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Changing up my transmision in my 1988 R 690S


Casper1988

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13 speed mack tranny od is .71    low is 13.91       your 2070 tranny is od .60   low is 14.16       the 2070 will run faster and have a slight lower low gear      my 2080 had a low of 20.08 and od of .60      with 5.73  gears I could start out loaded on a 60 degree incline and not burn the clutch       not a good tranny for the road thou in my opinion

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4 hours ago, luke andres said:

13 speed mack tranny od is .71    low is 13.91       your 2070 tranny is od .60   low is 14.16       the 2070 will run faster and have a slight lower low gear      my 2080 had a low of 20.08 and od of .60      with 5.73  gears I could start out loaded on a 60 degree incline and not burn the clutch       not a good tranny for the road thou in my opinion

After about third gear you need a splitter with the six,seven and eight speed trans in this series.    terry:D

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I put the information about the Tranny on the BigMackTrucks.com facebook page.  You may reference the photo there under the visitors section in the right hand column. Unfortunately I was unable to attach any photos to this forum or gallery.  Input on how to correct the issue is appreciated.

Thank you,

Luke

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Went to the shop yesterday to get oil, this is a well known shop in my area and talked to a Mack guy who has 30 plus years experience. really confused now, he said the 12 speed is big long and expensive to fix if there are issues with it . So he thought a 9 speed would be a good match up. Everyone does have a opinion on whats best for a swap out, still gathereing info and next will be to find some trucks locally and see what there running. I did take it for a ride yesterday after oil in the rears and king pin job, went real nice.

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Luke, a conventional diesel engine produces peak power at 2100 rpm and maybe 90% of peak power at 1600 or so rpm, so a 9 or more speed transmission is needed. A maxitorque produces peak power at 1700, and at least 90% of peak power from 1200 to 2100, thus as little as 5 speeds are needed.

 

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I have some time driving and shifting many different types of eqiupment around the farm (20 plus years ). I would say this 2070 is not the most easiest transmission to dial in but I am also in no hurry to get anywhere loaded. Once I drop the load though that .60 overdrive will get me home quick. Good advice on this site. Thanks all.

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