Kingcab/madcap diff research

[Muso31 122]

36 minutes ago, Collin said:

Exactly. Madcap/Kingcap is same/simular to Astute. On Madcap manual it shows ball cages made of the tree material so it is ABS. Well, dont ask me about my thoughts but here I am okay for a display car. At least for the moment...

 

 

 

ABS but injection moulded which would have a much higher strength. For a display car it wouldn't matter though, could leave the diff empty if it's not going to run 

[Kol__ 3377]

1 hour ago, Collin said:

Now am I right, there was one version with plastic ring from tree plus seperate ball bearings (Madcap)?
Another version, as showen in the manual, are complete thrust bearings with ring an ball, such as showen in the manual from Astute:

I believe both the Astute and King Cab/Monster Racer diffs, whilst almost identical to the Madcap/Saint Dragon diff, differ with the use a metal ring ball thrust bearing. And that ring piece (lol) in the Madcap diff is plastic. @Collin if you want an accurate restoration, you should source the metal ones. I have a set at home, so I can send you the part number for your search if you decide to look for them. I'm away until tomorrow though mate, maybe someone else has the part number to hand.

[Collin 1956]

20 minutes ago, Muso31 said:

ABS but injection moulded which would have a much higher strength. For a display car it wouldn't matter though, could leave the diff empty if it's not going to run 

True. In any perspectiv a very brave move by Tamiya
Yes this Astute would not run but I still like to keep components working. Printet rings are a cheap way to make the diff spinning.
 

9 minutes ago, Kol__ said:

I believe both the Astute and King Cab/Monster Racer diffs, whilst almost identical to the Madcap/Saint Dragon diff, differ with the use a metal ring ball thrust bearing. And that ring piece (lol) in the Madcap diff is plastic. @Collin if you want an accurate restoration, you should source the metal ones. I have a set at home, so I can send you the part number for your search if you decide to look for them. I'm away until tomorrow though mate, maybe someone else has the part number to hand.

Thanks I did found the number already but single metal caged bearings are nowhere available ant the full diff kit cost around 100 bucks uncl. shipping which is not worth it imo.

 

[Muso31 122]

Update from further housing testing... these things are running unbelievably well, the car is like a rocket. I had an old original diff installed that I thought was actually working well and problem free, but having changed the housings it's now more like a finely tuned race car.

As the diffs are new it's possible to overtighten them, which is resolved with the usual diff tweaks by breaking them in or backing off the screws a touch - but I'm quite confident these will never require shimming.

[bavee 1032]

Sounds great @Muso31! As you know the diff housings you send me are stuck at Customs. So unfortunately no testing yet. But it seems you figured it out yourself . 

[DGunn1 56]

Metal SC1 thrust bearings available here:

https://www.rcbearings.co.uk/index.php?route=product/category&path=54

 

[Muso31 122]

1 minute ago, DGunn1 said:

Metal SC1 thrust bearings available here

Would it be worth upgrading the madcap plastic part to one of these? Has anybody tried that? 

[DGunn1 56]

I've got them in a diff I rebuilt for a monster racer, if I recall everything else is the same, so should be a straight swap out with madcap.

[DGunn1 56]

Bigger problem I found is trying to find unpitted SC4 parts for rebuilds?

[Muso31 122]

Have a Google for 'shim washers' maybe? 

[Kol__ 3377]

I came home to a set of these diff housings in post waiting for me when I got in. They are little works of art! Look so much better than the original dull grey ones.

As you'd expect, the modern grade aluminium is very light and strong, so much, much better than the original pot metal ones... which were made from tin I presume!😂

[Misterp180 257]

3 minutes ago, Kol__ said:

I came home to a set of these diff housings in post waiting for me when I got in. They are little works of art! Look so much better than the original dull grey ones.

As you'd expect, the modern grade aluminium is very light and strong, so much, much better than the original pot metal ones... which were made from tin I presume!😂

They look amazing! Sounds like they run sweet too! I should probably get some for this rebuild now!!

[DGunn1 56]

15 minutes ago, Muso31 said:

Have a Google for 'shim washers' maybe? 

Sorry, I mean the thrust washers with the hexagonal centre, almost all the diffs I've managed to find have the race area badly pitted, and are a pain to find

[Thommo 1217]

 

I normally stop myself from posting in a thread about how good the content is but .... Wow.  How good is this !

I've seen everything about this diff and tried most but this work is clearly the easiest and most effective upgrades.  Minimal parts replacement, keeping it authentic with the ball diff or utilising the SA planetary gears, it's just the best work seen on TC  with this diff I reckon.

 

[Collin 1956]

Hi folks, do I got it right? The diff is usually fully scewed together and you set the diff strenght by using a certain number of .05mm shims? And this did not worked well because the injection-molded diff housings where too soft and did not delivered enought pressure when fully tightened?

 

[bavee 1032]

On 7/10/2022 at 2:37 PM, Saito2 said:

Traditional ball diffs use an adjusting screw that goes through the center of the diff, adjusting clamp load on the inner balls and thus the "tightness" of differential action. After a few previous attempts at center ball diffs in the Celica, Avante and Vanquish, Tamiya tried their hand at making a new-design ball diff in their new batch of cars, the Astute, Madcap and King Cab. Tamiya, being Tamiya, chose to use varying amounts of shims installed on either side if the diff housing halves to provide adjustment vs the traditional adjusting screw. The benefit would be that the diff would never "loosen up" as there was no adjusting screw to back out/off. The downside was their was a limited range of adjustment.

Unfortunately, Tamiya was very vague about what adjustment did or meant for novices in their instructions. The Madcap calls out no shims for the "standard setting" (whatever that meant) and to add a a pair is necessary. That means nothing to a novice. The Astute, using much the same style diff (different thrust bearing) just says it can be adjusted with more of less spacers. Without proper shims, the diff could slip. The diff's small size and limited balls meant it was not overly tolerant to the heat from slippage. I've seen King Cab diffs (same design) with the centers completely melted out of them due to the added stress of the larger tires. 

So the simple fix would be to add shims, right? No quite. The pot metal alloy diff halves would often bend and distort when tightened down if too many shims were added. Only the Egress (again using a similar shim design), which had superior alloy diff halves proved successful with his design.

If the diff is carefully and properly built with components in decent shape with the proper grease and a reasonable motor, it can be made to work. If the housings are warped, it may be tough to get it to adjust properly.

This. Courtesy of @Saito2.

[Muso31 122]

10 hours ago, Thommo said:

 

I normally stop myself from posting in a thread about how good the content is but .... Wow.  How good is this !

I've seen everything about this diff and tried most but this work is clearly the easiest and most effective upgrades.  Minimal parts replacement, keeping it authentic with the ball diff or utilising the SA planetary gears, it's just the best work seen on TC  with this diff I reckon.

 

Very kind thanks. The planetary diff will be arriving very soon 👍 then it'll be time to look at the spur/counter 

[bavee 1032]

@Collin, can you spot the problem @Saito2 was talking about?

Three shims on both sides were used to create this 

Now I can only wait until @Muso31 diff housings are released from Customs...

[Misterp180 257]

@Muso31 do you have any diff cases left? I would love ti get some.

[Collin 1956]

1 hour ago, bavee said:

@Collin, can you spot the problem @Saito2 was talking about?

Three shims on both sides were used to create this 

Now I can only wait until @Muso31 diff housings are released from Customs...

Oh thats really nasty. Now I am glad that Tamiya did not made any 1:1 cars

[Muso31 122]

1 hour ago, Misterp180 said:

@Muso31 do you have any diff cases left? I would love ti get some.

Yes I have an initial 50 pairs. Forum cost would be £12 each housing (obviously a pair needed at £24) plus whatever postage is. Feel free to DM me your details although I'm away until Wednesday

[bavee 1032]

Ok @Muso31. I think you and your product are truly amazing. Instant succes!

Received the new machined diff housings yesterday. Started cleaning the used ball diff yesterday evening. Then started sanding the pressure disks and thrust washers because they were really rough. Finished sanding this evening (did some sleeping and some work in between).

Gave the diff housings a quick sand to get rid of a small 'bear' where the m2 thread was drilled. Decided to use one shim on both sides (as per original Tamiya manual and because other than the housings the other parts are all used and pretty worn parts) and used a proper amount of ball diff grease building the diff. Bench test felt really good.

Installed the diff in the car. Carefully gave it some throttle on our polished wooden floor and there was wheelspin. Just what I want!

Took the car outside and carefully build up speed during the first few minutes. And then it was Go-time! Gave the car an almost full throttle launch. There was maybe a tiny bit of diff spin, the hood came up and it just took off. Unbelievable! 

Car drives so good!

Will break it in during the coming days / weeks to find out if I need to place an extra shim after running it a bit more. But for now it feels amazing. Thank you!

Ow. And I was so full of expectations building the diff I forgot to take pictures... .

[bavee 1032]

10 hours ago, bavee said:

There was maybe a tiny bit of diff spin, the hood came up and it just took off.

Now I think about it some more, tyres aren't glued on the wheels I used. So could have been the wheels spinning just a bit in the tyres also. Will have a look when I run the car in daylight.

[Kol__ 3377]

On 2/22/2023 at 8:59 PM, bavee said:

Ok @Muso31. I think you and your product are truly amazing. Instant succes!

I concur!! Tested with two shims same as @bavee and it works a treat with these housings. It's like a total reset of the diff back to factory spec, before any deformation of the pot metal original diff casings occured!

Bravo @Muso31, another excellent, very carefully designed and produced, high quality product!🙌🙌🙌😎👍👍

[Muso31 122]

A2 brackets are now available, £12 forum cost plus post - message me if you need one: