How Does Drivetrain Affect Handling? FWD vs RWD vs 4WD; Center Diff vs One-Way vs None; Bevel vs Oil-Filled vs Ball Diffs, etc.

[LMF5000]

I know not everyone will have experience with all of these configurations, but if we can each share some partial insights, I'm sure we can piece together a solid understanding.

I've always run shaft-driven 4WD models. Recently I picked up a Monster Beetle, and while it's a lot of fun, I've found it generally worse at accelerating, braking, and staying stable overall. I'm not sure how much of that is just down to being RWD versus the quirks of the ORV chassis.

As I'm considering my next model (possibly a RWD buggy) I'm weighing whether to go back to 4WD instead. I'd love to better understand how these different setups affect handling and behavior in practice.

Here are the drivetrain aspects I'm curious about, both from a subjective feel and performance standpoint:

1. FWD vs 4WD vs RWD

2. Center diff (e.g., VQS) vs one-way diff (e.g., Egress) vs no center diff (like most models)

3. Shaft-driven (most models) vs belt-driven (e.g. DB01) vs gear-driven (e.g., GF-02, G6-01)

4. Front/rear bevel gear diff vs oil-filled diff vs ball diff

Would appreciate any experiences or comparisons you can share!

[Twinfan]

The Monster Beetle is an, old top heavy, clonky beast of a thing.  Comparing it to a shaft driven 4WD buggy is always going to make it look like it handles like a bag of spanners    Same applies to the Lunch Box/Midnight Pumpkin.

Most of your questions relate to the finer points of 4WD buggies and results will vary depending on what type of surface you're talking about, is it for racing or bashing etc.

If you've never really had one, I would suggest trying a good 2WD buggy and seeing if you like it.  If not, you could then look further into the finer details of the 4WD stuff if you decide that's your preference.  I'd suggest picking up the currently cheap-as-chips TD2 and a diff nut Hop-Up.  That'll cost you £155 plus paint, which Time Tunnel Models can also supply:

• https://www.timetunnelmodels.com/live/catalog/tamiya-58697-astute-2022-custom-without-special-price-p-69007.html
• https://www.timetunnelmodels.com/live/catalog/tamiya-22029-diff-screw-p-69909.html

[alvinlwh]

Generally speaking here as I do not have that much experience.

A centre diff will allow you to run different F/R sized tyres on a 4WD.

Oil filled diff will allow fine tuning of the tightness of the diff with different oil. Dry gear diff generally only has 3 options, standard grease, AW grease or diff putty. 4 if you count hot glue as an option. 

Belt drive allows for more power than gear. Also it is quieter. 

F/4/RWD affects driving just like real world cars. Oversteer, understeer, etc... Then there is also motor location that can further affect handling. FF (FF-0x), FMF (M-05), M4 (TT-0x, R4 (MF-01X), MR (some 3R and MST drift chassis), RR (DT-0x, M-06), R4 (dragons), etc and etc... 

[Wooders28]

I'll add the, in my opinion....😏

FWD - Acceleration not as good as 2wd or 4wd, which is just physics.The weight goes back, and takes the weight off the driven wheels, but less twitchy when things get slippy. Good on the brakes though ,and turn in really well.

RWD - on high grip they're rapid, lightweight with less drivetrain. With a slipper set right, no wheelies and just putting the power down. Not great on the brakes, as you're basically handbrake turing into corners.

4WD - all 4 wheels putting power down, so you can get on the power alot earlier coming out of corners, and brake later with a 4 wheels braking.

******

4WD centre diff ,just like a diff on the rear or front, if front or rear loose traction, all the power goes to that. Some higher power larger scale 4wd trucks use oil weight in the centre diff to determine how much the front end lifts off (but turns the front tyres into 'pizza cutters' as the power gets transfered, but allows the front and rear to travel at different arcs without fighting each other (same as what a diff is for on an axle)

One way - makes a 4wd a 2wd under brakes, (basically a rachet) , so loose some of the benefits of a 4wd...Schumacher have a FAB unit (Front Adjustable Brake), which is a one way but like a slipper, so you can adjust how much one way you have.

No centre diff (no slipper) will wheelie with high power motors, the rear tries to push the front in corners, with a slipper there's no wheelies , but still pushes.

*****

Shaft driven aren't the most efficient but ge the job done (and I've seen a sly pic of seemingly Michal Orlowski shaft drive Schumacher 4wd prototype...) 

Belt drive, is the most efficient (so a big deal when nicads where 1200mah and you wanted to actually finish a race, with modern batteries it's not even a consideration), and really quiet. Schumacher used them in 2wd and still run belts on their current 4wd for now. Quite liked the 2wd ,as if you wanted more weight forward you could unbolt the gearbox out of the chassis, move it forward a few holes (3 options), fit a longer belt, and away you went.

Gear drive are the most inefficient, noisy and take up lots of room.

*****

Bevel gears work well on high grip surfaces, but as soon as one wheel looses traction, all the power goes to that wheel. This can make the car twitchy if you're on the power, and a driven wheel hits a bump ,leaves the ground, all the power goes to that wheel so it spins up to max rpm, then hits the ground and tries to drive the car left or right (depending on the wheel)

Oil filled is just a bevel gear , but in a sealed unit. This means you can fill it with different viscosity oils to give it less give (?). Some oils are thicker than treacle, so you can almost spool them if you want, so makes them less twitchy.

Ball diffs work a bit like an LSD in full size cars, so send the power to the wheels when the grip is low, but still allow some for cornering (when set right). On high grip, they don't give enough, so can cause a car to understeer. Not set right (or try and slacken them off a bit for high grip), or worn (require more maintenance than others) ,they can slip without driving the wheels, causing excess heat, melting the plastic gear. 

[markbt73]

I tried to generalize it, but I kept coming up with exceptions to whatever rule I came up with. But I'll do my best...

Generally, 4WD cars will turn better on-power than either RWD or FWD, simply due to the added traction. Shaft-drive cars sometimes turn easier in one direction than the other (looking at you, TT-02) becaue the motor's torque and the rotation of the driveshaft act as a gyro. Belt- or gear-driven cars, because there's no rotational force in the center of the chassis, don't suffer this. But belts are not meant for off-road, unless they are fully enclosed.

RWD cars can often be induced into on-power oversteer and "steered with the throttle" (think drifting or dirt-track racing), but 2WD RC buggies are often tuned to understeer at speed, for stability. Limited-slip diffs (ball diffs, thick oil, etc) or spools (no diff) make high-speed undertseer more pronounced and on-power oversteer easier to induce.

FWD cars understeer, sometimes quite badly, under power, but can snap into oversteer if you let off the throttle.

Suspension/steering tuning has a lot more to do with how a car handles than drive type:

Toe-in, front or rear = adds stability, but makes it harder to turn tight.

Toe-out in front = makes car more responsive, but sometimes unstable and twitchy. Rear toe-out is never used.

Too much toe-in at either end scrubs off speed and slows you down.

More negative camber (wheels leaned in at the top) = more stability over rough stuff, but too much kills tires.

Soft springs/shock oil = more traction, all things being equal. If front springs are hard and rears are soft, car will usually understeer. The reverse is also true.

Don't even worry about one-ways or anything like that until you can put the car wherever you want it to be on the track. The absolute 100% best "hop up" you can add to any car is driving practice.

Second best? Tires. If you're at a track, ask what the fast driver use and get those. If you're just messing around on your own, get a hard set and a soft set for each end of the car and mix and match to understand how it affects handling.

My advice: Get a good, well-known 2WD buggy with oil shocks and easily-available tire options, and start experimenting. Cheapest option is probably the good old DT-02 Sand Viper. Comes with oil shocks, full bearings, and adjustable camber and toe. Get yourself some different tires and wheels to mess with, and some harder and softer shock oil, and try stuff. You'll soon see what does what.

[Honza]

On 4/11/2025 at 3:40 PM, LMF5000 said:

• 1) FWD vs 4WD vs RWD

• 2) Center diff (e.g., VQS) vs one-way diff (e.g., Egress) vs no center diff (like most models)

• 3) Shaft-driven (most models) vs belt-driven (e.g. DB01) vs gear-driven (e.g., GF-02, G6-01)

• 4) Front/rear bevel gear diff vs oil-filled diff vs ball diff

1) that's a big one. Weight transfer during acceleration/braking has huge effect on available grip on front/rear axle. So which axle is driven is going to change handling quite considerably. Generally, under power/braking FWD is more likely to understeer, RWD to oversteer, 4wd depends on other circumstances, it has some characteristics of both.

What hurts RWD the most, is lack of front brakes. Braking by rear wheels just causes loss of traction and directional stability. There's reason why real cars limit rear braking power.

2) center diff allows front and rear to spin at different speed, which can help in certain situations, since front follows longer path in corner. The disadvantage is, that, depending on settings, it moves handling towards FWD characteristics under acceleration and RWD under braking, because torque is usually split 50/50, but weight on wheels isn't, so lighter axle is more likely to break traction.

One way diff also allows front to spin faster, but the tradoff is loss of front brakes.

No diff - since the wheels are locked, power is transferred proportionally to weight transfer. The disadvantage is, that in tight, slow corner, front and rear wheels will "fight" for traction - similar to spool on an axle.

3) that's more to do with overall packaging that's usually determined by drivetrain. Belt driven cars have transverse motor, which creates minor front/rear interta, while shaft is left/right. Also, shaft can twist the chassis a little, which may have an effect. Belts can somwhat dampen vibrations in the drivetrain.

 More complicated drivetrains are more about energy loss. GF01 and similar is very inefficient and take up a lot of space.

4) I definitely felt difference between ball and oil filled gear diff on a low grip. Ball diff was better. My theory is, that ball diff transmits more or less constant force to the more loaded wheel, when the other spins, while oil filled diff is more dependent on speed difference.

Open diff will just spin the inner wheel, outer wheel loses all the power when that happens. That moment is quite noticeable and it's not desirable.

[Juggular]

My view as a tinkerer/basher. (I don't race, I'm not a speed demon either).  

1. FWD vs 4WD vs RWD

I used to love 4WD. The Hotshot might have been the first one, and I loved the funky suspension and how the power was linked. You can go places you couldn't with the Grasshopper... but, driving it was somehow boring.  I drive 1:1 Subaru because we've got hills and snow in the winter.  It gets you to places. Not exciting, but it gets the job done.  That's what 4WD buggies feel like to me.  Of course on sand, and crawlers and trail trucks, 4WDs are a must.  

I loved seeing ORV Blackfoot running on a cracked concrete surface.  There is nothing precise about it. It runs like a bucking horse, which is fine as a basher.  Likewise, I like RWD buggies. Fast Attack Vehicle was my first independent suspension buggy.  It's fun.  For on-road cars, I kinda like FWD for now.  It's a puller. No fishtailing.  Easy for on-road novices.  I'm sure eventually I may like RWD just as much.  Generally though, I don't prefer 4WD anymore. It's like a videogame. No fuss, no finesse, which translates to less fun for me.  

2. Center diff vs one way. 

For a non-racer, one way was terrible.  You brake like RWD. You cannot back out of a ditch.  You just have power going forward. It might be beneficial for carpet racers.  I'm sure center diff does make a difference on a high traction surface as well.  Maybe best for on-road 4WD?  But RC cars are so light, I don't know if center diff would make much difference for buggies.

I would not mind if Tamiya builds more.  DB01 is supposed to be a good 4WD buggy. Partly because of 3 ball diffs, including a center diff. Plus 2 belts.  The other part being a midship weight distribution. I really need to find a pinion for this.  

The other one I have is a bit lacking (TLT-1).  The diff bolt for the center diff is a tiny 2mm screw that kept snapping (because it wasn't designed to grow up like below).  It has gears but it also has a tiny belt in it.  I think they are supposed to be the quirk.  If they close the gearbox and beef up the center diff, this could be a fun lightweight crawler.  When I did this, there was no sticky diff grease. I might try AW grease to see if it could almost lock the center diff.  

 

3. Shaft-driven (most models) vs belt-driven (e.g. DB01) vs gear-driven (e.g., GF-02, G6-01)

I don't mind mushy wire shafts.  They kinda sorta work like unintentional center diff.  When you accelerate, the rear spins, but the front isn't yet because the wire is mushy.  But the rear tends to slip on loose ground anyway. So it works out.  I have no idea how it would affect if you were racing.  (Of course, stiff shaft is better. All 4 wheels spinning at the same time would be ideal. But you can spin out if the ground is grippy and there is no give in the center.) 

For bashers it does not make much of a difference.  My DB01 and XV01 are not in running condition yet, so can't comment on them.  I like gears anyway.  They are bulletproof.  Teflon grease designed for model trains (like Labelle 106) is very thin, which makes the gears run smoother. It feels quiet. 

The three connecting gears below could have been a belt, connecting wo diffs.  That could've saved some weight.  Above mentioned TLT-1 was from 20 years ago, and the belt is still fine. But I don't trust it in heavy torque applications (unless it has two redundant belts).  Gears don't need tension adjusted, and they can take a lot of abuse like flying and landing on 2 wheels. I prefer gears on heavy bashers.  

4. Gear diff vs oil-filled diff vs ball diff

I like gears in the diff too.  The biggest "problem" is diff unloading. Diffs are not supposed to work this hard.  

I don't like to lock them either, unless they are crawlers.  But there are a few different kinds of grease you can use to turn them into limited slip differentials.  I use AW grease on on-road cars.  For off roaders, I use tackier things like 3Racing ultra high viscosity diff grease.  

Bad horsie diff lock grease (it doesn't lock. I'd say a bit stickier than 3Racing stuff). 

 

I can use bad horsie on old unsealed diffs like the Hotshot, Blackfoot, FAV, etc.  This much won't fling away.  

 Diff putty by Tamiya and other brands if you want them really stiff.  

I feel 4 different kinds are enough for me.  I can add more or, I can wipe some off.  I can wash them in alcohol if I want to use other kinds. 

They work like ball diffs that gets never undone. But I admit it took a lot of trial and error.  If I didn't know what to use, I may prefer ball diffs.  

Ball diffs are alright.  Adjusting them feels finicky.  But I don't mind them now, ever since I use faucet grease on ball diffs. In terms of stickiness, it's less than AW, more than ceramic grease. Tamiya's ball diff Grease is so watery, I don't like it in off-roader diffs. Tackiness of faucet grease makes it easier to adjust.  Far less likely to slip too.  

Below is a 1/4 inch steel ball, both faucet grease above make it stick to my finger for 1 second.  Watery Tamiya ball diff grease can never do this. 

I've been calling for tackier ball diff grease for years (for off-roaders). 

Today, I discovered that 4WD RC10 comes with something as tacky as faucet grease (the guy below end up going with 3rd party grease, but the point is that RC10 gives you tacky grease).  So, Team Associated figured it out.  (Hopefully, Tamiya will give us tackier grease for off-roaders. But a thumb-sized tube of faucet grease is only $4.)

I have NIB M07 and XV01, which calls for filling the diffs with oil. In principle, they are same as what I've been doing. Just using liquid instead of semi solid. 

I need to get 100,000 weight oil for my M07. Maybe something heavier for XV01.  Silicone oil is expensive, so I already don't like it.