Transmission downshift issue

[childo74]

Hey guys, new to this forum, so if I'm posting in the incorrect place, please forgive me.

 

I just picked up a used 2016 crew cab with the 5.3 & 6-speed tranny. Funny thing happens on the interstate when I give it enough throttle to downshift. The RPM's will jump up past where they should be in that particular gear, and then settle down a little bit. This really kills momentum when pulling my boat on the interstate. Here is the video:

 

 

[Mark Diedrich]

So I'm confused, is it dropping 2 gears instead of one?

Your only jumping 500 rpm....

[Mark Diedrich]

Won't the rpm jump by however much throttle input you give it to change that gear or gears?

So if you step on it harder, more gears and you might be at 4000-5000rpm....

[JimCost2014]

if you are going down an incline, you might be experiencing the grade braking system.

[Mark Diedrich]

I thought he said he was giving it throttle....

[JimCost2014]

Looks like he did. The way the tach was jumping looks like the grade braking downshifts.

[childo74]

No, no incline. So, I'm on the interstate, and I need to increase speed a little bit. I give it a little throttle, enough to go down a gear. When it downshifts, you can see the RPMs go up, and then come back down a little bit. In the video, I do it 3 times. On the 3rd time, it shifts down 2 gears. When it downshifts, that tach goes above 3,000 rpm, and then it goes back down under 3,000 rpms. It kinda reminds me of when you are driving a manual transmission, and you don't have your footwork just right. When you downshift, you have the clutch pushed in and give it too much gas, the rpms jump, and then when the clutch is let out enough, they come back down. I hope this makes it a little more clear...Sorry for the confusion.

[Donstar]

Is this concern based on similar testing with other vehicles you've owned? I couldn't see or hear anything extraordinary based on your video. If you think your transmission is faulty, you have plenty of warranty. Maybe take it to an objective third party transmission shop for a no-obligation professional opinion. RPM's do fluctuate based on road and wind conditions. Sections of roads may appear flat but are on an incline or decline. Welcome to this forum and enjoy your new truck!

[childo74]

I e just always experience that when a vehicle downshifts, it goes directly to the rpm that it should be running, and takes off from there. In this instance, when the truck downshifts, the motor revs a little past where it should be, and then comes back down to the correct rpm. Kinda like its not going immediately into gear, and its letting the motor rev a little past. Almost like the transmission is slipping a little when downshifting.

[GMcD]

Lets remove what the tach is doing out of the equation. Does the truck feel as if its not accelerating correctly or if the transmission is slipping/not shifting correctly?

[childo74]

It just feels like its losing a little momentum when the rpms go back down, especially when I am towing my boat or a heavy load. Again, if you can imagine, its like your footwork isnt right when driving a manual, you feel a little surge since the rpms jumped up, but when the clutch fully engages, it feels like it loses a tad.

[SteveCZ]

Sounds like torque converter lockup. It unlocks briefly then settles back in. Mine does it going up a hill in either third or fourth gear. Less noticeable now that it has fresh fluid in the tranny

[Mark Diedrich]

I was thinking torque converter also, locking/unlocking....... Just no idea from the video if it's normal.....

[garagerog]

A couple of observations and questions from the video, you will get the minor (maybe 100-200 rpm) fluctuation reading on the tach as the previous 2 posters have mentioned due to the TC unlocking then locking again, the big rpm drop was probably the transmission upshifting as your throttle input is not holding the transmission in the lower gear. The video was shot while the transmission was in D, might try the same test in M5. Now the questions to the OP about towing the boat on the interstate, are you using tow/haul mode and/or the Manual mode or D?