2007 LT with shudder when braking

[eqppwqqep]

Hi there, new member. I searched "converter", "shudder", and "rumble" to see if this topic had been discussed and it appears it has not been asked at least in this sub forum. Thanks in advance for any answers or help

My 2007 LT2 has 140k on it. Recently, it started doing this shudder type thing when you are coming to a stop. It feels like a manual transmission car in 4th gear starting to stall, but it never stalls. It's almost like running over rumble strips. I had the transmission fluid and filter replaced a month ago. Nothing else except maintenance done to the Tahoe. New cats, new brake pad/rotors, new brake light switch.

Any ideas? It does NOT do it when in tow mode...which makes me think converter. Stall speed test hit 1600 RPM

Thanks again

 

[OR VietVet]

Hi there, new member. I searched "converter", "shudder", and "rumble" to see if this topic had been discussed and it appears it has not been asked at least in this sub forum. Thanks in advance for any answers or help

My 2007 LT2 has 140k on it. Recently, it started doing this shudder type thing when you are coming to a stop. It feels like a manual transmission car in 4th gear starting to stall, but it never stalls. It's almost like running over rumble strips. I had the transmission fluid and filter replaced a month ago. Nothing else except maintenance done to the Tahoe. New cats, new brake pad/rotors, new brake light switch.

Any ideas? It does NOT do it when in tow mode...which makes me think converter. Stall speed test hit 1600 RPM

Thanks again

Although you can get a bad new brake rotor, when I first read this I thought you could have a warped rotor. Sounds like a torque convertor clutch problem. Any codes?

 

[eqppwqqep]

No codes and rotors have been replaced and are true. Converter stall speed test has the rpm at 1600. Converter locks up fine in drive

 

[Clean07Burb]

Had the trans fluid ever been replaced prior to the recent flush/exchange, or had the trans never been touched in its 140k mile life? I've seen many higher mileage vehicles that haven't had previous transmission service/maintenance done start having problems shortly after a service.

 

[eqppwqqep]

Had the trans fluid ever been replaced prior to the recent flush/exchange, or had the trans never been touched in its 140k mile life? I've seen many higher mileage vehicles that haven't had previous transmission service/maintenance done start having problems shortly after a service.

It had been serviced regularly and I decided to do it this time due to the shudder. I am almost fully convinced it is the AFM. I noticed it only happens V4 mode. I can off the highway on to a steep off ramp today and it stayed in V8 until I stopped and never shuddered. If I am coming to a stop, I can catch it shudder and hit tow mode and it stops. It will only happen when RPM dips below 600 so it's either a sticking TCC or the AFM is trying to idle in V4 mode and it catches on and corrects itself. It is way too consistent in behavior in my mind to be a sticking converter. Maybe a tune up is in order? Transmission shop said the transmission looked good and everything checked out. Other than this shudder the shifting and idle is smooth....

Sorry this took so long to write...I was staring at your avatar

 

[eqppwqqep]

I did some messing around on the drive to work this morning.

Test 1 - In D, normal driving, normal stop - When I get to about 15MPH, the truck is in V4 and tries to idle at 500-600RPM when the shuddering starts.

Test 2 - In Tow Mode, normal stop - When I get to about 15MPH, the truck is in V8 and about 800-900RPM, no shuddering.

Test 3 - In 3, normal stop - When I get to about 15MPH, the truck is in V8 and about 600RPM, no shuddering.

 

[AZSCTACO]

Mine did that before I had the AFM turned off during my tune. Good luck

 

[Clean07Burb]

It had been serviced regularly and I decided to do it this time due to the shudder. I am almost fully convinced it is the AFM. I noticed it only happens V4 mode. I can off the highway on to a steep off ramp today and it stayed in V8 until I stopped and never shuddered. If I am coming to a stop, I can catch it shudder and hit tow mode and it stops. It will only happen when RPM dips below 600 so it's either a sticking TCC or the AFM is trying to idle in V4 mode and it catches on and corrects itself. It is way too consistent in behavior in my mind to be a sticking converter. Maybe a tune up is in order? Transmission shop said the transmission looked good and everything checked out. Other than this shudder the shifting and idle is smooth....

Sorry this took so long to write...I was staring at your avatar

Maybe this is your problem (see what I bolded in your quote above). Your truck shouldn't be trying to idle BELOW 600 RPM. That's about where mine idles consistently, but anything lower than that and I can see where you'd feel it hesitating/trying to stall, etc.

And if you seriously think its the AFM malfunctioning by remianing in V4 for way too long, try disabling it with a tune or the Range Technologies AFM delete.

 

[eqppwqqep]

Maybe this is your problem (see what I bolded in your quote above). Your truck shouldn't be trying to idle BELOW 600 RPM. That's about where mine idles consistently, but anything lower than that and I can see where you'd feel it hesitating/trying to stall, etc.

And if you seriously think its the AFM malfunctioning by remianing in V4 for way too long, try disabling it with a tune or the Range Technologies AFM delete.

I agree....I just think it's either the TCC stays engaged and lugs the engine or the AFM doesn't kick back in soon enough. My test this morning seems to make me believe that AFM is the problem. If it is not in V4, it doesn't ever happen. Range V8 is on the way

 

[992dr]

15mph? It's od that it happens at such a low speed. I can see it happen when your TC locks up in 3rd but, 15mph huh.

I'm having a very similar situation with mine but it happens in OD when the TC locks up.

I am very curious to know how the Range devise works.
Please post an update or throw something up in the Tech section of the forums of your thoughts and a small review of it. I'm going to get my tuned flashed back to stock because of the jacklegs who "tuned" my truck screwed something up, it has not driven the same since. I'm going Dec 23rd for the re-flash.