. Gunna have to look and see if I added a diode. Thank you