View Full Version : Manual Overdrive engagement
03-26-2003, 10:15 PM
Hi all,<br>I was just wondering if a guy could run some wire from a power source on the truck to a switch in the cab and then to the O/D solenoid without frying anything. The reason I ask is because my computer controlled one has a temper like a woman... ::) Does what I want when it wants... Any thoughts?<br>
03-27-2003, 12:17 AM
Hi Spitz',<br><br>If I'm not mistaken the dash switch sends a ground pulse, not a positive signal to the tranny to select OD.<br>I'm pretty bad with electrics and I don't want to offer any advice on this one.<br>Are you having OD problems only? If so, what's it doing?<br><br>Bob.
03-27-2003, 07:18 AM
the soleniods in the trans are hot all of the time. they are ground switched. one of the wires comes from the solenoid to the puter. it is grounded by puter. you can tie a switch to this wire to ground. switch on wire is grounded, od works. switch off od off
03-27-2003, 12:52 PM
I just went through all this with mine. Click on the link below and read how to do it. One tip though, do not cut the orange wire, just splice into it. If your is not Orange it will be the smaller of the 2 wires going into the plug. The plug sits vertically high up on the drivers side of the tranny. Bill
03-27-2003, 07:54 PM
<br>I just went through all this with mine. Click on the link below and read how to do it. One tip though, do not cut the orange wire, just splice into it. If your is not Orange it will be the smaller of the 2 wires going into the plug. The plug sits vertically high up on the drivers side of the tranny. Bill<br><br><br>Just realized I forgot to add the link. Bill<br><br>Hotwiring The O/D (http://www.dieseltruckresource.com/yabbse/index.php?board=9;action=display;threadid=11927)
03-27-2003, 10:01 PM
one quick question, could this overdrive unit be used as a makeshift splitter for 1st and 2nd gears with a manual engagement switch, just a thought as i haven't sat down and studied the service manual on the 518, anyone tried it, how's it work?
03-27-2003, 10:07 PM
<br>one quick question, could this overdrive unit be used as a makeshift splitter for 1st and 2nd gears with a manual engagement switch, just a thought as i haven't sat down and studied the service manual on the 518, anyone tried it, how's it work?<br><br><br>Do Not, I repeat Do Not use Overdrive unless you are above 40 mph and a consistent 1800 rpm. And make sure you always shut it off when coming to a stop. It will wrok for a little while if left on al the time, but you are going to be spending some $$$ if you use other than the way it was intended. The only reason mine is hooked up this way, is because I don't have $200 for a TPS right now. As soon as I do it will be put back the proper way. Bill
03-27-2003, 10:41 PM
I would be tempted to replace the TPS with a cheap Radio Shack potentiometer. I think it is 5k ohms but you have to check. I know 1.3 volts causes 3 to 4 shift at 37 mph regardless of throttle. You could dial in your own fixed shift point. I pulled the shaft stub and fixed the TPS at 1.3 V with a metal plate under TPS with a small tab (cut with metal shears) to fix spring loaded slot in the TPS (bottom). The beauty is that the computer has the ability to shift 4 to 3 as speed decreases when stopping. I should have used a potentiometer but I am too lazy now with other priorities. I definitely would NOT hardwire at the solenoid as you or another driver are bound to forget one day. I have no idea what damage could be done. I would leave that question to Bill Kondolay on the DTT site.
03-28-2003, 05:35 AM
if i understand the rh valvebody od cannot happen until 3rd gear oil is applied. so if you use passing gear 3rd oil goes away and so does od. cant see how it can hurt trans except on full throttle upshift. with switch on full throttle you will get a 2-4 shift at about 40mi. per hr. trans will not stay in od when at full stop. it will drop back to low gear and lite throttle shifts will be normal. ran mine like this for 20 k with no problems. mine is a non lockup.
03-28-2003, 09:07 PM
Hi guys, this all sounds great, I'm going to roll myself under the truck first thing tomorrow morning and rig it all up. I think it's going to be less expensive doing it this way than spending the $300 the ******* wants for the wiring harness segment I need to fix the problem properly... At least now I'll have some control over the stupid transmission when at higher speeds... I guess you could call it a semi-automatic then [laugh] I'll let you know how it works out. Thanks for all the tips so far. I'm just so sick of this O/D problem...
04-01-2003, 10:29 PM
Hi guys,<br>Sorry I didn't write sooner but I got it all rigged up and working. Wow, what an improvement! ;D Works super!!! Now I can't let anyone else drive my truck... Hang on, that could be a good thing [laugh]<br>Thanks for all the tips!
04-02-2003, 03:30 PM
Sorry I didn't write sooner but I got it all rigged up <br><br>What did you do exactly spitzair<br>JJ
04-02-2003, 06:56 PM
Calvic,<br>I simply spliced a wire into the orange with green tracer wire coming out of the transmission, then ran the wire up into the cab along the parking brake cable and mounted (taped) a switch to my steering column. The other wire from the switch is spliced into the ground for the trailer controller (it was right there anyways) and away she went. Literally! ;D<br>Hope this helps.
04-03-2003, 03:15 PM
I sure am tempted to wire mine up. Any more thoughts about this. Spitzair, are you turning off o.d. everytime you slow down or just leaving it on. I'm getting tired of mine jumping in and out of o.d. its so intermittent it might go for a week and work fine then next time in and out. No rhyme nor reason. :'(<br><br>JJ
04-06-2003, 11:38 AM
Calvic,<br>Sorry I didn't write back sooner but now my computer is acting like my Overdrive was... :P I just can't win :'( At least my O/D is usefull now. When it comes to turning it on and off, yes I switch it off every time I slow below 80Kmh/50 MPH and on above, if I'm not going uphill. So far so good, Huge improvement! Have fun!
04-07-2003, 03:22 PM
Yep I may just try that. I futzed around this weekend tweeking and adjusting the TPS. It worked great for about 20 miles on the way to work then jumped in and out of O.D. about 3 times , then worked fine for the next 50 miles to work. This thing is starting to honk me off!!!<br> <br> JJ
04-10-2003, 06:54 AM
Thanks for the info on this guys. Mines been doing this for the last couple of months and that was with a brand new tps from cummins. I cleaned it and it worked fine for two weeks and started acting up again. I was fed up with it today and wired a switch up to the solenoid and it works perfect now! <br><br>Scott
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