Transmission 'disengages' while stopped in Drive

[Jmac509]

I just wanted to post a follow up. My transmission has done it a few more times where I get a grinding noise like gears wont mesh together or the clutches are slipping in first gear then it finally catches and takes off.

It's an intermittent issue so I hope they can find something to fix.

I'll keep everyone updated after the service. If it happens again after the service, I'll start a new thread.

Fingers crossed they can fix it.

 

[Jmac509]

I picked up my truck from service and they said they could not reproduce it and the transmission isn't throwing any codes so they have nothing to fix.

They said they reflashed the TCM, and it does appear to shift softer however I'm still getting the hard shifts and clunks from a dead stop.

Just a theory but I'm wondering if the transmission is losing pressure while the engine is off and when it kicks back on it takes a few moments for the pressure to build back up and then it's slamming into gear.

 

[lamerem]

This has been plaguing me for 2 years now. I've had it in and out of the shop multiple times. First the harsh shift, then the clunk. They determined the clunk was the nut on the spline adapter going in to the rear end had come loose. The replaced the nut and retorqued it. They then reset the transmission control module and all was well for 50 or so miles. The clunk was no longer there, however, the reset is what cured the issue. I know this because I've reset it a few times since.

The transmission does not have this hesitation or harsh shift when in tow/haul mode. Also, I can tell when it's disengaged when sitting at the stop light. If I keep pressure on the brake and apply a little gas, the truck reengages the transmission. This leads me to believe there is a transmission fluid pressure issue. Additionally, tow/haul mode downshifts to allow the transmission to slow the truck down. Therefore the truck is already in first gear before coming to a stop. Under normal conditions, I believe it coasts to a stop in second gear, changing to first once stopped.

I'm going to do a transmission fluid fluid and filter change over the winter. Just sucks that we have to change the entire pan as the filter is integrated.

 

[Jmac509]

Let me know if your situation improves. Today taking off from a stop light I had the grinding noise all through first gear and then into second where it felt like the transmission clutches finally grabbed.

 

[lamerem]

I’ve not yet serviced the transmission, however, I am going to order a new pinion flange. Perhaps when the original nut came loose, the spines somehow wore down causing too much slop. The dealer is not willing to do it, so I guess I have to pay for this myself. I have 55k on the truck and its 25 months old.

 

[Jmac509]

Let us know if it improves your situation.

I'm still under the theory that when the engine is off during the start stop all the pressure bleeds off the transmission and it tries to engage the clutches with low pressure on take off causing the clutches to slip. I'm getting noise and a feeling like the clutches are slipping when taking off in first then into second where they finally grab and the growling noise stops.

It still runs and drives fine the other 90% of the time so I'm just waiting to see if something actually breaks since I'm still under warranty.

 

[vincentw56]

Let us know if it improves your situation.

I'm still under the theory that when the engine is off during the start stop all the pressure bleeds off the transmission and it tries to engage the clutches with low pressure on take off causing the clutches to slip. I'm getting noise and a feeling like the clutches are slipping when taking off in first then into second where they finally grab and the growling noise stops.

It still runs and drives fine the other 90% of the time so I'm just waiting to see if something actually breaks since I'm still under warranty.

I don't think your theory is true because I have no issues with mine like your describe. No issues actually.

 

[Jmac509]

I don't think your theory is true because I have no issues with mine like your describe. No issues actually.

I'm glad your truck is working as intended. I wish our trucks could be without issues as well.

I want to say the majority of the time the truck drives as it should. But I definitely don't think a grinding growling noise taking off from first and a harsh shift into a second where the growling continues until the rpm and speed finally sync up and it stops is normal. Definitely feels like the clutches are slipping. The intermittent aspect to it is frustrating since the dealer is unable to replicate the problem to diagnose it.

 

[vincentw56]

I'm glad your truck is working as intended. I wish our trucks could be without issues as well.

I want to say the majority of the time the truck drives as it should. But I definitely don't think a grinding growling noise taking off from first and a harsh shift into a second where the growling continues until the rpm and speed finally sync up and it stops is normal. Definitely feels like the clutches are slipping. The intermittent aspect to it is frustrating since the dealer is unable to replicate the problem to diagnose it.

Didn't say it was normal. Just said that I doubt it is because of the start/stop system when it is working properly because mine doesn't do that. I think there is definitely something wrong with your transmission of it is making that noise and it is independent of the AS/S system.

 

[Jmac509]

I definitely agree with you, I think this is 100% a transmission problem.