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post #1 of (permalink) Old 09-04-2000, 02:01 AM Thread Starter
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What\'s whacking the floor pan now?!

While camping this weekend I took my Jeep to a local ORV area which is not very challenging but hey you gotta go right?

I was puttin' along at about 15mph in 2wd when I heard this whack and felt it on the tranny tunnel. My wife really felt it on the passenger side. I thought maybe I kicked up a rock or a stick. Well today (Sunday) when I got home I went out to wash the thing and drove it to a spray wash place. On the way it happened again - only this time there was a bit of grinding sound and it lasted for almost a second then stopped then it did it again for a split second. What the heck is it!!

I run a Vortec V6 and a TH350. The motor is loosely bolted in the motor mounts to reduce vibration at idle (Advanced Adaptors recommendation) and the tranny has nice polyurethane mounts also courtesy of AA and are just mounted snug. I have Labor Day off and I plan to crawl under there and see what's up.

Could it be 1.)starter not completely disengaging (bendix close to the flywheel)?
2.)Loose starter?
3.)bellhousing bolts loose?
4.)motor mounts to loose and bellhousing bumping the tub?

Anybody got any ideas???



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post #2 of (permalink) Old 09-04-2000, 09:14 AM
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Re: What\'s whacking the floor pan now?!

What about your x-case lever? I have a home built twin stick and it hits the floor pan sometimes.

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post #3 of (permalink) Old 09-04-2000, 11:58 AM Thread Starter
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Re: What\'s whacking the floor pan now?!

I checked the x-fer case lever and it looks OK. There is almost no way that anything can actually be hitting the tranny tunnel. The starter seems to be tight. I am taking the splash sheild off next and having a look.

Any more suggestions?



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post #4 of (permalink) Old 09-04-2000, 12:15 PM
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Re: What\'s whacking the floor pan now?!

Perhaps a little more detail would help.......are you coasting or is power applied? The only time I've ever had that sort of action was off the line with a bad universal. I do have a question about those AA motor mounts though.....are they "solid" motor mounts? Unless this is some "hot setup" to allow solid motor mounts and avoid the vibration of the low idle miss - I can't for the life of me figure why someone would recommend having loose motor mounts. My knowledge base is admittedly antiquated......so can you give me the rational that AA gave you for such a procedure? ......just curious......

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post #5 of (permalink) Old 09-05-2000, 11:42 PM Thread Starter
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Re: What\'s whacking the floor pan now?!

The mounts are not solid. They do have rubber bushings top and bottom but if you tighten them down to get a little "squish" on the rubber then it shakes like crazy at idle. Vibrates or rough idle would be better descriptions. AA said that leaving them loose would allow only vertical vibrations to be transmitted to the frame where tightening down the bolts would translate vertical and horizontal.

It happened most often at constant speed and once during an upshift at light throttle.

After spending some time under the Jeep yesterday I noticed one of the O2 sensors had bumped the tranny tunnel and knocked off a little undercoating. It resides about 3/8" away from the tub.

Surely it is not this little thing?

Everything else is tight and way away from the tub. I tightened down the motors mounts a tad more and so far no bump and grind.



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