FMTV Pre-Production Prototypes

fuzzytoaster

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**This thread may continue to develop as facts and documentation are discovered.**​


I had the fortune of unknowingly recovering 2 prototype MTVs this past week from a location not too far from the old Stewart & Stevenson plant in Sealy, Texas. I'm doing the due diligence of documenting the vehicles for record keeping and my personal interest that I want to share with the MV community should they find it interesting. I encourage observation and discussion in this thread.

These two MTVs are now referred to as an M1084 and M1088 by current military documents. Data plates, numbers, etc are simply not on the vehicles due to their earlier production year (pre-contract) or are missing but they will be referred to their model numbers for ease of discussion. Both trucks are technically pre-production prototypes and not "proof of concepts” by definition as most major components remained the same to the production phase. Other changes were made but overall the functionality of the vehicles remained the same. Now that all that is out of the way..

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M1084 & M1088​

These are 2 of 5 known prototypes released directly from Stewart & Stevenson before they were awarded the Army contract. The M1084 has no data plate in the cab but the rear crane is dated 92' as are the axles so it’s assumed to be of the same year. The M1088 has a data plate but is unstamped on year and so far no dates have been found. Each truck was either donated to or purchased by a VFD where they saw limited service and sat for years until recovered.

The M1084's main components were largely unchanged and made it into production. The cab, crane with outriggers, bed, and power train are the same as our contract made FMTVs with the exception of the axles being stamped "Rockwell International'" instead of Meritor that we all know today. The ratio is still 3.90 with the 2:1 hubs and looks complete unchanged without opening and confirming. Wheelbase is the same as a M1084 (I have one to directly compare). The transmission/transfer case is still an Allison 3070 wtecII like our first contract produced units as well. The engine is a Cat 3116 but the tag is partially unstamped or faded. The block serial doesn't come up in Caterpillar's online database either. Horsepower rating is currently unknown. The engine is largely unchanged except for more solid piping in some areas in place of flexible tubing.

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fuzzytoaster

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Now for the fun part..differences. S&S went with a spring cab suspension in place of the air ride. In fact there is no air assist system at all for the cab, suspension, spare tire assembly, etc. Each hydraulically driven system (excluding crane) is on a simple flow system that is isolated from one another with their own hand pump without reservoir. The "kneeling" system for compressing the suspension doesn't exist on this truck but is clearly labeled on the frame near the engine. The cab latch system has an additional hand latch which would have to be held while pumping up the cab for it to be released. They added a sensor to the cab latch mechanism to alert the driver if it wasn't latched and explains why our latch covers are threaded.

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The Grove crane assembly is almost 100% identical to my current M1084. Controls, hand/emergency pump, storage boxes, and all are exact. The electrical on/off switch that would normally be located on the control box is next to the remote cable plug it near the operator controls. Tail light assembly, bumpers, and even the rear mud guard are the same even in metal texture. The forward set of mudguards for the rear tires were removed on production trucks for reasons unknown.

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fuzzytoaster

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A unique feature is the addition of mudguards attached to the cab support assembly. It melds well with the black fenders and would explain why they went with that lipped style but begs the question of why they didn't make it to production. Cost cutting? Possible damage with the air ride cab? Who knows.. all speculation. The frame shows signs of a winch being installed at some point. I wouldn't be surprised if it did but again.. speculation as to why it was removed. I've not seen a M1084 with a winch yet either. Has anyone?

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Some of the more unique features include ABS (yes, on an "A0" truck), CTIS disable switch on the dash, and pull out battery box. There is no reverse polarity box behind the cab but rather a box beside the battery box that has a power disconnect switch, salve port, and other unknown tasks. The ABS module was located inside the cab on the rear wall probably just for testing purposes. I can’t see it staying there but it’s easy to access!

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fuzzytoaster

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The alternator is an unknown Niehoff 14v/28v S/N 00052 with no NSN or other identifying info on it. It too was made in 1992 supporting the production date of the truck itself. The one large plug on the unit goes down and feeds directly into the box beside the battery tray. The electricals in the dash are similar to the harness in most “A0” trucks with some improvements (too many to list). Under the PDP, the setup is nearly identical from placement of the CTIS to routing of wires. I’m fairly confident the TM could be used to sort out the dash.
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The instrument panel itself is largely unchanged. Odometer reads 46 miles! Only the function of certain toggle switches is different – CTIS Disable -> Lamp Test. There is a civilian ABS disable switch for off road application which is interesting. The heater unit is physically the same except for the blower cover which I’ve seen before on a few other early model M1078s. Controls and placement are identical including the PTO control panel and tach. All are also identical in function.

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fuzzytoaster

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The truck included 2 remote controls (one for a M1089) and a cable as well. The cab cover has a built in hatch. There is a red toggle switch on the left side of the steering column assumed to be a remove battery disconnect like later A1 trucks but has yet to be proven.

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Overall the truck isn’t in too bad of shape for its age. Tires are in route for it. It needs a deep power wash and removal of rusting components: turret cover, tool boxes, etc. and some rust neutralization. It worthy of being saved even if it wasn’t a M1084. I'll be posting a link later to more photos as the sit here only allows 10 per post.

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fuzzytoaster

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The M1088's history is still be researched. It is indeed a M1088 tractor but was converted to a cargo for VFD use at some point. I have some sources saying it was redone before S&S donated it to VFD as a promotion but I'm still looking for documentation.

This M1088 is closer to a "A0" truck in the sense of it lacking any unusual features like ABS, etc. It shares many common features with its sister M1084 including spring cab suspension, battery box setup, etc. and the powertrain is identical as well. I've not been able to lift the cab yet to check serials on the engine or components.

There are a door tags are present but you'll notice no "M" designation as the contract for bid is printed on the plate but wasn't awarded yet. This truck has a tachometer as a stock feature in the dash but was removed and full of water (oof..). The heater unit is identical to the M1084 but there is no winch/PTO control panel installed which is odd considering this truck has a winch but the PTO is routed to a pump for the bed.

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The most obvious unique feature is the rear cab glass which has been seen on other more unique "proof of concepts". I propose it was for better driver vision or was a civilian cab left unmodified which are both speculation. The bed is more in line with a modern M1083 bed including correct placement of stowage box panels, bed panels, etc. The setup behind the cab is reversed as the air cleaner is on the passenger side and dipstick and fill tubes are in the center of the truck. Very odd..

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fuzzytoaster

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The M1088 still has the dealer plate from 1985 and I'm digging to see if that was registered to S&S out of curiosity. Any work done in or to the bed I've assumed to not take to heart as it was modified for fire fight use. It's a simple design but effective.

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Who ever did the modifications routed the piping for the water cannon under the driver seat and wired in the remote controls. Overall the they did a clean job all the way down to the tail lights in the bed. It too has a lid in the turret cover so it must have been a stock feature the Army wasn't too keen on.

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fuzzytoaster

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The M1088 is worth the save as well and is in a little better condition than the M1084 rust wise. Both trucks could be combined to make a solid truck or even use modern M series parts to get it running. With 150 original miles on it I can't see this truck having been chasing any fires off road or abused. Tires are on order as well. I've got a comparison picture of this "grand-daddy" MTV next to the latest gen LMTV. There's only an 18 year gap between them production date wise so you can see what changed and what hasn't. It's just neat!

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fuzzytoaster

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Dang, nice freaken find
I think so too. They were literally sight unseen purchases.

is that an air intake (often for improved air cooling) on the back of the alternator? would love to see more pics of that if so.

These look near identical to the Steyr 12M18 cab suspension and rear side front fender w/bracket.
No it's just the air boot to the turbo. As for the suspension I see that there are springs very similar to it.
 

Gunny 0369

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VERY nice write ups Toaster, Great interesting read.
We purchased a PRE production MTV tanker, that was converted to a 1086 MHV LWB crane by Stewart and Stevenson to keep up with the ordered contracts.
It appears that they placed some of the pre production units in service/ contract when they were short of finished units.
Fun stuff.
 

fuzzytoaster

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VERY nice write ups Toaster, Great interesting read.
We purchased a PRE production MTV tanker, that was converted to a 1086 MHV LWB crane by Stewart and Stevenson to keep up with the ordered contracts.
It appears that they placed some of the pre production units in service/ contract when they were short of finished units.
Fun stuff.
Thank you. Any photos of this Tanker to 1086 conversion? I'm not surprised they did that as tehy were constantly behind on their delivery quotas. I've had a few people reach out to me on facebook about other FMTV oddballs but they've all been later "proof of concepts" with hybrid drives and one off stuff that never made it past that specific vehicle.
 

fuzzytoaster

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Here's photos of that hybrid unit. I was told it has a Cat (3116/3126) that powered a generator which power 2 electric motors. It looks like it has a T-1138 (M939 series) transfer case in it as well. These are not my photos and some are hard to understand due to perspective but it's neat. Major components are dated 2005 so this may have been a contender for their fleet rebuild program I'm guessing. Instead they reset trucks and kept them diesel with the C7.

This unit is for sale too apparently. I'm just tossing that out there.
 

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Gunny 0369

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Thank you. Any photos of this Tanker to 1086 conversion? I'm not surprised they did that as tehy were constantly behind on their delivery quotas. I've had a few people reach out to me on facebook about other FMTV oddballs but they've all been later "proof of concepts" with hybrid drives and one off stuff that never made it past that specific vehicle.
[/QUOT

The truck I received had the crane already attached, with the original NSN ID Tanker number still on the 94 Chassis. The truck transferred ammo from airfield to storage its whole life, with very little miles. Stickers still on the drive line.
 

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