Df-03 5.5t Ezrun Motor, No Drive

[Walsall-Basher]

(frowny face) hi i'm a total novice at this stuff, help needed!

my df-03 fitted with a 5.5t ezrun brushless got its new pinions today (85t spur and 23t pinion) so i took it for a test run at the local astroturf. everything was going great until it suffered a total lack of drive. thinking the motor may have shifted i brought it home to find it weasnt the problem. the pinion is still meshed nicely and the main drive shaft is spinning well but im getting no drive to the wheels.

before i start lifting out the front and rear gearboxes anyone want to prepare me for what i might find?

im not running a slipper clutch as yet, perhaps i shouldve done?

[Butler]

Ball diff come loose?

[stu22]

I doubt it's the ball diff unless the OP managed to mess up both of them. If they were loose and he ran them with the 6000kV motor I'm guessing they will be melted (did this to the front diff in my DB01 once.)

Somewhere there's a thread where I asked which buggy to get, and several members started discussing problems running a DF03 with a high powered brushless motor while convincing me to get a DB01. I believe the problem is with the main shaft getting stripped. There were some interesting fixes involving using a hardened pinion and creating a new main shaft.

Since adding a DF03 to my collection I've resisted the urge to throw an EzRun 9T in and kept it on a reasonably powerful brushed motor although I have read more than one post about a DF03 using the same setup without problems. If you are going to do this I would get a slipper clutch (and let me know where you found one, all my normal sources show it as discontinued.)

[Gruntfuggly]

Sounds like it might be Mark's infamous alloy idler gear...

@stu22 - I've been running a ezRun 9T in my DI (with a slipper) for a couple of years (admittedly not as often as I'd like) without any noticeable problems. I keep meaning to strip it down and take a look inside, but it just keeps running...

[Walsall-Basher]

I doubt it's the ball diff unless the OP managed to mess up both of them. If they were loose and he ran them with the 6000kV motor I'm guessing they will be melted (did this to the front diff in my DB01 once.)

Somewhere there's a thread where I asked which buggy to get, and several members started discussing problems running a DF03 with a high powered brushless motor while convincing me to get a DB01. I believe the problem is with the main shaft getting stripped. There were some interesting fixes involving using a hardened pinion and creating a new main shaft.

Since adding a DF03 to my collection I've resisted the urge to throw an EzRun 9T in and kept it on a reasonably powerful brushed motor although I have read more than one post about a DF03 using the same setup without problems. If you are going to do this I would get a slipper clutch (and let me know where you found one, all my normal sources show it as discontinued.)

thanks for the heads-up, i've just ordered one from tonys tamiya parts on the bay, was showing 6 for sale but modelsport is showing on order so im not hanging around.

ok ive got the front end off and have just been cleaning everything, havent taken the front diff apart yet but i have noticed its working in my hands and seems pretty solid. pretty confused right now! both the diff joints are a bit mashed, not where the dog bones sit inside but on the outer edges, they are torn up quite bad and have splits and chunks missing. did notice this starting when i was running the stock motor in it tho. obviously weak parts.

[TA-Mark]

Yeap, sounds like the mainshaft aluminium gear to me too. Undo the 5 screws that hold the rear top gear cover and lift it off and check the condition of the mainshaft and idler gear. No need to remove anything else to get the gear cover off. Look for a build up on greyish paste inside the rear gearbox, it's not dirt if it's there, it used to be the mainshaft gear. You will need to replace the idler/bevel gear as well if the mainshaft has wornout completely, and maybe also the rear ball diff gear too. I have 9 wornout Tamiya aluminium mainshafts, and 2 sets of destroyed rear gearbox gears... and didn't wearout 1 pinion/spur.

I would not recommend replacing the mainshaft with another aluminium Tamiya one. Get a Five Stars FS7038 (standard) or FS7039 (slipper) hardened steel mainshaft to stop the gear wear. They can be hard to find if you are outside of Japan. I managed to get one for my Boxart Dark Impact and it solved all the gear wear problems. I do however only run a 27T Dirt Tuned motor in this DF03. I sold my other Dark Impact and my DF03MS because I couldn't get my hands on any other Five Stars shafts and I went for a HPI Cyber 10b instead. The 10B is great and haven't had an issue with it to date.

The top shaft is a wornout Tamiya aluminium slipper mainshaft.

Middle is a wornout Tamiya aluminium standard shaft.

Bottom is a Five Stars FS7038 hardened steel mainshaft. The Five Stars shaft has travelled 4 times the distance as the ones above it and shows only minimal signs of wear.

[TA-Mark]

both the diff joints are a bit mashed, not where the dog bones sit inside but on the outer edges, they are torn up quite bad and have splits and chunks missing. did notice this starting when i was running the stock motor in it tho. obviously weak parts.

This sounds like you have the suspension set too high. The dogbone does not sit parallel to the lower arm and as the suspension drops the dogbone moves out off the drive cup. Ride height set too high and they pop right out and chip the hardened outdrive cups. Mount the dampers in holes that lower the buggy to a point where the dogbones cannot pop out.

[Walsall-Basher]

think ive discovered the problem

im sure that little melted blob of ball bearings and diff plate wasnt in the manual!

so where did i go wrong, silly motor, badly built, both?

[stu22]

think ive discovered the problem

im sure that little melted blob of ball bearings and diff plate wasnt in the manual!

so where did i go wrong, silly motor, badly built, both?

Looks a lot like what happened to the diff in my DB01 when the diff loosened up.

How's the front diff?

As far as wear on the ball cups, I'd have to agree with Mark that the dog bone is coming out of the cup. I really have not run my DF03 but this is a problem the DB01 has when you go to the TRF dampers and CVDs. The solution is to put an O-ring on the shaft inside the damper body to limit the down travel. On the DB01 this limits the suspension travel just enough to keep the CVDs from coming out of the cups.

[TA-Mark]

A slipping ball diff usually ends like this. The diff may have loosened on it's own if the thrust bearing jams, or you built it without enough pressure.

The idea of a slipper clutch is that the clutch will slip before the diff, thus saving the driveline from powerful motors.

[Walsall-Basher]

ive managed to order a new gear parts bag from japan and a new diff gear from TTP to rebuild the diff, only thing I'll be re-using (at the moment is the cap screw, lock nut and bearings, which look fine to my naked untrained eye

when i built the diff, having no experience, i just tightened everything til it felt right, i've just been reading a few posts about setting up a diff and obviously i didnt tighten it enough. i did the same with the front diff which stopped working on the first run and had to be re-tightened.

anyone got any golden rules about assembling and setting these specific diffs up so i might not melt the next one?

[qatmix]

ive managed to order a new gear parts bag from japan and a new diff gear from TTP to rebuild the diff, only thing I'll be re-using (at the moment is the cap screw, lock nut and bearings, which look fine to my naked untrained eye

when i built the diff, having no experience, i just tightened everything til it felt right, i've just been reading a few posts about setting up a diff and obviously i didnt tighten it enough. i did the same with the front diff which stopped working on the first run and had to be re-tightened.

anyone got any golden rules about assembling and setting these specific diffs up so i might not melt the next one?

As mentioned before, run a slipper clutch if you want to run a fast motor. The df03 is easily up for running a 5.5t brushless (I have sold mine now but my mate still has his). It's worth using the metal diff out drives from the front also on the rear. They are not expensive.

These cars are great fun, I still miss mine.

You want the diffs to be stiff (especially the front one) However dont tighten then up too much or you will break them.