Mikebates531@yahoo.com Posted March 14, 2016 Share Posted March 14, 2016 1967 mack R11 673 thermodyne 5 speed unknown rearend..firetruck whats my options to getup to speed limit? Quote Link to comment Share on other sites More sharing options...
j hancock Posted March 14, 2016 Share Posted March 14, 2016 Send your VIN to the Mack Museum with a donation and they can get the build records for your truck which will say which transmission and rear end ratio the truck was built with. What is the current top speed? Two ways to go would be to get an overdrive transmission for the truck or to up the rear gear ratio. Quote JimIt doesn't cost anything to pay attention. Link to comment Share on other sites More sharing options...
Mikebates531@yahoo.com Posted March 15, 2016 Author Share Posted March 15, 2016 thanks for response ,speedo and tach not working ,I would say 60mph is all ,with a little pedal left, not wanting to hurt the ol'engine..are the over drivetrans readlyavailble?,,how about the rearaxles? Quote Link to comment Share on other sites More sharing options...
j hancock Posted March 15, 2016 Share Posted March 15, 2016 Either should be available. First thing to do is see what your rear axle ratio is now and what trans you have. Quote JimIt doesn't cost anything to pay attention. Link to comment Share on other sites More sharing options...
Vladislav Posted March 15, 2016 Share Posted March 15, 2016 Exactlly as said above. Your R-model is by some reason just a R-model and lots of parts could be found off commercial trucks. 1 Quote Никогда не бывает слишком много грузовиков! leversole 11.2012 Link to comment Share on other sites More sharing options...
Mike Posted March 16, 2016 Share Posted March 16, 2016 RPM X Tire Diamemter divided by gear ratio x 336 = MPH Seems like most of these engines are 2100 rpm to the floor. Quote Link to comment Share on other sites More sharing options...
Freightrain Posted March 18, 2016 Share Posted March 18, 2016 The ol 673 will run on the governor all day(been there for lots of years). Look on the drivers side of the transmission for a flat spot that will have the transmission code on it. Same with rearend. Won't be hard to figure out what road speed you have. Quote Larry 1959 B61 Liv'n Large...................... Charter member of the "MACK PACK" Link to comment Share on other sites More sharing options...
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