Lower ends almost never fail- new guides from MB only. That's what I do for internal stuff... not worth re-work of off-brand parts.

x2. Bottom end is rock solid.

I wish I had replaced the chain/rails/guides on mine....but I didn't have the lower cover off when I rebuilt my top end on my 88 300TE. Not that it looked like anything was wrong....just simply for peace of mind.

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2016 Monsoon Gray Audi Allroad - 21k
2008 Black Mercedes E350 4Matic Sport - 131k
2014 Jeep Wranger Unlimited Sahara - 62k
2003 Gray Mercedes ML350 - 122k