Notchy SD

[MattWinyard]

Hey all.

Just rebuilt my SD (For the third time) ... From new it has had this notchi in the diff, every half turn. So I assume from this that the large diff gear in front or rear (or both) of the car is not running concentric. I have rebuilt the diffs 3 times, and rebuilt the entire car 3 times (blasted bearings the lot) so I have to assume that something is not concentric.

Does anyone else have this problem with the SD?

I used to get it also on my TC3 but that would fix itself after about 2 - 3 runs, this does not though :S

Thanks.

[MattWinyard]

Just found something thats kind of solved it, but I think the problem is still there... but covered up:

Went to halfords today, got some of that Teflon Grease in a tube stuff, but a small drop in each diff, free wheeled it and HEY PRESTO! problem solved... Car spins for about 6 seconds now!

[Chris Kerswell]

Where do you have the shimms in the diff and prop shaft?

You need the diff ones BOTH on the opposite side to the pulley and ditch two of the three that are on the back of the pinion gear on the prop shaft. This may help your problem.

[MattWinyard]

I have the shims on the diff in the position most pushing away off the teeth...

iI am only using 1 of the 3 in the front of the car though, and 2 at the rear...

[Chris Kerswell]

Hmm, shouldnt be notchy then!

Are any of the teeth damaged / got crap in them?

Chris

[MattWinyard]

I saw the post about the teeth being damaged, nope no damage...

And I clean them with motor spray every rebuild, and before I applied my teflon grease.

[Chris Kerswell]

Sorry, I didnt read the whole thread (my bad).

Ummmmmm check the bearings are all seatd properly?? - especially on the pinion gear for the prop shaft - this bearing is a very tight fit.

Errrr im running out of ideas now :(

[MattWinyard]

I push all bearings down with the other end of an associated driver (flat) found that method has always been best...

I think we just have to come to the conclusion that the main diff is not concentric, do you agree?

[Chris Kerswell]

Hmm, looks like it yes, however this sounds strange to me because I have never seen this.

If you take the prop-shaft out which end is notchy?

Then swap the diffs front to back and see if the problem transfers. If it does then its a diff/diff bearing issue if not its a pinion gear/bearing issue.

Let me know your results

Chris

[cobra81li200]

Shim the gears like on the manual and break them in using a stock motor @2 or 3V with no wheels during 5 or 6 hours.

This is what is recommended by Yokomo USA team drivers.

No molding process can for sure give a round part, especially gears. They need to be broken in. If you put less shim as on the manual, then you might have gear breaking by putting too much stress on some teeth of the gear.

[MattWinyard]

I did run the car in for about an hour with no wheels, I ran it at 4v...

The car did free up but still had all that notchiness... I have ran the car for 2 weeks now... and it still has not gone, to be honest I think I am just going to have to wait till it does run in!

[BC Rog]

My SD transmission is a little notchy when you spin it over by hand, after many many packs of cells (yes 7.2) on an old 540 motor.

The thing is that when they are running they will try to separate so the notchy thing is a little irrelervent.

If you guys can get away with running less than kit shims then good on you, might give it a try! Kit shimming feels about right though, to my fingers anyway.

The upside of gears that take a long time to run in is that it should take even longr for them to wear out!!

Rog

[MattWinyard]

Yeah but as soon as they are worn in they will be worn out!....

Glad to find someone with the same problem, not my built faults...

[Chris Kerswell]

Try the shimming as suggested.....

[atlas copco]

As Chris has said take out prop shaft to eleminate weather it is the front or back. Problems i have found is people dont put the gearbox pinion on the shaft all the way it is very tight drift it on gently. it is a very tight mesh between crown gear and pinion that is where i think you should look :)

Please make your real name visible on your profile to comply with forum rule 5.

[AzNDRAGster]

As Chris has said take out prop shaft to eleminate weather it is the front or back. Problems i have found is people dont put the gearbox pinion on the shaft all the way it is very tight drift it on gently. it is a very tight mesh between crown gear and pinion that is where i think you should look :)


If it won't go in by hand, use force, you have to tap it with a plastic hammer, that worked for me. Put a little grease there so it easily slides in.

[mark34]

I found in mine to get rid of the notchty feeling I ran the diff shims either side of the diff ( just 1 on each side) run the normal shims on the prop shaft and hey presto all runs very smooth! This should not cause you any problems with stripped gears as it is noty much of a change just slightly moves the gears apart. Works fine in stock and superstock have not tried in a modified
Cheers
mark

[whoopass]

says the guy who placed the rear diff in the wrong way round and the car did not even get off the grid!!! DOH!!!

[Chris Kerswell]

Is that not what the instruction book says?! :-

[mark34]

So it does got that wrong just looked at me car and it is 2 shims on the left handside I must be a bit thick today! sorry for the confusion and yes its true i did put one diff in wrong ( thanks Rob)

[Chris Kerswell]

LOL, I put a diff in the wrong too, then wondered why I couldnt pushthe car forwards :P DOH

[AzNDRAGster]

When the gearboxes are installed the diff gear should go on the ][glow=red,2,300]RIGHT SIDE

[Chris Kerswell]

thanks, do you man the RIGHT HAND SIDE or the CORRECT SIDE?

:P

Chris

[AzNDRAGster]

Say the front of the car is facing your way, (without the diff cover) you put the diff to the right hand side of the pinion in the gear box, vice versa for the rear. I didn't like the instructions because they don't have great angles for the pictures.

[Chris Kerswell]

Im not sure thats correct, the gear on the diff should be on the right hand side of the car at the back, and the left hand side at the front (when looking at the car from above). If that is what you have expalined then I am sorry for being dense :P

[Eddie]

I think you might be talking about what happened to me when building SD diffs.

Is the whole transmission notchy or is it as though there is a "high point" on the mesh? Also its always at the some place? rotate the wheels left or right and at the same point theres a "Click" and then continues to rotate to the same point agian and the same happens.

This happened to me twice and I'm jiggered if I can remember what it was but I think it was to do with the diff itself rather than shims or input shaft.

First time it happened I just rebuilt the diff (actually about three times) and it went. The next time of rebuilding I remember realising what it was but I just can't think.

[AzNDRAGster]

Im not sure thats correct, the gear on the diff should be on the right hand side of the car at the back, and the left hand side at the front (when looking at the car from above). If that is what you have expalined then I am sorry for being dense :P


Sorry that wasn't really clear, when looking at the car from top and the car is facing forward, the diff in the back should be facing to the right and the one in front should be to the left.

Diff
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Diff

Does the picture help?

[Chris Kerswell]

Heh, yes we were both describing the same thing - do you think everyone is nice and confused now?!

[mark34]

I bet you i will still put one in the wrong way when hurriedly changing between rounds even after all these explanations ;D

[AzNDRAGster]

Heh, yes we were both describing the same thing - do you think everyone is nice and confused now?!


The picture helps. :P