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Bulletproofing the gearbox

Overkill

Well-known member
Messages
122
Location
Birmingham, AL
Tekno RC's
EB48, ET48
Driving Style
Basher
The little plastic divider in between the pinion bearings in the gearbox can be damaged from impacts, flex, stress, heat, etc. If the plastic divider gets blown out you can damage a lot of parts and your day is over. I see this problem on a regular basis in the bashing community. I would love to see Tekno update the design and use a steel sleeve inside like Arrma does, as well as larger bearings, and easy access. :) My mission is to make everything as strong as possible.

5x13x4 flanged bearing
If the driveshaft/outdrive slams into the bearing, all the force goes to the outside of the gearbox instead of the plastic divider. As a bonus, the flange part is 1mm thick so now the driveshaft can only make contact with the outdrive and not the pinion gear.

5x7x2.45 shims
These go in between the bearings to take the pressure off the plastic divider.

Parts used:
Boca flanged bearing 5x13x4
SMF695-2RS

Boca regular bearing 5x13x4
MR695-2GS

HPI shim 5x7x1.45
103368

Serpent shim 5x7x1.00
909514

Using a total thickness of 2.45mm worked the best for me. I would suggest getting an assortment of thicknesses so you can shim it accordingly.

GearboxModification.png
 
Last edited:

2015GTRBE

Active member
Messages
40
The little plastic divider in between the pinion bearings in the gearbox can be damaged from impacts, flex, stress, heat, etc. If the plastic divider gets blown out you can damage a lot of parts and your day is over. I see this problem on a regular basis in the bashing community. I would love to see Tekno update the design and use a steel sleeve inside like Arrma does, as well as larger bearings, and easy access. :) My mission is to make everything as strong as possible.

5x13x4 flanged bearing
If the driveshaft/outdrive slams into the bearing, all the force goes to the outside of the gearbox instead of the plastic divider. As a bonus, the flange part is 1mm thick so now the driveshaft can only make contact with the outdrive and not the pinion gear.

5x7x_ shims
These go in between the bearings to take the pressure off the plastic divider.

Parts used:
Boca flanged bearing 5x13x4
SMF695-2RS

Boca regular bearing 5x13x4
MR695-2GS

HPI shim 5x7x1.45
103368

Serpent shim 5x7x_
909514

View attachment 1985
Will try this, thanks. BTW, I Pm’d You.
 

Overkill

Well-known member
Messages
122
Location
Birmingham, AL
Tekno RC's
EB48, ET48
Driving Style
Basher

smirkracing

Active member
Messages
36
Well, at first I didn't think I'd need this, but after a session of back and front flips, it seems clear I do. Thanks for posting these great instructions.

For max strength, do you recommend this flanged bearing mod, or the big bearing mod you posted in a different thread?
 

smirkracing

Active member
Messages
36
Also, anyone have a clear idea of why the inner bearing blows out? I lost mine today (after a bunch of backflips which I admit slammed the truck into the ground). I am still trying to figure out why exactly the force gets transferred to the inner bearing.

Here are some pics of the resulting damage (bearing blown out, and it spun its way forward, damaging the inside of the gearbox case).
tekno-gearbox1.jpg
tekno-gearbox2.jpg
tekno-gearbox3.jpg
 

Overkill

Well-known member
Messages
122
Location
Birmingham, AL
Tekno RC's
EB48, ET48
Driving Style
Basher
Well, at first I didn't think I'd need this, but after a session of back and front flips, it seems clear I do. Thanks for posting these great instructions.

For max strength, do you recommend this flanged bearing mod, or the big bearing mod you posted in a different thread?
Glad to help. I would recommend doing what's in this thread.

Also, anyone have a clear idea of why the inner bearing blows out?
The damage is usually caused by impacts. My buggy which sees up to 6,500 watts does not have this problem.
 

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