I've seen them overall black...but thats normally after a depot level rehaul

The 903s (on AAVs) we got back from rebuild returned in all sorts of colors. If the vehicles went through depot level maintenance at Barstow or Albany, the engines were either green or black. However, if it were only the engine that went through some sort of maintenance I’ve seen them return in overall white, green, gloss black and even had one return in a color I can only describe as Gumby green – bright, very bright green. The RAM/RS 903s came in an overall gloss very dark gray, and some were gloss black. The newer AAV SU engines are coming in overall bright red. The colors were all over the map and not confined to “camouflage appropriate” finishes.

The 903s I worked on were in the MLRS. Now that you mention it I do recall them being white also, maybe even recall some being yellow. When I went to depot level rebuild shops, I did see them in gloss black.

OK, new line of questions about the engine:

Out the back of the engine ( over the transmission and at about the level of the intake manifold ) there is clearly a gear box of some kind,

The Real Models instruction sheet is telling me to install what looks like the starter motor and the air compressor back there. Is this correct? I can find photos of the air compressor back there but nothing else.

The TM shows the starter and the air compressor as separate assemblies but again there is no overall engine photo/ drawing to show you where they mount??????

In this picture you can see the air compressor and a hydraulic pump.

At the bottom left side of the engine, down in the engine stand, you can see the front part of the starter.

This part of the gear box, drives the blower.

It was my understanding that the hydraulic pump mounted to the PTO on the transmission but now I am guessing that was an earlier version of the engine?

Actually, the pump for the hydraulic system may have been on a PTO on the transmission. The pump that I pointed out in the pic is probably for the steering system. Nonetheless, regardless of the oil it's pumping or what system it's going to, it's still a hydraulic pump, technically speaking. Lol

Mike, the gear box is called the gear drive or accessory drive. The air compressor is on the right and the pump to the left is the power steering pump.

On the subject of colors, total vehicle repaint at Depot level used to be CARC paint, Green, camo or sand. Repainting fleets just for weathering at CONUS/OCONUS field locations is not always done in CARC, and the "sand" color sometimes looks like coffee with lots of creamer, but only the externals are done, not inside cabs.

Individual mechanical component colors:
Again it varies tremendously, from new, through rebuild(s) by who and where.
The white color engines mentioned were overhauled by Prison Industries, no comment, but you won't see anymore out there.
Original earlier Detroit's come in whatever the contract calls for, but the vast majority are the blue/green, green/blue color for new and rebuilt's done by Detroit.

Original transmission color is aluminum, then it gets whatever color the vehicle becomes when new. Rebuilts from different rebuilders will usually come back black, then get painted whenever the vehicle does. Transfer cases can be red oxide, black, green, sand, whatever the contract calls for and how many rattlecans are available.
The funny green color engines if seen out around Irwin/MCLB are what used to be called "rattlecan rebuilds".

Like any large organization spread all over the world, if you are modeling a certain vehicle from a photograph, it looked like that at that point in time, not for all its service life.
Depending where you are you may see HEMMTs/PLS/Tankers with wheels that have different tread pattern tires on one or two wheels in any position along with one or more black/green centered wheels on sand colored vehicles, or HET trailers with grey road wheels as spares, or all or any combination thereof, the grey rims are new wheels that replace the bent rims and again get painted when the trailer does.

Hope the above helps.

hope you don't mind me adding to your thread but wanted to post some pictures of the HEMTT cab I have been working on.

Keith, I don't mind you posting your work on the cab, not one bit. First of all the more the merrier! Second, I ordered an etch cabin detail set myself and having seen your advance information on your build will help me (I hope) to do a better job building mine.

OK, another "accessory gearbox" question. I am guessing the following is a mistake on Real Model's part but I need to check with you guys. RM mounts the air compressor on the right rear corner of that gearbox which is OK but it is a DOUBLE compressor - it has FOUR cylinders!

It is clearly supposed to be two compressors on a common shaft. So, was there ever a HEMTT that either needed a high enough volume of brake air to need two air compressors or a HEMTT that needed a higher psi so they would run two compressors in a two stage arrangement to produce a higher output air pressure?

Can you post a photo of the part? I have never seen what it seems you are describing. My experience is from the OTR trucks I drove in the past with the 6v and 8v92 engines only.

Hi, Mike!

Been following your build- GREAT STUFF! Someday, I'll get the chance to build my HEMTT Fuel Tanker! I bought it about 10 years ago, but have been too busy with other stuff...

4 cylinder air compressor (I think) . . . . . . . . . . . . Mystery device


This is how they want you to put them together.


And they tell you to put them here.

Also; what is all that stuff on the transmission? Never saw anything like that but if I had to guess it is either some sort of cooler or an electrical generator????

I think now that maybe the person who originally mastered this engine model was not looking at a HEMTT reference, they were looking at a gen-set reference. An emergency back-up electrical generator set that happen to use the same engine as the HEMTT.

Never saw a compressor like that. Looks like it should be cut in half before you install it. That mystery devise is a mystery. Lol

All I have ever seen is a simple twin cylinder compressor bolted to the back of the accessory drive.

I cant help with the tranny question, sorry. But, for the earlier Hemtt it kinda looks like the Trumpeter tranny looks more right.

Taylor, my thought exactly - cut the compressor in half and make it look normal!

Also the other mystery device looks like two hydraulic pumps connected end to end. I was thinking of cutting that in half also.


Again I cannot figure out just what is going on with all that extra mechanism on the tranny. It looks great but it looks wrong.

I agree on the compressor and the p/s pump 100 percent. As for the tranny, I am not saying its wrong because I honestly dont have experience with it.

It seems the Hemtt had 2, possibly 3 trannies during the upgrades. It just seems to me that the Trumpeter trans looks much closer to the photos I have seen on the net associated with the earlier Hemtt.

Typical standard HEMTT transmission:






Must be a rebuild. (Photo by BlackManistan)

Partial exploded drawing of HEMTT air compressor.

Starter Assembly:

Typical Hydraulic Pump:



What you are looking at is only about seven inches tall but can put out enough force to run the recovery winch or the LHS equipment!