Pontiac G8 Forum banner

I just justified cam swap/dod delete...or at least tuning out afm

2K views 20 replies 8 participants last post by  GMCustomerService 
#1 ·
Ok so I am still new here, I've only had my car for about 3 weeks. It's an 08 GT with about 50k miles. I didn't notice it when i bought the car (because I was just excited as hell about the car) or maybe it just started happening, but i get a nasty vibration from about 1100-1350rpm. It has never happened in first or second gear, but right around 40mph on my local roads makes it very noticeable.

At first I figured this was a problem with the balancer. Even when I bought the car I noticed the balancer is plagued with a wobble, as I've seen all over on these boards. I figured no big deal, I'll slap an sfi rated balancer on there and call it a day (which is still the plan).

Well i was out driving today and realized that if I put in in manual mode, theres no vibration in any gears. Guess that rules out the balancer and means its the afm? Hopefully someone here can shed some light on the issue.

I would not mind doing a cam swap, and actually look forward to it, but I can't fund it right now.

I guess my question is- do you guys think it is in fact a problem with the afm, and do you think its doing any damage as it runs this way?

I know its hard to diagnose anyone else's problems through a computer, but any info would be appreciated!:drink:
 
See less See more
#3 ·
I guess i could have explained a little better. Lets say I'm cruising at 40mph, if I keep my rpm between 1100 to about 1350, I will have a steady vibration that does not go away until I give more throttle and exit that rpm range. The vibration is even noticeable to the girlfriend (who doesn't know jack **** about cars).
 
#6 ·
I have read a few guys complaining about the old mounts. I don't think that is the problem in this case (could be wrong) but it sure couldn't hurt. Anything I should tell them to make them cooperate and do the swap?
 
#5 ·
AFM does give an abnormal amount of vibratation as 768mph said. I noticed it on my car when cruising too.
 
#7 ·
Definitely the motor mounts. That's the first thing I had replaced under warranty after I bought the car. The updated mounts eliminated 80% of the vibration. You can still tell when it kicks in, but much less noticeable. AFM will always cause vibration as it changes the balance of the engine. The updated mounts are designed to absorb more of it.


Sent from my iPhone using AutoGuide.com Free App
 
#9 ·
Definitely the motor mounts. That's the first thing I had replaced under warranty after I bought the car. The updated mounts eliminated 80% of the vibration. You can still tell when it kicks in, but much less noticeable. AFM will always cause vibration as it changes the balance of the engine. The updated mounts are designed to absorb more of it.



Sent from my iPhone using AutoGuide.com Free App
Wow ok, good info. Thanks! Was it hard convincing them to swap mounts?
 
#8 ·
I thought the TSB on this issue stated that the dealer should replace the Transmission mount, not the motor mounts. I had the same issue....vibration and then a moaning sound....and the new tranny mount cured it.
 
#10 ·
Thanks! Good info, and I guess it couldn't hurt to have the motor and tranny mounts swapped! Only a few months left on the 5 year, so better now then later!

I guess you guys have successfully disproved my AFM theory......:whine:

I still want a bigger cam though!:driving:
 
#11 ·
Do the motor mounts. You can use the engineering mode to see when the AFM is operating when using normal mode.
 
#13 ·
Thanks for that information, Joe’sFastG8. As I’ve told many members, I’m not a technician by any means and you helped me to understand the vibration from the AFM more.

Happy Thanksgiving!

Michelle, GM Customer Service
 
#17 ·
Glad to help! Like I said I had the same issue and the first thing they pointed out was the aftermarket wheels and wanted to do a road force balance. That's when I explained that it stops immediately when switching to manual mode(without a gear change) which disables AFM and showed them the TSB for it. I told them I was positive it was from the AFM. They agreed and ordered the mounts. Maybe bring a copy of the TSB with you just in case.
 
#19 ·
Alright so she goes to the dealer Friday. The guy I talked to seemed to understand my problem and told me to just bring it in and they'll take care of it. Seemed pretty simple, so we'll see what happens.
 
#20 ·
Just as an update I did finally get the motor mounts done! After brining my car in for the first appointment, they confirmed my problem was the motor mounts and agreed to fix them. They ordered the parts and told me they'd call me in a few days once they were in. Well the holidays came and I couldn't get my car over there, but I finally made it and the job is done.

The new mounts absolutely dampen the vibration better, now the AFM can only be felt in the gas pedal.

Thanks to the guys at Granite run Buick and GMC!

She is parked for the winter now, but come spring time, the next step is long tube headers, CAI and tune. Cam within the next year hopefully!
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top