Zash

Ahoy chaps! I have taken some photos of the old diff and the new one. =============== 1. Old diff: The outer ring shows wear as a deeply scratched surface. I used vernier calipers to measure how much Aluminium had been destroyed - 0.4mm. For comparison, the diff washers are 0.5mm thick. Note the amount of putty - there is hardly any - this was all that was inside. The aluminium shavings have mixed with the putty, turning it a sticky grey. The destroyed silicone seal, and the scratched stainless washer, which was rubbing against the bare aluminium without lubrication: The no-lube sun gear with destroyed teeth. =============== 2. The brand new, never been turned differential: The factory 20M weight putty is, at best, half filling the differential. With this little putty applied, what will almost immediately happen is that the vast majority will clear to the middle and sides of the spider gears, becoming useless, as most of it will never then come into contact with the teeth. This picture shows a scratch free housing and the reverse of the sun gear. There is no lubrication here except a bit of putty. Because of its extreme viscosity, it will quickly seep out from the sides leaving virtually nothing between the washer and the bare aluminium. New sun gear from the new differential, showing no lubrication from factory. I rebuilt the differential today, using a combination of the original 20M weight putty, silicone ear plugs, and 10k weight silicone: a. Lube the aluminium housing in all its bare contact sections with 10k weight silicone, including spider gear brackets. b. Lube and insert the silicone seal c. Replace the Stainless steel washer with the Teflon washer on the Aluminium Housing side. d. Lube reverse of both sun gears and between their washers. e. Lube the internals of the Diff Ring gear - no lube was present. f. Re-assemble the differential, filling all gaps with Silicone Ear Plugs, removing any excess. =============== Notes: i. The different viscosities will eventually mix to some degree but this ought to provide significantly better resilience against abrasion breakdown compared to the factory Differential. ii. The ear plugs will make the differential stiffer, which will mean less movement. This will in turn intrinsically mean less wear. iii. Aluminium is like the putty of metals - it is soft. It can't even be filed or ground well without it sticking into the grinding stone/file. Having a stainless steel washer rubbing up against it constantly, under pressure, without lubrication, is insanity. Replacing Stainless steel with Teflon - I would rather the Teflon wears against the aluminium housing, rather than the Aluminium housing wears against the stainless steel washer. iv. On the ring gear side, the ring and the sun gears are hardened so will not wear against the Stainless Steel washer - we can leave that as-is. =============== All-in-all, these simple mods ought to vastly increase the lifespan of your X-Maxx centre differential. I took the X-Maxx out today after the rebuild. I have never seen it work so well. P.S. Traxxas has censored my post on the Traxxas X-Maxx forums, attempting to discuss this issue. ¯\_(ツ)_/¯

Cheers for the replies chaps. I'll take and share pics of what I found in mine - it's already disassembled, so it might be tricky. The thing was in such tatters that I just bought a brand-new centre diff assembly. New parts arrive tomorrow. @mydoddy69, Glad to hear it's not a short term issue. However, I bet you didn't have a chance to inspect deep inside the housing where the Sun gear rubs, to inspect for wear. Was there any lubrication in there? Regardless, when you earplug it, the earplug silicone is much thicker than the 20 million weight silicone from the factory - you effectively lock it so it doesn’t move unless it absolutely needs to. If there is no movement then there wouldn't be any wear. @lorrylemming, Unfortunately the sun gear compresses against the silicone seals, so grease cannot be used. I'll be using silicone lubricant as that is silicone seal safe. I'm not sure how long it will last however - grease better tends to stick to metal. @Kpowell911, Glad you haven't noticed much deterioration. Maybe it's a traxxas quality control issue. Certainly there were many a person complaining about the centre diff not being adequately filled with putty from the factory, whereas other people found it aptly filled. I hope it's just a quality control issue not affecting most parts, however, after opening a couple of aluminium diffs in the X-Maxx (I have replaced all diffs with aluminium ones), I can say that none of them had any lubrication on any of the sun-gear/housing sliding parts, which is a huge no-no.

Preface: Engineer here. The following post is my humble opinions... The centre differential has an aluminium housing which relies on sliding parts to work. Inside the housing, the sun gears revolve freely against the aluminium housing, with a Stainless Steel washer in between. In a traditional differential, the sun gear is lubricated by oil in the differential, however in the X-Maxx, there i no lubricant - only a 20 million weight putty. 1. The putty gums up the washer, causing it to bind against the sun gear. 2. The bound up stainless steel washer rubs against the small surface area of the aluminium housing, without lubrication, and wears it out. This in turn pushes the sun gears outwards, causing the teeth to lose full mesh, and strip. In the end: a. The aluminium housing is destroyed due to lubrication-less abrasion. b. The silicone seal is destroyed due to abrasion (Silicone has very low abrasion resistance) c. The Front Sun Gear is destroyed due to lack of mesh after the aluminium housing had become worn. d. The aluminium filings get into the 20M putty and changes its characteristics. All 4 items will need replaced often. Simply, the X-Maxx Centre Differential is poorly designed, and not fit for purpose. Worst is the fact that the Centre Differential is the most difficult and awkward part to get at, requiring significant disassembly of the X-Maxx. ====================== Mitigating the issue: 20M weight putty is NOT a lubricant. From factory, the **Centre Differential is assembled without any lubrication***. 1. Dismantle the centre diff and clean all parts. 2. Lubricate the sliding areas with thin silicone lubricant: Traxxas 10k weight is decent. Shock oil is also a good alternative. Any lubricant is better than no lubricant. Lubricate between: a. Aluminium housing b. Silicone seals - Silicone rubbing against a steel washer without lubrication is another huge oversight by Traxxas c. Sun gear rear d. *washer* - read on e. Lubricate the reverse side of the spider gears. The stainless steel washer is stronger, however the Teflon ('plastic' washers used in front and rear diffs) is one of the most frictionless materials known to man. The down side is that Teflon is weaker than Stainless Steel. So the choice: 1. Use steel washer and wear the Aluminium housing. (New housing = >$20) 2. Use Teflon washer and wear the Teflon instead. (New Teflon Washers = few cents) I shall use Teflon washers on this build, and see how long they last. I do not have the forces data, so it will be all about intelligent guess-work. It may well be that the Teflon is not strong enough, and we shall have to go back to the Stainless washers - albeit with lubrication this time round. Any more suggestions? Insights welcome 🙂

Interesting about the slipper - The damping from the Cush Drive + the punch setting on the ESC would decently compensate for a slipper-less power delivery. The problem is then mid-air control. A lower gearing would only allow more torque to be instantaneously delivered to the differentials, thereby breaking them more easily. I would say that higher gearing would help rather. I have gone with a 50wt/100wt setup - works great for climbing now. I think the turning radius is larger at speed, as it more easily tends to push through turns. I might go back to 30wt/50wt at the next diff rebuild.

What is your reasoning? [Max6, Stock Motor, stock 18/54 gearing] A higher power ESC will not give the motor more power. Even compared to stock ESC, the Max6 is barely noticeable in 'higher' power delivery. The standard motor has destroyed my rear diff and my centre diff. A more powerful motor would only kill the gearing faster, while draining the batteries quicker. I wish to take the strain off the diffs. Presumably, heavier tyres will cause more strain. I am wondering if a change in lubricant viscosity will help mitigate broken teeth 🙂

Remember gentlemen, ALL manufacturers lie about their C ratings. Here are TESTED C ratings as of June 2021. Note how no manufacturer actually goes past 45C:

Compared to stock tyres, the Trenchers are double the weight and 1.5x the circumference. Presumably a thicker or thinner diff oil might be needed? I remember this, however I don't believe it would be too helpful here: DIFF OIL THICKNESS CHARACTERISTICS ----------------- Front -- Thinner • Increases steering into corners (off-power) • If oil is too thin the steering may become inconsistent, especially it can lose forward traction (and steering) during acceleration out of corners -- Thicker • Increases stability into corners during braking • Increases steering on-power at corner exit ----------------- Center -- Thinner • Front wheels unload more during acceleration • Decreases on-power steering (reduces oversteer) • Easier to drive on rough tracks • If a high-power engine is used you could waste too much power and sometime “cook” the oil in the center differential because it “overloads” • More off-power steering -- Thicker • More all-wheel drive effect • Better acceleration • Increases on-power steering (reduces understeer) • Better suited on high-bite, smooth tracks • Car can be more nervous to drive especially if a high power engine is used - you might need to be smooth on the throttle ----------------- Rear -- Thinner • Increases cornering traction • Increases steering into corner -- Thicker • Decreases rear traction while cornering • Reduces wheelspin Stock: Front: 10Wt Rear: 30Wt I tried 30/50 but didn't notice any difference. I am thinking of trying: Front: 50k wt Rear: 100k wt Any thoughts?

Hello chaps! I have a Max6 X-Maxx 8s with stock motor running ~ 20/50 GDS gears. I want to upgrade to a Hobbywing 5687 (8mm shaft). https://www.hobbywingdirect.com/products/ezrun-max-motors?variant=18438418497651 This is a Maximum 5800 W motor. Max 6 can handle 160a continuous. A fully charged 8s is > 33v Current x Voltage = Power 160a x 33v = 5300 W <-- Total power Max6 can supply continuously. So it seems that the Max6 will be able to handle it just fine. I think it will be a good match. Has anyone tried this combo? What are your thoughts? Worth it? Battery life? Breakages? Wear? I see that a lot of people upgrade to Mod 1.5 with Big Motors, which doesn't allow for a Cush drive... I want to stay on Mod 1 GDS gearing (adapted to 8mm shaft) because of the Cush drive. Having stripped differentials and spider gears in the past multiple times, I think it would be a fool's errand to both increase power while simultaneously eliminating the only designed safety net preventing shocks to the transmission. Maybe 1.5 Mod Cush drive is possible? Has anyone tried staying on Mod 1 and NOT stripped the teeth? Advice would be appreciated, thank you.

A tad confused about battery cut-offs (or lack thereof)... I have an 8s X-Maxx with a Max6 ESC. The ESC and Receiver box are powered by the Lipos. When the LiPos run low, the motor power cuts off of course, but the steering servo/receiver box/cooling fans stay on. Presumably, if I forget to switch the car power off, the LiPos will drain to death. A costly oversight... Does anyone know if there is a secondary battery cut-off which shuts down /ALL/ electronics when the battery gets to a certain level? If not, shoudn't there be one because it seems like an easy mistake to make for dafties like myself? Appreciate insights - thanks.

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Unique Traxxas T-Maxx with the legendary OFNA HoBao Hyper 21 TURBO Engine + Roto Start + Many Upgrades - Significantly More powerful than the 3.3 Nitro T-Maxx. Unlike all Electric RC cars which last ~20 minutes, this will run all day! Total value of for sale items: £1,301.00 T-Maxx: £582 Upgrades: £567 Included Accessories: £152 Lots of Premium Upgrades: OFNA Hyper 21 TURBO Engine - £170 Brand New Roto Start (Drill Start) upgrade - £30 Aluminium suspension Coilovers with springs - £70 Double Slip Disc and Steel Spur Gear Kit - £30 Hardened Pinion Gear - £10 CVEC Tunable Exhaust System - £70 Brand New High Torque Metal Gear Servo - £20 Brand New Shell, never been used - £50 Shell installed with custom working headlights - £20 Super Size Air Filter - £20 New Custom 2500mah NiMH rechargeable battery pack - £30 Brand new Fuel Tank - £20 High torque Servo Saver - £10 Silicone Fuel Lines - £5 Premium Fuel Filter - £5 New OS #8 Glow Plug - £7 Upgrades Total: £567 Included Accessories: New Receiver/Glow Starter Multi-Charger - £20 New Glow Driver - Simply attach to 6V-24V power source - £20 New Glow Starter Battery £5 Glow Starter - £10 New Braces £20 New set (2x2) Suspension Arms - £20 Traxxas Retainer Clips Pack - £5 Engine thermometer - £10 Roto Start (Drill Start) Tool - £7 New Fuel Filler Bottle with Metal head - £10 Includes 2 spare Glow Plugs - £10 Spare Fuel Tank with Primer lever - £15 Accessories total: £152 Total Value: £582 + £567 + £152 = £1,301.00 Sale price: £345 or nearest sensible offer. If picking up from Cambridge and paying in cash/bank transfer, I would love to give you Premium 25% Nitro Fuel ~ 4L remaining. It cannot be shipped with the T-Maxx for obvious reasons, however there is £30 worth ready to be used. Some small niggles: The T-Maxx has been in storage for a while and needs a bit of TLC - I have rebuilt the engine with much love and ran 2 tanks of fuel through it today - new glow plug, new filter, new roto start, new metal steering servo, new rechargeable battery pack, and new fuel tank installed. As with all Nitro cars, it Requires Tuning (Google or take to Hobby Shop). The reverse is a little sticky due to storage - probably fine after a little use or lubrication - a lot of people simply remove it. I think the Bell rubber clutch slipped once today probably due to storage, however easily and cheaply replaceable for ~£10 if the need ever arises, but seems to be working fine now. One suspension spring looks a little bent but works fine otherwise. I have also provided as part of the sale: New Braces and Suspension Legs, as the ones currently on the T-Maxx are 'field repaired' and you might wish to replace them properly - 10 minute job. Experienced hobbyists will be well familiar with these little niggles as they come with the territory - they shall have them ironed out quickly; - but I thought I ought to mention them. The beast just requires a little spring cleaning - it has never been used in water or mud. No more pulling! - With the newly installed roto/drill start, the engine starts without any manual effort (I regret not installing it earlier!) - You'll need a drill / rotostart or something similar to start it - the insert tool is provided in the sale; - or you can install a pull starter for ~£15 if you want to. One of the amazing things about this legend is that T-Maxx spare parts are cheaply and easily available. I love this beast but have 2 babies now and obviously can't use it around them. Here is the beauty running today 29 April 2020. https://www.youtube.com/watch?v=yVN_MXFLqKA YouTube - Video will open in a new window. More Videos of other .21 engine beasts: https://www.youtube.com/watch?v=rUVrtdz3AWY https://www.youtube.com/watch?v=whrWFv2XuSI I humbly do not recommend for beginners for obvious reasons. Please bid with confidence as evidenced by my 100% Feedback. Thank you for looking 🙂 Also listed on eBay with more pics: https://www.ebay.co.uk/itm/Traxxas-T-Maxx-21-TURBO-Engine-Many-Upgrades-Faster-than-3-3-Nitro-TMaxx/174267563479