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2003 4l60e dropping out of OD

michael0584

michael0584

1/2 ton status
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Jun 7, 2005
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houston texas
I bought a 2003 suburban about 3 months ago with 155,000 miles on it. Everything has been fine on it till today on the way to work. It now has 160,000 miles on it. I noticed it seemed to be shifting a little later and when i got on the freeway it shifted to overdrive then starting dropping in and out of overdrive to 3rd. If I put the shifter in 3rd it stays in 3rd just fine. Its definitely dropping into 3rd and not the torque converter lockup. The rpm change is about 800rpms and when it drops out and I manually shift to 3rd there is no rpm change. At one point it was staying in OD and i pushed down the gas to see if it would downshift and the rpms shot up about 2000rpms, and speed did not seem to increase. Definitely felt like it was slipping and not a downshift. I did pull off the freeway and check the fluid level, it was in the hash marks and still looks pink. Maybe slightly burnt but not bad. I then killed the engine and cranked it back up and got on the freeway and it acted the same way. No service records on it but the drain plug looks like it has been removed before, so assuming it has at least had a partial fluid change at some point. Hoping this is fixable and not a complete rebuild. Any help is greatly appreciated.
 
[youtube]c7adLqXy-x4[/youtube]
Video is a little long so feel free to fast forward
 
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Loss of fourth gear and only fourth gear is usually a band that is slipping or a broken accumulator piston for 4th gear. With the miles that are on the truck it would be prudent to consider a rebuild if you intend to keep the vehicle a while.
 
Yeah, I am looking into rebuild options but was hoping for an easy fix. Looks like Century transmission is local and seem to have a good reputation. I'm also looking around on Craigslist and seeing what appear to be good rebuilds for half the cost of century. Just not sure which way to go. The suburban has a mild tune but I don't plan on doing alot of performance upgrades, but do plan on towing my travel trailer with it. So a mild upgrade from stock would be nice. Junkyard transmissions seem to run almost as much as the Craigslist rebuilds so doesn't seem worth it.

http://www.centurytransmission.com/econo-street-performance-transmission
http://houston.craigslist.org/ptd/5165326811.html
http://houston.craigslist.org/ptd/5138761445.html
http://houston.craigslist.org/ptd/5156728330.html
 
Century Transmission has a good reputation for quality, I would avoid the Craiglist rebuild if possible, that path is fraught with danger
 
So the 35 mile drive home was perfect. No delayed shifts, stayed in OD perfectly. So not sure what's up. I did notice it was idling a bit rough for a bit, but Trans was fine. It's also had an idle surge sometimes and I've assumed the intake gaskets are slightly leaking. Just waiting for it to throw a code before I replace them. That could be the cause of the rough idle yesterday. Maybe something stuck in the trans and caused it to mess up and when it cooled back down it unstuck? I will see how it does today. If it's fine I'm wondering if I should drop the pan and change the filter? Not sure if that would prolong it's life or potentially cause more problems.
 
Very uncommon for a gear to return like that unless the computer has shut down fourth and lockup because of an engine problem detected such as a Random Misfire. Get the vehicle scanned for codes and address the issue, you may have dodged the trans bullet.
 
Plugged up my scanner and no codes stored. Then connected my Diablo intune and data logged to view trans data. It shifted perfectly and held OD perfectly. Trans temp stayed around 150 degrees. Not sure what caused it to mess up but seems fine now. Crossing fingers it stays ok.
 
Oh and while I was data logging i noticed the engine temp would stay around 192 but would periodically drop and stay around 182-185. Looks like my thermostat may be sticking open. I'll order up a new delco and replace it. Maybe it stuck open and caused the temp to be really low causing issues. I know the temp will keep it from lockup but not sure about OD.
 
Well i've put on about another 100 miles and still shifting perfectly. No idea what happened that day but I will be replacing the thermostat.
 
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