TRX4 chassis

• Shock absorbersr
• Springs
• Links
• Portal housing
• Miscellaneous

It is probably the chassis that sees the most tuning work. The range of products on the accessories market is virtually endless; whether it’s stainless steel screws or anodised gearbox or differential housings, you can enhance or improve almost everything. The TRX-4 is certainly one of the best you can buy right now ‘straight out of the box’, but for true crawler enthusiasts, that’s far from enough to make the vehicle fully controllable.

TRX4 shock absorber

The original shock absorbers supplied by Traxxas® with the TRX-4 are currently hard to beat on the aftermarket. They are very responsive and perform almost perfectly. But of course, it is still possible to improve their response here too. With a couple of small tuning rings – available via one of the two Facebook groups – which can be screwed into the shock absorber housing, you can make the shock absorber even more responsive; the breakaway torque becomes significantly lighter and the shock absorbers respond much more quickly. A small investment with a big impact – what more could you ask for? You can also alter the response characteristics by using different oils.

Using 100, 200 or 300 cSt shock absorber oil makes a significant difference. 100 cSt oil has the lowest viscosity and is almost like water. However, if the vehicle is already very heavy due to weight tuning, using 100 cSt oil is not recommended. The TRX-4 is supplied with 350 cSt oil as standard.

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Suspension springs

As some people may wish to, or indeed need to, make adjustments to the chassis, here is an overview of the shock springs and their corresponding designations for Traxxas®.

The vehicles are supplied with the following springs:
8041 - Defender f, Bronco v+h, Tactical f, Kit f+r, Blazer f+r, G500 f+r, G63 f, Bronco 2021 f+r
8040 - Defender r, Tactical r
8043 - Sport f+r, Sport Kit f, G63 r
8044 - Sport Kit r

High Trail suspension springs

The vehicles are supplied with the following springs:
8155 - Ford 150 HT f+r, Chevrolet K10 HT f+r

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TRX4 Links

The suspension links are the steel rods at the bottom of the vehicle. The original weight of these rods is between xxx and xxx grams. This is one of the best ways to make the TRX-4 heavier.
There is no mass that a servo has to move with excessive effort, nor is there any flywheel mass that the motor has to drive whilst driving. The links are positioned low down on the chassis and keep the vehicle on the ground when climbing or on a slope. Brass links offer the option of increasing the weight to 250–270 grams.

Please note that the links vary depending on the vehicle (wheelbase). When ordering these links, please ensure you specify which TRX-4 model is to be modified. The Defender and Tactical require a set for a 324 mm wheelbase, whilst the Bronco, Blazer, Kit and Sport require the set for a 312 mm wheelbase. You will also need to order grub screws, should these not be included, to connect the brass links to the original ball joints (rod ends).

As well as the brass links, there are now also some made from stainless steel. These are probably slightly lighter than their brass counterparts (the specific gravity of stainless steel is slightly lower than that of brass), but visually they certainly look the part.
Here too, the main links have been turned to a diameter of 8 mm and the ends taper to fit the rod ends with a form-fit. The Panhard link and the link from the servo are correspondingly slightly thinner. Once fitted, there are no gaps whatsoever – that’s how model-making should be.
The links are highly polished and, as is sensible with stainless steel, the threads have been machined directly onto them. The dimensional accuracy is extremely good at 1/10 millimetre.
The price is slightly higher than that of the brass versions, but this is absolutely justified given the material and the workmanship. If you’re looking for something special for your little one, this is it!

When buying a handlebar, it should not be more than 6 mm in diameter, otherwise you’ll run into problems with the differential housing – there isn’t much space there. Otherwise, simply carry on using the old steel one

Brass links are available from the company RC-Links for various vehicles.
Stainless steel links are currently very hard to find on the market.

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TRX4 Portalgehäuse

The portal axles are small reduction gears that enable the vehicle to significantly increase its ground clearance. The drive shafts are redirected once more, giving the TRX-4 an increase in ground clearance of 25 mm. The housings are made of plastic as standard. However, the aftermarket offers solutions here too. Housings made of aluminium – which are slightly heavier than the original plastic ones – or brass are available. For example, you can replace the portal covers on the wheel side, which adds up to 200 grams or more per axle – a total of around 400 grams on the vehicle. Of course, you can also swap the inner portal housings at the front and rear, as well as the entire steering system, for brass versions.

Anyone planning to replace their original portal housings with brass ones should please replace the steering servo beforehand with a high-performance model, such as the HD-Power 25, the Xpert Servo WR7701 or similar. The Traxxas® servo will not be able to cope with this additional load for long.

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TRX4 Chassis – Miscellaneous

Axle weights provide a further means of making the vehicle heavier in the underbody area. These are bolted between the portal housing and the wheel carrier. The increase in weight is partially adjustable. You should consult your dealer on this matter. When using axle weights, you should not overlook the difference in weight affecting the steering servo. The steering point may be pushed very far outwards; in some cases, the track width changes considerably, which can lead to problems with the body or the steering.
The drive shafts can also be replaced. Traxxas® has fitted plastic shafts here, which can be replaced with steel ones. I must admit that in all these years I have never had a Traxxas® drive shaft break.
Of course, there are many other modifications you can make to the original TRX-4 chassis. Alternatives made from aluminium or even carbon fibre (battery mount) are available for almost all components. The possibilities here are almost endless, but so is the drain on your wallet. One modification that certainly makes sense is fitting underrun protection to the differential and gearbox. These two areas suffer a great deal on stony terrain; parts are available in stainless steel and aluminium..
Whether an aluminium gearbox housing really does improve the vehicle’s handling is certainly open to debate, but colourfully anodised components look fantastic.

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