WhiteHawkNYC Posted May 9, 2021 Share Posted May 9, 2021 Hi guys, New here. I just bought an 87 Mack R688st. First, I wanted to say thanks because I was able to fix a bunch of things on the truck just off of the information I found on this forum, so it's been invaluable. Anyway, I have a 12 speed e6 350. (I'm a new driver) Having a bit of an issue with the truck stalling, wondering if I should be doing something different. I turn the truck on. Build up air. Push in the brakes. Push in the clutch shift the truck to 1st direct and then the truck stalls. My question is: Should I be revving the truck as I'm letting off the clutch to get into 1st gear? Do I need to rev up a certain rpm? I.e. shift into 1st at 1200 rpm? Thanks guys Quote Link to comment https://www.bigmacktrucks.com/topic/66670-12-speed-shifting-question/ Share on other sites More sharing options...
67RModel Posted May 9, 2021 Share Posted May 9, 2021 Release the parking brakes. Yellow air valve on the dash. If you are doing this already ("push in the brakes") then the rear brake shoes are most likely seized to the brake drums from sitting. Quote Link to comment https://www.bigmacktrucks.com/topic/66670-12-speed-shifting-question/#findComment-473618 Share on other sites More sharing options...
WhiteHawkNYC Posted May 9, 2021 Author Share Posted May 9, 2021 So it shouldn't be stolen when I shift into first? Regardless of whether I give it gas or not Quote Link to comment https://www.bigmacktrucks.com/topic/66670-12-speed-shifting-question/#findComment-473619 Share on other sites More sharing options...
alex g Posted May 9, 2021 Share Posted May 9, 2021 Should move without giving any fuel. 67 R is probably correct when he says brakes are stuck on Quote Link to comment https://www.bigmacktrucks.com/topic/66670-12-speed-shifting-question/#findComment-473620 Share on other sites More sharing options...
Joey Mack Posted May 9, 2021 Share Posted May 9, 2021 1st direct is High range. isnt your shift knob round with an air switch that goes sideways? 4 positions. lo-direct, nuetral and reverse. Quote Link to comment https://www.bigmacktrucks.com/topic/66670-12-speed-shifting-question/#findComment-473621 Share on other sites More sharing options...
WhiteHawkNYC Posted May 9, 2021 Author Share Posted May 9, 2021 My shifter has h-d-n-r Yes, I expected it to crawl when i shifted into 1st direct My shift sequence according to the sticker is 1D 1H 2D 2H etc... Quote Link to comment https://www.bigmacktrucks.com/topic/66670-12-speed-shifting-question/#findComment-473623 Share on other sites More sharing options...
Joey Mack Posted May 9, 2021 Share Posted May 9, 2021 ok, what does it do in high?, if it crawls, switch the 2 air lines on the shifter.. Quote Link to comment https://www.bigmacktrucks.com/topic/66670-12-speed-shifting-question/#findComment-473624 Share on other sites More sharing options...
WhiteHawkNYC Posted May 9, 2021 Author Share Posted May 9, 2021 If the brakes are stuck could that make it stall? Quote Link to comment https://www.bigmacktrucks.com/topic/66670-12-speed-shifting-question/#findComment-473626 Share on other sites More sharing options...
mowerman Posted May 9, 2021 Share Posted May 9, 2021 Sounds like you’ve got electrical issues.. bob Quote Link to comment https://www.bigmacktrucks.com/topic/66670-12-speed-shifting-question/#findComment-473627 Share on other sites More sharing options...
terry Posted May 9, 2021 Share Posted May 9, 2021 2 minutes ago, mowerman said: Sounds like you’ve got electrical issues.. bob How would electrical issues relate to this? terry Quote Link to comment https://www.bigmacktrucks.com/topic/66670-12-speed-shifting-question/#findComment-473628 Share on other sites More sharing options...
Joey Mack Posted May 9, 2021 Share Posted May 9, 2021 stuck brakes for sure can do this.. Was a brake chamber replaced right before this and the lines were switched? I'm trying not to throw out a dozen things on this thread. I bet its a simple fix.. Quote Link to comment https://www.bigmacktrucks.com/topic/66670-12-speed-shifting-question/#findComment-473629 Share on other sites More sharing options...
blackdog2 Posted May 9, 2021 Share Posted May 9, 2021 I had a problem with 2001 Fruehauf I sprayed wd-40 in glad hand brakes were hanging up and changed glad hand to a quick release one on blue side good now......it would hold a little air back ? Quote Ed Link to comment https://www.bigmacktrucks.com/topic/66670-12-speed-shifting-question/#findComment-473630 Share on other sites More sharing options...
mowerman Posted May 9, 2021 Share Posted May 9, 2021 Well he didn’t mention anything about letting letting the clutch out and the engine governor is connected to the transmission (electric) Possibly shorting out and killing the engine 1 Quote Link to comment https://www.bigmacktrucks.com/topic/66670-12-speed-shifting-question/#findComment-473631 Share on other sites More sharing options...
Dirtymilkman Posted May 10, 2021 Share Posted May 10, 2021 Brake pedal pin can be siezed so it'd be stuck in the down position. Quote Link to comment https://www.bigmacktrucks.com/topic/66670-12-speed-shifting-question/#findComment-473648 Share on other sites More sharing options...
MACKS Posted May 10, 2021 Share Posted May 10, 2021 Jack it up and see if the wheels turn..🤷♂️ 1 Quote Link to comment https://www.bigmacktrucks.com/topic/66670-12-speed-shifting-question/#findComment-473655 Share on other sites More sharing options...
Swishy Posted May 10, 2021 Share Posted May 10, 2021 (edited) My 2 cents worth sez (Tax FREE) the engine brake is on or short n out n try n 2 stall the cold motor it twould make the engine sound like crap Butt There again Wot Would eye kno LOL cya Edited May 10, 2021 by Swishy 1 Quote Link to comment https://www.bigmacktrucks.com/topic/66670-12-speed-shifting-question/#findComment-473656 Share on other sites More sharing options...
Brian L Blaylock Posted May 11, 2021 Share Posted May 11, 2021 I have had mud get packed between the bottom of the brake pedal and the floor board and not let the brakes release completely and cause a problem similar to this Quote Link to comment https://www.bigmacktrucks.com/topic/66670-12-speed-shifting-question/#findComment-473702 Share on other sites More sharing options...
JoeH Posted May 12, 2021 Share Posted May 12, 2021 I think we're missing some more details. We don't have acknowledgement that hes releasing the parking brake. When did the truck roll last? Has it been sitting for a long time? What work did you have to do on it? 1 Quote Link to comment https://www.bigmacktrucks.com/topic/66670-12-speed-shifting-question/#findComment-473757 Share on other sites More sharing options...
JoeH Posted May 12, 2021 Share Posted May 12, 2021 Have you driven a manual trans before? Are you "popping" the clutch or easing it out slowly? 1 Quote Link to comment https://www.bigmacktrucks.com/topic/66670-12-speed-shifting-question/#findComment-473758 Share on other sites More sharing options...
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