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post #1 of (permalink) Old 05-28-2002, 06:49 PM
ArkyCrawler
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chatter in tranny?

Iím not a tranny guy and if you ask my wife Iím not mechanical guy ether!
I have installed a sm420 tranny in my CJ and all the gears sound good except for 4th.
While in 4th and supplying power there is no noise but when I let of the accelerator there is a
Chatter and if I get back in to the peddle the chatter goes away if I put it into neutral from 4th the
Chatter is there but a little different and it only happens in 4th gear. I went to the tranny shop that rebuilt
It for me and he says heís not sure what it is but he thinks itís ok, to drive. {I have lost all confidence in him}

Any thoughts would sure help.

Steve
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post #2 of (permalink) Old 05-30-2002, 08:25 AM
Nickmil
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Re: chatter in tranny?

Sounds possibly like rear driveline vibration. A rear driveline vibration will travel up through the rear output of the transfer case, up the rear output shaft of the transmission. It will show as a chatter or vibration in 3rd sometimes but primarily in 4th when the output shaft is locked to the input shaft. Has to do with speed and severity of vibration. Check rear driveline angles very carefully, condition of u-joints, driveline condition (play in slip yoke, dents or knocked off weights creating vibration), and make sure the yokes are phased correctly. Nickmil.
post #3 of (permalink) Old 05-30-2002, 09:41 AM
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Re: chatter in tranny?

in my old CJ, when i was in 5th gear at highway speed it sometimes made a rattling noise, it turns out the noise was detonation in my eninge at that load and RPM. but it really sounded like it came from the tranny....

just a thought
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post #4 of (permalink) Old 05-30-2002, 11:46 AM
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Re: chatter in tranny?

I have a '84 CJ7 (258) that has a rebuilt T-5 (8 months old) and it just started the exact same problem and symptoms you describe. Mine does it at highway speeds in 5th gear. I know that I have a bad seal and bearings on one of my rear wheels and it too may be causing the vibration. I am not convinced this is the cause and fear, as you probably do, expensive tranny work. I would be interested if you do find the problem to hear what it was. I am expecting to take mine to the 4x4 shop later this week. I hope nothing drops out until then
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post #5 of (permalink) Old 05-30-2002, 07:02 PM
ArkyCrawler
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Re: chatter in tranny?

Thanks Guys!

WellÖ..This is an old sm420, 1958 as a matter of fact. I ordered a new stick from Border Parts in San Diego. The 2 pins, on the side of the tower, that holds the stick in place are missing. Instead there are 2 7/16 bolts screwed in with about ľ inch of the bolts holding the stick in place. There was a LOT of slop with the shift pattern.

I found an old np435 in my shop (donít ask) and it had a set of pins, so using a punch I removed them then with the patience of a Saint I installed them in to the sm420. The fit was a little off, couldnít get the stick to fit between the pins, had to grind the pins a little. Now I have a real tight shift pattern.

On my first time the chatter was no where to be found. Went to the hills and ran around on some rocks and trails and had no problems then on the way back to the house I noticed that while in 4th and letting of the gas I could sometimes hear a little chatter. It came and went but no where near what it was and it only did it a couple of times.

I ďthinkĒ that the problem was and is possible with the shift forks. I have the cover on the floor above the tranny removed and Iím able to ďfeelĒ the chatter on top of the forks and I didnít feel it down on the side of the tranny.

To do this test it takes nerves of steel and the intelligence of a test lab mouse, also a 15 year old son holding the steering wheel while dodging local traffic and yard dogs chasing the jeep [img]images/icons/wink.gif[/img]


Thanks again, If you have any thoughts about this please let me know.

Steve
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