Ford F-350 - 3 speed issue

[darthvincor 0]

Hi,

I've been building an F-350 for a bit now, and have come to the stage that the mechanical and electrical stuff is pretty much done.

The manual now suggests I test the steering and shifting. Unfortunately, the shifting doesn't seem to be in order.

With my Futaba remote, I can shift the rod from left to center to right, but when using the accelerator, I only see two speeds. And I'm not sure which ones they are. 1 and 3? 1 and 2?

According to the remote's position: 1st gear gives me a slower speed, 3rd gear a higher speed. But 2nd either does not engage at all, or runs at the same speed as 3rd.

In short, my 3 speed has 2 speeds and a neutral (?).

Does anyone have experience with this, or some advice? I guess the only real option is to open the gearbox again, and see what's up, but I'd really rather not.

[TWINSET 1793]

Easiest way to start troubleshooting is remove link from servo and move the shift rod by hand - You'll at least see if the shift rod is binding etc.

Take the wheels off, and run the motor, shifting by pulling and pushing the gear rod - you'll hear the different 'speeds' engage.

Check the servo horn is vertical when the transmitter stick's in the centre -  2nd gear should be selected when you release the stick.

Also check your servo travel - it might be the servo isn't moving far enough in one direction to change gear, so the 'neutral' is it disengaging one gear but not engaging the next

The pic below should help show what gear you're 'missing' - Check the shift rod's ball stud position in relation to the reference line

 

 

[topforcein 1764]

you may not have put the gearbox together properly....did you follow the instructions to the tee making sure to follow the pics and the notes  if you did then it may also be the servo horn may need ajusting esp if it has the same as fitted on the 1/14 trucks does your servo saver look like the one in the fore ground if so then it might need to be ajusted either up or down a notch or 2

[darthvincor 0]

@Twinset: the shifting rod does actually travel all the way from left to right, and is only stopped by those c-clips on the rod. You basically get 1st gear, nothing, then 3rd gear, which takes up most of 2nd gear's 'space' as well. Sometimes instead of neutral you get a slight grind, of gears barely touching.

@Topforcein: I'm afraid you may be right. I think I followed it to the letter, but who knows. I've never built a gearbox before. My previous cars were a Boomerang, Super Clod Buster and Dark Impact.

In looking for a solution, I did come across a youtube video, in which someone had almost the exact same problem: (except my 3rd gear seems fine, but skipping 2nd)

Comments suggest it was: 'switched spools' or a loose 'grab screw'.

 

It's a shame the manual didn't suggest testing right after the gearbox assembly, instead of only after the servos were installed.

 

 

 

 

[Tamiyabigstuff 832]

Just watched your video clip - in 2nd gear the silver hexes are not turning which does not look right - appears to be an assembly error.

Take it apart and start again I think, check & double check at every stage.

 

[darthvincor 0]

I should have made it clearer, but that is someone else's video, not mine.

I have since removed the transmission/motor combo from the frame, removed a side cover, and to me everything seems fine. It shifts from 1 to 2 to 3 and back without a problem. So this is with the shift servo disconnected, and shifting done by hand. And if you let go, it goes to the 2nd gear by default.

I'll make a video of it soon and post it, so you guys can have a look too. I'll be back.

[topforcein 1764]

it will go to 2nd by default as that is from the stick being in the centre on the tx.

give us a pic of the servo and the servo saver plz.

[MadInventor 3884]

On ‎07‎/‎03‎/‎2018 at 1:45 PM, darthvincor said:

Hi,

I've been building an F-350 for a bit now, and have come to the stage that the mechanical and electrical stuff is pretty much done.

The manual now suggests I test the steering and shifting. Unfortunately, the shifting doesn't seem to be in order.

With my Futaba remote, I can shift the rod from left to center to right, but when using the accelerator, I only see two speeds. And I'm not sure which ones they are. 1 and 3? 1 and 2?

According to the remote's position: 1st gear gives me a slower speed, 3rd gear a higher speed. But 2nd either does not engage at all, or runs at the same speed as 3rd.

In short, my 3 speed has 2 speeds and a neutral (?).

Does anyone have experience with this, or some advice? I guess the only real option is to open the gearbox again, and see what's up, but I'd really rather not.

 

Sounds like the gearbox is assembled correctly, but the neutral point for the gearbox shifter is set wrong. To me it sounds like in the servo neutral position it's teetering between 3rd and the gap between 3rd and 2nd.. I'd try re-assembling, removing the shift rod from the servo to the gearbox shifter and note the neutral position of the gearbox shifter (This will be 2nd gear). With the power off, move the shifter servo by hand so that the shift rod lines up with the gearbox shifter and connect the shifter linkage, being careful not to move the gearbox shifter. Now watch the gearbox shifter closely and turn on the transmitter, then the model, and see if the shifter moves position. if it does you need to remove the servo horn and re-position it.

 

Hope this helps

 

[backtomyroots 432]

Mine have been packed up for a few years, so I'm a bit rusty. Is my  memory correct here, I think you have to keep the transmitter stick in the position you move it to and then accelerate.  Are you doing this or just returning it to neutral after "selecting" the gear then accelerating?

[darthvincor 0]

@MadInventor. I think you may be right. As a novice at the 3 speed transmissions, I assumed I did something wrong, but as Twinset also suggested, it may be the servo position.

Anyway, as promised, here's my video: it seems to me it is indeed working fine by hand, do you guys agree?

 

[Mokei Kagaku 2706]

I'm in no way saying that it's the case in your situation, but a common failure caused by the best intentions, is when the bronze bushings in part J7 are replaced with ball bearings.

J7 needs to slide longitudinally on the shaft and the friction caused by the steel inner race of the ball bearings is much higher than that of the bronze bushing. So using ball bearings increases the load on the servo and makes it harder to shift properly.

See excerpt from the manual below:

 

 

[MadInventor 3884]

2 hours ago, darthvincor said:

@MadInventor. I think you may be right. As a novice at the 3 speed transmissions, I assumed I did something wrong, but as Twinset also suggested, it may be the servo position.

Anyway, as promised, here's my video: it seems to me it is indeed working fine by hand, do you guys agree?

 

You're missing 1 spring off the shifter rod, there should be 4 on there, but I don't know if that will affect the performance., other than that it seems to match up with what's in the instructions

[Tamiyabigstuff 832]

21 hours ago, MadInventor said:

You're missing 1 spring off the shifter rod, there should be 4 on there, but I don't know if that will affect the performance., other than that it seems to match up with what's in the instructions

I see 4 springs on the shifter rod ?

2 at each end - looks correct to me.

[MadInventor 3884]

9 hours ago, Tamiyabigstuff said:

I see 4 springs on the shifter rod ?

2 at each end - looks correct to me.

 

My bad, the still at the start of the video looked to me like the leftmost spring is missing, just replayed the video and it looks fine. At a rough guess it go with my previous suggestion the OPs problem is down to an incorrectly adjusted neutral point for the shifter rod.

[darthvincor 0]

Thanks for all the tips and advice guys. I shall do as MadInventor says and reassemble and get the servo neutral position right.