How To seal the optima mid's drivetrain, and tips for easier maintenance

As many of you all know, th Optima Mid is not an easy car to work on, and maintenance work can be very difficult and time consuming. During my cteenage years , i spent alot of time taking apart the car and cleaing the gearboxes and diffs, i always followed everything in the manual and only used the car with original parts cause i couldnt really think for myself. Fast forward 20 years later, being and engineer designing machines, and applying my knowledge and experiments on touring cars, i managed to find a lot of ways to improve and lengthen time for teardowns and rebuilds on the optima mid.

I thought to myself, i must seal the gearbox properly and not allow any sand to get into the gearbox , and also must find someway that i dont neeed to take apart the diffs for maintenance.

Firstly look at the 1st pic, its selleys silicone sealent. The stuff works wonders, when its in it freshest state, its kind of jelly paste like, when it dries up, it becomes like a flexible rubber like substance,that can be removed by hand later by pulling it out, very good for sealing your optima mid's belt covers.

Buy this tube of sealent at your local hardware store, it fills and seals the gaps in between your belt cover joint areas.
To stick your beltcover on, use 3M high strength thin double sided tape.

The optima mids gearbox is made of high grade plastic, but the front gearbox is especially prone to stripping its threads after so many times removing and retightening the screws, and also form hard collisions. An easy way to remedy this is to drill through the mountin holes at the bottom. But it will expose the gearbox innards to sand. Drilling through with a 2.5mm drill bit will allow you to use longer screws ,in this case i used a 20mm screw to hole the bumper in the 1st front 2 holes, since there are 2 holes esposing the gearbox internals, use the silicon sealent to seal them, like shown in the picture. That T sysmbol is team Tanaplan.

Notice the silicon paste in between the belt cover and the front gearbox, and also in between the bottom of the gearbox to the chassis, also at the suspension mounts. I drilled a hole through the last 2 holes holding the gearbox to the chassis, so that i can place a nut to securely hold down the gearbox. You have to use a 14mm screw so that it will go beyong the suspension mounts. Since the drilling exposes the innards of the gearbox, you have to use silicon sealent to cover the hole back after tightening your nut. Dont forget to use sealent on the under belt cover under the upper deck.

See the 3M tape used to mount the upper belt cover, and the silicon sealent along the front seam of the belt cover to gearbox and top deck.

Sealent and thick double sided tape replaces the OT-103 sponge here to really seal the rear gearbox upper area.

Silicon sealent fills and closes the gap in between belt cover and rear lower gearbox.

Dirt can still get through one area , the diff side bearings, becuase ethere is asmall gap.

Use dishwashing sponge, cut up a thin slice, then cut up a hole in the middle with a curved scissors, the hole should be slightly smaller than the ball diffs output shaft. Yes i am using ball diffs again. Use silicon sealent to glue the sponge to the gearbox sides.To cut down times in between rebuilds, i bought ACER racing 3mm ceramic balls for my diffs, and greased the balls adequately. With the ceramic balls, and the side sponge sealing, you should not need to open the gearbox for at least 3 Months ! You only have to clean the wheel bearings and shocks, you dont have to touch the center part of the car! amazing isnt it?

The thrust bearings get dirty easily and contributes to the diffs gritty feeling. You can remove the diff outdrive like shown here, wihtout removing the gearbox ! Just unscrew the diff as shown, and pull out the output shaft, the bearings and spacers diff rings inside the gearbox will stay put becuse of the way kyosho designs them. Remove the thrust bearings, clean them then relube them, then simply place back the diff output shaft into the gearbox, voila, your diff is smooth again. If after you clean the thrust bearings the diff is still gritty, then you will have to open the gearbox and clean the main diff balls.But that should be a long long time before you need to that if you follow my tips ! Dont forget to put a small slab of sponge to cover up the thrust bearings to better protect your thrust bearings.