RC4WD 2 speed gearbox short transfer case upgrade

thingiverse

RC4WD 2 speed gearbox transfer case modification: This is to allows for bolting on the transfer case directly to the gearbox without the need for a drive shaft. It makes the gearbox/TC assembly a lot more compact and therefore easier to fit on short wheel base vehicle. It also looks more like an actual 4wd gearbox. What you need: a 15 teeth sprocket gear 32p and 5mm bore. commonly used on RC car ( such as this item: https://www.aliexpress.com/item/1005001858559306.html?spm=a2g0o.productlist.0.0.19bc450aQsKGkx&algo_pvid=39a565b3-bdd2-4abf-8916-777917940a02&algo_expid=39a565b3-bdd2-4abf-8916-777917940a02-0&btsid=0b0a050116185369723002639e32a2&ws_ab_test=searchweb0_0,searchweb201602_,searchweb201603_) 6 M2.5x8mm machine screws to secure the transfer case flange to the gearbox housing 4 M2x4mm plastic screw to secure the bearing cover to the transfer case flange Procedure: Prepare printed parts by redrilling all holes to the correct diameter before to assemble, transfer case takes 2mm bolts while the gearbox takes M2.5mm bolts. drill these holes at 2mm and perform M2.5mm tap. There is a cover that secure the primary shaft bearing, use M2 plastic screws (no need to re-drill those holes). Be sure to redrill the 3mm hole of the gear selector and make sure the selector can slide freely. Take the original transfer case apart and remove the input shaft and its pinion. Put these parts aside with the original transfer case flange. Take off the original back gearbox housing. Remove the secondary shaft assembly. take off the clips that retain the rear gear on the secondary shaft. Leave the rear gear in place and insert the 15 teeth sprocket gear just in place where the clips and was. Lock the sprocket gear on the shaft with its grub screw. the clips can be discarded as it is not needed anymore. The 15 teeth sprocket replace the original TC pinion gear. Insert the ball bearings (use the original one) on to the printed transfer case flange and reassemble the gearbox using the new printed gear housing. Note that the secondary shaft is just long enough for this trick. I wish it was a millimeter longer to fill in the bearing fully but it is working fine like that.