mackncheese Posted March 11, 2012 Share Posted March 11, 2012 I have a new to me mack dump truck and I really don't like the 7 speed and I want to make a change and I have read the entire engine and transmission forum twice and have a better understanding but I am still having trouble with what is the right choice for me. I need to maintain the off road ability and I live in a hilly area and tow a 20 ton tag with a 20 ton track hoe. If I can go 65 on the highway and am not redlining the engine that is good enough for me. Here is what i have:1999 RD 690s with a 400hp VMAC lll E7 ETECH. (uprated from 300hp at the Mack dealer)7speed T2070B with a 44000 rears with a final drive ratio of 5.32Tires are 11R22.5VIN is 1M2P264C5XM029458Right now I can go 75 on the hiway. I don't need to go that fast. We were hauling dirt the other day and my Ford LTL 9000 with a 400 big cam and a 13 speed (I think) would eat the mack up. there was a hill on the run and Mack no matter what you did would crest that hill at no more than 35 mph. the Ford would crest that hill at 55 all day long. the Mack's bed was larger and it was hauling about a 2 tons more dirt than the ford, but it would not have made any difference. First thru 3 is strong but once you hit 4th and 5th it dies and slowly builds rpms up to its power band. Very annoying with a line of traffic behind you.What transmission do you all recommend based on the info I have give you? What we will give similar performance as the Ford and what trans will swap out with the least hassle. Can I have the 7 speed modified to a 9?Thanks in advance for your help. Quote Link to comment https://www.bigmacktrucks.com/topic/23776-want-to-change-out-7sp-need-help-with-replacement-choice/ Share on other sites More sharing options...
randyp Posted March 12, 2012 Share Posted March 12, 2012 I wouldnt change a thing, ifn aint broke, dont fix it. Lil traffic behind you cant hurt anything. Thas just my 2.5 cents,,,,,randyp Quote Link to comment https://www.bigmacktrucks.com/topic/23776-want-to-change-out-7sp-need-help-with-replacement-choice/#findComment-106726 Share on other sites More sharing options...
Frmconcrete09 Posted March 12, 2012 Share Posted March 12, 2012 all our macks with a eaton fuller will pull better than the maxitorque trans. Once you get to road gear , just sit and wait , but those eaton's will self destruct way faster than the macks Quote Link to comment https://www.bigmacktrucks.com/topic/23776-want-to-change-out-7sp-need-help-with-replacement-choice/#findComment-106729 Share on other sites More sharing options...
cgallamore Posted March 12, 2012 Share Posted March 12, 2012 A 13/18 spd will help U get road speed quicker, but I wouldn't trade Ur hole gear for itThat 7spd has a great low and reverseI ran in a fleet of dm688 most had 7spd two had 13spd the 13 was great on the road but broke axles and an occasional bull gear in the soft stuffThe 7spds where bullit proof Quote http://www.bigmacktrucks.com/uploads/1272400769/gallery_4852_794_314995.jpg Link to comment https://www.bigmacktrucks.com/topic/23776-want-to-change-out-7sp-need-help-with-replacement-choice/#findComment-106734 Share on other sites More sharing options...
David Posted March 12, 2012 Share Posted March 12, 2012 "Can I have the 7 speed modified to a 9?"NoA 9, 13, or 18 speed would be a good choice but you will cut your top speed down to about 64. They have .71 overdrive, the 5, 6, 7, and 8 speed all have .6. Quote Link to comment https://www.bigmacktrucks.com/topic/23776-want-to-change-out-7sp-need-help-with-replacement-choice/#findComment-106742 Share on other sites More sharing options...
EWB555 Posted March 12, 2012 Share Posted March 12, 2012 Are you sure its set at 400 HP? The only reason I ask is we used to have a LTL with a 400 Cummins & 13 Speed, also had a 78 R Model with a 300 & 6Speed and 20MPH Difference on a pull seems about right to me (Both Tandem Dumps Hauling 65K) You also have to remember that Cummins is 855 Cubic inches and the Mack is 728 (Pretty sure), and if the Cummins is turned up any, the Mack will never run with it. I dont think a transmission swap would have a great enough effect on how it pulls to be worth the time & money. I would have the motor checked to verify current rating. Quote Link to comment https://www.bigmacktrucks.com/topic/23776-want-to-change-out-7sp-need-help-with-replacement-choice/#findComment-106778 Share on other sites More sharing options...
mackncheese Posted March 12, 2012 Author Share Posted March 12, 2012 Are you sure its set at 400 HP? The only reason I ask is we used to have a LTL with a 400 Cummins & 13 Speed, also had a 78 R Model with a 300 & 6Speed and 20MPH Difference on a pull seems about right to me (Both Tandem Dumps Hauling 65K) You also have to remember that Cummins is 855 Cubic inches and the Mack is 728 (Pretty sure), and if the Cummins is turned up any, the Mack will never run with it. I dont think a transmission swap would have a great enough effect on how it pulls to be worth the time & money. I would have the motor checked to verify current rating.thanks for all your responses. The Mack had the uprate done at the local mack dealer. It was not dynoed after the update but I could feel a difference. the dealer checked fuel and boost pressure and both were reportedly where they should be. the 400 big cam in the Ford has been turned up some but I don't know how much. You seem to think it is a horsepower thing where as I feel like if I could keep the Mack in its sweet spot it would pull much better. On the highway the ford can't stay with the Mack. It is the hills and getting up to speed where the ford is so much better. First thru third is strong but 4th and 5th are weak. Thanks again for all of you alls input Quote Link to comment https://www.bigmacktrucks.com/topic/23776-want-to-change-out-7sp-need-help-with-replacement-choice/#findComment-106780 Share on other sites More sharing options...
lucerne tractor Posted March 12, 2012 Share Posted March 12, 2012 The Mack E7 is no Cummins big cam or 3406, never will be no matter what you do, "no replacement for displacement". If you really feel the transmission isn't making it, most dump trucks out there are specked with an eaton fuller 8LL. they come in direct or od models. Most use direct. Never can go wrong with an 18 speed fuller, it's just an 8LL with a few more choices, there is always a right gear,except the one that gives you more torque then the engine produces, thats were he is getting you, when its needing to pull hard. Quote Link to comment https://www.bigmacktrucks.com/topic/23776-want-to-change-out-7sp-need-help-with-replacement-choice/#findComment-106788 Share on other sites More sharing options...
cgallamore Posted March 12, 2012 Share Posted March 12, 2012 I would disagree that an 18 and an LL8 are the sameI think the LL8 is the best non Mack trans for a dump truck18spd does not have the hole gear like the LL8I do think the LL8 is the best choice if he can't live with the 7spdI wouldn't change to a weaker tranny for a few minutes per load Quote http://www.bigmacktrucks.com/uploads/1272400769/gallery_4852_794_314995.jpg Link to comment https://www.bigmacktrucks.com/topic/23776-want-to-change-out-7sp-need-help-with-replacement-choice/#findComment-106806 Share on other sites More sharing options...
theakerstwo Posted March 12, 2012 Share Posted March 12, 2012 I would disagree that an 18 and an LL8 are the sameI think the LL8 is the best non Mack trans for a dump truck18spd does not have the hole gear like the LL8I do think the LL8 is the best choice if he can't live with the 7spdI wouldn't change to a weaker tranny for a few minutes per load Your right the 18 dont have the low reverse. Quote glenn akers Link to comment https://www.bigmacktrucks.com/topic/23776-want-to-change-out-7sp-need-help-with-replacement-choice/#findComment-106808 Share on other sites More sharing options...
cgallamore Posted March 13, 2012 Share Posted March 13, 2012 Can't believe spending my whole life around macks I've never driven a 12spd Mack. Older guys say that is the best dump truck tranny ever 1 Quote http://www.bigmacktrucks.com/uploads/1272400769/gallery_4852_794_314995.jpg Link to comment https://www.bigmacktrucks.com/topic/23776-want-to-change-out-7sp-need-help-with-replacement-choice/#findComment-106974 Share on other sites More sharing options...
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