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The TA series of 1/10 scale all wheel drive touring car chassis have represented the high end of the Tamiya line since they were introduced in 1991.  While the TA-01 and TA-02 were shaft drive, everything from the first TA-03 in 1996 and onward have been belt drive (the shaft drive lineup moved over to the new TB chassis series).  There were quite a few versions of the TA-03 which varied from front motor to rear motor and standard wheelbase (257mm) to short wheelbase (237mm).  Then there also were some special upgraded editions.  The TA-03 PRO (58177) replaced the plastic bathtub chassis with FRP plates and added ball differentials among other improvements.  There was an even nicer carbon fiber version released later as a replica of the chassis David Jun used in competition (58200) which included many additional upgrades such as aluminum shocks, universal axles, and a front one-way.  Finally, in 1998 and 1999 the two wheelbases of the TA-03 rear motor chassis were released with the TRF (Tamiya Racing Factory) moniker.  These were the first ever models to come with the TRF name and preceded the first standalone TRF 414 chassis.  The TA-03 R TRF (58227) was the rear motor, standard wheelbase version while the TA-03 R-S TRF (58243) was the short wheelbase version.  Both were dual deck carbon fiber standalone chassis kits that incorporated all of the upgrades from the David Jun special edition along with a few extras.  These models are as rare as hen's teeth, but I managed to get my hands on a short wheelbase version brand new in the box and I couldn't have been more excited about it.  This kit is riddled with beautiful aluminum parts, high quality hardware, and carbon fiber.  Tamiya hadn't settled on their bright blue aluminum anodizing yet, so there are colors and parts in this model that look different than anything else Tamiya has ever released.

Because of the short wheelbase, there are a fairly limited number of bodies that will fit on this chassis.  In fact, there are only four.  Three of them are from Porsche (two of which are the same body with different liveries) and the other is a Lancia 037.  I had other plans for the Lancia so I concentrated on the Porsche bodies.  By far my favorite is the Porsche 911 GT1, a glorious 200+ mph Le Mans racer introduced in 1996.  The Tamiya version came out a year later in 1997.  By the time I was looking though, it was impossible to find.  However, in 2020 Tamiya re-released the GT1, this time as the Straßenversion (street version).  This version of the car was just a road going race car made for homologation.  It still featured the same ridiculous (though slightly de-tuned) 3.2l twin turbo flat-6, the fender mounted side mirrors, the roof scoop, and the massive rear wing.  Tamiya used the identical body for this version which is not exactly right since the real road going version used 996 headlights instead of the racing version's 993 lights.  Technically, two prototypes were made with the older lights, so I guess the Tamiya version actually exists.  I much prefer the livery of the racing version so my plan was to buy the street version of the body and then get a set of aftermarket racing stickers from MCI.  This seemed like a good plan except that I couldn't find the body for sale for any less money than the full kit.  I finally decided to just buy the whole TA-03 R-S street version kit, steal the body from it, and then sell the chassis to try to recover some of the money.  It worked out well enough and also afforded me the opportunity to build both the standard and the TRF version of the chassis so I could compare them.  The chassis came with wheels but they weren't right for the GT1 so I replaced them.

This model drives like a dream.  I put a vintage Dyna Run brushed motor into it and I love the sound.  Due to the rarity, I'm pretty careful driving it but it does take it's turn on the road in front of my house along with all my other models.

This was an interesting project.  Because I took the Porsche GT1 body from a brand new Street Version kit, I was lucky enough to have both a standard TA-03 R-S chassis and a TRF version, both new in box, at the same time.  I decided to build both and take the same photos of each which allowed me to compare the two directly and highlight all the differences in the TRF model.  It turns out that there are a lot of them.  The TRF version represents a substantial upgrade.  For each step (except where noted), I've shown the standard chassis on the left and the TRF chassis on the right.
  
I was lucky enough to get this car new in the box.  The size and shape of the box is different from any other Tamiya I've owned.  It is much smaller than a buggy box, and not shaped like a typical touring car box.

These photos show the contents of the box.  There are no fancy internal boxes or blister packs here, just a single lateral divider.  As usual, all of the parts trees are individually bagged and the hardware is split into 4 bags labeled A-D.  The carbon chassis plates are loose in the box.  On the right I've knolled out all of the parts on my build table.  It doesn't look like much because most of the interesting parts come from the hardware bags.

All of the parts shown on the left are from hardware bag A and are unique to the TRF version of the chassis.  The picture on the right shows the parts from hardware bag B.  This begins to give you an idea of the vast number of special parts in this chassis kit.  The purple anodized aluminum parts are very unusual for Tamiya which hadn't settled on their signature electric blue yet.

The standard chassis uses open, unsealed gear differentials front and rear.  This is a standard Tamiya differential with sintered metal side gears and 3 spider gears.  The gears are lightly greased and provide very little resistance to differential motion.  The TRF model, on the other hand, uses a front one-way gear.  This means the axles are connected to the drive system when powered forward, but slip when braking or reversing.  Personally, I don't like these because it means the car only has rear wheel braking, but it is better for accelerating out of a corner.  Good for racing, bad for general driving.

Here are the two assembled gear diffs for the standard model which are the same in the front and rear.  The front one-way on the right looks nearly the same, but you can see a slight difference in the size of the output spline.  The external dimensions of the housing are the same (39T) meaning it can fit in the same bulkhead and use the same mating gears.

Now we'll assemble the front bulkhead.  The primary plastic housing parts are the same between the chassis versions.  The only difference is the use of shielded ball bearings on the TRF version instead of plastic bushings.

Here is the assembled front bulkhead.  Externally, you can't really see any difference between the two.

Here are the parts for the front counter gear assembly and upper suspension assembly which is combined with the shock tower.  Differences in the TRF model include ball bearings, sleeved upper arm pivots instead of step screws, and purple anodized aluminum ball studs instead of brass.  Note also how the hex on the counter shaft is split on the TRF model but continuous on the standard model.  I'm not really sure why this is different, but the hexes on the TRF shaft are 1/12 turn out of phase with each other.

Here are those same parts assembled.  The rectangular gap in the shock tower is for the belt to pass through.  The black plastic front drive gear (16T) is identical on both models.

Now we can prepare the lower front suspension assembly.  The lower plastic arms are the same between models, but the TRF model uses smooth hinge pins with E-clips instead of screw pins.

Here the counter gear has been installed, closed out with a cover, and the lower suspension assembly has been attached.  Only the purple ball studs reveal which assembly is which on first glance.

The standard model uses plastic pulleys while the TRF model uses aluminum.  The diameter and number of teeth (15T) are the same.

With the pulleys installed and the upper arm mount attached, the front bulkhead assembly is complete.  The appearance is very similar, but there are important differences inside.

You can see substantial differences in the front hub and steering assemblies.  Both models use the same plastic steering knuckles, but the TRF uses bearings, machined aluminum uprights, aluminum stepped king pins, and pre-assembled universal style axles instead of dogbones.  Completed assemblies and exploded views are shown below.  Note that the TRF model even has ball bearings on the king pins which I've never seen even on dedicated TRF 4xx chassis.

Take a look at these lovely steering assemblies. It is very easy to see that this is a special model with non-standard parts based on this photo.

It's time to complete the front bulkhead and suspension assembly.  Note again the hinge pins instead of screw pins.  Because the TRF model doesn't use a chassis tub, it needs to install the front bumper at this point as well.

Here is the completed front suspension assembly sans shocks.  Clearly very different, and there is no question which version is more expensive.

Both of these pictures are of the rear ball differential assembly of the TRF model.  The standard model uses the same gear diff in the front and rear so it was completed in Step 1.  The rear ball diff can be tuned much more easily for different amounts of resistance to differential motion. This ball diff uses a pre-assembled thrust bearing, five Belleville washers (disc springs), and eight 3mm balls.  The differential spur gear uses the same number of teeth (39T) as the basic differential so it fits in the same space and could be swapped if desired.

Now we can start on the rear gearbox assembly.  The plastic housing is the same, but the difference in the differential is very obvious.  Again, the TRF model uses ball bearings.

Here is a pretty big difference.  The lower part of the standard rear bulkhead includes a large curved section to attach it to the chassis tub and protect the motor.  Since the TRF model uses a carbon plate instead, it has a different lower panel.  The lower suspension arms are the same, but the usual difference in attachment hardware applies.

The lower suspension assemblies have been fastened.  There is no getting these two confused for one another.

Here is the hardware used to attach the lower suspension assembly to the gearbox housing.  The tiny bearings shown on the TRF photo are for a belt idler.

The lower suspension assembly has been installed.  The reason for the different geometry of the lower panel will be much more obvious once these are attached to the chassis.

The TRF model comes with two sets of gears.  The black gears are from the standard model, are made from regular ABS plastic, and use a combination of 0.8 mod gears for drive and 0.6 mod gears for the spur.  The white gears are Nylon and use a finer combination of 0.6 mod gears for drive and 0.4 mod gears for the spur.  Only the white gears are used for the TRF model.  The finer gears are quieter and offer more pinion options, but are also less strong.  The Nylon should offer better wear and friction properties as well.  It was a good idea for Tamiya to make these gears a different color because they cannot be mixed.
 
Here you can again see the difference in gears, the ball bearings, the purple ball studs, and the split hex on the counter shaft.  The white drive gear mates with the differential so it is the same pitch and tooth count (16T) as the standard gear.

Here are the assembled rear shock towers with upper suspension links and the gear sets for the rear transmission.

An exploded view with the gears, fasteners, and cover is shown here.  The other differences have been explained in previous steps, but the fasteners and gear cover are the same between the standard and TRF versions here.

Once the gearbox and suspension assemblies are complete, most of the differences are well hidden.  Only the purple ball studs and a peek at the white gears give away the TRF model.

Now the shock tower and upper suspension arm assembly can be installed.  This step also installs the rear pulley for the drive belt which is clearly different (metal) on the TRF version.

A few more little details differentiate these two assemblies if you know where to look.  Pretty subtle though.

You can't miss the difference between the plastic rear uprights of the standard model and the complex cast metal parts used on the TRF version.  A less obvious difference is the longer drive cup on the TRF which results in a mildly wider rear track.  More on that later.

Here are the parts needed to complete the rear suspension.  Apart from the uprights already discussed, virtually every other part is also different.  The TRF version uses lightweight aluminum dog bones, steel hinge pins with E-clips for lower pivots instead of screw pins, and flanged bushings for upper pivots instead of step screws.

Now that the uprights are installed, the differences between the standard and TRF versions are much more obvious.  They can't really be conflated at this point.  The difference in the lower housing is also pretty clear from this angle.  The standard lower panel connects to the chassis tub while the TRF lower panels connects to a carbon chassis plate.  This will be shown clearly later.

Both models use a C-shaped metal motor mounting plate, but while it is stamped on the standard model it is cast metal on the TRF.  While the standard models use a regular paper washer as a spacer, the TRF model adds the purple anodized aluminum plate shown.  The TRF motor is mounted with hex cap screws instead of JIS machine screws.  Finally, the standard plastic pinion gear cover is replaced on the TRF model with a nice metal heat sink version, though I'm not sure much heat is going to make it from the motor to this cover.

As previously discussed, the pitch of the spur gear is different between the models so the pinions must change to match.  The standard model uses a 14T 0.6 mod pinion (14T-25T possible) while the TRF model uses a 23T 0.4 mod pinion by default instead (20T-29T possible).  The standard model comes with the smallest possible pinion for the highest possible gear reduction ratio (8.51:1) which results in the slowest speed with the standard 27T silver can motor.  The TRF model does not come with a motor, but the stock 23T pinion results in an even lower 7.34:1 ratio with the recommended 13T Dyna Run Super Touring motor. The hotter motor adds even more difference and results in a much faster car.  Interestingly, if using a silver can the TRF manual recommends using the largest possible pinion (which makes sense) instead of the smallest possible pinion used in the standard model (which seems odd).  (The Dynatech 02H motor shown is just a placeholder until the right motor arrives).

For those who like to see the numbers:

• Standard
  • 43:14 x 25:22 x 39:16 = 8.51:1
  • Wheel speed based on 12,500 rpm standard silver can motor = 1469 rpm
• TRF
  • 63:23 x 33:30 x 39:16 = 7.34:1
  • Wheel speed based on 33,200 rpm Dyna Run Super Touring motor = 4523 rpm

 That's the completed rear bulkhead, gearbox, and suspension assembly.  Most of the mechanical guts of the model are right here.

While the standard model did come with decent oil filled plastic CVA shocks, the TRF model kicked it up several notches with these aluminum shocks.  Tamiya hadn't settled on their TRF shock design yet so these represent an early attempt, but you can see the aluminum cylinder with threaded caps, double o-ring seals with Delrin rod guide, Delrin piston, and volume compensation bladder.  The outside of the cylinder is not threaded for a preload adjustment ring so spacers must be used instead.  The front and rear are built differently with more internal o-ring spacers on the front (resulting in a shorter extended length) and different spring rates.  The pink and blue colored caps and springs help differentiate them and are unique to this model.  Even the very closely related TA-03 R TRF uses gold, red, and yellow instead.  This damper style originated in the David Jun Special Edition of the TA-03 F (silver and blue).  All 3 models share the same cylinder and spring part numbers despite being different colors.  Good luck getting the right parts if you ever need to replace them.

Here are completed front and rear suspension modules (with shocks) for both the standard and the TRF chassis.  Many external differences are pretty easy to spot with the TRF version being much more colorful.

Now we'll get to work on the chassis.  While the standard model uses a plastic bathtub chassis that is all one piece, the TRF version of the chassis needs to be built up from multiple parts.  We start with the carbon fiber base plate and work up from there.  The large plastic bits you see are for the battery holder and retainer.  I've used a low profile steering servo as a placeholder here, but a standard size fits fine and I'll be retrofitting one later.  Finally, the plastic spacer up front is just to adapt the forward bulkhead to the carbon chassis.

Both versions of the chassis use dual bellcrank steering, but while the standard version is all plastic, the TRF version uses aluminum cranks and a carbon bridge with ball bearings.