94LuminaZ34 Posted November 22, 2008 Report Share Posted November 22, 2008 OK heres another thing wrong with my car. If i'm driving down the highway in overdrive and I give it gas it downshifts into third but doesnt come back into overdrive no matter what I do? I have to pull over and restart the car then it will drive normal. There were no codes when I scaned it. Any Ideas? Where should I start looking? 1994 Z34 Lumina 3.4L Quote Link to comment Share on other sites More sharing options...
94LuminaZ34 Posted November 29, 2008 Author Report Share Posted November 29, 2008 I tried unhooking the various wires from the plug on the trans today and SES light comes on and I go into third gear I think so I assume this is limp mode? I have a idea, can I just unhook the plug and wire in 194 bulbs to act as the solenoids so the psm thinks thats everythings ok? Will my trans still shift without pcm control or the solenoids working? The trans is a 4T60E Quote Link to comment Share on other sites More sharing options...
Olds W31 Posted November 29, 2008 Report Share Posted November 29, 2008 it downshifts into third but doesnt come back into overdrive no matter what I do? I have to pull over and restart the car then it will drive normal. Do you mean that when this occurs (no OD), that if you pull over to the side of the road and try to take off it only gives you 3rd...or that you have 1st,2nd, 3rd, but no OD? If it is just no OD, then I would hazard the clutches (there are only 2, I believe) in OD are toast. If it is going into "limp home" that can be from a number of causes, not the least of which is a dirty/clogged main filter (the one in the pan). You have to have the PCM connected or the trans will not shift. I don't have the shift schematic, but there are 2 solenoids (1-2 and 2-3) that, depending on the combination (1-2 closed, 2-3 open; 1-2 closed, 2-3 closed; etc,) actually shifts the trans into the gear commanded. If you don't have them hooked up, you will get the default gear (maybe 3rd). Quote Link to comment Share on other sites More sharing options...
Olds W31 Posted November 29, 2008 Report Share Posted November 29, 2008 Just a clarification: The solenoids are labeled A and B. Shift Solenoid Patterns for each gear Range 1-2 Solenoid 2-3 Solenoid Park ON ON Reverse ON ON Neutral ON ON 1st Gear ON ON 2nd Gear OFF ON 3rd Gear OFF OFF 4th Gear ON OFF Quote Link to comment Share on other sites More sharing options...
94LuminaZ34 Posted November 29, 2008 Author Report Share Posted November 29, 2008 I think its my TCC I got a code P0740 which is TCC circuit so I might end up replacing all the solenoids if I have to pull the side pan. So I have to have the trans plugged in or it wont shift? Quote Link to comment Share on other sites More sharing options...
Olds W31 Posted November 30, 2008 Report Share Posted November 30, 2008 I think its my TCC I got a code P0740 which is TCC circuit so I might end up replacing all the solenoids if I have to pull the side pan. Is this the code you had before...or after...you unplugged everything.....you would have set at least 1 code when the SES light tripped. So I have to have the trans plugged in or it wont shift? Yes. You may be able to manually shift thru the gears, using the shifter, but I doubt it...I have never tried. Quote Link to comment Share on other sites More sharing options...
rockfangd Posted November 30, 2008 Report Share Posted November 30, 2008 If you have the 4t60-e you cannot disconnect the connector on the trans because it is electronically controlled. Sounds like your overdrive is going Quote Link to comment Share on other sites More sharing options...
94LuminaZ34 Posted December 1, 2008 Author Report Share Posted December 1, 2008 Yea I got the code before I unplugged everything P0740 which is a TCC circuit problem. I think I have to replace some solenoids. Quote Link to comment Share on other sites More sharing options...
94LuminaZ34 Posted December 2, 2008 Author Report Share Posted December 2, 2008 OK got some more info. I keep getting a code P0740 which is TCC circuit failure. Now when I drive it it will shift from third into lockup or fourth at about 55 mph and then 10 seconds later it will downshift into I think second and wont come back into third or fourth without a restart. It seems to do it everytime so I think I have to replace some solenoids what do you guys think? Also I have my abs and brake light on because of a code 51 which is rear abs motor freewheeling would that have anything to do with the trans? Quote Link to comment Share on other sites More sharing options...
Regal_GS_1989 Posted December 2, 2008 Report Share Posted December 2, 2008 What RPM is it running at when it Downshifts? If it does in fact kick down into 2nd and 55mph, the RPMs should be pretty high, i'd say somewhere around 4000. Quote Link to comment Share on other sites More sharing options...
Psych0matt Posted December 2, 2008 Report Share Posted December 2, 2008 MIne does this literally 50% of the time, wont shift into OD. I just shove it in neutral, shut her off, start her back up, shift back into drive and then it drops into OD like nothing was ever wrong. Weird. Quote Link to comment Share on other sites More sharing options...
LuckoftheGTP Posted December 2, 2008 Report Share Posted December 2, 2008 Weird. I have a similar problem. If i am crusing at 60-70mph for longer than 10 min. the car will down shift and kick to 3-4K RPM and stay there until I shut the car off. (Console has D 3 2 1) (oops sorry in my 94 GTP) this doesn't happen all the time. Quote Link to comment Share on other sites More sharing options...
Crazy K Posted December 2, 2008 Report Share Posted December 2, 2008 I have said before, and I will say again. both my 94 and 95 have fallen into "Overheat Failsafe Mode" while driving. Overheat Failsafe Mode = 1, 2, and 3 gears work, car will shift throught them, but NO TCC, NO O/D. can be 'quickly' corrected by re-starting the car. Matt, you are DEFINITELY suffering from Overheat Failsafe Mode. Luck, you might be too... the OP has a different problem it seems. those of you with OFM... GET A TRANSMISSION COOLER! Quote Link to comment Share on other sites More sharing options...
LuckoftheGTP Posted December 2, 2008 Report Share Posted December 2, 2008 Thanks Man. Not a trany guy. How hard is it to install. Did any one do a write up on it? Quote Link to comment Share on other sites More sharing options...
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