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Drive line about to break somewhere in 91YJ . Please HELP diagnose. and look at my gears.

The other day I was leaving my sisters house and as I sped up (35 mph ~2400rpm) I got this intense high frequency vibration or shaking feeling until I let off the gas and it would go away. I repeated this on the way back to my sisters house. I would put it in 2nd and just as it would approach 2400 rpm it would start to rumble and get progressively worse. The noise sounded like it came from the back, I had the rear window out. So I thought it was the rear differential after checking the drive shaft. I popped the cover off and looked around. The ring and pinion seem fine with no abnormal wear (that I can tell). The side gears though looked a bit shitty. They had small to large craters in them. No metal pieces in the case though, except for a few millings worth. Here are the gears :

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I put this back together thinking this damage is not the cause of my current problem and after maneuvering around a bit in the driveway the problem was still there and then the engine started to stumble and slowly peter out. I had the tranny in neutral and the clutch in and it still died out so I don't know if it is related. Then I put the Tcase in neutral and started it up again and it promptly started petering out again. ??? I dont think any chipped gears in the diff could cause the engine to crap out so it may be something else. Perhaps a sensor ? CPS ? If I put it in neutral shouldn't the engine be free of the rest of the driveline ?

Any suggestions on the gears (is this normal wear ??) or for figuring what part is broken/breaking would be extremely useful. Thanks Joe.

Reply to
Joseph
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Those spiders need replacing. Also you need to find out what caused that cratering - something got bounced around in there chewing em up. That's not wear. Right now you have a cheap fix, if they grenade and chew up your ring gear, then it's a different story.

Reply to
Desert YJ

Sounds like 2 different problems. The spider gears need replacing - cratered gears go pretty fast and the shrapnel can do expensive damage. Cheap,easy to do yourself but get both the gears and the cross shaft. As for the vibes, is it speed or engine RPM related? Pull it to Ist gear, the 2nd, the 3rd and see what happens at 2400 while accelerating/decelerating. The spider gears won't, by themselves, cause the vibration but a bad pinion bearing would and the wear pieces could be your reason for the pits. Any play in the input shaft is a no-no. The gear pitting could also be from water in the oil - been swimming lately? - but that would likely cause pitting on the ring gear as well.

I would first check the U-jo> The other day I was leaving my sisters house and as I sped up (35 mph

Reply to
Will Honea

Reply to
L.W.(ßill)

Ok, well I have a brand new TrueTrack and overhaul kit to install (bearings,shims, marking compound etc...) but I had not mustered up the guts and tools to do the job until recently. That will hopefully take care of the diff. I don't think the main problem is coming from the diff now. I think it may be transmission or clutch related. Could my clutch be slipping and vibrating at high rpms ? I replaced the original at 80K miles with a centerforce currently at 115K miles. Why is my engine choking and going out like it is trying to idle up a really steep hill all of the sudden. I put it in neutral and it still happens. Now it will only turn, sputter but not start. I have 18psi gas pressure at the rail.

What happens when your CPS goes ? The maintenance light has not come on nor are there any trouble codes stored in the computer. Except for the one that says I disconnected my batters in the last 50 starts, which is not true. A short maybe ?

The jeep is a 91 YJ 4.0 manual trans obviously :)

-Joe

Reply to
Joseph

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