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Just doing quick math the change from 4.42 to 4.17 will drop you 100 rpm.  4.17/4.42 = .94%. 

Your 65 mph at 1700 rpm x .94% = 1598 rpm.



1959 B61 Liv'n Large......................

Charter member of the "MACK PACK"


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Most of the changes  in gearing here we used to do was to change to  4.64 due to the V8 ! Anything over 400 would eat the 4:17/ 4:42 ratios for breakfast in the offroad type settings  here!  lots of hills! Used rebuild lots of these top gear sets would pit out and break! the above ratios were a simple top gear set change!

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5 hours ago, mrsmackpaul said:

I just calculated what I do, you dont wanna see my results

Give you speedy buggers nightmares lol



You could just about pull Christ off the Cross with That Paul...

"Be who you are and say what you feel...
Because those that matter...
don't mind...
And those that mind....
don't matter." -

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Or the ass out of the ocean lol 


Well thats why these old trucks are rated to 115 ton (215000 pounds) from new 

Originally had 5.73's someone pointed out to me a while that they had been changed as they are stamped 5.29 



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