Multifuel Reliability or The M35 itself

[Hummer Guy]

I've done a ton of reading, researching, & talking to others; I haven't seen any thread talk about it in a long time so I would like to hear some updated experience of the reliability with the 465 multifuels & the truck itself. I hear mix results from people, a lot say the engine is reliable and others who say the engine is expected to last only 50,000 miles. My assumption is that these engines only last 50k if you drive them at 2600 RPMs non stop & not caring about your EGTs. My truck have almost 35k miles and so far I've only had to do basic maintenance and fix things that I cause too break, now I finally got my first issue though, I have a small oil leak when the engine warms up, it seems to be around the injector pump (Don't seem like a big deal, gaskets gets old overtime) I typically keep my RPMs around 2200 and at the most 2300, my EGTs is around 900 Unloaded and 1200 at the most with a load. So, let's hear about everyone else experience, how reliable has your truck been & what issues you guys have?

I'm currently debating on going through my whole truck next year and possibly doing an engine swap, a 12 valve cummins comes to mind, but Im a big fan of the multifuels, I would prefer to rebuild an LDS with an HX40 turbo & head studs to help with the head gaskets with its high compression (Im only looking for around 250hp or so, reliability over power) but it's not worth it if the engine life expectancy is only 50,000 miles when a 12 valve can get 500,000 - 1,000,000 miles out of them. As for the rest of the truck, I know everything else is fairly bulletproof if maintained properly, Im not a fan of the spicer 5 speed but I can live with its short overdrive, Im hoping the 395 tires can bring my RPMs to 2,300 at 60mph, and for brakes Im planning on doing disc brakes in the rear.

 

[tommys2patrick]

for what its worth, a lot of vehicles of the period had what most people would now consider a short lifespan compared to modern vehicles. on the other hand we definitely live in a throw away/replace entire systems world now. The deuce is what I consider reliable. things that break and or wear out can be replaced repaired.in the fifties and sixties we still had a robust infrastructure that was geared to repair / replace thus keeping a vehicle on the road and reliable. most young men and some women grew up learning how to keep things reliable. not so much anymore. having a deuce be a daily driver requires a fairly serious commitment backed up by the right knowledge, tools, time, space and a certain amount of passion. one last thought, changing to a more "reliable" modern engine or transmission only deals with a relatively small part of the deuce. the entire truck and all of its subsystems were designed and built with this understanding. my two cents-which is what its worth on the open market these days.

 

[Redleg130]

I have 395s and do not have full swing on right hand turns. You also cannot keep spare in the spare rack since it wont fit there. Not show stoppers, but factors for consideration.

My thoughts - If you want a truck that is "as issued" then naturally you would have to keep the multifuel. I am about finished with rebuilding an M37 and finding a machine shop to do rebuild of engine is possible but on the good/cheap/fast thing, you only get to pick one (and its best to pick good). This will likely be the last rebuild of that truck since parts were fairly difficult to find (eg crankshaft). Parts availability for standard M35 parts seems less difficult than M37, but still limited, so not a perfect analogy, but something to consider as part of the thought process.
If you aren't limited by keeping it "as issued" then a more common engine will have better parts availability as time passes. One thing I love about my M35 is the unique sound it has (I think largely the turbo) so losing that in my case would be sad.
But as Tommys said, the whole truck as a system is the challenge so I would say 6 of one, half dozen of the other I suppose? In my case, I would balance all the intangibles and cost then go from there. Having worked with the M35 in service in the 80s/90s I would say its durability is pretty great, but that experience is with M35s backed by a maintenance support company and funded supply chain.

 

[Guyfang]

I agree with Red Leg. If you want to have a "stock" M35, you need to dig deep into the TM's, and have some serious tools and the time and money to keep it in good running condition. I would not try and "Improve" it with engines or other changes. It work, It works great, even when its broke. I was, on the one side, like Red Leg, in units that needed a DS, (Third Shop) to help support our M35's. And about the only thing our Motor Pool could not do, was engine and axle replacements. We called them Major Assemblies. Then later, as a Shop officer, ran a DS shop. So I have a little knowledge of the M35. About the only thing I would tell you to improve is the Hydo-Vac brake system. This is an incredibly robust truck. A fellow CWO and I once found a M35 that had a fire in the cab. All controls and wires burnt up. No one could move it. The owning unit was uploading for Desert Storm, and it had to be gotten out of the way, ASAP. We told them to simply push it and pop 2nd gear. It started right up. We put a German beer case in it as a seat, and drove it away. With just a little care, it will run until you are long dead. The one thing it is not, is a car. You can not hop in and go for years without maintenance upkeep. If you are not up to that job, get ready to find someone who is, and be ready to pay them their price.

 

[NY Tom]

I almost don't understand why they replaced them with LMTV. OK creature comforts help and people can't drive manual trans. But they can teach kids to operate high tech missile systems? I can't imagine convoys needing to run much over 50 to get anywhere especially if any tracked vehicles in the unit. Quite capable off road. Very simple and easy to repair. Cheap. Oh well I am too old school...

 

[SCSG-G4]

I've done a ton of reading, researching, & talking to others; I haven't seen any thread talk about it in a long time so I would like to hear some updated experience of the reliability with the 465 multifuels & the truck itself. I hear mix results from people, a lot say the engine is reliable and others who say the engine is expected to last only 50,000 miles. My assumption is that these engines only last 50k if you drive them at 2600 RPMs non stop & not caring about your EGTs. My truck have almost 35k miles and so far I've only had to do basic maintenance and fix things that I cause too break, now I finally got my first issue though, I have a small oil leak when the engine warms up, it seems to be around the injector pump (Don't seem like a big deal, gaskets gets old overtime) I typically keep my RPMs around 2200 and at the most 2300, my EGTs is around 900 Unloaded and 1200 at the most with a load. So, let's hear about everyone else experience, how reliable has your truck been & what issues you guys have?

I'm currently debating on going through my whole truck next year and possibly doing an engine swap, a 12 valve cummins comes to mind, but Im a big fan of the multifuels, I would prefer to rebuild an LDS with an HX40 turbo & head studs to help with the head gaskets with its high compression (Im only looking for around 250hp or so, reliability over power) but it's not worth it if the engine life expectancy is only 50,000 miles when a 12 valve can get 500,000 - 1,000,000 miles out of them. As for the rest of the truck, I know everything else is fairly bulletproof if maintained properly, Im not a fan of the spicer 5 speed but I can live with its short overdrive, Im hoping the 395 tires can bring my RPMs to 2,300 at 60mph, and for brakes Im planning on doing disc brakes in the rear.

The Hercules/White engine was used in farm tractors (Oliver line) and they lasted 9,000-12,000 hours before a rebuild, but were hardly ever revved above 2200 rpm's. How many hours on your engine? 9000 hours at 40 mph is 360,000 miles.

 

[tommys2patrick]

the ldt engine, lds as well, will likely leak oil from time to time from one place or another. it is not uncommon to have to replace a head gasket. like most things mechanical it will need some maintenance. it is definitely not a toyota engine. i've put 300,000 plus miles on more than one and never had so much as a hickup . i did do basic maintenance. generally speaking the ldt/lds is built like a tank and even with an occasional rebuild from minor to major it will likely outlast your plans. do they occasionally throw a rod--its been known to happen. the military had facilities placed strategically around the globe for major overhauls. they supported the vehicle with the best available resources. generally speaking is it a good choice for a daily driver-no. have people done just that anyway-yes.

I have known people that took a 1969 roadrunner and restomoded it into a relatively reliable daily driver. about the only thing that was left stock was the interior and body. could you do the same with an M35-yes. people that do this to a 69 roadrunner usually find the cost to be outrageous and that what they have left can only be called a 69 roadrunner for outward appearance sake.

only you can decide what you want to accomplish and why. this site has plenty of resources and lots of folks that care about old military vehicles. we would love to see what you come up with for your vision of an m35.

 

[Hummer Guy]

I almost don't understand why they replaced them with LMTV. OK creature comforts help and people can't drive manual trans. But they can teach kids to operate high tech missile systems? I can't imagine convoys needing to run much over 50 to get anywhere especially if any tracked vehicles in the unit. Quite capable off road. Very simple and easy to repair. Cheap. Oh well I am too old school...

Clutch replacements is probably the main reason, no matter how much training you do, vehicles in service are driven by 18 year olds that would dump the clutch at red line

 

[Hummer Guy]

The Hercules/White engine was used in farm tractors (Oliver line) and they lasted 9,000-12,000 hours before a rebuild, but were hardly ever revved above 2200 rpm's. How many hours on your engine? 9000 hours at 40 mph is 360,000 miles.

Mines only have around 300 hours, hearing that definitely gives me more confidence since 2200 RPMs is about the most I run

 

[G744]

Years ago, I was at the Yermo USMC base in Barstow, Ca to pick up an M37 I bought from DRMO.

I talked to a mechanic there, and the topic went to the Multifuel engine. He escorted me to a fenced acre full of hundreds of pallets, each with a multifuel with the center web blown out.

The story was there is a harmonic problem with those engines, not related to maintenance but design.

His description was "They're like light bulbs, you never know when they will burn out".

Nothing like proof to affect one's thinking...

 

[Hummer Guy]

Years ago, I was at the Yermo USMC base in Barstow, Ca to pick up an M37 I bought from DRMO.

I talked to a mechanic there, and the topic went to the Multifuel engine. He escorted me to a fenced acre full of hundreds of pallets, each with a multifuel with the center web blown out.

The story was there is a harmonic problem with those engines, not related to maintenance but design.

His description was "They're like light bulbs, you never know when they will burn out".

Nothing like proof to affect one's thinking...

Yep, I've heard about the harmonic balancer failure with these engines, that's on the top of my list of things that scares me with these engines, I don't mind the extra maintenance with these trucks because I'm all about keeping up with maintenance, but the fact the harmonic balancer can give out at any time and damn near destroy the engine is one of my main concerns.

 

[SCSG-G4]

We had problems with deuce engines in Southeast Asia, but it was mainly 18 year olds red-lining the engines to avoid ambushes (or try to get out of them). At one point they shut down the production line for complete trucks just so they could ship engines (by air) to replace the ones that blew up. Higher the RPM's, the more stress on the harmonic balancer.

 

[Computerdoc08]

I‘ve only been working on my multi-fuel for a couple of years now and haven’t got into any major engine mechanicals yet…

but would some thing like a Fluid Dampr product to replace the OEM harmonic balancer help with it’s possible issues?

Fluid Dampr

 

[G744]

What I witnessed wasn't attributed to the harmonic balancer failing, said by the old mechanic. It was a dynamic fault in the design.

I don't now if Hercules ever really did any research, or maybe later Continental did.

There were at least 4 iterations of the MAN-patent engines; 427, LD-465, LDT-465-1, and the LDT-465-2 (as found in M656 and M767 trucks).

 

[fuzzytoaster]

I almost don't understand why they replaced them with LMTV. OK creature comforts help and people can't drive manual trans. But they can teach kids to operate high tech missile systems? I can't imagine convoys needing to run much over 50 to get anywhere especially if any tracked vehicles in the unit. Quite capable off road. Very simple and easy to repair. Cheap. Oh well I am too old school...

It was a shift in Army mentality based on personnel and expenses. Less fresh recruits were able to drive a manual and the long term expenses of this was something they aimed to reduce. There is a publication out there (I'm racking my brain for the technical name but basically a military dissertation) that laid out a lot of info about it in the 80s. This thinking is what ultimately killed all manual transmissions for the Army. The M809 were the first to feel the sting as AMG was pushing for a upgraded model with CTIS but the mandate for an automatic transmission stopped it cold. The M939 series was born and went on from there.

There were some oddball prototypes made on the M35 chassis to meet requirements but ultimately failed. Cost and chassis age being the driving concerns from what I remember. The one prototype that comes to mind has a 3208 Caterpillar and some early Allison (unknown) but also a M939 cab on it.

Why the FMTV? Oh jeeze.. it's more than I want to write at this hour. To simplify it: cost, speed of delivery, and condensing the fleet. COTS (commercial off the shelf) sounded good to the Army for cost reduction and the FMTV had 83.X% parts cross compatibility. Freightliner, Stewart & Stevenson, and International Harvester were the big 3 able to meet delivery schedules. The family of trucks could replace all those in service/class: M39, M809, and M939 series 5 tons plus all M35 2.5 ton variants.

 

[G744]

Coulda, shoulda, woulda.

The three most defeatist words in the English language.