Shuddering on Mild Acceleration L99 SS

[qcman]

Hi just like the title says I have minor shuddering I guess you can call it when the car is under light load at some highway speeds. Firstly I am told I have a bent front rim which I'm waiting to get sorted from my insurance from a curbing a couple months back.

Should be corrected soon but I don't think this is related somehow.... I just put new tires all around BFG Geforce Sport Comp 2's and they seem fine and were Road Force Balanced. But the guy noted my rim needs repair or replacing so I'm in the midst of correcting that. I noticed this shuddering before changing tires too.

I know its not the AFM (trust me on that...). I have read here of Torque Converter problems on V6 autos but nothing on the V8's so thats why I started a new thread. Basically at a constant speed if I accelerate lightly I feel a vibe in the gas pedal and the steering wheel to some degree. Nothing huge mind you. Could it be the torque??? I'm not going to get the car looked at until I sort the rim issue out to make sure it isn't from that but I can't see how it could be. I do get some shimmy from the rim at higher speeds if anything but its not throttle sensitive either.

Any help would be appreciated!

Thx,

Cam

[Rock-It Man]

Wait 'til the rim is fixed or replaced. The road force balance is worthless on the bent rim.

[RobertRS]

Get the car up to speed on a stretch of empty roadway , maybe a feeder road,where it shimmies and bump it into neutral and see if your problem persists.

[qcman]

Thx for the replies both of you. Yeah I'll get this rim thing sorted out and see if it has anything to do with what I'm noticing. I know that is a problem for sure right now so hopefully get that fixed in the next couple of weeks.

Cam

[d3ktrix]

I notice this with my L99 also, feels almost like the engine is lugging.
Only really notice it when the trans is in a high gear and traveling at slow speeds.

I've never had any computer updates done since I bought it in 09, so hoping maybe newer software can remedy it.

[qcman]

Originally Posted by d3ktrix

I notice this with my L99 also, feels almost like the engine is lugging.
Only really notice it when the trans is in a high gear and traveling at slow speeds.

I've never had any computer updates done since I bought it in 09, so hoping maybe newer software can remedy it.

Yup thats what I notice too but mine is a 13 so thinking there aren't any computer updates not sure though.... Its most noticeable in 6th gear. As you say like its lugging as it is at lower RPM's it seems.

Cam

[Demon War Horse]

Think it is the AFM kicking in? Does it do it if you use the paddle shifters? I heard this keeps the AFM off. Not sure though. I used to notice it on mine, but just around 70MPH.

[qcman]

Originally Posted by Demon War Horse

Think it is the AFM kicking in? Does it do it if you use the paddle shifters? I heard this keeps the AFM off. Not sure though. I used to notice it on mine, but just around 70MPH.

Thx no its not AFM I don't use it

[d3ktrix]

Mine doesn't do it when trying to maintain a speed. Only when trying to lightly accelerate when the trans already is in a high gear from cruising. Not giving it enough pedal to make it downshift.

I feel like it still does it when using the paddles but not sure because i normally manually downshift before applying throttle in manual mode.

[qcman]

Originally Posted by d3ktrix

Mine doesn't do it when trying to maintain a speed. Only when trying to lightly accelerate when the trans already is in a high gear from cruising. Not giving it enough pedal to make it downshift.

I feel like it still does it when using the paddles but not sure because i normally manually downshift before applying throttle in manual mode.

I agree with everything you just said to a "T" you nailed it!

Cam

[Thatchevyguy]

I actually had this exact issue. took it to the dealer. they said it was my torque converter. after they changed it out under warranty, never heard or felt that shuddering vibration again.

[qcman]

Originally Posted by Thatchevyguy

I actually had this exact issue. took it to the dealer. they said it was my torque converter. after they changed it out under warranty, never heard or felt that shuddering vibration again.

Thx I know there were issues noted here on the forum with V6 Autos but I couldn't find anything on the V8 Autos.... If it persists after getting my rim problem sorted I'm going to have it looked at by the dealer.

Cam

[qcman]

So bit of an update.... I had the bent rim replaced at the dealer under my earlier insurance claim and the high speed vibe seems okay now....

But the car just doesn't feel right there is juddering of sorts on acceleration (felt in steering wheel and gas pedal lightly). Last night had it on the highway Tapshifted down to 4th stepped on it and the car was hesitating some. It didn't seem to persist long though... But it seemed like an exaggerated condition of what I have been experiencing.

Called my dealer and they said to bring the car in this week and they will have the Shop Foreman roadtest it. So I'm going to do that. Man I loved this car and now I don't even enjoy taking it out anymore ugh!

One other thing I notice is if I accelerate pretty quick up through the gears it seems more noticeable as the gears get higher. Going to take the car out later and see what conditions make it most noticeable to help with his test drive assessment.

I even took the car back to the tire shop where i got my new rubber a month ago to have them inspect the tires in case they were the culprits somehow.

Thx for hearing me vent anymore insights are welcomed!!

Cam

[Redslayer15821]

Could be a slight deformity in the tires as well. I experienced this on my 13 2lT RS when I got a new set of perellis, I had a tire that had a slight factory defect that would reverberate through the pedal and steering . Got it replaced and road forced balanced the wheels and tires while on the car and the problem seems to have subsided. Hope this helps