New transmission troubles

[dan_man5000]

Hi guys, I have a HSP 94122 and it was all going fine until I pulled the engine out to do something, put it back in wrong, started it, drove it away and stripped all the original plastic gears. I then ordered a metal replacement transmission off Ali express that I had to assemble myself and it’s been trouble ever since. I’ve rebuilt it 3 time both with the plastic housing off of the original transmission and the metal housing off the new transmission and it’s just always stiff and ‘rattly’ if that’s the right word? But it definitely doesn’t sound right.

I’m quite new to the nitro rc word so any help would be much appreciated.
Thanks!

I did also post this in the welcome page by accident and someone said check the bearings.

 

[tudordewolf]

Hi guys, I have a HSP 94122 and it was all going fine until I pulled the engine out to do something, put it back in wrong, started it, drove it away and stripped all the original plastic gears. I then ordered a metal replacement transmission off Ali express that I had to assemble myself and it’s been trouble ever since. I’ve rebuilt it 3 time both with the plastic housing off of the original transmission and the metal housing off the new transmission and it’s just always stiff and ‘rattly’ if that’s the right word? But it definitely doesn’t sound right.

I’m quite new to the nitro rc word so any help would be much appreciated.
Thanks!

I did also post this in the welcome page by accident and someone said check the bearings.

The issue you're running into is called "gear mesh".

You'll notice how the engine mounts in the chassis are slots rather than holes, this is to let you shift the engine around until the gears are just the right distance apart. You can use a strip of paper to set the approximate distance, it should just barely fit between the gears with no wiggle room left between them.

Once you've done it a few times you can just do it by feel.

The 94122 is one of my favorites, I have 2, but I'll admit the transmissions are a bit of a pain on that model, and the aftermarket ones aren't really an upgrade.

An issue you'll have to address that doesn't even have to do with your current problem is that the replacement plastic gears / gearboxes are missing an 8mmx2mm metal pin pressed into the smaller gear where the shifter grabs it. Without this, the gear will fail after just a few shifts. They manage to include it stock, but I've had to improvise a replacement for even replacement gear I've bought. I bet that single issue has caused many people to give up on the model entirely...

 

[gandalfnz]

Great car as @tudordewolf said.

Ended up as my favorite racer, amongst Kyoshos and HPI's.
Although mine received so many upgrades, its hardly a standard HSP anymore.

 

[dan_man5000]

The issue you're running into is called "gear mesh".

You'll notice how the engine mounts in the chassis are slots rather than holes, this is to let you shift the engine around until the gears are just the right distance apart. You can use a strip of paper to set the approximate distance, it should just barely fit between the gears with no wiggle room left between them.

Once you've done it a few times you can just do it by feel.

The 94122 is one of my favorites, I have 2, but I'll admit the transmissions are a bit of a pain on that model, and the aftermarket ones aren't really an upgrade.

An issue you'll have to address that doesn't even have to do with your current problem is that the replacement plastic gears / gearboxes are missing an 8mmx2mm metal pin pressed into the smaller gear where the shifter grabs it. Without this, the gear will fail after just a few shifts. They manage to include it stock, but I've had to improvise a replacement for even replacement gear I've bought. I bet that single issue has caused many people to give up on the model entirely...

Wow thanks man I’ll have a play around with it!
Is that replacement gear box pin issue just on the plastic replacement boxes or the metal ones too, as I’m using metal gears.

 

[tudordewolf]

Wow thanks man I’ll have a play around with it!
Is that replacement gear box pin issue just on the plastic replacement boxes or the metal ones too, as I’m using metal gears.

It's not an issue with the metal ones, that bit is just a solid piece with the rest of the gear.

 

[dan_man5000]

The issue you're running into is called "gear mesh".

You'll notice how the engine mounts in the chassis are slots rather than holes, this is to let you shift the engine around until the gears are just the right distance apart. You can use a strip of paper to set the approximate distance, it should just barely fit between the gears with no wiggle room left between them.

Once you've done it a few times you can just do it by feel.

The 94122 is one of my favorites, I have 2, but I'll admit the transmissions are a bit of a pain on that model, and the aftermarket ones aren't really an upgrade.

An issue you'll have to address that doesn't even have to do with your current problem is that the replacement plastic gears / gearboxes are missing an 8mmx2mm metal pin pressed into the smaller gear where the shifter grabs it. Without this, the gear will fail after just a few shifts. They manage to include it stock, but I've had to improvise a replacement for even replacement gear I've bought. I bet that single issue has caused many people to give up on the model entirely...

Okay so I think I found the right gear mesh, although it’s still has a bit of a grinding noise, when the car is started and the accelerator is pressed the car doesn’t move at all but the gears are spinning so obviously lined up right?
I’m a bit stuck so any heap here would be much appreciated again.
Cheers.

 

[tudordewolf]

Okay so I think I found the right gear mesh, although it’s still has a bit of a grinding noise, when the car is started and the accelerator is pressed the car doesn’t move at all but the gears are spinning so obviously lined up right?
I’m a bit stuck so any heap here would be much appreciated again.
Cheers.

Could be the one way bearing, or loose set screws. Both gears are engaged and are able to turn without the wheels turning, in either direction?

 

[Greywolf74]

Slipper too loose maybe?

 

[dan_man5000]

Could be the one way bearing, or loose set screws. Both gears are engaged and are able to turn without the wheels turning, in either

Could be the one way bearing, or loose set screws. Both gears are engaged and are able to turn without the wheels turning, in either direction?

Both gears move when the car is pushed forwards and whilst the engines running but not when pushed backwards. Actually the gearbox sounds very smooth when the car is being pushed backwards instead of forwards (where there’s a sort of grinding noise i think comes from the gearbox connecting with the engine clutch bell or whatever it’s called).
When I lift the car off the ground and turn the gears with my finger, the front left and both rear wheels move.
Hope that makes sense.
Cheers

Slipper too loose maybe?

Sorry but what’s the slipper? lol I’m new to all this

 

[tudordewolf]

Both gears move when the car is pushed forwards and whilst the engines running but not when pushed backwards. Actually the gearbox sounds very smooth when the car is being pushed backwards instead of forwards (where there’s a sort of grinding noise i think comes from the gearbox connecting with the engine clutch bell or whatever it’s called).
When I lift the car off the ground and turn the gears with my finger, the front left and both rear wheels move.
Hope that makes sense.
Cheers

Sorry but what’s the slipper? lol I’m new to all this

I'm just guessing here, but that sounds almost like the main gear got turned around and the one-way bearing is backwards. The gears should be forced to turn when you push the car backwards, and able to freewheel / not move if you hold them still while you slide the car forwards.

This particular model doesn't have a slipper, it's a feature on the truck version though, 94188.

 

[dan_man5000]

I'm just guessing here, but that sounds almost like the main gear got turned around and the one-way bearing is backwards. The gears should be forced to turn when you push the car backwards, and able to freewheel / not move if you hold them still while you slide the car forwards.

This particular model doesn't have a slipper, it's a feature on the truck version though, 94188.

Thank you so much tudordewolf, I finally got around to fixing it today. Turns out the whole cog with the one way bearing was around the wrong way.
Time to order some more mods now!