Hobby Boss
M4 High Speed Tractor

Hobby Boss Kit No. 82408
1:35th Scale

Review by Terry Ashley

Hobby Boss

Following on from their initial M4 HST 90mm/3inch (kit #82407) Hobby Boss have fairly quickly released the second announced kit of the Later M4 HST 155mm/8-in./240mm which is the kit most modellers have been waiting for as we already have the AFV Club kits of the 155mm Gun (kit #AF35009) and 8inch Howitzer (kit #AF35S06) to hitch up to the back.

The M4 18-ton High Speed Tractor was designed as a prime mover for towing large field artillery pieces such as the 90mm AA gun/3inch gun and the 155mm gun, 240mm and 8inch Howitzers. In addition the M4 HST carried ammunition in cargo space racks with one type configured for the 90mm/3inch and another for the 155mm, 240mm and 8inch ammo. A crew of ten plus the driver could be carried with the M4 HST entering service in 1942 and was still being used up to around 1960.

This new kit from Hobby Boss as you would expect carries over many parts from the first kit with just a single large sprue F included for the revised rear ammunition box for the 155mm/8-in./240mm ammo as well as new correct drive sprockets and a new set of vinyl T48 rubber chevron tracks.

The kit represents the later configuration 155mm/8-in./240mm type the features of the later type return rollers and mountings, later ammo bins with side louvers along with the ammo loading crane and later rear hull features. This configuration appears from available references to be more applicable to very late WWII or Korea era vehicles with most WWII vehicles having the earlier ammo bins without the side louvers. A pair of post war rear view mirrors for the cab in also included as the model appears to be based on a preserved late model HST but more on that in the markings section below.

Also still included is the full cab interior and a comprehensive engine and radiator assembly that can easily be seen through the finely etched engine bay grills and while you didn’t get any actual 90mm/3inch ammo in the first kit you only get two (2) 155mm rounds with this kit.

Given much of the kit is the same as the first kit the review below is mostly from the first kit review with additional and updated comments for the new parts to save re-inventing the wheel.

The Kit:

Contents of the kit sees 267 parts in light grey plastic, 16 clear plastic parts, 50 finely etched parts including the large engine bay grills plus a set of full length vinyl T48 Rubber Chevron tracks, a length of twine and fine chain and as a bonus a small sheet of pre-cut masks for painting the cab windows.

Standard of moulding has fairly crisp details with just a hunt of occasional flash and some pin marks to contend with but overall is quite good being on a par with some recent Trumpeter kits and while not quite to the current AFV Club/Dragon/Tristar standards is still perfectly acceptable. This leaves room for additional detailing but the kit will still scrub up okay if built straight from the box depending on your preferences. The inclusion of the etched parts certainly helps lift the level of detailing most notable with the engine bay grills as well as for things like the head light guards.

Etched parts, chain and thread
Hobby Boss
pre-cut window masks
Hobby Boss

Lower Hull/Suspension:

The lower hull tub has nice panel details on the bottom with bogie, idler and final drive mounting bracket detail moulded on with separate late style return roller mountings and return rollers as well as nicely depicted final drive housing also separate for good definition of the hull details.

The large rear idler wheels and mounting are similar in design to those of the M3 Stuart but larger with the idler arm consisting of two halves with a separate shock absorber unit with the idler wheel trapped between the two arms. The idler wheels themselves have the open spoke detail although the cut-outs should be slightly more rounded at the outer curves when compared to photos. Each idler has separate outer circles to form the rim lip but the fit is not good and you will have to coax these into place carefully gluing around the lip as you go. After gluing the rims there are prominent join seems to be filled and sanded resulting in a bit of work to get right.

Each of the four bogie units are fairly simplified with just five parts each including the wheels which are standard Sherman type open spoke wheels, the inner and outer swing arms in one piece each the upper spring unit. Assembly is very straightforward but there are a couple of minor issues in that the spring unit bosses are undersized and the cut-outs in the swing arms slightly oversized and there are some additional bolt heads that can be added to the bogies. But overall they give a good representation of the M4 HST bogie units that fit together without any problems and also fit the hull mountings easily. As mentioned there are the later style return rollers and mounting and again assembly without any problems.

The kit gives you a set of the open fancy smooth drive sprocket which is more appropriate as most photos of WWII era HSTs have this style of drive Sprockets fitted. The detail on the sprockets is nicely done with inner bolt head details and the appropriate hub detail for the HST sprockets.

The final drive housings are in two parts with additional lifting eyes added and these fit neatly in place to the hull and include the hub axle detail. There is a small gap between the final drive and the hull that may be hidden by the drive sprocket and you should also watch the direction of the lower plate (part F41) as this can be easily fitted the wrong away around if not paying attention to the instructions.

The new lower front hull plate is separate and has the correct details for the later configuration with just two intakes with etched mesh screens and separate covers allowing you to show these open exposing the mesh or closed which offers a nice choice. The mesh is added from the inside of the plate before fitting to the hull tub and you also add the cab floor sections inside the tub with the fit good for these parts and mounted on the middle of the plate is a large towing pintle attachment.

Just watch the instructions as one of the images still shows the older lower hull plate with the three intakes but all the others have the new plate shown so this shouldn’t cause any confusion as the parts are numbered correctly.

At the back is new rear plate again with the correct later features of three cut-outs instead of the single long one on the early plate and added to this are the towing pintle mount and shackles with the fit of this plate to the hull being good.


As mentioned you get full length vinyl T48 Rubber Chevron track which is seen in some HST photos but not as common as the previous kits T49 track. The detail is quite good for this medium with the end connectors in the correct positions and small gap between each link for good definition. There are a few mould point marks on the inside but these should be easy enough to remove with a sharp blade and will be mostly hidden in any case. You will have to heat weld the connecting pins together as they don’t react to normal plastic cement.

Hobby Boss

Lower Hull Interior:

As mentioned this is quite complete with the Driver’s station getting foot pedals from plastic and etched parts plus the gear levers and seats and the large ammo box on the left cab side and at the back is the full winch drum, motor and transfer shafts with the twine provided used for the winch cable. This assembly is fairly basic in detail but it is mostly hidden inside the hull after the rear ammo bin is fitted so is probably adequate for the job.

The main feature as with the first kit is the full Waukesha 145GZ 6 cyl. Gasoline engine and radiator assembly and this is quite detailed with all the fundamental engine accessories such as the top cover, manifold, distributor, carburettor and front air compressor and fan belt assemblies and the large radiator hoses in four parts with about the only addition being the myriad if wiring and some finer details for an excellent assembly.

Added to this is the radiator with separate coaming and fan along with the support frames and air cleaner and once fitted above the engine the radiator hoses connect up to the engine and with the etched side grills much of this can be seen after assembly.  


The main cab is a large shell with side entry openings, top machine gun ring and separate windscreen “glass” and the separate side canvas doors also have the glass in clear plastic and Hobby Boss have again provided pre-cut masks to use when painting the model to make the job easier.

Added inside the cab is the central bulkhead with fire extinguisher as well as separate inner front panel for the instrument panel and other details but this has some quite large pin marks than may take a bit of effort to remove before adding the details.

The instrument panel has moulded on details with a decal for the instrument dial faces along with the other main features and again only needs the finer details added to enhance this further and there are also the inner windscreen latches in etched metal either folded or extended depending if you show the windshields open or closed.

On the outside are the front head lights that have clear lens glass and etched bush guards that need careful bending to shape before fitting. While these are finer than could possibly done in plastic they suffer the usual etched issue of being flat in profile when the actual guards are round wire. Also provided as etched parts are the two windscreen wipers that are nice and fine and it would be best to add these after the main painting due the screen masks to avoid problems.

The top machine gun ring is made up of three parts with the MG race and support being separate parts but the M2 .50cal MG provided is quite basic by today’s standards and could be enhanced considerably by using any of the metal .50cal barrels currently available.

Other detail on the roof are the pioneer tools with moulded on tool brackets and the two storage boxes along with a section of spare track and the two part siren.

The engine compartment roof has the outside muffler and inside muffler and channel that mates with the engine as you fit the roof and care will be needed when fitting this to ensure everything lines up okay.

As mentioned the impressive feature here is the large side engine bay doors/screens are in finely etched metal and really do add to the overall look of the final assembly and these can be fitted open or closed if you wish to show off more of the engine and radiator assembly.

The most obvious update for this kit is the new ammunition box for the rear and this is made up of the exterior walls which are all separate and the inner perforated racks for the ammo rounds but there are some pin marks to be removed from the panels which should be easy enough as they are all flat panels.

The louvered panels on the box sides are not opened up but this shouldn’t be that noticeable on the finished kit and there is also the crane jib and crane hoist made up of five parts with the lengths of chain provided added to this.

The crane arm is fairly basic and also has three substantial pin marks on one side and replacing this with a length of plastic I beam would give better detail definition and solve the pin marks in the one go.

On the rear panel the lights are the same as at the front with clear lenses and etched bush guards as well as etched inner guards and this whole assembly fits easily to the rear chassis with more chain used for the rear door stays is showing this open?

As mentioned there is just two 155mm rounds provided which leaves the box rather empty and acquiring additional ammo to fill this would make for a better appearance.


These are the usual exploded view drawings that are fairly easy to follow in most cases but as some of the sequences are quite busy and seem to overlap each other at some points and careful study of the instructions before hand will be of benefit to avoid problems.


The small sheet is nicely printed with fairly thin carrier film cropped close to the printed image and has markings for just one M4 HST. As mentioned above this appears to be based on a preserved HST in the markings of 987th Field Artillery Battalion which saw action in NW Europe after D-Day and Korea. See the additional page on the kit markings.

Decal sheet and Clear Parts
Hobby BossHobby Boss


Overall this kit again will build into an excellent kit of later M4 HST with the 155mm, 8inch/204mm ammo box and sees the AFV Club 155mm “long Tom” and 8inch Howitzer just waiting to be hitched up although you will have to find the ammo load elsewhere.

While there are still some minor detail issues, the suspension being the most obvious the amount of detail provided with the interior and compete engine/radiator assemblies as well as the etched parts will satisfy most allied modellers.

The markings and some later details are not clear for building a WWII era vehicle and hopefully someone can provide additional info on the markings provided, thanks in advance.

Highly Recommended 8/10

The Sprues:

Click on thumbnails for larger view
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Detail images
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High Speed Tractor

Ampersand Publishing
By David Doyle and Pat Stansell
112 pages soft cover. Book

US WWII M4, M5 and M6 High Speed Tractors
Tankograd Technical Manual Series - No 6002

Thanks to my credit card for the review kit.

Page created December 28, 2007