Hello,
I’m sorry about my first post being a novel but I’m looking for a little assistance and I figure the more info the better.
2002 Chevy Silverado 4X4 - VIN# 1CGHK23G92F117982 (PCM VIN: 1GBJC39G71F100063 appears that the PCM has been replaced at some time before I bought the truck)
8.1L GAS with a Allison 5spd transmission, 135,000 miles
I’ve owned it for 4 years and just over the last month it has started to intermittently throw a P0776 code.
What trips the code:
Cold start in the morning (I'm in S.E. Michigan) OR after sitting a few hours in cold weather. I remote start the truck, let it run for about 4-5min. Get in and drive to the nearest main road about 5 blocks away, no problems but I only get to 3rd gear and about 30mph. I get on the main road and try to accelerate up to around 50mph. About 75-80% of the time it will try the 3-4 shift but only for a brief second and then it will shift back to 3rd and stay in 3rd. Engine light will come on and it will stay in 3rd even if I come to a complete stop. I can shift to park, reverse, neutral and drive. They all work except drive is only 3rd gear. I have to come to a stop, shift to park , shut the engine off, restart and then put it in drive and it will then almost always shift normally through all gears up to 5th. The problem pretty much won’t happen again until another cold start (at least 3 hours in cold temps).
This morning it was fine starting and getting on the freeway (got to 5th) drove 10 miles to work and shut it off. Came out 3hrs later (35deg outside) cold start, drive a few blocks to the freeway without a problem but might not of gotten to 4th gear by then. Turned on to freeway on ramp, trans shifted normally until the 3-4 shift and it acted up. Acted like it wanted to go to 4th but settled back to 3rd and the rpm’s were up there. I pulled off at the next exit, pulled over and placed the shifter in park, shut the engine off, restarted and drove away, got back on the freeway and it shifted fine up to 5th. Most of the time it will not acted up after the first initial 3-4 shift/restart. I’m pretty sure I can drive it all day stop and go and it not act up again until a cold restart.
I replaced the SOF as soon as the problem started with no change. I do not accelerate fast, I don’t tow with it. It hasn’t been “hopped up” in any way. I actually baby the truck. The problem can happen in 2wd or 4wd and with tow/haul button on or off. I have a OTC Genisys EVO that I can hook up and monitor the sensors but I need to know what to look for.
From some of the threads I’ve ready I should:
Watch the output speed sensor for drop outs or glitches (Should I / Can I compare the OSS output to other sensors at the same time to help diagnose?)
Pull out the rear most transfer case mounted output speed sensor and stick my pinky in the hole to see if that wheel is loose.
Any other suggestions?
Thanks,
Josh
Dearborn Heights, Michigan
By the way, here is my first attempt to "see" what was wrong. What do I need to load up on the screen to see at once.
I’m sorry about my first post being a novel but I’m looking for a little assistance and I figure the more info the better.
2002 Chevy Silverado 4X4 - VIN# 1CGHK23G92F117982 (PCM VIN: 1GBJC39G71F100063 appears that the PCM has been replaced at some time before I bought the truck)
8.1L GAS with a Allison 5spd transmission, 135,000 miles
I’ve owned it for 4 years and just over the last month it has started to intermittently throw a P0776 code.
What trips the code:
Cold start in the morning (I'm in S.E. Michigan) OR after sitting a few hours in cold weather. I remote start the truck, let it run for about 4-5min. Get in and drive to the nearest main road about 5 blocks away, no problems but I only get to 3rd gear and about 30mph. I get on the main road and try to accelerate up to around 50mph. About 75-80% of the time it will try the 3-4 shift but only for a brief second and then it will shift back to 3rd and stay in 3rd. Engine light will come on and it will stay in 3rd even if I come to a complete stop. I can shift to park, reverse, neutral and drive. They all work except drive is only 3rd gear. I have to come to a stop, shift to park , shut the engine off, restart and then put it in drive and it will then almost always shift normally through all gears up to 5th. The problem pretty much won’t happen again until another cold start (at least 3 hours in cold temps).
This morning it was fine starting and getting on the freeway (got to 5th) drove 10 miles to work and shut it off. Came out 3hrs later (35deg outside) cold start, drive a few blocks to the freeway without a problem but might not of gotten to 4th gear by then. Turned on to freeway on ramp, trans shifted normally until the 3-4 shift and it acted up. Acted like it wanted to go to 4th but settled back to 3rd and the rpm’s were up there. I pulled off at the next exit, pulled over and placed the shifter in park, shut the engine off, restarted and drove away, got back on the freeway and it shifted fine up to 5th. Most of the time it will not acted up after the first initial 3-4 shift/restart. I’m pretty sure I can drive it all day stop and go and it not act up again until a cold restart.
I replaced the SOF as soon as the problem started with no change. I do not accelerate fast, I don’t tow with it. It hasn’t been “hopped up” in any way. I actually baby the truck. The problem can happen in 2wd or 4wd and with tow/haul button on or off. I have a OTC Genisys EVO that I can hook up and monitor the sensors but I need to know what to look for.
From some of the threads I’ve ready I should:
Watch the output speed sensor for drop outs or glitches (Should I / Can I compare the OSS output to other sensors at the same time to help diagnose?)
Pull out the rear most transfer case mounted output speed sensor and stick my pinky in the hole to see if that wheel is loose.
Any other suggestions?
Thanks,
Josh
Dearborn Heights, Michigan
By the way, here is my first attempt to "see" what was wrong. What do I need to load up on the screen to see at once.
