Bruce Amacker Posted June 17, 2012 Share Posted June 17, 2012 I've received a request for help from a good friend/shop owner: Patient: 06 expedition 2wd 5.4 vin# 1fmpu175x6la20334. Miles;153,159 symptom 1,2,3 shift before 5mph or about 3 seconds. shift manually and it drives fine, highway speed step on it, it downshifts fine. No trans codes, vss on scanner seems fine, tps checked with known good unit, any ideas? He has an IDS so I'm sure it's at the latest flash level and DTC info is correct. Thanks, guys, and Happy Father's Day! Quote Link to comment Share on other sites More sharing options...
Jim Warman Posted June 18, 2012 Share Posted June 18, 2012 This car has the 4R75E. I'm going to assume trans fluid is at proper level with good colour and no odour?? Engine runs well (though most engine concerns that affect shift quality/timing will give a late or no upshift). Anything I can think of should, at the very least, set a code - but I'm not old enough to say "I've seen it all....". I'd start with making sure that the 1-2 and 2-3 are being commanded and that the trans can perform them. PIDs to watch would be GEAR_RAT and TRAN_RAT. GEAR_RAT is the gear commanded by the PCM and TRAN_RAT is the gear ratio computed using TSS and OSS inputs. Probably an idea to monitor TSS,OSS and MPH PIDS just for shits and grins while a guy is at it. TRAN_RAT should read should read 2.84:1 in 1st, 1.55:1 in 2nd, 1.00:1 in 3rd and 0.70:1 in high. At rest, in gear, tran rat will look goofy. What this will do for us is to help identify if we are going to look inside the trans... or outside the trans. Just for grins, let's make sure that the PCM hasn't been changed out recently for any reason, too. Quote Link to comment Share on other sites More sharing options...
mrbudge Posted June 18, 2012 Share Posted June 18, 2012 I know it is a 2wd, but is there a 4wd low pid? I had one that the pcm thought it was in 4low and modified the shift schedule accordingly, but it was a 2wd. Quote Link to comment Share on other sites More sharing options...
Bruce Amacker Posted June 19, 2012 Author Share Posted June 19, 2012 Here's what my buddy responded today: Gear ratio and trans ratio look proper. TSS OSS pids look proper. Trans Rat reads all ratios and is goofy at rest as noted: Still original PCM. All updates complete. 1 2 3 shift before 10 MPH or so. All fault pids OK 4WD module "not responding" (it's a 2wd truck) Today it stalled twice going from N to D so maybe it's inside time..... Thanks, Duane Quote Link to comment Share on other sites More sharing options...
Bruce Amacker Posted June 26, 2012 Author Share Posted June 26, 2012 Update: The fix was a new TCC solenoid. For some reason the TCC was locking too early and for an unknown reason the tranny decided to shift 1-2-3 almost immediately when this happened. I don't really understand why, but that's because I'm not a tranny guy. Quote Link to comment Share on other sites More sharing options...
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