2006 2500 HD Tranny Hard shift after driving

QwickerRon · February 11, 2014

Have an 06 2500 HD w/123K miles. Transmission will drive all day long at speeds under 50 mph and never shift hard. If I drive 7-8 miles at 65-70 mph, like on the interstate, once I slow down and stop and start again, tranny will shift hard between 1, 2 and 3rd. Once I park it for 15 minutes, it's back to normal and no hard shifts. Tran temp gauge does not indicate any overheating. As long as I'm putzing around at speeds under 50, I can drive all day long and never a hiccup. Fluids are okay

Doug_Scott · February 11, 2014

Could you be possibly accelerating harder after getting off the highway, then pulling away from full stop? I have noticed a long time ago, that my driving habits are different after getting of the highway, and driving surface streets. Sort of like how driving at 30mph after running on the highway at 70mph feels so slow.

Have you tried using trailer/tow mode to see if it behaves the same way?

Your truck have the Allison trans?

QwickerRon · February 12, 2014

Not an Allison. I have not tried trailer mode but will try that today. Mr Transmission said I needed to replace the entire transmission. Two other tranny shops say they've never heard of it before. One said perhaps the MAS sending erroneous info to the computer. Just too many tranny shops out there looking for a reason to sell me a 2500.00 tranny. Have a trans shop I'm taking it to next week for more diagnostics to see what they think. A real lack of trust with transmission shops. I'd like some sense of what's going on before taking it

Doug_Scott · February 12, 2014

Have you considered taking it to the dealer? If you have a dealer nearby that sells a lot of the 2500/3500 series trucks they may also have an experienced transmission mechanic.

From what I have seen at transmission shops is that they may have experience on many transmissions, they tend to only really have useful experience on the poorly designed transmissions. By poorly designed I mean the transmissions that seem to fail on a regular basis. The transmission mechanic at the dealer should have useful experience in the repair of the same transmission you have.

A transmission shop that says you need a complete transmission is not actually diagnosing your issue. They are hoping that something is not right inside your transmission, and that replacing the assembly will correct it. They do not actually rebuilld anything in-house, they simply order a replacement trans from head office, and send your complete trans back as a core for the next rebuild.

I don't have any first hand experience in how transmission rebuilds are handled at the dealer level these days, but, it used to be that they would rebuild the transmission that came in. At least I know that I did that. Back then there were only the two automatics, the 904 and the 727.

QwickerRon · February 12, 2014

Check engine light came on and it was throwing a P0894 code. Did try trailer mode but no change in hard shift. That's just a internal slip code so still not sure what it is. Taking for diagnostics test tomorrow morning.

Suspect torque converter.

QwickerRon · February 12, 2014

Thanks. Taking it to my dealer Tuesday morning who says they have an excellent transmission mechanic.

oldscsc · February 12, 2014

Interested to hear the verdict. My parents had a Suburban with the 4L60E that had identical symptoms to the ones you're experiencing. It ended up being traded in before it was diagnosed.

gmtech4 · February 13, 2014

Check engine light came on and it was throwing a P0894 code. Did try trailer mode but no change in hard shift. That's just a internal slip code so still not sure what it is. Taking for diagnostics test tomorrow morning.

Suspect torque converter.

you have a 6.0 liter with a 4l80e right ?

what is the oil condition ?

i was a tranny guy for awhile at a dealer and if the oil is dark at all,for this code ,it would be a rebuild ,,,

its either TC related or 4th clutch ,,,,i rebuilt a ton of these trannies ,,,,and the 60 's lol

Edited February 13, 2014 by govtech4

Doug_Scott · February 13, 2014

I have zero experience on these transmissions, but, near as I can tell, the only way the TC could cause a hard shift (hard meaning fast, no slip, shift kit type of shift) is if the lockup in the TC is not releasing. Is the lockup part of the converter applied hydraulically or electrically? Is the release of the lockup done just by releasing pressure or is it an actual shift event (like solenoid applied, and solenoid released)?

gmtech4 · February 13, 2014

I have zero experience on these transmissions, but, near as I can tell, the only way the TC could cause a hard shift (hard meaning fast, no slip, shift kit type of shift) is if the lockup in the TC is not releasing. Is the lockup part of the converter applied hydraulically or electrically? Is the release of the lockup done just by releasing pressure or is it an actual shift event (like solenoid applied, and solenoid released)?

a solenoid does it ,,,,,hard shifts are also a default when a code is present (max line pressure)

i know what your thinking doug ,,,i had my TCC on a switch on my old 93 ,when it forgot about it and slowed down or punched it up a gear ,,,it was not good is all im gonna say lol

Doug_Scott · February 13, 2014

a solenoid does it ,,,,,hard shifts are also a default when a code is present (max line pressure)

i know what your thinking doug ,,,i had my TCC on a switch on my old 93 ,when it forgot about it and slowed down or punched it up a gear ,,,it was not good is all im gonna say lol

When Chrysler first brought out the lockup convertor in late 70's it was basically a hydraulic clutch. I had a buddy that was running a 69 340 Dart with a 4 speed and 5.38 gears. He had a hard time getting the shift right every time. For some reason, he would move both arms when he shifted, the 1-2 shift was also a left turn. He wanted me to build him a 727 with manual shift valve body. He was a machinist/millwright with access to the necessary machines. Between the two of us we built a 727 with manual control over the convertor. These transmissions have zero electrics in them. Broke a few converters on the 1-2 shift at 7200rpm. Car should have had a higher stall convertor, but, that seemed counter-productive to me. With the gears, and light weight, engine was not long at low rpm anyways. Weak point was the convertor, but the "never miss a shift" convinced him to go to a clutch-flyte trans. Now that was a slick setup.

laborde2122 · December 24, 2019

On 2/11/2014 at 5:42 PM, QwickerRon said:

Have an 06 2500 HD w/123K miles. Transmission will drive all day long at speeds under 50 mph and never shift hard. If I drive 7-8 miles at 65-70 mph, like on the interstate, once I slow down and stop and start again, tranny will shift hard between 1, 2 and 3rd. Once I park it for 15 minutes, it's back to normal and no hard shifts. Tran temp gauge does not indicate any overheating. As long as I'm putzing around at speeds under 50, I can drive all day long and never a hiccup. Fluids are okay

Was this solved? I have a 1500 with identical issues. Paid for a rebuild. They then replaced other things. Then got me a new transmission. Still same thing as you. Only shifting hard after highway speeds and resets if I turn the truck off.

help!

bhart00 · July 26, 2021

I have a 2005 Silverado 2500hd with about 123,000 miles on it with similar issues. I’ll drive it for about 15 minutes going about 45-50mph but once I stop and then accelerate again it will start to shift hard the rest of the way to work. And then once I leave or take lunch it’ll shift beautifully. Also throwing code P0894.