Community Forums

dynacopas · 06-03-2014, 08:46 AM

Hi guys got a quick question. I know there are a lot of C4500 owners that have Dmax/allison combos. My question is are there any that have an 8.1L powered truck. I am close to acquiring one with the 8.1L/Allison combo. Additionally it has 5.13 rear gear much like the workhorse motor homes. I do have a Newmar Kountry Aire 39RKWB which is quite heavy. The reason for going to the MDT is the fact that it can stop the rig safely etc. Gas mileage I know won't be the greatest but I have had gas powered 1 tons forever. My theory is for the cost of the diesel in most cases 10K or more...I can buy a lot of gas with that money.
Also current 1 Ton gas powered dually has 462K on the original engine and transmission NO REBUILDS yet. Thought I would throw that out there to stop the diesel war.

From what I have read the MDT diesels 3128 Caterpillars and a few others really aren't cut out to do this kind of work. And suffer on low power levels. Dmax diesels in the C4500 are known to be de-tuned power wise to keep from burning the engine up with the increased weight and MDT drivetrain. 8.1L engine in a larger heavier duty truck seemed to me to be the next step.

The few that have the 8.1L powered trucks I am curious to hear your opinions. Mileage? How does it do on long grades? Have you been able to do any performance tuning? Any other upgrades to the transmission or engine that help. Looking forward to comments and insight.

chiefneon · 06-03-2014, 12:55 PM

Howdy!

I had a 2005 C5500 with Duramax/Allison the truck did OK towing our large 5er. I traded it over a year ago because I begain to have problems finding parts for it. GM stopped making all their MDT's after the bailout. I now have a 4400 International 2L Custom hauler, great truck and does a much beter job towing our 5er.

"Happy Trails"
Chiefneon

dduerden · 09-04-2014, 03:20 AM

I'm currently towing with a 2005 GMC Topkick C6500. I picked up chassis from Schwan's that has a propane powered 8.1 engine. We did the build up with a custom sleeper/box, fifth wheel, etc. the current trailer is a 40' race/living quarters trailer that is 22,000# loaded, including cargo in the truck I've had it scaled as high as 34,500# total. It is an allison trans with a 5.57 gear, which turns the motor only about 200 rpm higher on the highway than my 3500 dually with the same motor. This truck has 22.5 tires, if yours has 19.5 then your gear makes sense to turn about the same rpm.

I've had good luck towing with this, the dually was pretty scary at that trailer weight, and the 6500 does a far better job handling the weight as far as stability and braking. You hardly know trailer is back there except of course for the weight on hills. Power is not great, but I can just hang with the semis on a grade. This one is governed at about 73 mph and it'll run that nicely on the flat. I could probably figure out how to get rid of that, but it kind of keeps me out of trouble since I don't have cruise and the speed limits are all 70 here in the east anyway. It has a little less power than my dually, but the truck and extra cargo is 12000# vs 7500# for the dually, so I attribute it to the extra weight. Fuel mileage is poor, the dually only got about 7 with that trailer, and the 6500 gets 5. But propane is generally cheaper than gas if you know where to buy, and I generally top off locally at my neighborhood welding supply that gives me a good deal so my cost per mile is better than the dually.

I've had a bunch of 8.1 gas duallies over the years and got a bunch of miles out of them maintenance free as you mentioned. Yeah, we get less mileage than a duramax, but the truck is cheaper, maintenance is cheaper, and we can drop in a whole crate motor if need be for about the price of just replacing the injectors on a diesel. And the fuel is cheaper. I am definitely a fan of the 8.1 for a dually. Maybe a bit light on power in a mdt, but I am towing heavier than the average fifth wheel guy. We are going later this week to pick up a 37' fifth wheel toy hauler the is only 13000#, so I suspect with that trailer I won't even know it's back there compared to the current rig. I'll let you know how that goes.

consolenut · 01-24-2015, 07:42 PM

The 4500 with 8.1L and six speed allison does an awesome job hauling the kountry aire. Averaged 8.2mpg over 500 miles. At 65mph its only turning 1700rpm according to the tach. Easy to stop and pulls it much easier then the 1 ton.

consolenut · 01-24-2015, 07:47 PM

http://i1346.photobucket.com/albums/...psl7mmwiae.jpg

Have a look hooked up. Little nose high not bad

maddczech · 02-13-2015, 03:41 PM

I recently bought a 07 monroe conversion kodiak. 127 on the clock with the duramax and 6 spd allison with rear air suspension and air ride cab. I swear its as good a ride as my buick if not better for posture with lumbar adjst. We pull a 38 alfa see ya tri-axle, 13500# mt, 18500 loaded rating. Like you, I wanted big brakes for downhill braking w/o warping and heating up.
No troublewith power, plenty of that. Good braking through Tennessee to Florida. My wife drove the whole way as I followed with our older 95 class a coachman28. Btw the kodiak drives very well even bobtailing, no sore backs after 500 miles. And she handles like a car ! The price was cheaper than most 3500s and 350 and 450s, and that's crew cab , goose hitch, hd receiver, chrome runningboards and stacks, 5k on the tires. It was a no brainer for us . I feel the Iinterior is cheap plastic , on the side panels and accessories pedestal ,chevrolets bad !
The air suspension allows to dump air to lower truck bed for hooking up to our goose adaptor bolted to the lippet box.
As far as diesel/gas goes , I don't see what that's all about. Personally its a matter of preference. I actually considered an 8.1 unit, and would not be afraid of it, especially at gas prices. We are not on the road constantly, parked in fla till weather is warmer elsewhere, so fuel not an issue. We got 15mpg bobtailing on our first trip up north, but not going to even check what city driving is.
My writing is kinda just thoughts as they arrive in my memory here. Imho there are lots of available Monroe kodiaks out there for sale. They are no longer made by chev since 09. Monroes are only about 700 annually. The monroe people were nice and courteous to me when asking questions. Monroe apparently had some issues with contractors on items as sunroofs, headlight adjustments, steering mods, clearance lights. Ours had cracked marker lights which I sealed with silicone. That has seemed to stop the sunroof leaking issue. We have no steering issues. I do notice lousy headlight coverage at night, but simply don't relish night driving anyway. One drawback I don't like is that compresskrs run constantly on both 12 volt compressors. One for air horn and seats, one for rear suspension. Im in the middle of installing a remote switch in cab pedestal to shut of the accessories one as it is annoying and alarms pedestrians when it relieves like the loudest elephant fart you ever heard. I'm reinventing the mounting holes in the pedestal (cheap chev brittle plastic).
Our Kodiak is the Monroe p/u Box version with the goose hideaway ball. I caution anyone toting 5ers. Its easy to be towing high in front with that version, as that air suspension is not adjustable, its either off or on. In retrospect, I would definitely consider a toter body as opposed to p/u box. And don't trust a sales person at Caming World to tell you "no problem" hooking up to anything unless he owns the same setup you intend to purchase. Sales people at .... nevermind, I'm totally biased on that completely different subject, lol.
I'd be glad to answer any questions about our setup. And welcome all comments on anything rv. My opinions are based on my experiences, not hearsay.

consolenut · 02-14-2015, 04:45 PM

I adjusted the b&w conpanion down and adjusted the tube style pin box up. That cured the nose high condition. I even added a half tank of fresh water to inprove ride quality a little more. No air ride on my truck though.

maddczech · 02-15-2015, 01:09 AM

Yup I may adjust the pin box up a notch. However , I'm concerned that the distance between camper and truck box rail may get too close for comfort. The Alfas a low rider, the kodiak a high rider. I'm thinking also there's got to be a way to control the height of the truck air bag system. Whether that's advisable is yet to be determined, jury still out on that.

consolenut · 10-25-2016, 09:10 AM

Quick update. I've added the trailer saver tslb air ride hitch. Also added rear shocks to the truck. As mine came without rear shocks. The trailer saver hitch is worth its weight in gold. The ride quality is sooooo much better. Mounting it to the frame of the truck was a challenge but all is good. Don't hesitate buying a trailer saver.

consolenut · 10-25-2016, 10:13 AM

Pic of the hitch mounted in anyone is interested

maddczech · 10-26-2016, 08:21 AM

Quote:

Originally Posted by consolenut

Pic of the hitch mounted in anyone is interested

Nice setup.
My issue with that type of set up is that it takes up so much freight space.
Most recent project for me was hauling 28ft sailboat which I fitted on a gooseneck 5ver, custom adaptation.

grassy · 11-18-2016, 06:48 PM

So far I am averaging 13 mpg with my cat 3126B engine..with no power problems.. however, since cat has gotten out of the truck market, there are some diesel shops that won't work on them.

Would I ever go back to a pick up to haul...not that I can imagine..