LT230 questions and concerns - bearing failure. - Defender Source
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  #1  
Old January 13th, 2006, 07:47 AM
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Kip Hartzell
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LT230 questions and concerns - bearing failure.

Hi, I have a '95 NAS D90 with a LT230T T-case that recently had the input gear and associated bearings replaced to the new cross-drilled gear when I converted to a ZF automatic (the old non-drilled input gear had worn about half of the R380 splines away). Soon after the gear replacement, I started having a leak with the front t-case seal and later the parking pawl was not activating properly. It was just discovered yesterday that the new front bearing on the new input gear had disintegrated into pieces which looks to be the cause of my various problems. Two questions; first, what could cause this bearing failure? Low fluid level, or bad bearing, or ...... Secondly, can the box be cleaned up and the bearing replaced without a full rebuild/strip down? I had a significant amount of metal shavings mixed with gear-oil and I am concerned that the center diff got "contaminated". I have attached a photo of what it looked like when I removed the PTO cover. Incredible enough, other than the bearing, the input gear still looks good. We haven't look closely at the ZF yet. Your opinions would be most helpful. Thanks.
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  #2  
Old January 13th, 2006, 08:05 AM
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Hmm, did they check the preload on the input gear? Did they replace the raceways (the part the bearings ride on) when they replaced the bearings?

Your best bet would be to rebuild it if the chunks off the bearings are big. I tried just cleaning mine up after a similar incident and the bearings on the intermediate shaft were eaten up shortly after, and when those bearings went I needed a new t-case as it ate up the input and intermediate gear and wore a hole in the t-case after driving it like that for 2 miles to get it home.

You can get a rebuild kit from RDS, but it is a bit of a job and you may need a few special tools to do it.
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Old January 13th, 2006, 08:59 AM
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I would strip the whole box. It looks like the preload may have been too tight. You need to inspect the case and make sure neither of the races spun. If that happens the case is usually ruined. I would remove the gear and both bearings and races and inspect all of the parts carefully for damage. Also, Usually when you replace the input gear with the new style, you have to replace the transmission output stub shaft with the new type with the longer splines to match...verify that this was done and that the shaft is still ok. I personally, would also remove the extension case and inspect the park mechanism, too.
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  #4  
Old January 13th, 2006, 10:01 AM
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Kip Hartzell
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Thanks Rob and Mike for your quick responses.

The ZF transmission coupler shaft was replaced with the longer splines at the same time the new input gear was installed (as you implied, this was required for the longer splines). I am not sure what was done for pre-load, so I will need to check on this. Also, the plan is to removed the governor housing and take a close look at everything since I was having parking pawl issues too. The ZF output and LT230 seals will need to be replace too. With the case out of the truck and the covers off, can the unit be effectively "flushed"? Otherwise, I may look into getting a remanufactered unit since this one has 115k on it. The input gear swap has been the only thing done to the box since the truck was new (besides fluid change).
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  #5  
Old January 13th, 2006, 01:56 PM
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kiphartzell
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Kip Hartzell
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Rob,

A new t-case is in order. The front race spun and the case is damaged. We have not pulled the case out yet to see how the ZF was affected. A picture is attached for viewing pleasure of the damaged race/case. Could the bearing have been manufactured poorly, not tempered properly? The input gear was supposedly pre-loaded during installation.
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