garynjr

Hey All, I'm having problems with my t-spec and it's Ball Diff.
Well, I'll be honest, I am Ball Diff chalenged or something!
I had problems with my Mini T one too! What is the deal with those things anyway?
How do I go about not slipping? If I tighten it up too much I get no Diff action but if I keep it even slightly loose it slips like crazy and I can't get the power to my wheels.

Now My rear wheels don't spin at all! I took the whole thing apart, Cleaned it lubed it and put every one of those anoying little balls back in to place on the screw and the plate. I polished my discs, and within 30 seconds it was slipping permenantly again!! What's the deal???

Does anyone know if there is a better diff to get for the T-Spec? Will the Tc3 diff fit???

What maint tips can you offer to help with these tricky diffs?
Thanks!! G.

S.A.E.W.O.T.

is ur slipper loose?..... tighten it right down....same with ur diff...[] i got a ball diff on my evader st.... and the thing pisses me off soooo much!!!![:@][:@][X(] well if ur gonna race run ur slipper loose and diff tight!

garynjr

Well, On road cars don't have sliper clutches like off road buggies do but thanks...

If anyone out there is good with Ball diffs Please help us! Thanks...

Johnboy Walton

Gary,

One guy at our track had the EXACT same problem with the rear diff in his on Friday.
He had asked a friend to rebuild it, and near as we can tell, he over-tightened it and
completely wiped out the thrust-bearing washers that take all of the load from the
diff spring.

He ended up getting a whole new rear diff assembly, since it seemed really beat-up.
Since the gentleman who runs our track hadn't been able to get parts, he took apart
his own car as a parts donor. Of course, the donor diff we got was siezed, so my
friend rebuilt his entire diff for him while I helped with track repairs.

Last I knew, Trinity was having trouble getting parts out to suppliers. If you can get
a replacement diff assembly, it's probably your best bet. Otherwise, see if you can
get the thrust-bearing washers and replace those. You probably want to replace the
diff balls and thrust balls while you're in there.

And yes, we're starting to look at what other diffs might fit. I just rebuilt mine last
week, and they were so fragged the chrome had completely worn off one side of the
diff plates.

When you do get your diff put back together, just tighten the diff down enough so that
it doesn't slip, give it a few good turns, and make sure it still doesn't slip. I haven't
had one of these diffs loosen up on me, so I'd say it's better to err on the side of loose.

Good luck, once you get 'em hooked up, these cars are a blast to drive.

Oh yeah, and if your shop lets you make any mods in your spec class (ours does),
change out the rear springs for some medium or medium-softs. The stock springs
are so hard it's almost impossible to get the rear to hook up with them. And also
change the steering bellcrank ball-studs to the inner ackerman positions. Finally,
get the rear swaybar out of there. These three things more than anything get
these cars hooked up solid on the track.

Mike

garynjr

Hey Mike, Thank you! That helps a lot. I actually just read my last copy of Extreme RC and sure enough there was an artical on how to setup your ball diff. I opened my diff back up and sure enough that was the problem. I must have tightened it too much and it messed up my Thrust washers. Although, I have always had the slipping problem with that car. I love the car for the price other then that. And the fact that it's a pain to get to the diffs!! Do you know of any company that has parts in stock? Or any rebuild kits that would fit? My presure washers are all grooved as well and I'm sure the balls are a bit messed up too. Has any of your buds ever tried a TC3 diff in there?

I'll try your sugestions for setup too. Thanks! G.

jakjr

My Feedback: (18)

I have a simular problem with my nitro evder, I keep breaking breaking the thrust bearing, then my diff does like yours and just slips.

I know its not from overtightening as I keep it relatively loose, aleins8mycow told me he thought it might be because I had it too loose.



The balls in your diff. are probobly the standard size, 3/32" diff balls, 1/16" thrust balls, but Ive seen other sizes so try to find out exatly what size they are.

For the washers, try to measure their inner diameter, width, and outer diameter, once you get those measurements you can get on tower hobbies website and just start comparing your measurements to that of all the other diff. washers.

Johnboy Walton

Gary,

Maximus Hobbies in York, ME just got a big shipment of parts in.
Heath, the gentleman who runs the shop is great to work with. His
number (at the shop) is (207) 351-1520. That's the only place I
know to go for these parts.

The size of the diff/thrust balls is listed (I believe, not at home at
the moment) in the manual in the section on building the diffs. I'll
have to check if they are metric, and if they cross-ref to a convenient
SAE size.

I honestly think the thrust washers on these things are made from
grade-A hardend butter. The one in my rear diff was distorted as
well, but the whole diff still works fine. When I found mine was
deformed, I put it back together the way it came out, with the upward-
bent part of the washer facing into the thrust balls again, so it
serves to capture the balls. I can't promise that this will fix yours,
but hey, anything's better than buying lots of parts.

There have definitely been a few different revs of this car built.
Mine was an earlier rev with chrome rear lower-arm pivot pins.
The two newer ones I saw at the track last week both had black-
colored hinge pins. All the screws on mine were over tightened,
so half of them are stripped. It looks like the newer cars are
torqued to a lower spec, since the one I was working on had good
bite in all of the screws. The one with the failed diff was one of
the newer cars.

If I remember, I'll try to pick up a TC3 or PRO-4 diff kit at the
shop this Friday when we race and see if I can reuse the ring
gear with all new hardware. I'll let you know how it goes.

Mike

garynjr

Hey Mike, That would be great! Thanks man. That's funny, i was thinking the same thing Grade A butter! That's funny.

Itneresting enough, I'm putting to gether a Tamyia TLT1 right now and the ball dif in that comes with this wonderful little thrust bearing all set up already in an enclosed little washer set like ting... It's the best I've seen! No worry of them falling out that is for sure! I imagine they will be a ***** to clean though. Or maybe no worse then normal bearings. Seems to me that the thrust bearing is the most critical part of the whole diff and it's also the most neglected in most cases.

I look forward to hearing about the Tc3 diff plates. Thanks, G.

Johnboy Walton

Gary,

I checked the diff balls in the TC3 manual, and the differential
balls are a direct replacement (3/32" = 2.4mm) for the T-Spec.

The thrust balls are a little bigger. The T-Spec is 1.5mm = 1/16",
where the TC3 is 5/64" = 2.0mm. I don't know that that's exactly
a problem, and I think that may be why ours frag so badly - it's
like little point contacts, vs. the Associated with larger balls.

I also checked the PRO4 diff. It looks pretty much like the Assocaited,
with the larger thrust balls. Its clamp bolt is smaller than the T-Spec,
so the thrust washer has a smaller ID, so we couldn't use it with our
diff screw. I also think we'd have trouble fitting the larger diff balls inside
our outdrives without using the smaller diameter clamp bolt.

I'd be willing to bet that this is where most of the trouble with the T-Spec
diff is coming from. Those tiny thrust balls are just too small and the
washers too weak to withstand a serious cranking on the clamp bolt.
The force may be the same, but with those small balls, the pressure is
enormous.

I'm definitely going to try to get a TC3 or PRO4 diff now. Looking at
the Associated pictures, they are almost identical in design, now it's
just a question if the whole diff assembly (with the stock ring-gear)
will just drop into a T-Spec. If so, that'll be the ticket. Hopefully I
can get one this weekend. I'll let you know how it goes.

Mike

garynjr

Sweet. Yeah, I'd be excited to know if it works! I'm also going to try my Thrust bearing from my TLT to see if that fits. It's a hell of a Trust bearing! Plus I locked my center diff on the TLT with epoxy weld no need for that little guy anymore...

Thanks again, i lok forward to hearing the result! G.

Johnboy Walton

Alright, here's what I've found.


The PRO4 diff is 'sorta' a drop-in replacement.

I took the PRO4 Ball Differential Set 39Tooth (P/N 75141) and cross-bred it
with the stock T-Spec diff. The only part I retained from the T-Spec was the
ring gear. Everything else (clamp bolt, thrust bearing, spring, diff plates,
diff balls, and outdrives) came from the PRO4 kit. One nice feature is that
the two bronze bushings that the outdrives run on inside the ring gear are
replaced by ball bearings with the HPI kit. The diff set cost me $40+tax.

The unit thus built dropped right into the T-Spec diff case, though I did
replace the outdrive bearings with new parts, since mine were a little
gritty.

There are only 2 things I'm not 100% happy about, and I think they're
related. First, the diff balls running in the stock ring gear run right on
the very edge of the PRO4 diff plates. The second was that the diff
seemed to loosen up after every race. I'm hoping the problem is that
the diff screw keeps loosening. Worst-case, the diff balls may be wearing
agains the ring gear, which will ultimately cause the gear/diff to fail.

As it is, I ran a hard practice session, 3 heats, and a main with it last
night, and the only problem I had was a fragged outdrive on the new
diff (of course!!!) from a mis-adjusted dogbone. I may look into running
PRO4 CVDs too, just to get rid of that problem.

So there's the bad.

The good news is that this thing is so silky smooth it's scary! The stock
diffs in the T-Spec were gritty from the day I bought the car, so it's
been really hard to tell whether they need to be rebuilt or not. The HPI
diff is so much better, I can't wait to put one in the front, too. The car
was very much smoother throughout the track, and it just seemed more
planted.

In addition to the improved performance, the diff plates on the HPI
diff are NOT chromed, so you don't have to worry about it peeling off.
Also, they are about 2x the thickness of the T-SPec, so I expect them
to last a LOT longer, even without being chromed.

Our first points season is over, so I won't have a chance to run it
against other cars until after the new year, but by then I'll have swapped
the front as well and repaired the rear, so I'll be able to give a much
better report on performance. I'm going to try some Loctite to keep the
diff from loosening, so I'll let you know how it worked. Frankly, even if
I had to replace the ring gear every few weeks, the improvement in the
diff action would be worth the expense.

Now, a word on legality - at our track, we are allowed to do pretty much
anything. As long as we run the stock body, motor, and battery, anything
else goes. My understanding is that this modification would be very illegal
for a true T-Spec class, and certainly for the national race they've got
planned.

Also, at $40/diff, $80 seems a little steep to spend on a car that only cost
$150 new. That said, I'm hoping to start running my T-Spec in the stock
class (with the HPI diffs, of course), so I expect this will help quite a bit.
Compared with the $325 for a new PRO4, it's not THAT bad a deal just to
get my feet wet.

Depending on your local rules and your pocketbook, this may or may not
make sense for you. If you can't find any T-Spec parts, though, and your
track is willing to let you, this seems like the best option going right now.
Otherwise, I'd suggest upgrading the diff balls to a quality aftermarket set,
keep new diff plates in it as often as you can afford, and try to find some
thicker washers for the thrust bearing.

gene465

My Feedback: (10)

This is good info here just wanted to bump it up!

aalzuhair

One year after and still good info