Re: upgrading np231 chain
Theoretically this could be done. Haven't seen anyone go to the trouble though.
By getting a new chain(don't buy a used one, b/c they stretch over time and no reason to go and do it again later) and either a used or new set of sprockets for the 231D x-fer.
I would stay with the NP231J gear set b/c of the ability to use a TeraLow set up. Haven't heard of anyone breaking the planetary gears in the 231J either.
The only part of the 231J that breaks often is the out put shaft. So, I would like to caution you about purchacing mechined stock output shafts. Get one of the kits now produced that offers the larger shaft and the 32 splines as opposed to the stock 27. Just avoid the ones that require a core charge and you will be OK.
The 231 is a good case, all in all. Some slight building with the proper parts and they will last a long time.
Actually, how many people have you heard of that have broke the chain. I can think of only one and that guy didn't check his fluid, his case was dry. What I am trying to say is this is one of those things that you might want to wait until it breaks, then upgrade it.
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<font color=green>llll '90 YJ</font color=green>
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