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Hello All,

I just picked up a very mint condition 1994 RD steel body tri axle dump truck for local dirt work. I searched for a long time to find the specs I was looking for and this truck finally popped up, however the only thing it does not have is a set of Jake Brakes. It is a fully mechanical EM7 with a Mack T2070 transmission and 6.06 Mack rears on 46k Camelback suspension. Can this version of the E7 be set up with a Jake Brake? Does the slow speed 1750 governed rpm prohibit the installation of a Jake brake? I realize braking power would be less than a 2100 rpm engine, which is why I'm guessing a lot of the EM7s were never equipped with them from the start. But I have also heard that taking this engine to 2100rpm is not overrevving it. If jakes can be installed can you run this engine to 2000 - 2100 rpms on a downhill?

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Nice Find! Governed rpm is just that  2100 will not hurt it! Nice Find ! Likely a 300 hp! trucks built in that era were evolving  to drive by wire 350hp and up! I believe 93 was the last year they offered a mech 400! Your rpm and lack of gears indicates its likely 300 maxidyne!

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  • 2 weeks later...

I have retrofitted Etech engines but never E7 mechanical. You are better off not even pursuing this endeavor because you will be very disappointed. Those engine brakes did not do much in engine braking.  If you plan on doing this, i would like to hear back on the braking performance. 

V

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i put jakes on a 91 dm with a em7 300    definitely doesnt brake as much as other engines i hear but still sounds cool    i wont do it either if its going to cost you a lot of money     i believe the jake number you would need is a 680 model     i think the 690 model is for the etech

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ok... so it's been a long time, and it's a good bit of work. "V" is right, what you get after the effort and cost is not worth, the effort and the cost. Where do I start first. It's been a while. doe's the wire harness in the dash have the wires labeld "engine brake"? There should be a fuse socket in the panel as well. if these are not there, No sweat... you can use an in-line fuse and your own wires..  Come off the acc. relay with  power, with the key "on". got to the dash switch, then to a micro switch at the clutch pedal, ( you need to get this switch).. Then from there go to the microswitch at the throttle arm on the injection pump, (there is a small bracket needed to mount the switch. it needs to offer adjustability so you can set the switch position). from this switch, you go to the jake heads, you will need valve cover spacers for engine brakes. this setup will operate both brakes at the same time. if you have ever driven one of these, youll remember that the brake stays on at stop sings and you ether shut it off or rest your foot on the clutch pedal..  Do you have the 680 Jacobs heads, and exhaust rockers? I have an E-7 book, If you need info, I may be able to help... Ok, so now is the time for others, here to fill in some of the things i left out... Jojo Just keep in mind what "V" said!

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If you do install a Jake (?)  don't be afraid to set the lash about 20 or 30 thousands more than what's it's supposed to be.  You can sneak a little more retarding power out of it.  IDK ?? if the truck has a low axle ratio (like your's)  it might not be a total waste of time. They're better than nothing, but not much (lol)  

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Thanks for all the info. At least I know it can be done and the correct part number. I am going to run it as is for now and see how it works out. Braking power aside, I would think they would have come standard to help get the rpms down faster when upshifting with those huge rpm drops in the t2070 and t2080 transmissions 😄. Who knows, if it ends up being a good reliable truck, and I am looking for something to do next winter in the shop maybe it will happen. Thanks again for the information.

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