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About macattack

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  1. my 96 mr688s seems to loose a bit of air when releasing the park brake. so i thought quick release valves, but on mine they look different. instead of one supply there are 2 supplys and 4 outs? per axle??? here are a couple of pics
  2. thanks bud. the oem is #3MT237P7 gauge. the one i got is from allison, but the sending unit with the new gauge is a single wire the original sending unit is 2 wire. the allison gauge has your basic send and ign terminals. but there is 2 smaller bolts with an insulator between them one is labelled + and the other - . dont know what that is about. but your probably correct. thanks again
  3. gonna replace my tran temp gauge and the original says neg ground stamped on the back. the replacement does not say anything. is there a way to find out if the gauge is neg or pos ground? thanks
  4. thanks for the info. i am thinking i will splice a long wire from the sending unit (ground wire) and route it inside the cab and when the gauge decides to act up i could touch that wire to a ground source inside the cab just to see if the gauge stops acting up. think i will leave the sending unit hooked up as original but run a jumper from the ground wire to inside the cab. thanks again
  5. this is on a 96 mack mr688s truck. trans temp sending unit has 2 wires going to it. one is the send is the other wire for ground? dam gauge wants to jump all over the place.
  6. does mack have instrument panel voltage regulators? cant seem to find out
  7. thanks j hancock. took me a while, but got it figured out. came close to replacing the trans. what a relief. so after a couple filters, relays, and a shitload of testing also a tcm ended up being that governor. took 30 mins to change.
  8. happy days are here again!! yes got it figured out. my problem ended up being a worn trans governor. gear on governor looked fine but the inners were sloppy. replaced governor and put truck into reverse and she engaged every time. !!!!!
  9. well still screwing around with this. anyways thinking possibly a switch issue of some sort. with engine off, if i shift into rev and back into neutral a couple times and then start the truck. it goes into reverse, but only once. seems something not switch, what do you think would the nss do this? could it also be an input speed sensor? any help would be great.
  10. how could i check these. my rev switch is on the pass side and the nss is on the drivers side. what is the best way to test them? thanks for your info.
  11. trying to do some diagnosing on my refuse truck allison ht740rs trans. sometimes reverse sometimes no. also at times it wants to kill the engine as soon as i put it into forward gear. with truck stopped and off if i put the shifter into reverse then into neutral and start the truck it will go into reverse ONCE. wont go twice until i shut off the truck shift into reverse then neutral and restart the truck, goes into reverse. also the acc/solenoid relay seems like its getting pretty warm more hot than warm. has anybody dropped the pan to replace the shift solenoids in the alli
  12. would this breaker box be approx 3x4 inch. one wire on one side and 4 on the other. i found this under the center dash. maybe it is something else.
  13. hi.

    i think i found the ground block.

    would it be about 3x4 inch black.  has one nut terminal on one side and 4 terminals on the other side.

    found this under the center dash panel just south of the fuse box.   

    held down by 2 screws.

    i tried a test lite to check for ground or power and i got nothing.  key on or off.

    just dont know if that is the ground breaker box.

    thanks for any help


  14. anyone know how to test a oil pressure switch and also can a person run a test on a pneumatic/electric solenoid? this solenoid has 2 same color wires coming off of it.
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