Help! My van clunks into 2nd gear

[Cyclist1]

I am hoping someone here can help me diagnose my troubles with my van. I have a 2012 Express AWD passenger van, with a torsion key lift and 265's for my tires. Just recently while driving home my van started to hesitate while shifting from 1st into 2nd. This happens only after I accelerate from a stop, reach about 20km an hour, slight hesitation then feels like it clunks/slam into second. This seems to happen only after I've been driving for a while, once the van warms up. The gear changing is normal and smooth at other times.
I have taken my van to a mechanic, and of course it drives smoothly when he takes it for a spin. They checked all fluids, bearings and ujoints and everything checked out ok. Unless it happens while the mechanic drives my van, they said there's not much they can do.

Anyone here have this happen to their vehicle? Looking for options on where to go from here.....

Thanks in advance for any help!

 

[Bikersmurf]

Park it at the mechanics overnight and let him drive it first thing in the morning.

 

[Mwilliamshs]

Miles, maintenance on the van?

Entirely different equipment I know but this sounds exactly like the behavior of a Ford AOD whose Torque Converter has developed the famous "flutter" due to the fluid & filter being changed too infrequently. Not saying it's behind schedule per se, but possibly behind need. Had another case of this in a Jeep AISIN trans which are very very reliable but it was used without regard to temperature and started the slip/bang 1-2. Both the AISIN and AODs were drain/fill, pray, rebuild cases but a likewise neglected 4L80E recovered wonderfully with just a drain/refill and a little Lucas Trans Fix (or whatever they call theirs). Heard several folks praise the Lucas Trans juice, including Jp magazine, and never heard it cursed. I'm typically very skeptical of snake oil and ez fixes but whatever unicorn tear/leprechaun sperm mixture Lucas uses has worked for me.

 

[Cyclist1]

Thanks for the input!
Unfortunately I can't park it at the mechanics. It's my only vehicle and I live in a rural area. So if I need to leave it longer than a day I'll have to get a rental vehicle.

As for the maintenance, I pretty sure I have never done the torque converter fluid and filter. I'm the second owner and picked up the van with 28,000 km's on the clock. I now have 94,000. I've done the regular oil changes, diff fluids, etc... with the basics.

Also another concern of mine is whether or not it's ok to drive for the next few days. I've got about 400km of commuting to do from now until Xmas.

 

[boardrider247]

Cyclist I did send you a PM with some info. Probably not all that helpful though:ylsmoke:

I am 95% certain these 1/2T AWD vans all use the 4L60E transmission. I believe GM sells them as a "no service" transmission. that said I did have mine flushed at about 80K and still have the occasional hard 1st/2nd shift. I may give the lucas stuff a try as I have also had good experiences with their products.

 

[Cyclist1]

Cyclist I did send you a PM with some info. Probably not all that helpful though:ylsmoke:

I am 95% certain these 1/2T AWD vans all use the 4L60E transmission. I believe GM sells them as a "no service" transmission. that said I did have mine flushed at about 80K and still have the occasional hard 1st/2nd shift. I may give the lucas stuff a try as I have also had good experiences with their products.

Hey!
Yes i did just get your pm. Thank you for your insight. I'll try the transmission flush and the Lucas stuff. Hopefully that'll help.
The problem does seem to be periodic. Today I've been out running errands and smooth shifting all day. Whereas yesterday, most of the afternoon the van was doing the harsh shift.

 

[instantkarma]

From what I have read, the 4L60E will increase the line pressure in the system after a slip is detected to prevent any future slippage, which causes firm shifting. It normally happens on mine after a long highway drive. If I clear the faults on the ecu when driving, it immediately goes back to shifting smoothly.

 

[Stroverlander]

There are shift kits you can purchase to help with delayed 1-2 shift like the Transgo 4L60E-HD2, Sonnax etc. There are plenty of videos that walk you through the shift kit install.

I'd also recommend the largest transmission cooler you can fit.

 

[tgreening]

I experience most of those symptoms myself, including the diappearing act when I go to get them checked out. My doc says not to worry, it's just a sign of getting older.

 

[Cyclist1]

Thanks everyone for posting up your replies and suggestions. So far the van has been shifting smoothly for the past 2 days. Had a long commute yesterday of mostly highway driving and still shifted smoothly after being warmed up. I did add a bottle of the Lucas Transmission fix fluid. So fingers crossed that the problem has now gone or at least minimalized. I'll post back here in a few days to let you all know whether the Lucas fluid fixed the problem or not.
Thanks again for your help!

 

[LYlqoY2Fo]

Just throwing this out as an FYI. Might be related, might not. From my 2008 Express AWD Manual...

If your vehicle has StabiliTrak®, it combines anti-lock brake, traction and stability control systems and helps the driver maintain directional control of the vehicle in most driving conditions.

When you first start your vehicle and begin to drive away, the system performs several diagnostic checks to ensure that it is working properly. You may hear or feel the system working. This is normal and does not mean there is a problem with your vehicle. The system should initialize before the vehicle reaches 20 mph (32 km/h). In some cases, it may take approximately 2 miles (3.2 km) of driving before the system initializes.

Mine shifts hard from 1st to 2nd every morning leaving my house. After a couple minutes, all is good.

 

[Cyclist1]

Hey All!
So it's been awhile since I've posted in this thread. Here's a little update as to what is happening with my problem.....

My hard shifting problem has not gone away. Since it first started, it only happened occasionally. Never consistent. So recently in the last couple of weeks the problem has become consistent. After about 50-80 km of driving, the hard shift happens. Then persists for the rest of the day. So I took my van in to a transmission shop and they scanned the computer for trouble codes. Turns out a trouble code, P0717 has been stored. It's a faulty sensor in the transmission. Input/Turbine Speed Sensor. The transmission shop suggested I take it to the dealer because it should be covered under warranty, it's part of the powertrain warranty. If it's not covered under warranty, I'm looking at about $1000 job. $80 for the sensor and approx 10hours of labour to replace it. Unfortunately the transmission will need to be removed and partly dismantled to get at the sensor. Fingers are crossed that the "stealership" will cover it under warranty.

 

[GHI]

I have a 2011 Express and received a letter from Chevrolet in February 2015. I'm not sure if the information is helpful or related to your issue, but here is some of what it said.

"Some 2011 model year vehicles may have been built with a condition in which high duty cycle use while pulling trailers etc. can exceed the target energy input to the clutch. This may lead to a faster torque converter clutch friction material wear than expected. Some operators of vehicles with this condition have reported a driveline vibration or shudder feeling."

It says they will fix it via Chevy dealership within 10 years of original purchase date or 120,000 miles.