Walt1967 Posted March 20, 2015 Share Posted March 20, 2015 Hi guys looking at 1990 superliner,truck has 400 mack motor,13 speed mack trans 4.64 rears. I was told by a trans man that you can make a mack 13 speed a 18 speed by changing shift knob and switching air lines.is this true? Also what kind of mph am I looking at with those rears? Would it be better to change ring gear to get lower ratios?thanks for replies.truck will be grossing 160000. Quote Link to comment https://www.bigmacktrucks.com/topic/39342-mack-trans/ Share on other sites More sharing options...
RowdyRebel Posted March 20, 2015 Share Posted March 20, 2015 I've heard the only difference between the Mack 13 and 18 transmissions is the shift knob. Don't even have to change the knob...just knock out the pin that locks out the high split in the low range. AS for the gearing, 4.64 rears should handle the weight just fine,although tire size will play a roll in the speed & driveability as well. Smaller tires = easier to get the load moving, but slower top speeds. Bigger tires just the opposite. For comparison, the 11R24.5 tires I run with 4.17 rears would be like 3.73 rears with LP22.5 tires. Especially if you're due to replace tires anyway, it is cheaper & easier to go up or down a size or two if you can than it would be to change gearing. Quote When approaching a 4-way stop, the vehicle with the biggest tires has the right of way! Link to comment https://www.bigmacktrucks.com/topic/39342-mack-trans/#findComment-283319 Share on other sites More sharing options...
bts-4120 Posted March 20, 2015 Share Posted March 20, 2015 4.64 on tall 24.5 and a mack 13 should be a 72mph truck at 2000rpms? Quote Link to comment https://www.bigmacktrucks.com/topic/39342-mack-trans/#findComment-283326 Share on other sites More sharing options...
Keffer inc Posted March 20, 2015 Share Posted March 20, 2015 If thats the case, try leaving the trans in low range, but flip to high range without shifting, then try spitting it. Quote Link to comment https://www.bigmacktrucks.com/topic/39342-mack-trans/#findComment-283333 Share on other sites More sharing options...
rick harper Posted March 20, 2015 Share Posted March 20, 2015 you don't have to change shift knobs. Just nibble off the lock tab that locks it in so you can split the low side too. Quote Link to comment https://www.bigmacktrucks.com/topic/39342-mack-trans/#findComment-283339 Share on other sites More sharing options...
1965 Posted March 21, 2015 Share Posted March 21, 2015 If you cut the lock tab on a 09 model truck would you have to reprogram the computer? Quote Link to comment https://www.bigmacktrucks.com/topic/39342-mack-trans/#findComment-283349 Share on other sites More sharing options...
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