Vibration at hard acceleration

[Blueraven]

Howdy, new here.

I just purchased a 99 Explorer 2d AWD. This truck runs good, however whenever I accelerate quickly I get a vibration. I don't feel it in the steering and it is less pronounced when I accelerate slowly.

I once had a Dodge P/U and it kinda was doing something similar and it turned out to be a "carrier bearing".

Does any have a good place for me to start looking?

Thanks,
Blueraven

 

[techieman33]

If it's a 2 door than it's not awd, it's automatic 4 wheel drive, only the v8's got awd, and no v8's were put into sports. That being corrected, I would check your u-joints first.

 

[Blueraven]

Thanks for the correction, you are certainly correct it is Auto 4X4.

I certainly think it could be a u-joint and it is acting like that. I also thought about the front half shafts, however I don't hear any noise when I'm turning.

I plan on raising it this weekend to taking a thorough look at it.

It's got 128K on it, but doesn't appear to have been abused.

It was purchased for a newly licensed 16 year old.

 

[techieman33]

it could also be the front driveshaft, the auto 4x4 might be kicking in under the hard acceleration. Check out the boot at the end near the transfer case, look for any tears in it.

 

[explorer4982]

check your spark plug cables, my 00 mountaineer was doing the same and it was the spark plug cables i need it new ones. check for any cracks on the cables

 

[Blueraven]

OK, I've been able to put tank of gas through and here's what I've noticed:

99 4X4 Sport with I believe is a 5R55E transmission (I haven't verified that), 128K miles

1) Easy acceleration- everything is smooth
2) Cruising down the hwy at 70 mph, everything is smooth and it drives straight
3) Hard acceleration- there is a vibration and there is slippage. I don't know if it's the transmission or something in the axle, however it does shift and I don't notice any increase in RPMs between shifts, (I believe that is called shift flare)
4) When going into drive from reverse, there's a 2-3 second hesitation before the transmission kicks in.
5) When I switch to 4X4 High and accelerate, it pulls hard to the right. I have not tried 4X4 low yet and I am on dry payment.

Does any of the above symptoms ring a bell to anyone?

Thanks, Blueraven

 

[Blueraven]

anyone?

 

[4.0 power]

nothing in the axle will slip, if its anything its the transmission. the 2-3 second delay might be a bad modulator, i am no expert though.

My truck vibrates under hard acceleration as well, i have a carrier bearing that is on its way out and 2 u joints on the drive shaft that need to be replaced.

as far as the truck pulling right in 4 wheel, its probably a bad auto hub. One of them is not fully engaging or at all, they are notorious for going bad.

 

[Blueraven]

Thanks for the advice. There are no grease fittings on the u-joints, so I assume they are original so replacing them probably is not a bad idea.

I read a post about the delay when going from reverse to drive, but I can't find it again. I'll keep looking.

As for the "Auto-hub", I'll look into that.

Thanks,
Blueraven

 

[ljungberg3]

Throttle position sensor, thats what happened to mine. look into it

 

[Carguy3J]

OK, I've been able to put tank of gas through and here's what I've noticed:

99 4X4 Sport with I believe is a 5R55E transmission (I haven't verified that), 128K miles

1) Easy acceleration- everything is smooth
2) Cruising down the hwy at 70 mph, everything is smooth and it drives straight
3) Hard acceleration- there is a vibration and there is slippage. I don't know if it's the transmission or something in the axle, however it does shift and I don't notice any increase in RPMs between shifts, (I believe that is called shift flare)
4) When going into drive from reverse, there's a 2-3 second hesitation before the transmission kicks in.
5) When I switch to 4X4 High and accelerate, it pulls hard to the right. I have not tried 4X4 low yet and I am on dry payment.

Does any of the above symptoms ring a bell to anyone?

Thanks, Blueraven

#4 above: It could be slippage or someother problem in the trans. While nothing SHOULD slip in the rear, if you have a ton of excessive backlash, or a really bad pinion bearing, that might introduce enough "slack" in the drivetrain that it takes a second to reverse the "load" , and then you feel it when all the slack is finally taken up. Chekc these thing out, but I would also take a real good look at the motor and trans mounts. Slop/delay/bang when going from park to D or R / or when going between D & R is a classic sign of a worn mount somewhere. Don't just look at them, have someone torque them , with the vehicle in gear while you watch. Do it in both D and R. Have them shift between them as well. It should be pretty easy to see if they're moving too much.

Thanks for the advice. There are no grease fittings on the u-joints, so I assume they are original so replacing them probably is not a bad idea.

I read a post about the delay when going from reverse to drive, but I can't find it again. I'll keep looking.

As for the "Auto-hub", I'll look into that.
Thanks,
Blueraven

There is no such thing as an "autohub" on these vehicles. The front axle is "live" all the time. There is no disconnect bewteen the front wheels and the differential. The "thing" that engages/disengages 4x4 on these trucks, is the clutch in the transfer case. Now, what he might have been referring to is the front wheel bearing/"hub" assembly. They are known to go bad on these trucks, but that would not present the symptoms you are describing.

Basically check the mounts on everything: motor/trans/ bushings on control arms and springs, sway bars, and the rubber mounts on the front differential to chassis mounts (there's 3)

Also, you might want to clean and grease the slip yokes on bith driveshafts. They are known to dry out, and "clunk". Carefully remove the old metal band, and gently lift up the boot corner. Slip in the end of the grease gun and fill'er up. ( I used a 2cycle oil mixing syringe from walmart and injected the joint w/ cv grease)

 

[Blueraven]

Update: Got it back from the shop today. They didn't provide too much detail, however they stated it was a total transmission rebuild and the parts price was $900. Total bill was $1800 "ouch"

 

[rego]

Try adding friction modifier to transmission fluid. That stopped my transmission shudder. If that's the problem then have the fluid flushed.