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Duramax Coach Lessons Learned
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LCAC_Man
Posted 2017-04-25 8:35 AM (#4555)
Subject: Duramax Coach Lessons Learned


Elite Veteran

5001001001002525
Location: Oceanside, CA
So I just finished my critical path/milestone 1650 mile round trip from Oceanside, CA to Moab, Utah and back. Loaded to the gills I estimate I was at 23000lbs GCVW. If you know this route at all you are familiar with all the mountain grades you have to climb and descend, there must be a dozen 5+ mile long/6+ degree grades between here and there topping out at nearly 8000ft. For the entire trip I squeaked out 10.2mpg...given the wind I was driving in on most of the return trip I'm ecstatic with that! There was a 2hr period where I was at 40mph with my hazards on and that was after setting at an exit ramp for 2hrs waiting for the wind to reduce from 45mph to 30mph..
From a power standpoint there isn't much(pratical) limitation, I could have pulled even the steepest/longest grades at 45mph, I had to back off that on this trip because I couldn't hold my boost pressure sustained beyond 15-17psi without risking blowing a boot off the tubing (which happened twice and will be solved with better boots and clamps) the system is designed to work at 23-25psi so that was a severe power limitation.
On the way out I suffered cooling limitations on grade climbing(high 240's), my huge cooling fan was more than the clutch could hold I had to pedal it the rest of the trip and run real slow in 3rd gear for the climbs which was frustrating.
Once I got to Moab I pulled the fan, drilled through the clutch and bolted it, making it direct drive; this completely solved all my cooling issues as I never saw north of 193dgs the entire return trip. I had been concerned about noise and fuel economy but that turned out not to be an issue at all...it's still super quiet and the mpg's really didn't change much on the second leg..
The tap shift function is a godsend, both on climbing and engine/trans braking on descents.
The coach brakes were surprisingly capable even with them only being at about 50% wear on the shoes and some fair wear on the drums...new drums on the way and I'll reline the shoes so I'm sure that'll be a huge improvement..
Running the new forward A/C on the inverter with the large secondary alternator worked flawlessly...I didn't even start my generator on this trip.
Trans temps never exceeded 190dgs...the Allison is as good as advertised..

Edited by LCAC_Man 2017-04-25 8:35 AM
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dkarnath
Posted 2017-04-25 11:07 AM (#4556 - in reply to #4555)
Subject: Re: Duramax Coach Lessons Learned


Elite Veteran

5001002525
Location: Medford, OR
Sure is nice to see #'s coming in from FMC road trips. Good road/campsite fix on the clutch fan Len
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BigRabbitMan
Posted 2017-04-25 3:38 PM (#4557 - in reply to #4555)
Subject: Re: Duramax Coach Lessons Learned



Expert

100010010025
Location: Cottage Grove, OR
From having been running an FMC with the Duramax and 6 speed Allison, your experience was about what I expected it to be. Its a good pulling rig with good mileage and the 6 speed tranny with the tap shift is absolutely great.

Congratulations on a very successful trip! Many more to come.
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LCAC_Man
Posted 2017-04-26 4:29 PM (#4558 - in reply to #4555)
Subject: Re: Duramax Coach Lessons Learned


Elite Veteran

5001001001002525
Location: Oceanside, CA
I patted myself on the back for having modified the fan shroud to a two piece design and fabricating stand alone radiator mounts...it allowed me to pull just the passenger side half of the shroud out and get right to the fan...in the original configuration I would have had to pull the entire radiator/shroud assembly for the same repair.
New 5 ply turbo elbows and heavy duty spring tension clamps on the way, so, that problem should soon be solved as well...oh...and I had a chirping belt tensioner so I'll swap that out as well..
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LCAC_Man
Posted 2017-05-06 8:56 PM (#4580 - in reply to #4555)
Subject: Re: Duramax Coach Lessons Learned


Elite Veteran

5001001001002525
Location: Oceanside, CA
Some details on the 5 ply boots and heavy duty clamps I used:
http://www.dieselplace.com/forum/63-gm-diesel-engines/374-frankenst...
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journeyman
Posted 2017-05-10 12:16 AM (#4593 - in reply to #4555)
Subject: RE: Duramax Coach Lessons Learned


Contributor

25
LCAC_Man - 2017-04-25 4:35 PM


The tap shift function is a godsend, both on climbing and engine/trans braking on descents.


What's a "tap shift" function?
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LCAC_Man
Posted 2017-05-10 7:06 AM (#4594 - in reply to #4555)
Subject: Re: Duramax Coach Lessons Learned


Elite Veteran

5001001001002525
Location: Oceanside, CA
It's an electronic shift function (momentary rocker switch) that allows you to "tap" up or down a single gear at a time; it's really handy for the grade climbing and descents where you'd typically be using your large shifter handle and waiting for the transmission to allow the shift. With the Allison you just put the shifter in the "M-Manual" position and use the tap shift switch for all gear selections afterward. Here's a picture of my switch setup, it's right in front of my right knee, while driving I can rest my hand on my knee and the switch is right there for shift changes:
http://www.fmcowners.com/mbbs22/photos/show-album.asp?albumid=127&p...
The trans/engine braking you get with the duramax/allison combo is a huge advantage on the long steep downhill grades and will really save your brakes. I'm also going to pursue activating the Exhaust Brake circuit that will close the turbo vanes (or an external exhaust "jake brake" valve) for even more engine braking power; this is the same function that Stephen gets with his Banks Tuner "speed brake" function, details are here:
http://www.dieselplace.com/forum/71-information-place/19-do-yoursel...
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dkarnath
Posted 2017-05-10 12:56 PM (#4598 - in reply to #4555)
Subject: RE: Duramax Coach Lessons Learned


Elite Veteran

5001002525
Location: Medford, OR
You said "new brake drums are on their way" earlier in this thread. Where did you find these?

Thanks Len
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LCAC_Man
Posted 2017-05-10 2:51 PM (#4602 - in reply to #4555)
Subject: Re: Duramax Coach Lessons Learned


Elite Veteran

5001001001002525
Location: Oceanside, CA
Gregg Miller coordinated a group buy with a vendor in Salinas, CA. Based on the original timeline they should be coming soon..
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fmc708
Posted 2017-05-10 6:36 PM (#4611 - in reply to #4555)
Subject: Re: Duramax Coach Lessons Learned



Veteran

100
Location: Soquel, CA.
Yep. They are supposed to be done this month. I had to order a batch of 8 as a minimum. Turns out that Durabrake is doing 20. As of right now, they are all spoken for. I bet it would be fairly easy to get a few more FMC owners to order another batch. I happen to be going through Salinas Truck Parts. But, I imagine one could go direct too.
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Darren
Posted 2017-05-15 12:13 PM (#4643 - in reply to #4611)
Subject: Re: Duramax Coach Lessons Learned



Contributor

25
Location: Washougal, WA

fmc708 - 2017-05-11 4:36 PM Yep. They are supposed to be done this month. I had to order a batch of 8 as a minimum. Turns out that Durabrake is doing 20. As of right now, they are all spoken for. I bet it would be fairly easy to get a few more FMC owners to order another batch. I happen to be going through Salinas Truck Parts. But, I imagine one could go direct too.

You can add me to the list of interested parties. 

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