krismoriah Posted December 8, 2012 Share Posted December 8, 2012 going through my new to me 1986 RD688 i found that it has a jacobsen 680A engine brake. Does anyone know anything about this engine brake? Does it have good stopping power or just another noisy but worthless jake? Quote Link to comment https://www.bigmacktrucks.com/topic/28751-jacobsen-680a/ Share on other sites More sharing options...
theakerstwo Posted December 9, 2012 Share Posted December 9, 2012 It is a jake brake made for a mack engine. It is good as you can get for a mack but a mack engine does not have much braking power and many beleive they show slide the tires but is not meant to be used but only on hills.I have one with jakes and one with dynotard and they work good if you use your imagination and open both doors with windows rolled up. Not difference in the two. Quote glenn akers Link to comment https://www.bigmacktrucks.com/topic/28751-jacobsen-680a/#findComment-150178 Share on other sites More sharing options...
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