210: Gearbox binding with gear diff?

[Origineelreclamebord]

Hi everyone,

Today I got my gear diff in. I built it as per instructions on TD website. I just put the diff in and... it won't move freely inside the casing when it's tightened/closed. Even after removing the copper shims it's just tight.

Any thoughts what's at fault and how to solve it?

[mattr]

If you overtighten the bolts running though the gearbox, it binds. Try backing them off 1/4-1/2 a turn.

And the gear diff doesn't need the shims AFAIK.

[jo90]

Double check you have seated both the large bearings fully home on the casing. I found when i bought a new diff the casing was very tight where the bearings went on and one wasn't seating full home against the case correct, causing it to get nipped up on the gearbox case when closed up. A quick rub of wet and dry around the GD casing where the bearing sits and it goes on tight, but goes fully home. No more binding.

[Origineelreclamebord]

I am no Hulk and I don't try to be.

I have to loosen the gear casing until you ca see a gap between the two parts for the diff not to bind. In fact, upon the first build I was having problems with a layshaft spacer that caused the layshaft to bind... so I'm starting to think the gear casing is actually a little off. I wouldn't be too surprised about that, it came from the very first batch, and there were other parts with problem areas as well (wheels warped to a degree that they're not of much use for racing).

Could anyone measure their diff's width between the surfaces against which the bearings sit (without the bearings or shims), like this:

Ball Diff:


Gear Diff:


On my diffs it's clear to see the gear diff is wider. With shims on the ball diff and none on the gear diff there's still almost 0.4mm between the two. However, it could well be that the gear diff is just wider and my casing too tight, so I need to need to make sure.

I've also contacted Durango about this.

[mattr]

Looks like a dodgy diff.
Think mine is "about" 19,5mm across the bearing seats (not written the measurement down), the first, oversize one that i had was 19,8mm (i had this dimension written down in a PM, and was told it was probably one of the early oversize ones).
So over 20mm = probably a bad diff, it may be part of the first batch.

(and the gear diff should be a little wider, not that much tho!!)

[pugboy]

Does the diff still bind without the idler gears in place? There are a couple of possible causes but I grappled with a similar issue. It can be caused by what the posts say above or if you have nipped the diff screws a little too tight it can cause a slight distortion of the diff gear thus causing a tight spot in the mesh with the idler. Good luck and hope you sort it.

[Origineelreclamebord]

Thanks for the suggestions everyone

Unfortunately I can't check all these things until friday night or saturday, but I'll definetely look through them. I also hope Durango respond to it soon.

The car is from the first batch of DEX210s, the gear diff was bought a few days ago at JEModels - I don't think they still have diffs lying around from the first batch

[AndyG]

had the same problem, so never went back to the gear diff.

[j.d.roost]

I had a similar issue. (gear diff measured wider than the ball diff). It was fine until I tightened the case bolts. I ended up playing around with different manufactures diff.bearings until I found a set that let me get the cases "tight enough" with no binding. We are talking very slight differences in bearing width..not enough to measure with the crappy calipers I have...but enough to make a difference once it was all bolted up. I don't know who's bearings I ended up using...must have 100's of different ones throughout my years of racing lying around. Maybe try doing a sandpaper "rub" (ie.diff ring sanding) on the side bearings? Never tried this but it might work..

[Origineelreclamebord]

It's a strange issue, but I'm going to solve it As suggested I've checked the seating of the bearings on the gear diff. They were tight to put on, but are properly seated against the edges of the diff. Also, with only the diff in the tightened casing, it still binds.

I think I've just got the wrong combination of a wide diff and a tight gear casing, resulting in a tight layshaft at first and now a tight gearbox with a gear diff. The layshaft was solved by 0.2mm shimming, so the gear casing could be as little as 0.15mm too narrow. The wide diff is 0.4mm wider than the ball diff - quite considerable, but keeping in mind the stuff is all injection moulded things like this can happen.

I'd like to see Durango respond soon to the email I've sent them. In the meantime I'll have to take matters into my own hands. The gear casing would be the cheaper choice to mod if anything goes wrong, and I have dremeled out bearing seatings for my TRF to fit a gear diff... but it's a risky job. I'd much rather take some material from the gear diff's side plates as it's more accessible Stay tuned!

Edit: Ok, it worked... but I feel really stupid! After dremeling 0.4-ish mm off it was rotating smoothly. I cleaned the diff and the housing, but before re-assembling the whole thing I decided to check on the gaskets to make sure the brake cleaner hadn't reached them. It was all good, so I closed it again, but this around I have overtightened two screws!

I can now feel it's not tight in one part, then in a small part of the rotation you can feel teeth rubbing each other, as if a motor is cogging. I guess I'll be making Durango happy with another sold item, though not the way I was hoping to...

[Origineelreclamebord]

I had ordered a new gear diff housing/plastic parts, and with those too, the gear diff was too wide. Some Dremeling means now it has about 1mm of room to move back and forth. Luckily though, thanks to the tight fit on the bearings, it stays put and moves smoothly. So either the gear diffs are always too wide, or it's indeed my gear casing that's at fault.

That's the complicated part of the story - here is the nice part. I've had contact with Durango - they responded quite quickly and stated they'd send a new gear diff and gear casing right away

Last Friday I got a note from the post office, so I went there after the weekend and the package felt quite heavy. Guess what? They've sent me a complete DEX210RTR gearbox + a NIP gear diff

I've had experience with the Durango customer service before and it's always been positive... but this is way beyond my expectations! Thanks Durango!

And no, I'm not just reacting enthousiasticly on that: The RTR gearbox moves more smoothly - the diff comes in at 19.85mm - at 0.1mm wider than a ball diff with the copper shims it is a tad wide, but that's a very reasonable tolerance within which both diffs should work nicely.

[OneKiwi]

Nice to hear you or TD got it sorted.

One thing I did find with my gear diff is if I tightened the screws heavily then the little lip that the small diff screws should sit in would bend out and this would catch on the inside of the gearbox causing a rough patch like something was catching.

This took a while for me to figure out. I ended up cutting off the little lips and sanding a little on the inside of the gear box to insure clearance.