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RPM fluctuating

MrNasty
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MrNasty Enthusiast

MrNasty

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I have have noticed that my needle in the RPM gage is fluctuating. I cant feel the truck surging but I can hear it in the exhaust. Has anyone else experience this issue? Truck seems to run fine otherwise. It does it when I get up to speed like 50 or so and I level off and stay at that speed for a bit, then needle starts to pulse up and down and I can hear the exhaust note change.

 

 

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mookdoc6 Senior Enthusiast

mookdoc6

Posted
Posted

Your a feather foot! You will not notice if your RPM's are higher....It will always do it because its part of the deal with v4/8 switching. Other option is defeat the V4 or go with a FERD ecoboost? I would recommend you go with tune or stay in manual Mode to defeat the V4!

MrNasty Enthusiast

MrNasty

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I do have the V4 turned off. If i keep it at a steady speed is when the needle jumps up and down. I haven't gotten on the freeway and checked it out yet. I heard it in the exhaust first and then started to pay attention to the rpm once I heard it and saw it jumping up and down. Its not a lot but its moving. I dont know if its its been doing it the whole time I have owned the truck or just started because you cant really feel. Just hear it then see it in the gage. Figured I would have dealer check it any way. Im sure they will say its normal at guys have had some obvious problems and dealers seem to blow them off, but worth a shot.

 

 

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lba0213 Enthusiast

lba0213

Posted
Posted

Mine started this way. Now I have full on shudder when the needle jumps. Do you feel any vibrations when the needle jumps? The tach is jumping bc the torque converter isnt working properly. Do you have an 8 speed?

truckguy82 Senior Enthusiast

truckguy82

Posted
Posted

Mine started this way. Now I have full on shudder when the needle jumps. Do you feel any vibrations when the needle jumps? The tach is jumping bc the torque converter isnt working properly. Do you have an 8 speed?

if it's a '15 6.2, he has an 8speed

Towerhog Enthusiast

Towerhog

Posted
Posted

I had a shudder in the truck when under a slight load (slight uphill), and the RPM's would fluctuate at that time.

 

The dealer replaced the torque converter and fluid. No more shudder and it drives smooth.

Billy346 Enthusiast

Billy346

Posted
Posted

I noticed my truck doing the same thing when I bought it. RPM's would fluctuate when the transmission was in a higher gear with the engine in a low RPM and under load. (Also called "lugging")

 

I did some research and found out that this is normal for GM trucks. The torque converter unlocks momentarily, causing RPM's to rise, sending more power to the rear wheels. The torque converter then continues locking and unlocking, causing RPM's to fluctuate until speed increases, you let off the gas, or the transmission downshifts. It does this to avoid downshifting while lugging. I'll admit that I thought it was a little strange the first time I noticed it.

 

My last truck was a Ford F-150, which behaved differently. Instead of the RPM's fluctuating, the transmission would downshift at the slightest increase of pedal pressure when going uphill. It had a 4 speed transmission, so when it would downshift, it really downshifted. I'll admit, I find the RPM fluctuation in my Chevy less annoying than the overly sensitive transmission in my Ford.

lba0213 Enthusiast

lba0213

Posted
Posted

Mine is no slight sudder, the steering wheel shakes hard enough to jingle my keys. Feels like going over rumble strips. Ive had the converter replaced but it fixed nothing. Theres always a chance the tranny tech, did a poor job though.

MrNasty Enthusiast

MrNasty

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So far I dont feel anything in the truck. I only started to notice it because the exhaust I installed you can hear the exhaust note change. So then i started watching the tach and speedo to see if something was wrong. Once you level the speed and are cruising the tach starts to bounce up and down. Just slightly but you can see it. I will try to shoot a short video tomorrow and see if I can post it. I tried with AFM on and with it off and does the same thing. I have an appointment to take the truck in on Saturday so I will see what the dealer tells me. I have read posts from people with more serious issues than mine and there dealer tells them its normal, so Im not getting my hopes up.

 

 

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mookdoc6 Senior Enthusiast

mookdoc6

Posted
Posted

I noticed my truck doing the same thing when I bought it. RPM's would fluctuate when the transmission was in a higher gear with the engine in a low RPM and under load. (Also called "lugging")

 

I did some research and found out that this is normal for GM trucks. The torque converter unlocks momentarily, causing RPM's to rise, sending more power to the rear wheels. The torque converter then continues locking and unlocking, causing RPM's to fluctuate until speed increases, you let off the gas, or the transmission downshifts. It does this to avoid downshifting while lugging. I'll admit that I thought it was a little strange the first time I noticed it.

 

My last truck was a Ford F-150, which behaved differently. Instead of the RPM's fluctuating, the transmission would downshift at the slightest increase of pedal pressure when going uphill. It had a 4 speed transmission, so when it would downshift, it really downshifted. I'll admit, I find the RPM fluctuation in my Chevy less annoying than the overly sensitive transmission in my Ford.

Ok, this makes sense I would have to agree. Look at the new 6speed in Tacoma's compared to the previous 5speed. Owners are furious that you put it in Cruise mode and the slightest incline sensed and bamn back a gear! I do remember the Fords doing it now and I will take the RPM fluctuations if it keeps me from hunting gears!

MrNasty Enthusiast

MrNasty

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https://vimeo.com/190696634

 

The first big rpm jump is when it shifts into 8th gear. Then you can see the needle start bouncing. Its better or worse at certain speeds.

 

 

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15_silverado Enthusiast

15_silverado

Posted
Posted

I've seen my 2017 6 speed do the same thing. No shudder or noises; rides smooth, but I have seen the needle bounce exactly like yours in high gear (6th gear) at low rpm at constant light throttle.

I'm assuming it's normal, but please let us know what you find out from the dealer or anywhere else. Thanks.

MrNasty Enthusiast

MrNasty

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Perhaps it's the torque converter locking / unlocking.

Thats what another member said and hopefully thats all it is. Just want to make sure because I'm about to be in West Texas with my wife and there isn't any help for miles. I will post what the dealer tells me this Saturday.

 

 

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  • 4 weeks later...
Brandon5799 Enthusiast

Brandon5799

Posted
Posted

I'm going through the same issue now, dealer performed a service bulletin to flush the system and it still does the shuddering in 8th gear. I've noticed lots of guys lately have had similar issues around 10-15k miles. Everyone who's had the torque converter replaced has fixed the issue so mines going back into the shop for that next.

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