I am looking for the correct procedure to adjust the diff for maximum performance. I have a Custom Works but the instrucion manual did not recommed how tight to get the diff.

I adjust mine till I can hold both wheels and try to spin the spur gear it should be a little hard to turn then I test the car on take off if it spins too much I tighten it. I also use it to get my take off just right if the car plls too much to the left or right I will loosen it a little to make it take off straight.

Another Good Way To Do It Put It On The Track And Push The Car Backwards And Sqeeze Your Radio To Full Throttle You Want It Spin For About A Half Second Then Snap And Take Off If You Have No Free Spin Then When You Go Around Corners Both Whells Will Have To Spin Together Instead Of It Actually Working Like A True Diff

If your diff is built well, you should not be able to turn the spur gear at all while holding both rear wheels. Also, you should be able to hold one rear wheel and get the other wheel to spin freely a couple revolutions or so.
This is my opinion.

I copied this from the RC-Oval site. It is by-far one of the best write-ups on diffs.

Building one with the thrust bearing in the hub works GREAT!!!

Diff building

Now that we have the pod built right, it’s time we tricked out the diff. If built in the correct way it can be an asset to the operation of the whole car. If not, it will be a detriment.

Keep an open mind when reading this part because it may not be anything close to the way you build your diff. All I can say is give it a try before you dismiss it. Most of what you read here has been “donated” to us by Kevin Champion so it may be a good idea to give it a close look. The “blue bearing” part is an addition that I put in and may not be for everyone but it saves the dickens out of the 1/4 x 3/8 diff bearing.

Unfortunately, most of the parts that come in your kit will not be used in this building process; they will be replaced by aftermarket products because of quality, usefulness, or performance. Mainly performance. The drive hub will have to be of the type that will accept a non-shouldered bearing. In other words it has to have a bearing recess cut into it and not have a strait hole going all the way through.

Lets look at the axle itself first. This may be one of the few things you keep form the kit. A good fiberglass axle is good and should not be discarded just because it’s fiberglass. They will take a little more beating than the graphite axle and usually runs pretty true. Trueness is very important. Whatever axle you use it must be true and strait. Personally, I like the graphite axle that Niftech makes. With the aluminum shaft in the middle of the graphite, I have yet to find one that is truer but it’s just my own opinion. No matter what brand you use it must be pinned along with the hub to eliminate any diff ring slippage.

Diff rings on the other hand, do not seem to matter much unless you get into the porcelain type. I have never had any long-term luck with those and when you weigh price vs. advantage, I think that price wins out. Again turning to Niftech , their Rocket rings are a bit lighter but they require a LOT of lapping in making them flat. I take the extra time to work them in because of the weight difference but again; it’s just my personal opinion.

OK, lets build the thing…

Assuming that your axle and hub are already pinned, let’s start with the diff rings. A few years back if you had told me that I could sand a diff ring and make it better I would have laughed in your face. Today, I know better. A new, off the wall diff ring needs a lot of attention.

Start by using a real flat surface such as a piece of glass as a surface to work from. Lay a sheet of 600 grit wet sand paper on it. The term “wet paper” is just what it implies, it’s made to be used wet. The water on the paper prevents the build up of sanding debris from clogging the paper and scratching the surface of the diff ring (or what ever you happen to be sanding). Rinsing the paper under tap water several times during the process is recommended. You can use the drive hub as a tool to hold the diff ring while you are doing this and that will save you the money of buying a tool made for this purpose but they are available if you still want to use one.

With the ring on the wet paper, use a figure eight pattern and sand the ring until you c an see a flat surface all the way around it. High spots and low spots are easy to see. The scratches are the high ones and the parts that have not being sanded yet are the low ones. Once you have the ring flat, switch to 1000 grit, color sanding, wet paper. This will begin to put a slight gloss to the surface. Again, watching the high and low spots, keep at it until the whole ring has this gloss. Now repeat the process with 2000 grit paper.

There is a way to speed this process up though. Find a broken, pinned a xle and chuck it in a drill. Start the drill and work the ring in a small circle while putting light pressure on the drill. It’s a bit tricky so be prepared to “catch” the r ing a few times until you get the hang of it. It’s sort of like learning how to us a buffer to wax a floor.

If you use this method put www.capecodpolish.com on the glass and polish the ring with the drill. You will be able to see your face in it although this picture doesn’t do it justice.

What kind of “balls” do you have?

Diff balls are definitely not created equal. For years I bought diff balls by the hundred at a local bearing business for three bucks a pop and they seemed to work just fine. (Of course this was about the same time I didn’t think sanding the diff rings was a good idea too.) I could see no use in spending the money for the high dollar stuff. As long as I changed them every week, the el cheapos looked real good to me. Now I look at things a little different. While I still see no need to buy the REAL high dollar rings or balls; I do like to use a better ball. We can change the balls so easily, unlike say, the Touring Cars, it’s just cheaper and just as well to use a “better” ball but change them often.

As far as spur gears go, I am hard headed about using Kimgrough gears. They are well made, they run true, the diff ball holes are spaced well and they have this great dust cover that really cuts down on the times that you have to re-build them. Where I use to re-build every week, I can go two or three weeks sometimes before I have to tear it down.

Building the diff

A few “different” things you are going to need with this system are 3 to 4 ¼ in. axle spacers and 2 ¼ in. non-shouldered bearings and only one ¼ in. shouldered bearing.

First though, use the tip of an Exacto blade and put a dab of diff lube in each diff ball hole of the spur gear. Install the new diff balls and put just a light film of diff lube on your polished diff rings. Keep in mind the pressure between the diff balls and the rings is so high that a lot of diff lube is not necessary and will just be thrown off. In fact some builders just put a dab of diff lube in the palm of there hand and rub the diff balls in it and that’s ALL they use! Just remember that all the excess is going to be thrown off.

Assembly

Starting with an empty axle put one ¼ in. spacer on first. Lay one of the diff rings in position and then put a non-shouldered bearing in the spur gear and slid it on. Now add another ¼ in. spacer (or maybe two depending on how much recess is built into the hub). The purpose of the spacer washers is to keep the bearings from rubbing against each other but you also do not want to put them in a bind. Install another non-shouldered bearing in the drive hub and lay the other diff ring on it. Slid the hub onto the axle making sure it all stays in place. Now you have an option . You can install a shouldered ¼ in. bearing, cone and adjustment nut as usual and it’s together or you can do it another way. (This is the part that I added to Kevin’s method)

This “other way” requires an Associated blue (three part) thrust bearing, a plastic BRP cone, another non-shouldered ¼ in. bearing and a drop of CA glue.

Slid the ¼ in non-shouldered bearing in the outer half of the drive hub, again the hub must have recesses cut into it for the bearing otherwise they will not stay in place. Add one more ¼ in spacer and then one of the thin thrust washer rings. These rings need to be polished in the same manner as the diff rings. Smear a light coating of your diff lube on the blue bearing and slid it on next. Now the other thrust washer ring. On some axles, you have just run out of space! If this is the case for you, put a drop or two of CA glue on the “Bud’s” cone and glue the last thrust washer on it. Slid it on and add the adjusting nut.

I like the latter way of doing it because it REALLY saves on the outer bearing. No matter what type of shouldered bearing you buy, none of them are made to be thrust bearings and they will wear out very fast and get real scratchy. With the blue thrust bearing I have found that the hub bearing last for a very long time without having to replace them because there is no pressure or thrust, on any of the four bearings in your diff. I find NO loss of performance what so ever. In fact I honestly think that it makes the diff better. The last thing to do is to add the spur gear covers by K imbrough. They snap in place firmly and will not come off, even in a hard hit. Just a side note about the gear covers. These things really work and will save you a lot in diff re-building (and bearing buying).

At this point the diff is built. You should be able to hold it in your hand and work it and not feel ANY scratch what so ever. If you do, something is wrong and you have to do it again. It will either be a bad bearing or a bad set of diff balls. Most likely, it will be a bad bearing.

Just tighten the adj usting nut until you only have a slight amount of pressure on it. Install the axle and diff assembly in the car and bolt on a set of rear tires. Hold the tire on one side and spin the other one a few times, then rotate to the other tire, hold it and spinning the opposite side. Go back and forth a few times then add a little more tension to the diff. Repeat this process until the diff is tight. It should still feel very smooth with no scratch or drag.

Using the right diff lube is important. Try a few different brands until you find the one that will give you the best performance. Associated, clear lube is good as is Nifetch’s . I’m sure you have your favorite but don’t be afraid to experiment with others. The picture above shows the completed diff without the Kimbrough dust cover so you can see how the diff lube will through out if you use too much on.

So there you go. Everything is built except the front end. This is so extensive and SO Important that we have decided to let it be an article within itself in next months issue. I would not hesitate to say that 75% of all handling problems can be attributed to a poor front end and most of this is in the way that it was built. So check with us next month and we will show you (with the help of some friends) a few tricks to building a good one………………………………………………………………………… RCO

I've been doing it the RC-Oval's procedure for years. Works great and the bearings seem to last forever. Diff's are silky smooth.

RC

one thing to remember when running the thrust bearing type rebuild is that 1/2 of the diffs smoothness is in the thrust bearing assembly.So when you re-build the diff always clean, inspect,and re-lube the thrust assembly when you re-build the diff.Also one of the tricks we used to use when the thrust bearings came on 1/12 cars is to replace the steel balls with carbide ones, and use associated black grease in the thrust bearing just like you would on a touring car or dirt car diff.

Thanks everyone for their advise on diff building and adjustment. I have one to rebuild tonight

Anyone have a part number for the Associated Thrust Bearing mentioned in the article?

Anyone have a part number for the Associated Thrust Bearing mentioned in the article?


not sure on the AE#, but I use the Trinity #SS2014..
Don't know if one is any better than the other.. but I like it.

Might this be the same thing? (from LeftHander R/C)

http://www.lefthander-rc.com/catalog/product_info.php?cPath=28&products_id=1351

Can't find the BRP Cone anywhere, but I have several laying around that might work.

You can save yourself a whole lot of time and effort and just buy Slapmasters thrust bearing. I have had mine on my pan car since October and it is just as smooth then as it is now. Build the diff the same way as you usually do and just the Slapmaster bearing on the outside the flanged bearing on the hub.

I agree that the rc-oval article with the old thrust bearing has worked well for me for years now this other is the same concept just a lot simpler and smaller.

Thanks, Dan and Ken...

I ordered the Trinity one as it's the only one I could find readily available and get with the rest of my parts. I hate ordering online as I like to support the local shop, but I'll have him order some in for the rest of the local crew and my next oval car. I like the thrust bearing way much better than what I currently use...just makes more sense.

MAN i really need to update that article it's just a tad outdated LOL. But I still like the thrust bearng

You don't need the BRP cone washer. Get LOSA9941. They are the bearing spacer/axle washer set for the XXX series of cars. The axle washer has a 3/16" ID and fits in the hole of the outer thrust washer to align it on the axle.

Also, you can use an outer diff hub that is drilled straight through. Get a piece of K&S 1/4" I.D. aluminum tubing and cut a piece the proper length to space the unflanged bearings at each end of the outer hub.

Been doing this, and using the Trinity thrust bearing for 2-3 years now.

You can get thrust bearings from McMaster-Carr for $1.95. Haven't tried these because my Trinity bearings haven't worn out yet.

That's the neat thing about this system, you can make your diff really smooth and very tight and none of the bearings wear out for a very long time. Mine are over a year old and the thrust bearing is ancient!

Thanks, ta_man. I have several parts from my XXX cars to work with and noticed that the axle spacer would work. I run a KSG and the hub has recesses for non-flanged bearings. I picked up some Boca LBT carbide diff balls at the LHS and already have IRS lightened rings, so I think I'm set. Getting the pressure off the hub bearings will be the biggest improvement, I think. I'll experiment over the next couple weeks building it with the IRS rings and then switch to the ceramics that came on the car, but I doubt I will like the difference...I tried ceramic rings in my XRAY cars and hated them.

I'm not about to spend $50 on my KSG diff...I just want the diff to be smooth for more than a week. I've been following what our local fast guys do for a year now, but some of them are set in their ways, and there is always room for improvement.

Wow, I've never had a pan car diff that smooth...it's almost as smooth as my XRAY diffs! LHS had the Trinity bearing. I spent about an hour on it and got the rings fairly polished. Seems alot freer at the same tension as before, but much smoother. Any advantage to putting the rings on a 6000 Wet Stone?

Any advantage to putting the rings on a 6000 Wet Stone?
I dunno. I barely sand mine and the diff is smooth and lasts forever. I only run pan cars during my club's winter/indoor season and haven't had to rebuild a diff mid-season since I started doing this. If you use Kimbrough spurs and their diff covers, no dirt gets at the balls and the diff stays smooth for a long time.

PRS spurs accept the dust covers allso all the ones I have 100 up do anyway.

Jake

Yeah, the diff covers are on their way. Will be trying out the car tomorrow...it's been down and out for several weeks, so this will be a good test! Thanks for everyone's help.

You can save yourself a whole lot of time and effort and just buy Slapmasters thrust bearing.


Any online shops selling this or do you have to get it directly from SlapMaster?

RC

Slapmster sells them direct. We stocked them for a while but the locals didn't think $25 for a bearing set that would outlast anything currently used (regular flanged bearings) was worth it. So after the initial order we did not reorder.

Slapmster sells them direct. We stocked them for a while but the locals didn't think $25 for a bearing set that would outlast anything currently used (regular flanged bearings) was worth it. So after the initial order we did not reorder.
Given that a $3 Trinity thrust bearing lasts for years (Per McLin and my experience), I can see why guys might not want to spend $25 on one.

Diff worked great...I now have a split chassis from a battery bar coming loose and allowing the car to coast not-so-gently into the wall, but the diff worked! :)

You dont have to pay $25.00 for your perfect diff.:thumbsup:

http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXPC40&P=7

You dont have to pay $25.00 for your perfect diff.:thumbsup:

http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXPC40&P=7

Are you using this one?
Was wondering how well that 5mm bearing fits on the 1/4" axle?

Are you using this one?
Was wondering how well that 5mm bearing fits on the 1/4" axle?

You flip the axle spacer to ride on the outside of the hub bearing.
Wide end puts even pressure on the hub up to the threaded alxe.

Install the thrust bearing and nut.

Best diff you ever had!:thumbsup:

These are the thrusts I use:

http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXFKL0&P=7

If you take an Associated .125 axle spacer and counter sink it, it will ride on the outer race of the bearing. The spacer gives just enough clearance so that the thrust rides on the threaded part of the axle. The 4mm hole on the thrust bearing fits snug around the threaded stud of the axle, so you don't have to worrie about trying to center it up.

Or, you can just buy one of the axle nuts that Muddslide sells. From what I understand, when you tighten the nut down it actually rides on the outer race of the bearing. Sounds good, but I haven't tried them yet.

These are the thrusts I use:

http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXFKL0&P=7

If you take an Associated .125 axle spacer and counter sink it, it will ride on the outer race of the bearing. The spacer gives just enough clearnace so that the thrust rides on the threaded part of the axle. The 4mm hole on the thrust bearing fits snug around the threaded stud of the axle, so you don't have to worrie about trying to center it up.

Or, you can just buy one of the axle nuts that Muddslide sells. From what I understand, when you tighten the nut down it actually rides on the outer race of the bearing. Sounds good, but I haven't tried them yet.

That's AWESOME!!!

Thanks for the info..

Tony Moffre is who showed me what would and wouldn't work. So you can thank him for the info!! LOL!

Thanks buddy!

Just installed the Slapmaster set-upon my 2 KSG axles, and The results were awesome. Super smooth feel and the knowledge that this will last a long time, that's worth every penny because I didn't have to rig something up, it is the right tool for the job!

Just installed the Slapmaster set-upon my 2 KSG axles, and The results were awesome. Super smooth feel and the knowledge that this will last a long time, that's worth every penny because I didn't have to rig something up, it is the right tool for the job!

On the KSG diff hub -- did you change out the unflanged outer bearing with a flanged outer bearing to use with the Slapmaster thrust bearing ??

Thx !

The Slapmaster is a lot easier to put together than using the Trinity thrust bearing. You have to space out the bearing with a washer and take out the flanged bearing in the outer hub etc. Slapmaster is about 1/3 the size and you just add it to the standad diff setup and you are done.

I installed one tonight in my KSG -- I just swapped out the outer bearing in the diff hub with a flanged one so that the nylon collar would clear the end of the graphite axle.

It's smooooooooooth !

It said that it doesn't need any grease on the thrust bearing -- is anyone using any ??