I've never heard this one before!

My brother got my dad's '93 3.3L Grand Voyager given to him in '98 with about 130k miles. It currently has about 250k miles. I can recall 3-4 times in the past 1-2 years where the alternator belt has come off when driving on bumpy roads. A mechanic told him that this particular vehicle was notorious for having the belt jump off when driving on rough roads and during snowy or rainy/muddy conditions. I've never heard this one before! Why didn't my dad have the same "notorious" problem during the first 130k miles?! I know that he has a newer belt because it was replaced the first time that it fell off, and I put a new tensioner on it last summer. Any ideas as to what's causing the problem? Your opinions, as always, are greatly appreciated!
Rob

Someone, maybe GATES sells a keeper mod for the belt on these cars, and yes, there was an issue especially in wet weather of having the belt come off. I have a '96 and rive it in all weather conditions and have never personally had this problem.

Gates sells a grooved tensionser and a belt with grooves on both sides. That solves the problem permanently. The belt is known for coming off under wet or snowy conditions. If it's coming off from bumps, that points to a weak tensioner.

Thanks for your responses. I'll look into the belt tensioner mod and let you know what I find out.

Check both water drains on the bottom of the wiper cowling, particularly the passenger side tube. If the tube loosens or cracks, water can drip on the belt, causing it to jump off.

Funny that I am reading this I thought this weekend when it was raining a monsoon that my belt broke but it jumped off because of to much water running of the passenger cowl now I know this is not a personnal problem that I have,