66rmack Posted December 6, 2015 Share Posted December 6, 2015 So I cleaned the crud off the drives last night and found it the truck has 4:17 gears. With the 5 speed and the 3 speed aux and 24.5 tires. It seems pretty slow so my ? Is if I remove the aux how can I figure pi what my top speed would be? Quote Link to comment Share on other sites More sharing options...
david wild Posted December 6, 2015 Share Posted December 6, 2015 What is the 3 speed aux ??? most low, low low, direct and over is in a 4 speed aux, 2 speed fuller 1202 is a low and direct, low is a 50% reduction same as 4 speed in low low, spicer is or has built a 3 speed aux that is/was low, direct and over. if your referring to a Mack late model 2 stick trans then it should be reverse, low and direct. so it depends on what you have ???? Quote Link to comment Share on other sites More sharing options...
Superdog Posted December 6, 2015 Share Posted December 6, 2015 4:17's with a straight 5 speed on 20" rubber will give you 62 mph at 2100 rpm,the tall rubber with gain you about 5-6 mph . so depending on the O.D. ratio of your aux.trans.,I'd say you'll have no trouble running at least 75 2 Quote Link to comment Share on other sites More sharing options...
66rmack Posted December 6, 2015 Author Share Posted December 6, 2015 The 3 speed aux I'm not sure what it is its def. not factory. It's In line after the Trans. It seems to hurt the speed rather than help it I'll check what it is tonight. 60mph seems to be about 1800rpm right now. Quote Link to comment Share on other sites More sharing options...
Superdog Posted December 6, 2015 Share Posted December 6, 2015 The 3 speed aux I'm not sure what it is its def. not factory. It's In line after the Trans. It seems to hurt the speed rather than help it I'll check what it is tonight. 60mph seems to be about 1800rpm right now.I've never heard of a aux. that would hinder speed? How are you shifting it? hi split(overdrive)should be towards the dash Quote Link to comment Share on other sites More sharing options...
66rmack Posted December 7, 2015 Author Share Posted December 7, 2015 Honestly I shifted it to figure out where high was. To the right and twords the dash. And just leave it in hi it seems to take off fine. With no prob. I am wondering if I should just remove the auxiliary all together and just have it like it is supposed to be from the factory? Quote Link to comment Share on other sites More sharing options...
terry Posted December 7, 2015 Share Posted December 7, 2015 Is there a tag on it to figure out what you have? Quote Link to comment Share on other sites More sharing options...
Bigdogtrucker Posted December 7, 2015 Share Posted December 7, 2015 Bring her up to max RPM's also. Quote Link to comment Share on other sites More sharing options...
85snowdog Posted December 7, 2015 Share Posted December 7, 2015 i"m not sure, but maybe some shift patterns will help figure things out. Some advice from the experts will probably be needed also. Quote Keith Link to comment Share on other sites More sharing options...
Vladislav Posted December 8, 2015 Share Posted December 8, 2015 i"m not sure, but maybe some shift patterns will help figure things out. Some advice from the experts will probably be needed also. Shift paterns.jpegShift paterns 1.jpegShift paterns 2.jpegNot almost about that.The patterns you posted are of the Mack built TRD/TRT/TRQ factory transmissions.They were generally used on the B-model era trucks.An auxilary gear box wich is mentioned in the first post is mounted separately right after a main (stock) tranny.It could be low/direct or low/direct/fast or other.Telling anything about its influence to the road speed might be done knowing its gearing only.So some basic research on that unit's matter is required. 1 Quote Никогда не бывает слишком много грузовиков! leversole 11.2012 Link to comment Share on other sites More sharing options...
AZB755V8 Posted December 25, 2015 Share Posted December 25, 2015 First what are you dealing with, got a 5 speed, sound like direct in 5th. A 3 speed Aux, box is worth about 200 to 300 RPM's in overdrive. Like Superdog said it should be good to 75 MPH @ 2100RPM. I like 4.17's got them in my B with a double over Quad and 75MPH is 1800RPM on big rubber. 2 Quote Link to comment Share on other sites More sharing options...
Mack Doctor Jr. Posted December 25, 2015 Share Posted December 25, 2015 The trans with L N H is kinda what's in my dads R 600. It has R1-5 on the right stick. And L-N-H on the left stick low is toward the back of the cab. High is against the dash. It is the .78 od Truck will run 75 mph with 4.17 at 2400rpm when you put it in OD it drops rpm to 1200 at then she will be in pass those big talking fast Peterbilt gear. Lol. It should gear out at 130+ Quote Link to comment Share on other sites More sharing options...
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