~Driveline~
Center drive shaft
Especially on lcg models, the center driveshaft is common to bend and is definitely a weak point. Currently, there is only one good upgrade for this.
Tekno Big Bore Center Driveshaft($29.99)
This offers a lot of strength over the stock center drive shaft and also solves another problem. This center drive shaft offers enough flex for the chassis to absorb impact, but not enough for it to crack. This CD can replace the need for a chassis brace as well. This CD will require a little bit of dremeling to make it fit. You have to dremel down the underside of the chassis right between the bell crank.
CVDs
The stock driveshafts are very weak. They are a very common casualty but luckily, there are a few upgrade options.
MIP X-DUTY
$72 x2 Front / $72 x2 Rear
These are very beefy and are a massive upgrade over stock. They are however quite heavy and pricey. When installing, make sure to use locktite and check/maintain them frequently. These pieces are very expensive to buy if lost.
Tekno M6 driveshafts
$49.99 x2 Front / $54.99 x2 Rear
These are less beefy and lighter than the MIPs but still, offer a great upgrade over the stock. With these, you are required to use their plastic hub carries. They are weaker than the common aluminum upgrades but do offer greater tuning capability. You also have to use their plastic hex hubs because the outputs are 6mm. This kit comes with everything you need to install.
XO-1 Driveshafts
$38 x1 Front / $38 x1 Rear
This is a nice option directly from Traxxas. They are not a direct drop though. They need a bit of modding to fit because they use 6mm outputs instead of 5mm like stock. Traxxas has a nice guide. Some people have had luck with these, while others haven't. They cost about as much as MIPs do, and I honestly think the MIPs are a better deal.
Traxxas Extreme HD
$12 x2 Front / $12 x2 Rear
In the New Ruslter 4x4 and Slash 4x4 Ultimate Traxxas has included new "Extreme Heavy Duty" driveshafts. If you need a cheap option these will be slightly stronger than the older stock driveshafts. I wouldn't expect too much from them though.
Motor mount
The plastic motor mount that comes stock with the truck is often not too long lived. It has a tendency to melt and warp from the motor's heat.
Hot Racing($33.88)
Blue / Black
This is the most common motor mount upgrade. It is made out of strong but light aluminum. It has a stronger over-sized bearing and is telemetry compatible. It also comes with an O ring to help control vibration which helps prevent bearing wear. The O ring can make it difficult to take the bearing out. The Hot Racing motor mount also sometimes needs slight modifications to fit.
King Headz($41.99)
Blue / Black
This is another popular option. It is very similar to the HR one, but is more expensive, almost double the weight, and doesn't have an O ring. The upside is that it is always a direct drop in with easy bearing removal. If you want a performance part without any theoretical difficulties, this is your best bet.
STRC($39.99)
Red / Silver / Gun Metal
This motor mount just comes in different colors. It does not have an oversized bearing and will offer less performance than the other two.
Bearing adapter
The plastic bearing adapter often melts and can cause other problems like a ruined motor mount as well. Good News, this is a very cheap upgrade.
You can aluminum bearing adapters from both traxxas for $5 and from king headz for $6.99. There isn't a large difference between the two, but the King headz is made out of a stronger aluminum. Robinson Racing's slipper clutch comes with a brass bearing adapter, which can also be bought separately for $8.25. It has proved to be strong too. They are all good choices.
Motor Plate
- If you somehow manage to bend your motor plate or want that little extra bit of cooling, you could get an "upgraded" motor plate. STRC has one for $10.99 (can be found much cheaper) in blue, red, silver, and gunmetal. Hot Racing also has one for $9.88 in black. They both have heat sinks, and look better. Traxxas also offers a green colored stock motor plate for $7.
Differentials (F/R)
Your differentials could go wrong a few different ways especially if your running higher voltage. If you want to prepare for the future, or fix a messed up diff; there are a few things you can do.
The most common upgrade is directly out of an XO-1. The XO-1 diffs are the slash diffs with an I-bar which reinforces the cup, and a stronger cup. You can buy the entire diff off of a chop shop for $24.47 a diff, or just the parts needed if you don't need full new diffs. I bar ($15 x1) / heavy duty diff cup ($4.25 x1). The XO-1 diffs/diff parts directly drop into the Slash.
Ring Gear
Traxxas also offers spiral cut gears for $45 a set (front; rear). They are stronger and quieter, but also much more expensive. The stock gears are difficult to break or strip. You probably won't need these.
As far as tooth count, there aren't really any other options other than 37/13.
Aluminum Diff Cup / Housing
There are aluminum diff cups and housings around but I don't recommend them. I haven't heard of any good aluminum diff cups yet. Just stick with the Heavy Duty diff cup. As for aluminum diff housings, there are a few decent ones, but the diff house is a cheap plastic part. If it breaks, it's not expensive to replace. But chances are if you break a plastic housing, you probably would have bent an aluminum housing. Fixing it would be very difficult and replacing it would be very expensive.
Slipper clutch
The clutch very often cannot handle higher voltage. There are a bunch of good options though.
This slipper is much stronger than the stock slash slipper and is a great upgrade for a budget price. For this upgrade, you need the alloy slipper pressure plate($8) and the heavy duty rebuild kit($9.50). You should also get the T-Maxx pads($2.75) because they cover more surface area than the aluminum pads and are harder to melt. These pads will need a bit of modding in order to fit. You will need to drill out holes and sand the pad down about 0.5mm. You will also need to use the front hole on the slipper shaft instead of the rear.
Robinson Racing Gen 3 Slipper($48.50)
These units are much larger and much stronger than stock. The pads are also much bigger. This slipper uses louder, hardened steel gears but they are very difficult to strip. This unit uses a hardened 54t 32p spur. Unfortunately, that is the only spur gear you can use with this unit. They do offer a large number of hardened 32p pinions for $12.50 each. The pinions all fit on 5mm shaft, but RR sells a reducer sleeve($3.95) for use with smaller motor shafts. All of these pinions will work without the RR gen 3 slipper as long as you have a hardened spur($19.50).
Hot Racing Double Up($18.88)
Another good option is the Hot Racing Double Up slipper. It replaces the stock pressure plate and fits double the amount of pads. The Double Up is compatible with both regular($7.50 x3) and aluminum($9.50 x3) stock friction pads. However, you would have to buy another rebuild kit if you're reusing pads, or two full rebuild kits if you want to use better aluminum pads. Hot Racing does offer compatible pads for their slipper. You can get three long pads which come in aluminum($7.88) or carbon fiber($8.88), or six short pads which also come in aluminum($6.88 x3) or carbon fiber($7.88 x3). These pads are expensive and don't match the performance of the T-Maxx pad. Which is why I once again recommend it. The T-Maxx pad is harder to melt and will cover more area for a mere $2.75.