Warden

Any idea of gear ratio & top speed? 12000' frt is a little lite for me but could work ! Thanks. Warden

Mr688 heavy / auto/ ac/ jake / wet line a plus ! 90s and newer ...845 626 3412.

Ok , i have been using this truck daily , its near perfect for my use , it rides awesome . Handles great , it. Stops very well with its 4 wheel disc brakes. (Air ) the power is good mpg is an honest 10.1 avg ...great heat and ac , The auto trans and air throttle are flawless ! I need 2 things and it will be my daily driver , i woud appreciate all input and ideas , im hoping for an option i have not considered , my truck has an air diff lock rockwell btw ! Ok. I need to cruise @ 75 mph @ approx 1700rpm ( i have a 4:30 rear ) Without losing start from dead stop on a hill ! My trans is a 654cr allison 1:1 in 5th ( wish it was .70 :1 ! Re 2nd i need an exhaust brake , a nice loud and affective unit that is affordable hopefully used ,,, A clean used oil pan for the E7 250 would be good also. Any ideas are welcome , im an equipment mechanic and capabile of Making it happen once i have a plan ...im far from a mack expert ! Im shocked that i fell in love with this unit ! I want to make it as perfect as possible ! On the interstate 57 - 64 mph is tops verified by gps ! 2 slow ! Thank you for your help !!

I found my brakes are meritor kit 16515pm. Per wheel $275 ,,, for just pads .... Ebay and other on line $85 per wheel warden

I put my 6" gage from my old engine analyzer in the cab with me and drove around loaded , it got as high as 34psi but most of the time 20 - 30 psi .... Its automatic so the boost varies allot according to what the converter does ... EGT stays real safe ! It runs strong down low , and weak on top ! Im getting 10.1 mpg avg ... Just checked again tonite and used my gps ! It could use a little more fuel on top .. Anyone know if these speedos can be calibrated ? My gps said the speedo reads 5 mph fast and the odometer reflects same ! Warden

I spoke to a mack dealer today and they seemed a bit confused at first , but they finally came up with the data that told them that i have a full mechanical injection pump with an electric shut down and an air throttle pedal with air slave on the inj pump , and that the engine is dressed to be 300hp but the pump is turned down to the 250hp setting ! So they say ! They still seemed confused with the truck specs . Triple frame ... Air throttle .... Disc brakes ... And various other options that the person i was speaking to claimed to not have seen similar specs in his 25 Mack years at the dealership ! Common for me to get the strange one ! Lol. Not always a bad thing! He said by my build date , i just missed the electronics and added that what i had for an E7 was "in his opinion the last of the real good and simple units" but he also said a triple frame single axle and some other items made no sense , but he pulled up svc records and verified the 35,000 miles as real and all components original ! I can try and tweak the pump a bit , (i have done hundreds of other diesels with great success ) this thing is touch 40psi of boost under High load . But it dont have the fuel to make proper use of it ! It burns cleaner then my 08 stock Duramax ! I need a jake pretty bad , i seem to use allot of brakes with this auto trans , the truck is nimble and quick , not fast tho !! Can anyone tell me if a jake install will be an issue with this eng and trans ? I have a switch on the dash to lock up the converter l Thank you. Warden

Hi , thank you , i dont know how to tell what E-7 it is ? Here is a pic of the engine tag attached , does that Tell what i need to know ? Warden

If i have to do a trans swap , its not an issue ! But my buddy that is 100% mack with over 35 trucks on the road , just told me about an E7 -250 hp. That he scrapped after trying 3 times to make it a 350 , and having many issues , like broken cams and other items ! So i guess my real question is , are all E7s capable of more hp reliably ? I would prefer 25-50 Hp more in the upper rpm range , this unit pulls hard from 1200 to 1700 assuming its tach is accurate , i can live with 65 mph if it will do it up hill ! Is there a "CPL" with mack ( critical parts list ) like cummins , or Detroit ? If this unit actually pulled to 1950rpm i would be pretty content with the gear ratios ! Im amazed at how much weight it will start and pull to 50mph , but it lacks top end power and falls like a stone to 1500rpm on hills ( even empty ) but i know there is more power in there , cause it pulls too good in a certian rpm range to be this weak on top ! I have people giving me info that is allover the place , some say tuned with a lap top , others say injectors , pump , & turbo ! I would love to hear accurate power boost info , if too involved , then i will just add a propane kit , done that to a couple of hundred diesels with great success , it dont really boost hp a ton on the dyno but it make them run perfect and smoother and pull way better ! I make my own kits ! Very mild , thank u ,,,warden

Its a rockwell according to the line sheet and the tag , the build ticket says delete 4.10 rear & add 4.30 with inter axle connect /air/switchable ...im not quoting exact verbage , but its close ! What should it have ? I just put the gps on it tonite and 65 mph down hill or with a tail wind ! Delivered 2 small excavators 2 nites ago 220 miles round trip in hill country and power was not bad , Fuel MPG was outstanding @10mpg on the nose , top speed coming home empty was lacking , traffic on the tway was moving @74 mph. I was at 64 tapped out ! Truck is a keeper , this thing rides like a half ton chevy pic up. And turns as well or tighter ! I cant give up the air locking rear , not for my use (very important ) i did not study the trans blue print yet , many allison 5 speeds are realy 6 spd double overdrives but the valve body has to be modified to stop the 3rd planatary back instead of the second , that would be perfect. But not sure this unit has the correct layout , any help or ideas would be appreciated , i cant go larger on tires ... 1100x20s already , bed is 53" high already. Thats bout 5" more then perfect , thank u ,',, warden

Hi , 4.30 rear. And 1100Rx20 tires 482 revs per mile !

Hi , just picked up a mr688p with a E7 250 hp and auto , i love it , its a roll back 1995 with 30k orig miles Allison auto , my queston is , can this engine safely be turned up and not hurt itself or the trans ? If so how much ? Truck is heavy for a single axle 23,000. Tripple frame ! I know with my cummins and detroit series 60 , there was a critical parts list controling hp avail ! This single ax truck has a gvwr of 44,000 ,,,, i could use a bit more power and another 100- 200rpm. To cruise the thruway nicely , any advise ? Thank u warden.

Hi , new here , owned many macks over the years , many trucks in general , but i must have been asleep for a long while cause i just bought a 1995 mr 688 and it has disc brakes all the way around ! Im kinda shocked , Anyone here tell me any info on this ? Good , bad ? Common ? I never seen this before and i hope its not some emorphadite thing i cant get parts for? I absolutely love this truck , and i do need to learn about the brakes ! Thank u. , this is my first post Warden