Ok this may end up being a long post but im going to try to be descriptive. My girlfriends 01 bravada has been driving me insane. It has the 4.3 with the 4L60E trans. Problems with the transmission started a couple months back. When in overdrive the torque converter would go from lock up to not locked up, in and out, in and out while driving. It wouldnt do it all the time, just after driving for 20 miles or so. The rpms would jump up and down 200 rpms and car would kinda shudder. I Actually thought it was the engine causing this cause the check engine light was on, so i bought a scanner and replaced the oxygen sensor, and replaced fuel filter along with a bunch of little maintainece things, no help. Then took it to my local mechanic because of an abs issue (the abs would kick in under normal breakin and car wouldnt stop) he said i needed a front wheel sensor and that there was a trans slip code about 230 miles ago and that the engine had gotten hot... The coolant was a little low before I had done all that maintainence mentioned previously. I figured ok the coolant was low, it got hot, trans slipped, and most likely tranny was going out soon. So i fixed abs and told her to drive it till it pukes. Then a few weeks ago she calls and says its doing that shudder thing really bad, I said well drive it home, park it and i'll look at when i get there. Before she got home she stopped somewhere, went to leave and it wouldnt move with gear selector in overdrive, had to manually shift it to get it going. When I got home, I took it for a drive and beat the hell out of it and it was working fine, after 10 miles or so I stopped and went to take off and it wouldnt move in overdrive. If i shifted to a lower gear it would take off in 2nd gear and shift through other gears and reverse fine, no 1st. Called tranny shops and they all said trans needs rebuilt, not wanting to pay 1100-1500 for them to rebuild it (thats if i pulled and installed it) I bought and installed a junkyard trans. It seemed to work fine for 2 weeks and now its doing the overdrive in and out crap again... Now do you think i got a junk trans or is this a PCM issue? I was thinking it was a solenoid issue in the original trans but the tranny shop said "no the trans needs rebuilt" so i took their word for it and now i got the feeling i wasted my money buying the other transmission. I hope someone can point me in the right direction. I consider myself a descent mechanic but this computer crap is driving me nuts. Again sorry for the length of this post i just figured if i layed the whole story out there it may help. Any input would be appreciated. thanks

 

It could be the computer for thte tranny. What is bothering me is did you flush the tranny fluid when you changed tranny's? I ask this because coolant isn't a consumable fluid, it had to go somewere. I have seen crazier stuff but could it have gone in the tranny fluid? Also if the old tranny was tanking I'm sure there was spent metal in the tranny cooler and swapping another tranny would just suck all that crap right back into the tranny. And theoretically cause the same problems and inadvertantly cause the same damage.....

 

Yes I have seen trans coolers go bad and coolant get in the transmission, my old mans jeep cherokee, but I didnt see any signs of contamination on the bravada. The tranny fluid was pretty dark and stinky and the normal build up on the magnet in the pan. Also when i had the trans out i blew compressed air, brake cleaner, and more compressed air through the cooler lines till i had no more trans fluid just brake clean coming out so i think it was clean enough. Im thinking its the powertrain control module but hate to throw more money at the thing and have it not work.
I love that "Hombre, screwed over s-10" hahaha

 

700R4s and 4L60Es both use a TCC solenoid to lock up the converter. Since you changed transmissions and the problem followed, it could either be a coincidence, or the PCM. If you know someone on the inside(so it's cheaper), you could try having it reflashed (aka the factory setting downloaded into it again). I think some parts stores can do it, but there again I don't know what it costs.

Aside from that, I know the OBDI ALDL diagnistic ports had the TCC signal running to them so you could actually add a test light to check operation and voltage while driving. You could try looking for a pinout of the port and see if that is still an option on the OBDII ports. Adding a small bulb or meter would tell you if voltage is dropping out to the converter lockup or not (to rule out PCM or tell you if it's the solenoid).

The only other thing would be to maybe check the connector for a bad connection.

As far as the slipping, that could be because of the converter, but I read that at some point around '01 or '02 they added input speed sensors to the transmission. If that is the case, you may very well have something wrong with the transmission to cause the slipping.

 

Thanks for the tip, I didnt know you could get the pcm reflashed. Im still out of town so i'll let ya know what i find when i get a chance to look at it. From what the old lady said its doing the torque converter lock and unlock again, or jerking as she puts it. I dont think this trans is slipping yet but i had her stop driving it till i can check it out. Thanks again for the advice.

 

I think the TCC valve is less than $30. You just drop the pan, unwire, and unbolt. I know I leave it connected when I've rebuilt them(transmissions). I'm pretty sure they are hardwired in so you'd probably have to cut the wires and splice it in if it only comes with pigtails.

 

Well sorry i didnt repost sooner but basically when i drove it i didnt really think it was doing anything too out of the ordinary at the time so i just had her continue to drive it. And I was busy replacing other things like the rear axle, front drive shaft, and the countless other things that went to hell in the past few months. I actually think the big thing that was causing the jerking feeling was a slightly plugged cat converter. One day it decided to blow the guts out of the front converter and completly plugged the rear one to the point it would start but wouldnt rev up then eventually quit. After fixing that it runs and drives like new. And hey she left me so that piece of crap isnt my problem anymore lol! I just picked up a spotless 94 that a guy I work with give me but its got trans issues too, No 3rd or 4th gear, and it caught on fire cuz the muffler got glowing orange hot for some reason! I got the fire put out before any real damage was done though with some serious snow scoopin lol.