jimbud22 Posted April 27, 2003 Report Posted April 27, 2003 I posted this question on a couple of other site but I'm just trying to a idea on this before I bring my car in to be looked at. I have a early shift problem on my 4T60E in a 95 Monte 3.4. Other then the early shift points the trans. works fine, no clunks, hard shifts or any thing like that. The only other person that i could find that had the same problem fix his problem when he found a vacuum leak. Does our PCM use vacuum as a factor when sending a signal to the transmision to shift? Is there a sensor that opperates off of vacuum? Thanks in advance. Quote
Robby1870 Posted April 27, 2003 Report Posted April 27, 2003 Even the 4T60E uses vacuum to control shifts. And, like you said, I think the PCM uses vacuum to control the shifts unlike the 4T60 which relies on the acutual vacuum and doesnt go through the ECM. However, I dont know where this sensor is, but look for vacuum lines running from the TB. There should be a number of vacuum lines. See if any go to the trans or are attached to a sensor or something. Thats really all I can tell ya. Hope maybe some of this helps. Robby Quote
brian89gp Posted April 27, 2003 Report Posted April 27, 2003 The shift tables are based on TPS and MPH alone, though there are some TCC disengagement tables based on vacuum. That and your 95 is MAF and has no MAP sensor (ie no way to measure vacuum) anyway. Is this early shifting the only problem, or does the engine act up as well? Quote
jimbud22 Posted April 28, 2003 Author Report Posted April 28, 2003 The engine runs great Brian, no other problems at all. The transmission is fine at highway speeds and downshifts. I replaced my cone filter with my stock air box and the problem may have disapered. I'm starting to wonder about my MAF sensor. Does air flow readings going to the ECM affect shifts? I haven't had time to drive it more then just around the block, but for now it seams fine. You mentioned TPS, what is that? Throttle pos. sensor. Any other input on sensors that afect shift points? Thanks for your help you guys!!! Quote
brian89gp Posted April 28, 2003 Report Posted April 28, 2003 MAF is probably only used to disengage the TCC when there is extreme load. Yes, TPS = throttle position sensor. The shift tables are TPS% vs MPH, in all my searching I have not found any reference to vacuum or air flow, so its gotta be those 2 sensors. What type of trans did this other guy have? If it was a regular 4t60 then it could make sense, but a 4t60e, well, it makes no sense at all. Quote
jimbud22 Posted April 28, 2003 Author Report Posted April 28, 2003 The other guys car was a 92 3.4 z34 with 4T60E. I emailed him last night and herd back from him this morning. So the 2 sensors I should keep a eye on are the TPS and MAF sensor? Is this right? How about the VSS? THe speedo works so I'm guessing its working. Thanks so much for your help. Quote
brian89gp Posted April 28, 2003 Report Posted April 28, 2003 Thats strange a vacuum leak would cause that, I guess you might wanna look for a leak then If the speedo works and is accurate, then the vss sensor is fine. If the MAF sensor were bad, the car would run like shit. TPS I am not sure what a bad one would cause. This is all puzzeling at the moment. Quote
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