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Unread 04-05-2013, 01:21 PM   #1
adamsclarke
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More 4.0 noise ?s

OK, so 1991 4.0 TF999 with a few noise problems. Tell me what you think.
I was having a horrible noise at high RPMS...mostly at the 55 MPH+ range. My TF99 input seal was leaking, and I assumed the 12k mile tranny was wearing out and blamed the noise on the converter or pump. Well, I just swapped out the trans for a good one with a new converter and the noise is still there. It's only at high RPMs is noticeable when the throttle is applied, but more present when I just left off the gas and it coast back down to a lower RPM. It's more than the normal sewing machine noise. I loose no oil (other than needing a new valve cover gasket and oil pan gasket) and it doesn't burn any. I run 15W40 diesel oil right now. It was a rig that was sitting for a few years, so the motor has been through several oil changes in the last 500 miles.

Everything thing else is new and rebuilt, 1 tons, xfer case, driveshafts etc...so now after the tranny swap I am positive it's motor related.

It does do it when it 1st starts up from time to time, but stops after a second or so. SO is there any I should know to avoid a rebuild? Does it sound valve train related? I figured bottom end would be so bad it would have been catastrophic???

Cam, oil pump, rebuild head?????

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Unread 04-05-2013, 04:49 PM   #2
Chrisnvegas
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1992 YJ Wrangler 
 
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When was the timing chain last replaced?
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Unread 04-05-2013, 05:24 PM   #3
adamsclarke
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No idea? At 124k, would that slapping around cause any other symptoms?
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Unread 04-05-2013, 05:43 PM   #4
Chrisnvegas
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1992 YJ Wrangler 
 
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Try this. Check the slack in your chain. Loose timing chain symptoms vary but usually produce a rattle at different times. I wouldn't think the chain is worn with only 124k miles though.

Go to post #12.

http://www.jeepforum.com/forum/f19/t...mileage-13030/


What is the noise? Rattle, whine, click, tick?
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Unread 04-05-2013, 06:46 PM   #5
adamsclarke
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It's a rattle for sure, but I'll have to have a listen up front and see how it is. I though it was the converter or tranny oil pump for the longest time...but bed lined floors allows the sound to move quite a bit. I though about the bottom end, but a spun bearing would be giving me many other symptoms....
I'll check it out. It is a idle and start up noise and mostly at high RPM 2600+...so that would make sense that the chain has too much slack!
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Unread 04-12-2013, 06:03 AM   #6
adamsclarke
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Well, I took some time to check the timing chain today....and it looks like it will be the source of the noise. I can move the crank with a wrench about 1" before I get any engagement on the distributor. That looks like a lot of slack to me which would explain the chain rattling noise. I'll pull it apart next week and swap it out and update with pics for anyone hoping to diagnose that noise.

I always thought it was coming from the area right near the tranny/engine block area....but I am learning that noises travel quite a bit when there is no carpet and just bed liner.
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