PROBLEM : OD light flashing and 1st to 2nd shift point very high

I have a problem and would appreciate any suggestions to fix it. I have a 2000 Excursion 7.3 2wd auto trans. (4R100) with 395k miles. I have a PHP tuner with custom made tunes and larger injectors and injector cups that I replaced about 2 years ago. I have a John Wood Trans. that was built at 203k miles. 18 months ago (16k miles ago) the trans. was freshened up because a plug blew out pulling a roller coaster street in San Fran. with a 24 foot enclosed trailer behind me putting 21 qts of atf on the street. Shut it off right away and no internal damage and surprisingly all the clutches looked like new and did not need replaced even though many of my miles are pulling a trailer. So fast forward to now. Most of the time my OD light is flashing. The overdrive performs like it should. The first to second shift point is very high (3200-3400) unless I back off the pedal. The other gears shift normal. My trans. guy said that the shift solenoids in these trannies very rarely go bad. I replaced the rear end speed sensor a few days ago and no difference. My friend hooked up his expensive scanner and it showed that the rear end sensor was working perfectly. The scanner also showed that the shift solenoids were good. It also showed that I have about 20 codes…some are glow plugs circuit etc….by the way it starts up perfectly every time, batteries are charged up and the charging system checks out ok. It has plenty of power and everything else is working well.

Here is a list of the codes in numerical order: P0232; P0301; P0302; P0303; P0307; P0380; P0500; P0541; P0670; P0684; P0721; P0732; P0781; P0782; P1000; P1105; P1106; P1107; P1211; P1760..The general consensus from a few mechanics is that I have an electrical problem and possibly a bad ground. Does this sound like my problem? How many ground cables are there and where are they located? Any suggestions would be greatly appreciated. I need to be on the road with my trailer in a few days and do not want to break down and hurt expensive parts. Also, driving short distances without a trailer do you think it would hurt anything? Thank you in advance. I am in So Cal (Los Angeles/Orange County area)

 

Are you sure that it's not shifting 1-3?

Not saying that your problem is intermediate sprag related, but it's a common failure. These transmissions use a mechanical one way clutch to perform a 1-2 upshift and if it fails, the transmission will lose 2nd gear in the normal "OD" range. The PCM commands 2nd, but nothing happens until the vehicle speed is high enough at a given accelerator pedal position to command 3rd gear at which point, it shifts to 3rd (often mistaken for 2nd) and after that the transmission appears to be normal.

Here's a question: When you finally get the transmission to upshift and let off of the accelerator a little (say 28-30 MPH), then get back on it (to force a 3-2 downshift), does it feel like neutral and just rev up? Also, does shifting to "2" on the lever give you 2nd gear?

 

Excellent points..i will check and.report back..thank you fkr your advice..greatly appreciated

 

Here is an update as of today: Most of the time it shifts from 1st to 2nd...however if the RPM shift point in first is a little higher (3500 rpm vs. 3300 ish) it seems to maybe hit 2nd for a second then into 3rd...Manually upshifting does not work...but manually downshifting does work into 2nd. I did a electrical parasitic draw test by disconnecting both positive terminals and putting a test light from the + battery terminal to one of the + cables and the light comes on dim..I pulled one fuse at a time from all the fuses and relays under the steering wheel and under the hood and the light stayed on each time...I did not leave the fuses out after each one, I reinstalled each one after each test. Some videos on youtube recommend disconnecting the Neg. terminals for this test...dont know if it makes a difference or not. Whenever I connect the test light on the POS. term/cable there is a light buzzing noise coming from the ignition switch area or under the dash below the radio or ?? I disconnected the emergency flasher/blinder assy. and the noise stayed the same. I think the noise stayed the same with the ignition switch out (but Im not sure if I checked it this way)...ONE BIG QUESTION I HAVE: if i pull my one car 24 foot enclosed trailer and drive 2k miles, do you think I can hurt the trans.? Give me your best (educated) guess, I will not hold you responsible if I blow up the trans....thanks again for any advice..Ron

 

Yes, I think you will blow up the trans.

To fix this you're going to need to look at data to see what's happening. Get Forscan at www.forscan.org. You can monitor live data with this. You need to look at commanded gear and actual gear ratio. This will tell you exactly what's happening in the trans.

 

I wrote a tune for a guy 5-6 years ago that skipped 2nd gear when his intermediate one way clutch took a dump but he didn't have money to fix it. I never heard back about how long he ran it that way but I know it worked for a while.

I think that if this is your failure and it's not a fragmentation grenade failure, it would probably run a long time......but not fun to drive and there's no telling if it would cause a failure in 5 miles or 5000 miles. Once the transmission is in 3rd or 4th, the one way clutch isn't doing anything; the times that the intermediate clutch applies and tries to utilize it to stop drum rotation though......it might catch one more time and BOOM!