LST Forward Only Transmission FAQ and Mods
 

Ok, so I recently built a E-LST and did it with off the shelf parts. But I have another project truck and decided to approach it in a different way.

The main goal of this thread is to show the various methods to lock the trans so that motor braking can be used. Also I do not like the reversing and brake servos, as they occupy the area the battery tray fits best, so I will show how to remove them too.

If you have a lst tranny (the one with the manual high/low selector and reverse) you have a few options. You can purchase the losi forward only conversion:

http://www.horizonhobby.com/Products...rodID=LOSB3130

It replaces the main and secondary shafts and gears, deletes the high/low gearset and the reverse gears as well. The kit includes all of the parts and plugs to accomplish this.

Heres a before pic of a std lst tranny, I did remove the forward/reverse selector lever, but it is otherwise complete:

http://i206.photobucket.com/albums/b...p/DSCF2947.jpg

And heres a pic of the tranny with the losi FOC installed, note the lack of any selectors and the case plugs that fill in the reverse gear bearing hole (blue plug on the left side)

http://i206.photobucket.com/albums/b...SB3130-450.jpg

Also note that the aftershock comes with the FOC installed stock, it does not have and reverse or high/low gearing in it. So if you find a deal on an aftershock tranny it may be a good purchase.

Ok, so we have covered tranny internals, now onto the fun stuff!

For my new project I decided that I wanted to retain the high/low function but remove the reverse gears. The high/low function is manually selected by a knob on the tranny, and reasonably simple in operation. The 2 gearsets are in constant mesh, and a stout dog clutch engages between the gears, so it is sturdy enough to handle brushless (IMO).

So here is the stock tranny pic again:

http://i206.photobucket.com/albums/b...p/DSCF2947.jpg

And here is the tranny with the reverse gears removed and a few simple spacers in place to hold the forward/reverese dog clutch in place so that it is in constant engagement with the forward gears.

http://i206.photobucket.com/albums/b...p/DSCF2945.jpg

Here is a pic of what I used to lock it in place. A 8x12 bearing fits over the shaft perfectly and hold the sliding clutch against the forward gear. The al spacer is a cable stop, happened to be the exact length to fill the area the reverse gear left. Alternately you could just leave the reverse gear in place. I drilled the center of the cable stop out with a 15/64 drill bit so that it will match the 6mm shaft. After that I just use a traxxas teflon washer to take up the slack in the top shaft between the bearings, it is placed between the cable stop and the left most bearing.

http://i206.photobucket.com/albums/b...p/DSCF2946.jpg

So now we have a tranny with the hogh/low selector and no reverse gears, or selctor. That means the forward/reverse servo can be removed. A small plug or tape will be required to cover the 2 holes left by the removal of the forward/reverse shifter and the lower reverse shaft outer bearing.

I will detail the locking of the second gear clutch in a few, that way we can remove the mech brakes and servo and use motor brakes.

If you do the normal FOC, gutting everything, you can gain some top end by putting the TiNi gear on the top shaft. It is about a +2.

Yep, I did this on my lst. You will have to clearance the case to get the larger 23t lower gear to fit on the upper shaft. The two gears are 22t and 23t so the ratio goes from .956 to 1.045. The speed calc has both so you can figure it each way for gearing tests.

Yeah, I forgot to mention the grinding of the case.

Pretty easy, I used a dremel with a sanding drum and it took at 1 minute.