M816 Cummins egine mods needed

[Jersey4x4]

So I have had the wrecker for about a week and now it is time to make some changes. It is very loud with the fan spinning all the time so I am looking into swapping out the fan hub with an air operated fan clutch and looking into adding an engine brake like the "C Brake" or Jacobs engine brake. Has anyone done anything like this but still be able to retain military parts. I want to keep the 24v system and dont want to lose the Military feel of the truck but want a little extra user friendly add on's. Possibly even adding an air throttle to replace the cable unit from the drag winch control. Also adding a manual unlock overide to the transfercase for the 6x6 function to be disabled for normal driving. If there is any input let me know. Also want to add the trolley brake to the truck but am not sure how exactly that would work with the juice/air brake system used on this truck. Thanks

 

[sandcobra164]

The 800 series wreckers are about as basic as they come. I doubt you could put a jake brake on it without spending a ton, an exhaust brake may work but I've not seen one on a N/A Diesel. The transfer works fine as is, it'll jump in if you're spinning the rears which you shouldn't on a truck that weighs this much unless it and the load you're pulling really does not want to go. Check the load.

 

[Jersey4x4]

I found the C Brakes which are made by Cummins for about $300.00 for all 3 of them and in the grand sceme of things with this truck that is not that bad. The fan would be the more important thing on my list to get a clutch on. I run it yesterday with no belts and the sound and even RPM difference was amazing. The RPM climb rate was super quick, it was almost like driving a normal truck, and how nice it was not hearing the HUEY under the hood. As for the transfer case, I am noticing in first and reverse at tight turns it is binding like the 6x6 is locked in and I hear an air switch of some kind when shifting in that range from R to N to 1st but not in any other gear and if I put the Case in low and use second I don't get the bind. It just feels like the front axle is locked in and I was thinking if it was connected to lock the sprague in directly in reverse and first maybe I could install a manual air switch to keep it unlocked for maneuvering and such. That and I like switches, I would fill the dash with air switches if I could think of uses for them.

 

[R Racing]

Dont think your switch idea is going to work. The air you hear is switch from the forward to the reverse sprague . It uses air on both sides not just 1 like the duece for the front wheel drive. there are several posts about it on here. also without the turbos boost im not sure how ur jake brakes going to work. have you thought about a clutch fan instead of a air clutch ? the air clutch units minus the fan and temp operated air switch are close to a grand if I remember correctly. There is also a post on here about that as well. Try a search. Good luck .

 

[Floridianson]

Yea you could get rid of the fan and get an electric one.
I would think for the most part a engine brake or what ever you think you need to slow down would be a waste. Your not a simi with 80k behind you going down a 13 mile steep grade.
The truck is heavy, slow and underpowered so don't try and drive it fast.
I would say outher than the fan leave it alone or if you can find a nonover drive transmission put that in and be happy.

 

[area52]

My M816 came from the military with a Jacobs brake already installed. They had to put a "box" in the hood to clear the raised valve covers in the rear. There are several posts about putting an air cut off for the sprag t-case to put it in "neutral".

 

[supermechanic]

I put a viscous drive fan on mine, now I don't sound like an A-10 when I go down the road.
I had to do some machine work on the hub, cut and balance the blades, and modify the fan shroud, but the end result was worth the effort.
I think the fan donor was a GMC Brigadier with a 6v-92 detroit, most likely an easier swap out there, but the fan was free to me and I have a well stocked shop, so machine work wasn't an issue.

 

[Jersey4x4]

I am a collector that actually uses the trucks for what they were built for and beyond so I need added slowing when loaded. The Juice brakes are not strong enough to stop a 36000lb truck with a loaded 10 ton trailer which is spec for the 816 but I will be doing this often and the added engine braking will help allot. The engine brake will help to save the brake system n the truck from extreme heat when slowing down saving the brakes for actual stopping. Also if it had the trolley brake I could use the trailer as it was intended to slow down the truck and save the truck brakes. Neutraling out the sprague is exactly what I was looking to do, so maybe i will try that to see what happens. As for the fan, I have a complete machine shop so I can do anything. I have a 6v92 engine in an Amertek 2500L and it uses a Kysor fan clutch but it does not look anything like the cummins hub. Can you maybe post a pic of it and some more details. Yep the A-10 Warthog is a good comparison to the sound when standing in front of the truck while the crane is in operation. I do not want electric, i want to keep the mechanical fan so it at least still looks military to a point, I dont want it to look like a rice car under the hood. Thanks

 

[DaveP]

The Jake brake idea is a good one. with these single circut brake systems the engine brake could very well be your only means of slowing the thing down if something fails. dont even bother reaching for the parking brake at speed because all it will do is roll smoke.

jakes will not fit without some slight modification of the hood. I had a set on one of mine. they fit with the crossbrace in the hood cut out and a slight bump made rite where the front rocker box cover hits the hood. also the lifting ring at the rear will need to be cut off just above the brace for the coolant tank. the front ring will need to be deleted.

as far as the fan drive mod--------- this will be a little tricky with such little room at the front.

the noise reduction and the fuel savings would make it worth all the trouble.

please document and share your findings with us if you make it happen.

heres a shot of the front with rad and fan removed.
as you can see the fan is mounted very low compared to most 855's. this makes it tough to find civi parts to do the swap with.

 

[Floridianson]

I still would lean towards maybe a turbo up grade over a jake just to improve the truck alone.
Seems like the way the truck was intended was to assist in recovery and maybe tow something slowly home.
Maybe the choise of wreckers should have been the 900 series with air brakes. I just feel the 916 with is juice brakes should not be driven hard, fast or drag heavy loads at highway speeds. OK the Goverment add a jake to some trucks but if driven like the age and ability of the truck calls for your looking at 45mph.

 

[jaxsof]

Maybe I'm missing something here, but you do have trailer air brakes, if the weight of the trailer is whats concerning you most.

I like the fan-depowering idea.

 

[jwaller]

check my topics for the turbo swap and spin on oil filter kits. Turbo upgrade was the best mod I've done so far.

 

[Jersey4x4]

There is trailer air brakes but there is no way to control them without the trolley brake in the truck. The trailer brakes are only active if the brake peddle is pushed in the truck and by then it is not really saving the truck brakes at all.

Maybe I'm missing something here, but you do have trailer air brakes, if the weight of the trailer is whats concerning you most.

I like the fan-depowering idea.

The turbo idea is great but for now I need it to stop better under a load and be quieter when driving/in operation. The turbo can come later when the truck actually starts to pay for itself. The turbo will not help slow down the truck and an exhaust brake is way less effective then the engine brake system would be.

 

[jwaller]

you need to brake down and put jakes on it. you will need to clearance the hood for the front rocker box but other than that it goes on just fine.

 

[Jersey4x4]

That is what I have been leaning tword but have not had any luck finding them.

you need to brake down and put jakes on it. you will need to clearance the hood for the front rocker box but other than that it goes on just fine.

 

[jaxsof]

My mistake, brother. I have seen 816's with the trailer brake handle. Checked my manuals, and they were only issued with 815, 818, and 819s. If you find an 818, theyre everywhere, its an easy addition.

 

[R Racing]

Mine runs good but wont climb a hill to save its life so i'm thinking turbo is next on the list for it. I don't see how some people get away with the 16.00 X20 tires ? Mine has a new engine with almost 10 hrs on it. Replaced the fuel filter and all fuel lines.

 

[m16ty]

For the fan clutch, I'd just get a air clutch off of a newer Cummins engine. All modern Cummins have air clutches and I'm not 100% sure but I think it would be a direct bolt on. Should be able to find one in a truck salvage yard for $100 or less.

An exhaust brake doesn't compare to an engine brake. I can hit the Jake on my FL with 400 Cummins and it will make you lean foward in the seat.

 

[OPCOM]

looking at this, where does one add an A/C compressor? Anyone done that?

Several people have said the NHC250 is already maxed out on power and does not have piston coolers, but I don't know.

also jwaller - -your website link http://www.wallerperformance.com is some kind of "advetisement farm". Did you get the domain name hijacked?

 

[R Racing]

I'll have to look at belt routing but either above the Alt, or beside the crank on the drivers side looks possible.