McGuiver
03-04-2002, 03:13 AM
Build A Better Front Diff!
In reference to building a none binding diff i have the following solution.
*First check that the brass diff pinion gears(HPI Part #73403a) rotate freely on the shaft pin (HPI Part #73404b) that is supposed to hold them in place. Mine were a press fit and to tight. I did have access to a lathe so I used the next best thing, my drill (cordless).
*Second I chucked up the gear as seen in picture (Pictured Below).
*Third I went through my tool box and found my round needle file. I then proceeded to file the inside bore if the gear. The drill chuck was turning and I used a in and out motion with the needle file. You need to check the looseness of the pin fit carfully. It doesn't take very much filing. About 15 secs. for me on each gear. I have also included picture (See next Picture) to see how the needle filing was done.
*Fourth I didn't like how there was a brass gear spinning on the inside of the diff case (HPI Part#73404-1). I then took the 2 little black washers (HPI Part #Z275c) which were supposed to go on the motor mounting screws. I replaced the motor mounting washers with some other I had that were silver in color (no big deal). I then installed a little black washer (HPI Part#Z275c) between the brass gear (HPI Part #73403a) and the fron diff case (HPI Part #73404-1). All the parts fit in the front diff. case. It is tight but worth it when you feel how silky smooth it is when assembled. Then reassemble as normal.
I figured out that the little brass gear (HPI Part #73403a) was making the pin shaft (HPI Part #73404b) spin in the diff case(HPI Part #73404-1). The pin is not supposed to spin in the case. It gets pressed in place. If it spins it is likely to wear out the diff case and mabey destroy the inside of the puple anodized diff pipe(HPI Part #72338). I forgot to take pictures of the assembly, but will do so if needed.
In reference to building a none binding diff i have the following solution.
*First check that the brass diff pinion gears(HPI Part #73403a) rotate freely on the shaft pin (HPI Part #73404b) that is supposed to hold them in place. Mine were a press fit and to tight. I did have access to a lathe so I used the next best thing, my drill (cordless).
*Second I chucked up the gear as seen in picture (Pictured Below).
*Third I went through my tool box and found my round needle file. I then proceeded to file the inside bore if the gear. The drill chuck was turning and I used a in and out motion with the needle file. You need to check the looseness of the pin fit carfully. It doesn't take very much filing. About 15 secs. for me on each gear. I have also included picture (See next Picture) to see how the needle filing was done.
*Fourth I didn't like how there was a brass gear spinning on the inside of the diff case (HPI Part#73404-1). I then took the 2 little black washers (HPI Part #Z275c) which were supposed to go on the motor mounting screws. I replaced the motor mounting washers with some other I had that were silver in color (no big deal). I then installed a little black washer (HPI Part#Z275c) between the brass gear (HPI Part #73403a) and the fron diff case (HPI Part #73404-1). All the parts fit in the front diff. case. It is tight but worth it when you feel how silky smooth it is when assembled. Then reassemble as normal.
I figured out that the little brass gear (HPI Part #73403a) was making the pin shaft (HPI Part #73404b) spin in the diff case(HPI Part #73404-1). The pin is not supposed to spin in the case. It gets pressed in place. If it spins it is likely to wear out the diff case and mabey destroy the inside of the puple anodized diff pipe(HPI Part #72338). I forgot to take pictures of the assembly, but will do so if needed.