relyt120 Posted December 30, 2015 Share Posted December 30, 2015 Hey guys. This is pretty out of no where but yesterday when I was leaving work I put my truck in drive and it seems like its in a higher gear than it should be. What I mean is I give it some gas and it has to rev up for a good little bit before I get any kind of speed, as if in too high a gear when driving a manual. Decided to utilize the 3 and 1-2 selections on my shifter and when I put it in 1-2 and then switch to 3 at the appropriate time and the to Drive after that I can get it to go through the gears just fine. Thus, The problem seems to be with the automatic changing of gears while in Drive. I have not done anything to try to remedy the problem yet but my first thought is something must be up with the TCU. Someone at work suggested it may be something with the torque converter but I not want to go down that road if I do not have to. Anyone have any thoughts? For now my plan is to pull the TCU and clean it up and apply electronics cleaner to both ends of the plug. Suggestions appreciated! Link to comment Share on other sites More sharing options...
MJam86 Posted December 30, 2015 Share Posted December 30, 2015 Possibly trans solenoids going out Link to comment Share on other sites More sharing options...
gogmorgo Posted December 30, 2015 Share Posted December 30, 2015 This is indeed the way the transmission behaves when the tcu is unplugged and/or the trans fuse is removed/blown. I would look at the fuse first, and then the connections, like you're doing. Also check the wiring under the truck and in the engine bay, trans connector are near the trans dipstick. Make sure the wiring's ok before dicking with solenoids or the torque converter. Pretty sure if a solenoid went bad that it wouldn't shift at all. Link to comment Share on other sites More sharing options...
HOrnbrod Posted December 30, 2015 Share Posted December 30, 2015 http://comancheclub.com/topic/47262-does-not-shift-into-4th-gear/ Link to comment Share on other sites More sharing options...
gogmorgo Posted December 30, 2015 Share Posted December 30, 2015 Your link opens up this same thread just in a new tab, at least on my phone... Link to comment Share on other sites More sharing options...
HOrnbrod Posted December 30, 2015 Share Posted December 30, 2015 Your link opens up this same thread just in a new tab, at least on my phone... :doh: Fixed it. Too many AW4 threads at the same time.............. Link to comment Share on other sites More sharing options...
gogmorgo Posted December 30, 2015 Share Posted December 30, 2015 Figured that's what it was :thumbsup: Link to comment Share on other sites More sharing options...
cruiser54 Posted December 31, 2015 Share Posted December 31, 2015 Check to see if the TCU fuse is blown or corroded first. Link to comment Share on other sites More sharing options...
relyt120 Posted December 31, 2015 Author Share Posted December 31, 2015 Your link opens up this same thread just in a new tab, at least on my phone... :doh: Fixed it. Too many AW4 threads at the same time.............. I noticed that. Thanks everyone. I checked the 7.5 fuse at the fuse box and it was good. I'm going to check the inline fuse near the tcu next. Will report back with findings. Link to comment Share on other sites More sharing options...
cruiser54 Posted January 1, 2016 Share Posted January 1, 2016 The 7.5 amp fuse in the fuse box only affects the Power/Comfort switch and the reverse lights. Link to comment Share on other sites More sharing options...
relyt120 Posted January 1, 2016 Author Share Posted January 1, 2016 All right so I pulled the lower dash panel and checked the inline fuse near the TCU and it was good. Just for the hell of it I replaced it anyway and checked to make sure I have 12v on both side with my volt meter. Since the fuse was good I went ahead and pulled the TCU and cleaned both sides of the connection with QD electronics cleaner. I also went ahead and did the same for the two plugs near the dip stick. After all that the symptoms have not changed. I am still convinced its the TCU since I can drive it just fine by manually shifting with the 1-2,3,and Drive selections. Anything else I should try before searching for a replacement TCU? Link to comment Share on other sites More sharing options...
HOrnbrod Posted January 1, 2016 Share Posted January 1, 2016 Disconnect the firewall connector and check the three solenoid coils with an ohmmeter (pins E, F, and G to pin B-Ground) on the transmission side, especially S2, for ~15 ohms. If S2 is open it won't shift into second or third gear. Image Not Found http://comancheclub....-into-4th-gear/ http://www.naxja.org/forum/showthread.php?t=1053970 Link to comment Share on other sites More sharing options...
relyt120 Posted January 1, 2016 Author Share Posted January 1, 2016 Disconnect the firewall connector and check the three solenoid coils with an ohmmeter (pins E, F, and G to pin B-Ground) on the transmission side, especially S2, for ~15 ohms. If S2 is open it won't shift into second or third gear. Image Not Found http://comancheclub....-into-4th-gear/ http://www.naxja.org/forum/showthread.php?t=1053970 Thanks hornbrod. Ok, so I back probed the white, violet, and blue wires at the TCU with the meter and got 13.3,13.2, and 13.4 respectively. I tested with everything plugged in and the truck off. Link to comment Share on other sites More sharing options...
relyt120 Posted January 1, 2016 Author Share Posted January 1, 2016 Assuming I've tested it correctly, decided it was easier to test at the TCU as per \/\/\/, I think my solenoids are testing good. You can also check the solenoid coils via the TCU connector, pins C14, C15, and C16 to ground, with the firewall connector plugged in of course. . The AW4 manual says 11-15 ohms; replace if reading is above or below the specified range. Mine all read on the high side (~15) within .5 ohm of each other. Link to comment Share on other sites More sharing options...
HOrnbrod Posted January 1, 2016 Share Posted January 1, 2016 Yep - the solenoids are okay. TCU time........... Link to comment Share on other sites More sharing options...
relyt120 Posted January 2, 2016 Author Share Posted January 2, 2016 Can it be a TCU from any year or Renix only? Truck is 89 Link to comment Share on other sites More sharing options...
gogmorgo Posted January 2, 2016 Share Posted January 2, 2016 Renix definitely. I've seen a couple members say they've had problems swapping between years, but can't really confirm that it is or isn't a problem. Link to comment Share on other sites More sharing options...
HOrnbrod Posted January 2, 2016 Share Posted January 2, 2016 There are pinout differences between the HO and Renix TCUs. Link to comment Share on other sites More sharing options...
relyt120 Posted January 8, 2016 Author Share Posted January 8, 2016 Replacement TCU did the trick! Shifting normally again. Thanks everyone! Link to comment Share on other sites More sharing options...
HOrnbrod Posted January 8, 2016 Share Posted January 8, 2016 :thumbsup: Just for grins, pop open your old one just to see if there's anything obviously wrong, like broken solder joints, burnt components, open connections, etc. Would be interesting to see................ Link to comment Share on other sites More sharing options...
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