Vehicle feels like it is going over bumps on slow coast from a dead stop

[mdmcinti]

Hey guys,

Yesterday I was in Reno for my wife’s doctors appointment and I went to pick up McDonalds for my daughter since she was asking for a happy meal. Anyways when I was in the drive through, when it was time to move up in line, this feeling of going over bumps after I let off the brake to move forward would occur. It would feel like if I was going over rumble strips or something. No weird noises or anything. It only does it when inching toward using the idle engine power to move the vehicle forward like when moving up in a drive through from a dead stop. When doing normal acceleration from a stop I don’t fell anything. Is this the abs kicking on and I need new hubs? Is this a torque converter issue? I can’t seem to find anything in the internet of this issue. You can feel it sitting in the front. My wife was In the second row and said she couldn’t feel anything. This for a 2003 Yukon xl 4x4. If anyone has experienced this, please share your experience and how to remedy this problem. Thanks!

 

[OR VietVet]

How many miles on the tires? I would want to check to make sure you don't have a belt starting to slip in a tire. Likely not since you only feel at that idle speed. You may have a brake dragging but who knows. When you say you feel it, is it in the steering wheel, thru the floorboard and feel in your feet or in the seat of your pants?

 

[mdmcinti]

How many miles on the tires? I would want to check to make sure you don't have a belt starting to slip in a tire. Likely not since you only feel at that idle speed. You may have a brake dragging but who knows. When you say you feel it, is it in the steering wheel, thru the floorboard and feel in your feet or in the seat of your pants?

The tires are brand new with 7k miles on them. I feel it in the floor and in my seat.

 

[OR VietVet]

Ok, I am gonna do a WAG. Exhaust shield touching somewhere under the front area, motor mount or trans mount problem or possibly the harmonic balancer. I am just grasping at straws here. Check all belt pulleys and tensioners/idlers as well.

 

[mdmcinti]

Ok, I am gonna do a WAG. Exhaust shield touching somewhere under the front area, motor mount or trans mount problem or possibly the harmonic balancer. I am just grasping at straws here. Check all belt pulleys and tensioners/idlers as well.

All my belts, tensions, and idler pulleys are good because I replaced them all this year so I know it’s not those. I was kind of wondering it is motor or trans mounts as well since I am sure they are original and the truck has 252k on it. The trans mount looked fine to me when I inspected it a few days ago when I changed the oil. I was also thinking if it was the abs kicking on due to rust and crap in the hubs, but everyone mentions the problems occur when you are braking.

 

[mdmcinti]

Ok, I am gonna do a WAG. Exhaust shield touching somewhere under the front area, motor mount or trans mount problem or possibly the harmonic balancer. I am just grasping at straws here. Check all belt pulleys and tensioners/idlers as well.

All my belts, tensions, and idler pulleys are good because I replaced them all this year so I know it’s not those. I was kind of wondering it is motor or trans mounts as well since I am sure they are original and the truck has 252k on it. The trans mount looked fine to me when I inspected it a few days ago when I changed the oil. I was also thinking if it was the abs kicking on due to rust and crap in the hubs, but everyone mentions the problems occur when you are braking.

 

[clandr1]

How many miles on the tires? I would want to check to make sure you don't have a belt starting to slip in a tire. Likely not since you only feel at that idle speed. You may have a brake dragging but who knows. When you say you feel it, is it in the steering wheel, thru the floorboard and feel in your feet or in the seat of your pants?

Could it be a brake caliper sticking and causing a studder on one of the wheels?

 

[OR VietVet]

How did you inspect the trans and motor mounts? They can LOOK fine but could be separated and you will not see it till you try to lift the trans/transaxle and see if separates. If any of the mounts are compressed/collapsed enough, the metal can hit and cause a feeling of a vibration.

 

[mdmcinti]

Could it be a brake caliper sticking and causing a studder on one of the wheels?

I have no idea. It doesn’t make any noise or anything weird like that of a stick caliber, but who knows. This truck does 97% highway driving so idk how the brakes could do this when they are seldomly used.

 

[mdmcinti]

How did you inspect the trans and motor mounts? They can LOOK fine but could be separated and you will not see it till you try to lift the trans/transaxle and see if separates. If any of the mounts are compressed/collapsed enough, the metal can hit and cause a feeling of a vibration.

I just looked at it lol. I noticed the idle is a little rougher in park. But I am trying to rule out worn spark plugs for that case. How bad should vibration feel on a worn motor mount? I know I should do the pop the hood and see how bad the motor jerks test.

 

[OR VietVet]

I have no idea. It doesn’t make any noise or anything weird like that of a stick caliber, but who knows. This truck does 97% highway driving so idk how the brakes could do this when they are seldomly used.

You can have good thickness on brakes but if you are in an area where salt is used on the road, that can wreck havoc on caliper slides and hardware and such, 97% highway driving or not. I doubt the brakes are the problem but I was giving options.

 

[mdmcinti]

How did you inspect the trans and motor mounts? They can LOOK fine but could be separated and you will not see it till you try to lift the trans/transaxle and see if separates. If any of the mounts are compressed/collapsed enough, the metal can hit and cause a feeling of a vibration.

I just looked at it lol. I noticed the idle is a little rougher in park. But I am trying to rule out worn spark plugs for that case. How bad should vibration feel on a worn motor mount? I know I should do the pop the hood and see how bad the motor jerks test.

 

[mdmcinti]

You can have good thickness on brakes but if you are in an area where salt is used on the road, that can wreck havoc on caliper slides and hardware and such, 97% highway driving or not. I doubt the brakes are the problem but I was giving options.

Nevada uses a salt brine on their roads. We did drive it on the highway during all the snow we got. The calibers have some rust on them. More than my previous all AZ their whole life vehicles have ever had.

 

[Doubeleive]

are you feeling this thru the brake pedal? or is the whole truck making a vibration

 

[OR VietVet]

Yep, I live in Oregon and we don't deal with rust here. I was in heaven when I ran shops and moved from salt on the roads, KC, Mo., to Eugene, Or., no salt on the roads.

 

[mdmcinti]

are you feeling this thru the brake pedal? or is the whole truck making a vibration

Its through the whole truck. My foot was not on the brake at all.

 

[Bill 1960]

I’m thinking a slight misfire or stumble at idle. Disappearing under normal acceleration.

I’d try duplicating the conditions with someone else behind the wheel while you walk alongside and watch and listen. A misfire you can hear at the exhaust or if you leave the hood up you’ll probably see the engine shuddering a bit.

 

[mdmcinti]

Yep, I live in Oregon and we don't deal with rust here. I was in heaven when I ran shops and moved from salt on the roads, KC, Mo., to Eugene, Or., no salt on the roads.

Only in one place in Oregon they salt because that pass gets really bad weather.

 

[Doubeleive]

Its through the whole truck. My foot was not on the brake at all.

I would chock the front wheels and jack up the rear wheels and put it on jack stands and then start it up and put it in 1st gear and see if can hear any noise from the rear end or transmission, apply the brakes if needed to keep the speed slow. If it's not the abs and the brakes are not worn down to nothing then it may be something in the drivetrain. maybe a bent wheel? (just something to check)

 

[mdmcinti]

I’m thinking a slight misfire or stumble at idle. Disappearing under normal acceleration.

I’d try duplicating the conditions with someone else behind the wheel while you walk alongside and watch and listen. A misfire you can hear at the exhaust or if you leave the hood up you’ll probably see the engine shuddering a bit.

That is one of my guesses too because I know those plugs need to be changed. We will find out if that was the cause in a few months. I have a baby on the way soon so I don’t have time right now.

 

[mdmcinti]

I would chock the front wheels and jack up the rear wheels and put it on jack stands and then start it up and put it in 1st gear and see if can hear any noise from the rear end or transmission, apply the brakes if needed to keep the speed slow. If it's not the abs and the brakes are not worn down to nothing then it may be something in the drivetrain. maybe a bent wheel? (just something to check)

Would a bad u joint cause this?