knock at take off?

Burley · Oct 8, 2003

Guys,

On my '98 I have a weird knocking sound when i hit the gas hard from a stop. If i start out from a stop at a some what normal speed it doesn't happen, but when i have to really hit the gas i hear a tap or knock about three or four times really fast then it quiets down. It seems to be coming from under the passegers feet area somewhere. Any idea? This one has me stumped!

TIA

Burley

Rev Den · Oct 8, 2003

Sounds like a u-joint.

Rev

Burley · Oct 8, 2003

Rev Den said:
Sounds like a u-joint.

Rev

That is the first thing i thought but the u-joints seem to be fine. It also sounds like it may be coming from some place higher than that in the engine compartment.

90red · Oct 8, 2003

I agree with the U-Joint making the noise. I thought mine were okay until I took them off. The u-joint in front coming off the tranny was the one that was bad. It will take about 30 min to change them out. And they arent very costly at all. Even if they arent the problem, its not a bad idea to change them, especially if the vehicle is high mileage and they havent been changed in a while.

90red

Burley · Oct 8, 2003

Would you guys consider 124,000 miles high miles on that u-joint?

Burley

Rev Den · Oct 8, 2003

Burley said:
Would you guys consider 124,000 miles high miles on that u-joint?

Burley

You are kidding right?? If you ar'nt, then yes, thats allot. How are you checking your joints? Trying to twist them will not show the failure until too late, you need to try and move it in a horizontal/vertical plane to the joint.

Rev

StevenJ · Oct 8, 2003

I had the same thing when taking off from a dead stop but it was more of a thumping sound. It went away after I changed by trany mount. It was totally collapsed.

SJ

Burley · Oct 8, 2003

Where is this mount? Is this on the top side of the cross member? Sorry for the stupid question.....

Edited to say that ianswered my own question. Yes it is. But can I tell what kind of shape it is in by looking at it while installed?

Burley

Burley · Oct 9, 2003

Well I looked at the tranny mount and the rubber looks brand new. I tightened up the bolts holding it to the cross member and I still get the knocking sound. It sounds like something is hitting the under side of the body/frame. I check all the hard ware I could see and nothing seems loose or out of place. This driving me insane!!!

Any other ideas? Could this be a transmission problem resonating through the floor?

Burley

MaXJohnson · Oct 9, 2003

Your exhaust takes a very slight kick right where it passes over the transmission crossmember. There isn't much room getting over the crossmember and at the same time under the floor. If the exhaust is even slightly out of shape or the the motor mounts are a bit loose or worn, you will get a knocking sound around this area when you first take off. Movement of the engine/tranny from torque reaction moves things even closer together.

Burley · Oct 9, 2003

Rev Den said:
You are kidding right?? If you ar'nt, then yes, thats allot. How are you checking your joints? Trying to twist them will not show the failure until too late, you need to try and move it in a horizontal/vertical plane to the joint.

Rev

Well my '88 has almost 250,000 miles on it and runs great, so no I'm not kidding. I think you should be able to get more than 124,000 miles out of some parts on a (almost) bone stock vehicle. That isn't asking that much IMHO. If I couldn't expect to get that out of jeep parts I wouldn't be driving two jeeps.

M. Lake · Oct 9, 2003

Check the motor mount on drivers side. Or pass side. When my drivers side went out, it felt like someone was kicking the floor panle from the outside. Thought it was a CA bushing.

knock at take off?

Burley

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