Hi all... 2speed transfer + 3 speed transmission question

[rendeverance]

Hi all,

So I have a plan, it's an unusual one and once the project is finally under way I will share the build here and on YouTube ��

I cannot seem to find anyone that has attempted something like this... Any advice and guidance welcome as I have 20+ years RC experience (mad projects mostly ), but am generally new to the crawling scene.

So I have a Trail Stomper chassis, with a Hilux abs body, and I have a 3 speed bruiser type transmission from a P407. The main reason for this is to try something a bit different so I can have 4wd crawling but also make her drift in rwd ;) (well it's got a locked diff and tonnes of torque... so why not lol)

So I've been considering the crawling side of the build and would like to have the ability to overdrive, on the fly. I've come across 2 speed transfer cases, only the issue is that if I use this as intended, all gears will become 4wd.

The box has 0.71:1 and 1.81:1 ratios.

So I'm considering getting one of these and fitting it in line with the rear axle only, thereby giving me selectable front and rear overdrives (but lose the locked centre). To avoid damage where there is grip and using rear bias (1.81) I am then considering to use a one way bearing (or other option? ) On the front drive shaft, so the fronts only turn in 4wd if the rear slips, and if fwd bias is selected, it will overdrive the front and drag the rear.

Obviously I will lose front wheel brake, but then my thought is I could add a disc brake when I modify the driveshaft? Then I can control front and rear braking balance or even control them independently (8ch radio)

Ideas or thoughts welcome. Alloy axles and driveshafts will be added at the same time for strength.

In total that would give me a silly number of gears:
4wd, front 29 Percent overdrive (4wd low)
4wd, only on rear slip, (4wd high)
And 4 rwd gears lmao (less useful)

I mean I could consider a different setup using two of these transfer boxes instead, but it gets a bit expensive ��

[ferp420]

shat about a dig transmission it freewheels or locks the rear wheels just flip it around then you would have front free for rwd and front locked for burnouts or 4wd it wouldent overdrive or underdrive anything though

[rendeverance]

Thank you Ferp... I'm still trying to get into the specific lingo used in the crawler world... A dig transmission? Is this in the axle or the transmission itself?

I was looking specifically to overdrive, but I'm still interested in this. The p407 box is already rwd only in 2nd and 3rd, hence why I acquired it. Very curious if there is a better way
..

Thanks again

[rendeverance]

AHH I see what it is ��

Interesting... It definitely seems a worthwhile mod thanks.
I was basically trying to achieve the same thing but with the choice of both rear or front bias. This would definitely be simpler, but only does half the overly complicated thing I'm trying to achieve ��

... I never build anything standard, I clearly like problem solving too much lol

[lonleycreeper]

Originally Posted by rendeverance

AHH I see what it is ��

Interesting... It definitely seems a worthwhile mod thanks.
I was basically trying to achieve the same thing but with the choice of both rear or front bias. This would definitely be simpler, but only does half the overly complicated thing I'm trying to achieve ��

... I never build anything standard, I clearly like problem solving too much lol

If you use the new portal axles, or old Axial axles, you can put the overdrive in the axles.

A Vanquish Hurst dig mounted backward, or with the dig facing forward would give you selectable 4wd/2wd.

Mount your 3 speed up front and use the dig trans as a transfer case with a driveshaft between them.

[HumboldtEF]

I love this idea, I've always wanted to try a selectable 4WD.

EDIT: you're on the right track with using dig up front.

I would worry about the 3 speed tranny being too long when combined with the rest of the drivetrain.

What about a 2 speed? Those are much more compact and there are actually multiple options out there (also should hold more power).

Losing the front braking is something I wouldn't worry about. You'll be drifting at that point right (?) rear bakes just means handbrake turns!

[rendeverance]

My concern about front braking and overdrive is I still want to trail it off-road, and drift in the carpark �� multifunction model! Lol

I will first get the three speed in, giving me 4wd / rwd, then consider a 42/13 in the back (underpricing the back of the rig so the front is overdriven in 4wd, which is only for loose surfaces.

That would get me functional, then I'm going to see if I can source a dig to play with, thanks guys