Product Review: RC18T Differential & Transmission Components

Posted: May 9, 2015 in Product Reviews
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  • July 2017: Apologies to PROJECT RC Readers! Firstly I would like to thank all the sponsors, subscribers and readers of my blog for your support. I would like to apologise for the recent image outage in my articles. The image hosting site I have been using, ‘Photobucket’ has recently decided that they will no longer host images to websites, blogs, etc unless you pay a ridiculous fee of $500 – This is particularly infuriating since there was no notice given. Since Photobucket has resorted to extortion for their users I will no longer use their services forever. This means that I will have to move all my article images to another platform and embed new coding for all those images which is a real PITA and a lot of work. Anyway I am in the process of doing that so I kindly ask readers to understand the situation and please be patient. PROJECT RC article images will soon be operational again.

This review will discuss some of the various aftermarket and factory differential and transmission components available for the Team Associated RC18T, RC18MT, and RC18B. This article coincides with the current build article;

Custom Build: RC18T Modified Custom Build – March 2015

Differentials and transmission components are probably one of the most upgraded, modified and worked on parts on any RC car. When first upgrading I would argue that it is pragmatic to address these components first before upgrading other parts as they receive the most stresses and punishment and are critical to getting the best performance and reliability from your vehicle.

There are many aftermarket options available for the RC18T. Over the years I have experimented with many different combinations, some better than others. This pictorial review will look specifically at differential outdrives, bevel gears and driveshafts I have used in some of my RC18T builds.

1.0: TEAM ASSOCIATED RC18 PLASTIC DIFFERENTIAL OUTDRIVES.

1.1 – Profile View: (Stock) Team Associated RC18T plastic differential outdrives. PART#: ASC21027

1.2 – Diff Plate View: (Stock) Team Associated RC18T plastic differential outdrives. PART#: ASC21027

1.3 – Weight in Grams: (Stock) Team Associated RC18T plastic differential outdrives. PART#: ASC21027

1.4 – Fitment: (Stock) Team Associated RC18T plastic differential outdrive fitted with Team Associated diff plate and large bevel face gear.

1.5 – Fitment: (Stock) Team Associated RC18T plastic differential outdrive fitted with Team Associated diff plate and large bevel face gear.

These stock Team Associated plastic outdrives are fitted to all RC18 RTR kits. This is one of the first parts I upgrade as they are quite weak and prone to flex. When running with the stock brushed motor and NiMh battery they might last for a while but the performance of the diff degrades rapidly. It is also important to use the FT alloy collars which fit over the dogbone cups to prevent the slot spreading. Running high-powered brushless systems usually destroy these plastic outdrives in a very short time.

2.0: 3RACING ALUMINIUM DIFFERENTIAL OUTDRIVES.

2.1 – Profile View: (Upgrade) 3Racing Aluminium differential outdrives. (Discontinued)

2.2 – Diff Plate View: (Upgrade) 3Racing Aluminium differential outdrives (Discontinued)

2.3 – Weight in Grams: (Upgrade) 3Racing Aluminium differential outdrives (Discontinued)

2.4 – Fitment: (Upgrade) 3Racing Aluminium differential outdrive fitted with Team Associated diff plate and plastic large bevel face gear.

2.5 – Fitment: (Upgrade) 3Racing Aluminium differential outdrive fitted with Team Associated Diff plate and plastic large bevel face gear.

These 3Racing aluminium outdrives have surprisingly lasted for quite a while, even with a high-powered brushless system. The main problem I have experienced with them is the dogbone cup wearing (2.1). They are the second lightest at only 1.3g heavier than the stock plastic outdrives. I did not experience flex or deformation using these and their fitment to the diff plates and bevel face gear were satisfactory, with little or very minimal wear, although I found there to be insufficient enclosure of the outdrive with the bevel face gear (2.5). These alloy outdrives I believe are now discontinued, although I think that Integy may still make them, and possibly the online store, ‘The Toyz’ may still stock them.

3.0: MIP STEEL ‘SUPER DIFF’ DIFFERENTIAL OUTDRIVES.

3.1 – Profile View: (Upgrade) MIP steel ‘super diff’ outdrives. PART#: MIP1444

3.2 – Diff Plate View: (Upgrade) MIP steel ‘super diff’ outdrives. PART# MIP1444

3.3 – Weight in Grams: (Upgrade) MIP steel ‘super diff’ outdrives. PART#: MIP1444

3.4 – Fitment: (Upgrade) MIP steel ‘super diff’ outdrive fitted with Team Associated Diff plate and plastic large bevel face gear.

3.5 – Fitment: (Upgrade) MIP steel ‘super diff’ outdrive fitted with Team Associated Diff Plate and plastic large bevel face gear.

This MIP steel ‘super diff’ is probably the most commonly sought after diff upgrade in this group. It is very good. The machining is spot on and precise and is what you would expect from MIP. I have used these in my past builds and have not experienced any problems with them. These outdrives are by far the heaviest in this group (3.3). At 10.1g they are almost double the weight of the Titanium outdrives below. This added weight translates to slower ‘spool-up/down’ speed of the differentials and transmission. They are however very strong and durable. One design aspect I personally do not like is the vastly different sizes of the diff plate mounting surfaces (3.2). When compared to the Titanium outdrives it seems that the smaller diff plate mounting surface on the left half (3.2), creates an unbalanced contact pressure between the two halves. This was recently noticed when servicing  another RC18T fitted with these MIP outdrives, where there was unequal wear on the diff plates.

4.0: eRACING PRO TITANIUM DIFFERENTIAL OUTDRIVES.

4.1 – Profile View: (Upgrade) eRacing Pro Titanium differential outdrives. PART#: n/a

4.2 – Diff Plate View: (Upgrade) eRacing Pro Titanium differential outdrives. PART#: n/a

4.3 – Weight in Grams: (Upgrade) eRacing Pro Titanium differential outdrives. PART#: n/a

4.4 – Fitment: (Upgrade) eRacing Pro Titanium differential outdrive fitted with Team Associated Diff plate and plastic large bevel face gear.

4.5 – Fitment: (Upgrade) eRacing Pro Titanium differential outdrive fitted with Team Associated Diff plate and plastic large bevel face gear.

These Titanium outdrives by eRacing Pro are my top choice for the RC18T differential. The machining is very good with a high level of precision and I have never had an issue with installing them with other components. They are the third lightest at only 2.3g heavier than the aluminium outdrives (4.3). Based on previous use, they are by far the strongest and most durable outdrives in this group, comparable if not better than the MIP steel outdrives. I particularly like the appropriately sized diameter of the diff plate mounting surfaces on both outdrive halves (4.2) which spreads the diff plate load evenly. You will notice that the outdrive half fitted with the plastic large bevel face gear completely encloses the rear of the bevel gear adding extra support and preventing excessive loss of grease (4.5) in contrast to the 3Racing outdrive (2.5). Through my online searches I have only managed to find two places which sell these titanium outdrives. The outdrives above are branded eRacing Pro, and the other I found are branded Hot Racing, from closer inspection they look identical to each other.

5.0: GPM CARBON GRAPHITE DRIVESHAFT

5.1 – Weight in Grams: (Upgrade) GPM Graphite Main Shaft. PART#: GAR025

5.2 – Machined Ends closeup: (Upgrade) GPM Graphite Main Shaft. PART#: GAR025

This CF driveshaft by GPM is ok. It is made from a solid CF shaft with an aluminium hex hub where the spur gear fits (See far right of shaft). The stepped ends are machined to allow for the fitment of the small bevel gears and bearings. When testing fitment with the stock Team Associated plastic bevel gears and an aftermarket steel bevel gear, the stock bevel gear fits much more secure than the aftermarket gear. My major criticism of this CF driveshaft is the exposed (unsealed) surface of the machined ends (5.2). When CF is exposed to oils and grease the fibres can be compromised and become weak which can lead to the bevel gear stripping the driveshaft end. Although not ideal, this can be easily rectified by reinforcing the surface with a coating of Cyanoacrylate glue and sanding to fit.

6.0: TEAM ASSOCIATED ALUMINIUM DRIVESHAFT

6.1 – Weight in Grams: (Stock) Team Associated RC18 driveshaft. PART#: ASC21089

The stock Team Associated RC18 Driveshaft is a good component. It may not be as exotic as the CF driveshaft above but gears and bearings fit tightly as they should. It is slightly heaver than the CF driveshaft by 2.2g which is not too much of a concern as I would rather have better fitting gears and bearings. Additionally this stock aluminium driveshaft is a third of the price of the CF driveshaft.

7.0: GPM STEEL BEVEL GEARS vs TEAM ASSOCIATED PLASTIC BEVEL GEARS

7.1 – Weight in Grams: (Upgrade) GPM steel diff (35T) & input gears (14T). PART# SAR035T14T

7.2 – Weight in Grams: (Stock) Team Associated 18T plastic diff & input gears. PART#: ASC21022

7.3 – Comparison: (Upgrade) GPM steel bevel gears vs (Stock) Team Associated plastic bevel gears.

The black gears you see are the GPM steel bevel input gears, PART#: SAR035T14T. The tan gears you see are the Team Associated 18T Diff & Input gears, PART# ASC21022. There is a large difference in weight between the two gear options, with the GPM steel gears at 4.4g more than the stock plastic gears. The steel gears are definitely stronger than the plastic, that is obvious, however proper fitment of the steel input gear was an issue for me. The other consideration was the size of the diff ball holes in the large bevel face gear. I found that the plastic bevel retained more grease surrounding the diff balls compared to the steel bevel (7.3). Additionally I found that the steel bevel created more wear on the diff balls due to the metal to metal friction. The plastic bevel setup runs quieter and in my opinion smoother than the steel setup. I have chosen to use the plastic bevel gears on my new modified build as I have not had any durability issues with them in the past with my other high-powered RC18T builds, and they perform better and last longer than the steel bevels. Additionally the plastic bevels are 1/10 of the price of the steel bevel gears and are more readily available.

8.0: BEVEL INPUT GEAR FITMENT ON DRIVESHAFTS

8.1 – Fitment: (Upgrade) GPM steel input gear fitted to Team Associated aluminium driveshaft

8.2 – Fitment: (Stock) Team Associated RC18 plastic input gear fitted to Team Associated aluminium driveshaft

8.3 – Fitment: (Upgrade) GPM steel input gear fitted to GPM Carbon Graphite driveshaft

8.4 – Fitment: (Stock) Team Associated plastic input gear fitted to GPM Carbon Graphite driveshaft

As you can see from the photos I found some issues with the fitment of different combinations of the input gears and driveshafts. For my current build, my decision was to use the Team Associated plastic bevel gear and aluminium driveshaft combination due to its best fit. Alternatively if I were to use the GPM Carbon Graphite driveshaft I would choose to use the Team Associated plastic bevel gears as this combination provides the best fit (8.4).

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