03' Big Red

I guess I’ll give it a good drive and see how it rides 

sounds like the best bet is to swap out the whole thing, and yes it has the 5” wide springs versus 4” for the 44 & 46 

i am buying a truck with 58,000lb rears but would like to go down in weight rating in the spring to get a nicer ride. will the 58,000 lb differentials fit into a 46,000 lb housing ? i am looking into swapping in a Haulmaxx cutoff but in the interest of saving money would prefer to keep the differentials and transfer them over.

that's my thought especially if its governed at 1750

hey gang,

i am looking to purchase another truck . it is a 1992 DM that has a EM 7 300,Eaton 8LL and 5.73 axle ratio, i thought EM 7's are governed at 1750 rpm, the seller states peak torque is around 1700 rpm and  it will pull up to 2100.

am i wrong ?

On 9/5/2019 at 5:07 PM, Mack Technician said:

Considering that I’d flash it to 330/350 and install some K&S injectors to push out an extra 20-30HP? I haven’t price a VGT lately, but guessing the cost of a upgrade turbo would make the next leap expensive.

Can someone attach a link for the K&S shop ? I’d like to talk to them but not sure of the location of the shop.

Ok

I’ll ask this question another way, can a E7 be turned into a EM7 ?

what would have to be changed ?

i like that the EM 7 has  peak torque way down at 1020 rpm, if my AMI made torque that low it would a game changer.

21 hours ago, JoeH said:

Are you talking about mechanical or electronic e7's? I love the idea of an em7 -350 mechanical,  but I think maxidynes peak at 300 hp. 

I think it's just about all in the fuel pump. For the most part, at least on mechanicals, the injectors will put as much fuel in as the injection pump tells them to. But I think it's also important to have a lot of oil pressure so you aren't hurting crank and rod bearings by lugging it. It's critical to have a good film of oil as the the engine is making 1000-1200 ft lbs of torque at 1000rpms. That's only 350 rpms off idle. 

Would be great to get an em7-300 fuel pump and have it turned up closer to 350. You'd likely need to upgrade the transmission too. And personally I'd go Maxitorque trans.  The T310-M might be a great pairing with a maxidyne em7, you'd always be in your power band with room to spare.

it seems the differences are in the  pump,turbo and injectors on a mechanical EM7 300.

I'm not completely sold on the Mack trans over the Eaton, although I have never run the newer Mack trans, only the ones found in a 83 R model.

i don't want to lose the ease of shifting and the gear spread i have in my 8LL, maybe i just need educated but from what i hear the T2080 type trans has big jumps between gears especially going into OD, that seems like one could get fatigued after a long day on the job. i would appreciate someone who has real world experience driving one of these  to educate me

1 hour ago, JoeH said:

Are you talking about mechanical or electronic e7's? I love the idea of an em7 -350 mechanical,  but I think maxidynes peak at 300 hp. 

I think it's just about all in the fuel pump. For the most part, at least on mechanicals, the injectors will put as much fuel in as the injection pump tells them to. But I think it's also important to have a lot of oil pressure so you aren't hurting crank and rod bearings by lugging it. It's critical to have a good film of oil as the the engine is making 1000-1200 ft lbs of torque at 1000rpms. That's only 350 rpms off idle. 

Would be great to get an em7-300 fuel pump and have it turned up closer to 350. You'd likely need to upgrade the transmission too. And personally I'd go Maxitorque trans.  The T310-M might be a great pairing with a maxidyne em7, you'd always be in your power band with room to spare.

i am talking about a mechanical EM 7 300

seems a Eaton 8LL amd 4:42 axle ratio would be a great set up, i see how well that set up works with my AMI 370, that's rated at 1480 ftbl @1300 rpm

1 hour ago, Mack Technician said:

EM7 was 250-275-300 mostly...unless someone finds a 350?

so what is different on the EM7 ? is it in the pump or are other things involved  ?

here is a hypothetical question, can a E7 be turned into a EM7  ? also what is the highest HP rating for the EM7 ? seems to me ive seen a 350 hp listed some place.

seems if one had the right transmission and axle ratio the EM7 would be quite a sweet set up. My AMI 370 runs just wonderful but  i like the idea of the EM7 max torque way down at 1025 rpm versus 1250 of the AMI

i understand that the EM7 is governed at 1750 rpm and the AMI at 2150 rpm but honestly most times i can shift at 1700-1750

i am typically loaded around 72,000-73,000 lbs in a dump truck.

3 hours ago, j hancock said:

What is the transmission model number?

no idea, its listed as a 6 speed Maxitourqe that and the 1997 model year is the only info I have right now.

I am confused with the 4:42 axle ratio, I thought the mack trans had a .60 OD and typically used a 6:00 or lower axle ratio

I am looking at a 1997 Mack DM with a 6 speed maxitorque transmission, its a ready mix chassis with 4:42 axle ratio

can someone tell me what ratios this transmission would have, I've searched the internet briefly and haven't found the info. I am most curios about 1st gear and 6th gear ratio.

thanks in advance for any info

i have a question about the Mack air ride used in dump trucks, i saw a AL461 suspension rated at 46,000lbs, is this a true Mack suspension ? I have  heard they are built by Hendrickson  and it looks like the Primaxx does this suspension offer the stability and articulation like the Primaxx  ?

the big issue i find now is price, I have been told $25000-$30000 by two different shops, i don't understand how that could be possible, especially if i find a donor truck. i should be able to find a single axle RD with a E-Tech and Allison for a fair price.

the 750 drd has a much lower 1st gear than the 4000 unless you jump up to the 4700, if i go with the 4000 series then i'll need a computer and harness and the cost is much more. i dont want to get into that, i want to keep it simple.

thanks for the info, i run a 4:42 so my top speed will be about 55mph or so at 1900, not so bad since my work is mostly within 30 minutes and in a 55 MPH work zone. i have  finally got a contact who did this swap a few times on a Mack and they are able to answer all my questions about flywheel housing,flexplates and tooth counts to keep the E tech happy.

2 hours ago, BlueDogDozing said:

 I cannot help you with part numbers and such, but I do have a 1996 Mack RD688S with an Allison HT 750 DRD  in it from the factory.   I can take some pictures of it if you need them. It is mated up to a E7 300. 

 

I would assume that the frames on our trucks are very similar. 

 

 I am currently having some work done on the transmission, there is a company called Clarke Power that has facilities all around the United States. They specialize in Allison transmissions. You might give them a call, they’re doing my work and seem pretty knowledgeable.  My local Mack has them do Allison trans work for them. 

What axle ratio does your truck have ? Also does your trans have a rear support? I know the 4000 series requires one.

i know that I need to pay  close attention to tooth count on flex plate and tone ring/ speedometer gear to make things work.

I have a few questions about parts interchangeably,

will a Allison 700 series bolt up to a 4000 series flywheel housing and flex plate?

is a spacer needed ? If so what p/n ?

also what is the tooth count on the 700 series speedometer? 

My Final question, will  the output shaft yoke from  a 4000 series  fit a 700 series

this is for a conversion project in a 03 Mack RD688s that currently runs a Eaton 8LL

On 12/2/2006 at 5:48 PM, AutomaticMack said:

I have a quad axle 85 R686st with a HT 750DRD Allison. Mack and Allison make for a very strong set up !! It's a blast to drive on and off road. However I would stay away from those auto-shifts for any off road or dump truck use. With the older Allisons make sure your modulator cable is adjusted properly and change the fluid regularly.

If and when I ever buy a new dump it would have an Allison.

What was the axle ratio on your truck ?

Is that HT754CR going to hold up to a E9 ? I thought the torque rating was much lower than the 750DRD 

Am I correct the 1st gear ratio is 8.0 ? Or something like that on the 754

my truck has the AMI 370 and I would be pushing the torque limits. It’s around 1480 ftlb 

Ok folks 

i am still  working on the details of this swap, I have a vin From a 2000 rd with a Allison, can anyone tell me which Allison this unit has and 1st gear ratio and also the axle ratio ?

Vin 054124

also talked to another Mack tech and he says all that’s needed for the engine computer is to change the top gear ratio and change it to A designation for the automatic..

i would appreciate any other input in this swap, I plan to use to 750DRD for simplicity 

I also need to know what bell housing,flexplate and mounts to use.

Did I say 1300 rpm ? My bad, it’s more like 1500 rpm, I am still considering the manifold and turbo ..

I have not as of yet, just hit the 90,000 ish mark on a in frame, the engine really loosened up and runs excellent, I can shift at 1300 rpm now and it has the power to keep pulling, until recently I had to rev to 1800 or so. This is a tri axle, the gross weight here in PA is 73280 lbs

The AMI has a much better rpm range

1200-2150 rpm and the torque rise is considerably more maybe 40-50% thats just a guess since I don’t recall exactly what it is... the AMI should out run the E7