Setting up your bulkhead

[CHKMATE ELUDER]

Hey guy's, thanks again for this great thread! everything I have read everywhere on this suggests that 30k is stock in front and rear but some chose to run 50k in the front, just going over my owners manual and it states that 30k is stock in the rear but 50k is stock in the front, if I wouldn't have read the manual I would have just put 30k in both, so with that said I guess I need to order some 50k before I do the fronts, I ordered to complete diff for my sons digger front end since I trashed the first one I put in there and I assume that has 30k in it? so I'll change it to 50k before I put it in, here is what it says in the merv owners manual about 30 and 50k.

Tuning the Sealed Gear Differentials
You model is equipped with sealed, bevel gear differentials. The
differentials allow the left and right wheels to spin at different
speeds while turning. You can increase or decrease the torque
transmitted between the left and right wheels by changing the
viscosity of the silicone oil inside the differentials. The viscocity
of the oil is indicated as a weight (W). Higher weights are more
viscous, meaning the oil is “thicker.” Lower weight numbers are
less viscous, meaning the oil is “thinner.” Filling the differential
with higher viscosity (thicker) oil “tightens” the differential,
transferring more power to the wheel with the most traction.
Filling the differentials with lower viscosity (thinner) oil “loosens”
the differential, transferring less power to the wheel with the
most traction. Traxxas sells a variety of differential tuning oils
specifically designed for use in your model.
Your model’s gear differentials have been tuned specifically to
provide balanced handling and precision power slides. The front
differential has been filled from the factory with high-viscosity
50,000W silicone oil. The 50,000W oil allows the front wheels to pull
the model through the turn when counter steering through a drift.
Increasing the fluid viscosity increases the authority of the steering
while drifting, but decreases the steering when not drifting (“grip
driving”). Increasing the front differential viscosity too much will
make the model difficult to drive (“twitchy”). Decreasing the front
differential viscosity will decrease the ability of the model to drift,
but will increase steering response when grip driving.
Front Differential oil viscosity tuning suggestions
• For drift cornering with a single Series 1 battery (6-cell
NiMH), use the stock differential oil.
• For drift cornering with dual Series 1 batteries (12-cell
NiMH), use thicker/higher viscosity differential oil (higher
weight number).
• For grip driving with single or dual batteries, use thinner/
lower viscosity differential oil (lower weight number).
Tuning the rear differential fluid will allow you to fine tune the
amount of angle the model will exhibit during a drift. The rear
differential is filled with 30,000W oil to keep the rear of the
model from sliding out completely when drifting around a turn.
Increasing the viscosity of the fluid will cause the model to overrotate resulting in a spin. Decreasing the viscosity of the fluid
will reduce the model’s drift angle. For grip driving, lowering the
viscosity will allow the model to turn more easily.
Rear Differential oil viscosity tuning suggestions
• For drift cornering with a single Series 1 battery (6-cell
NiMH), use the stock differential oil.
• For drift cornering with dual Series 1 batteries (12-cell
NiMH), use thicker/higher viscosity differential oil (higher
weight number).
• For grip driving with single or dual batteries, use thinner/
lower viscosity differential oil (lower weight number).

[50togo]

Think of thicker fluid as more of a posi effect - less slippage where the inside tire in a turn doesn't turn fast enough to keep up with the outside tire
The first turn I made in the rain in my big block nova after putting a posi unit in the rear end I spun out because I wasnt use to it.
So 30k is stock and better for turns 50k works good for bashing helps to put more power to both wheels. Being a thread on how to shim that all I will say!

[graham_h]

Done ours today
2 shims in the front and two in the rear.
Haven't run it yet but seems ok. No slop at all

[Supernova]

Hi, would like to confirm the right way : I almost have to loose all the screws (roughly 40 screws for front and rear diff) to open the gear box to get the diff out. This makes me aware if I have made it wrong. My question is after putting shims, should I need to wholly re-assemble everything to verify the shim number, then repeat this procedure until the optimal shim numbers are known? It will be much appreciate if anyone can tell me if any simple way to verify it. I have a lot of screws on my table now, and are still puzzled if I can put the right screws back to the original slot. Any comment will be appreciated.

[firemanJBI]

Aside from the weight of the diff fluid, how much is in there ??? When I shimmed mine a few weeks ago, there was some in there but not much. I didnt loose any, so didnt add any

[JimmyNeutron]

I found all my diffs to be very lightly filled... they are supposed to be nearly overflowing.

Supernova: Post #1 explains all that needs to be assembled to check mesh.

[firemanJBI]

Jimmy the fluid I found in my diff was like a grease, not so much an oil ? Like bearing grease, the truck was new when I shimmed it.

[JimmyNeutron]

Are you sure you are not talking about the lubricant found in the bulkhead and not the differential?

[firemanJBI]

So your "differential" is where the 3 spider gears are ? Yes, I was talking about the grease in the bulkhead. But I found similar lube in diff.

[JimmyNeutron]

Yes, that is the differential... where the 3 spider gears are.

There should have been diff fluid in there...


Even though this is a 1/10th scale diff, it should give you the right idea... unlike the one below:


This one looks like they have diff fluid all over inside the bulkhead... where it should be dry or dry lubed in my opinion due to the area not being sealed from dirt.

[DialedInRC]

1. My bulkheads do not have a long screw to hold the two halves together. Is this going to be a problem?

2. If it is ok to use the above bulkheads should I just use a clamp or rubber band around the two halves to determine if I have enough shims? Or should I attach some of the other pieces of the car that normally hold the two halves together?

3. Is 60k in the front and rear and 100k in the rear ok to use? I also have the same brand 5k that I could mix in to thin the 60k.

4. Do you think I can get by with my old diff seals or will I need rebuild kits? I have green slime if that helps.

[JimmyNeutron]

1) No. When/if they break you will probably be replacing them with the new style as the style you have is no longer in production.

2) Rubber bands are not going to hold the halves together tight enough to determine shim count.
Leaving the arms off, bolting the skid plate on, attaching the bulk to the chassis, just sliding on the blue tie bar (8 screws total) will hold it together enough to determine shim count.

3) Oil weight is a personal preference... I ran 30k/50k/30k and was pretty happy.

4) I reused my diff seals many times before they required replacement.

[DialedInRC]

Thank you for your detailed answers and for this topic Jimmie. You've been very helpful.

[JimmyNeutron]

No problem!

[DialedInRC]

I'm have a problem that I can't seem to solve. There is a rough spot in my ring and pinion mesh. If I watch the ring gear I can see it wobbling a little as I turn it and this is causing the rough spot. All of this is with the aluminum plate and skid plate in place. If I try even one shim it will cause the rough spot to grind. The loose places need shimmed though as I can hear clacking and I can see play. The only info I could find with a quick search was here. http://traxxas.com/forums/showthread...ough+spot+diff

I've tried pulling the large bulkhead bearings and cleaning where they sit. I've tried loosening the 3 diff screws and tightening them back up. Before I disassemble the diffs again I wanted to hear from those more experienced. I'm thinking it is either something I assembled wrong in which case somebody has experienced the same thing. Or it's a manufacturing defect in the bulkhead or the diffs.

[robl45]

its probably because the large plastic piece that the 3 diff screws go into is not sitting completely flat. Mine isn't flat and does the same thing. I left it as is as my son will just break it in a month or less and I'll get a new plastic piece and seal or a whole new diff at that point.

I'm have a problem that I can't seem to solve. There is a rough spot in my ring and pinion mesh. If I watch the ring gear I can see it wobbling a little as I turn it and this is causing the rough spot. All of this is with the aluminum plate and skid plate in place. If I try even one shim it will cause the rough spot to grind. The loose places need shimmed though as I can hear clacking and I can see play. The only info I could find with a quick search was here. http://traxxas.com/forums/showthread...ough+spot+diff

I've tried pulling the large bulkhead bearings and cleaning where they sit. I've tried loosening the 3 diff screws and tightening them back up. Before I disassemble the diffs again I wanted to hear from those more experienced. I'm thinking it is either something I assembled wrong in which case somebody has experienced the same thing. Or it's a manufacturing defect in the bulkhead or the diffs.

[DialedInRC]

its probably because the large plastic piece that the 3 diff screws go into is not sitting completely flat. Mine isn't flat and does the same thing. I left it as is as my son will just break it in a month or less and I'll get a new plastic piece and seal or a whole new diff at that point.

I'm thinking the same thing. I can't tell if it is my fault or a manufacturing flaw. If it is a manufacturing flaw I wonder if filing the plastic a bit where the high spot is will help.

If anyone else has come across this issue please post your thoughts or fixes.

[GReaper]

One thing I noted, when shimming my new HR bulkheads yesterday, is that you haveto be carefull if you're also shimming the pinion gear.
After I shimmed both the ring and pinion gear, and assembled the bulkhead, I mouted the center axle, and suddenly it was impossible to turn the gears.
I found out, that i've added a too thick shim to the pinion, so that when I fastened the axle, it would bind against the bearings.


Also I shimmed the gearbox, so that there is no slack in the axles. Combined with cheramic bearings, it results in a car,. where the wheels turn for over 10 seconds, if i spind them fast by hand.

[zach23]

Combined with cheramic bearings, it results in a car,. where the wheels turn for over 10 seconds, if i spind them fast by hand.

With motor engadged or not?

[robl45]

Hi,

I saw it before, but can't find it now, someone listed some other shims that work besides the associated, I believe there is a Kyosho set that has different thickness shims and includes a lot more in the package. Can someone help me out with the part numbers please?

Thanks

[Maxx_Adam]

3 racing. I use them on everything.

Sent from my SGH-I317M using Tapatalk 2

[Northern Adventurer]

I use 3 racing for all my other shims, for the 1/16s I use Associated ASC21141.
.

[robl45]

The kyosho ones are kyo96644. Appears you get 30 in the package of 3 different thicknesses. About 7 dollars shipped. Seems a better deal then the associated 21141.

When you shim it, after shimming, the bulkhead should still fit together normally right? Like when you put the bolt back in, you shouldn't have to press the bumper side together?

[lando calrician]

Great thread, helped me a ton, probably saved my diff!

[Shisimona]

I just recently did this with my rear diff, as I stripped the ring and pinion gear. So I got a ring and pinion gear set. Order 2 packs of those shims cause I wasnt sure how many I needed. In the end all I needed was one shim. Put 50K weight in, and it runs better then before. Will be doing the front once I feel like it.

[RcSummitVXL]

Here is another video:

Morning Jimmie,

Would you happen to know the title of this video? For some reason it is not playing for me. Appreciate it in advance!

[JimmyNeutron]

No I do not... looks like the poster/owner removed it.

[nixzero]

After hearing all of the warnings to shim the diffs on these cars, I tore mine apart and found that it was already tight, adding even one shim caused the diff to bind inside the bulkhead. Is this a preventative thing you need to do to all new MERVs, or something that has to be done after the parts begin to wear?

[Jimdog]

This is preventative but it can be done after the parts begin to wear. Your diffs may not need any shims. They may need 4-5 shims though also.

lipo power!!!!!

[nixzero]

Haha, just tried 3s for the first time, on stock gearing... I could see how the diffs might get a little loose over time, that little road rocket screeeaams!

[1badrz28]

Thanks again, The rear diff clicked from the start added the shims and a center differential and the E Revo works like a champ. Why doesn't the factory add these shims or at least check when they are assembling these? Anyway's its nice to have the unit working agin.

[1badrz28]

back to the top, Has anyone used the HR or Integy rearbulkhead with good results? I don't mind spending the money of it's a worthy cause. I'm trying to make the rear as bullet proof as possible for my 7 year old. I know he's not landing under full power he just likes to bash and do speed runs with the 31p/50spur on Summit tires.

Is the Hot Racing diff worth the extra also? I'd gladly spend 110.00 on a rerarend that will not strip out under 3s power.

I haven't seen many reviews online about the bulkheads.

Thanks, Jim

[redhat zach]

my hobby shop sold me 500k diff fluid. is that too thick to use on my summit vxl? also what do you consider a dry lube?

[JimmyNeutron]

Dry lube is dry after it is applied.

500K in a 16th is basically a locker with a little bit of slip... and may be too much unless you want to make a crawler out of it.

[redhat zach]

thanks jimmie
i will try to return it tomorrow. would you consider liquid silicone spray a dry lube?

[redhat zach]

thanks jimmie
i will try to return it tomorrow. would you consider liquid silicone spray a dry lube?

[Jimdog]

I use modeling clay in my diff for drifting. That locks it up fairly well. The hot glue ended up getting torn to bits and came unlocked.

lipo power!!!!!

[JimmyNeutron]

If it is dry after application, it is a dry lube.
I have not used liquid silicone spray to be able to tell if it is dry after application or not.

In all honesty, after my can of dry lube ran out I stopped using it... I ran the bulkhead dry for 200+ packs without any issues. As a matter of fact, those diffs are now in Australia being bashed on 3S and still going strong.

[Summitfarmer]

I'm have a problem that I can't seem to solve. There is a rough spot in my ring and pinion mesh. If I watch the ring gear I can see it wobbling a little as I turn it and this is causing the rough spot. All of this is with the aluminum plate and skid plate in place. If I try even one shim it will cause the rough spot to grind. The loose places need shimmed though as I can hear clacking and I can see play. The only info I could find with a quick search was here. http://traxxas.com/forums/showthread...ough+spot+diff

I've tried pulling the large bulkhead bearings and cleaning where they sit. I've tried loosening the 3 diff screws and tightening them back up. Before I disassemble the diffs again I wanted to hear from those more experienced. I'm thinking it is either something I assembled wrong in which case somebody has experienced the same thing. Or it's a manufacturing defect in the bulkhead or the diffs.

I encountered this problem too. Man it took time trying change something and putting together and so on. What seemed to work was to change the position of the plastic end at the gear end of diff. As there are three screws there are three positions for the end plate in relation to the body or gear of the differential. So in one position the resistance to rotation was about equal in all positions of the gear. The only thing that seemed to have any real effect. Not very impressed with the quality in this case.

Working with this, I think I may have noticed something else worthwhile. Looking at the differential ring gear and then trying to "drive" a screw driver down the Groove between teeth, it would allways stop at the outer rim. So there is obviously a significant burr around it. This may explain, why people have to keep adding shims some time before breaking in is complete. And the effects of the burr could also easily been seen in the pinion gear base as it was shiny metallic and elsewhere black.

The burr reminded me of tractor start ring gear located around flywheel. It happens to develop a burr in time, that should be filed off, when chance. So it could be with this. Whit dremel or what ever it might be done easily, only 39 grooves. Just an idea.

[USA1]

Wish I would have ordered the Associated shims last order.