gear grinding noise??

[Tobermory]

Hi again,
i just took out my shengqi hummer (Firehammer mt) and i noticed a very loud grinding noise. its really bad when i take off and sounds abit like a straight cut gearbox when its moving lol. another thing that i notices ages ago and it stall hasnt stoped doing it is,when i drive over bumps and stuff it makes a clicking noise??
btw the two gears the spur gear and im not sure what the other one is called (its the big one) have chips out of them but that doesn't seem to be the problem.
if anybody could tell me what it may be before i start dismantling it again it would be much appreciated
thanks
Toby

 

[atom3624]

Hi again,
i just took out my shengqi hummer (Firehammer mt) and i noticed a very loud grinding noise. its really bad when i take off and sounds abit like a straight cut gearbox when its moving lol. another thing that i notices ages ago and it stall hasnt stoped doing it is,when i drive over bumps and stuff it makes a clicking noise??
btw the two gears the spur gear and im not sure what the other one is called (its the big one) have chips out of them but that doesn't seem to be the problem.
if anybody could tell me what it may be before i start dismantling it again it would be much appreciated
thanks
Toby

Hi Toby, if the Spur's got chips out of it, it probably is part of the problem.
The main problem may be that the gears are out of alignment - possibly.

It's possible the motor has loosened, and moved slightly, or has moved with a few jumps, hits, rolls, etc.

First thing would be to check the alignment.
Second, to consider metal motor mounts and possibly gears as well.
Some get away with plastic without a problem, but defo consider metal motor mounts.

Al.

 

[Tobermory]

Hi Toby, if the Spur's got chips out of it, it probably is part of the problem.
The main problem may be that the gears are out of alignment - possibly.

It's possible the motor has loosened, and moved slightly, or has moved with a few jumps, hits, rolls, etc.

First thing would be to check the alignment.
Second, to consider metal motor mounts and possibly gears as well.
Some get away with plastic without a problem, but defo consider metal motor mounts.

Al.

Thanks atom,
this may be abit of a stupid question but is there any easy way to check the motor mounts without taking the engine out.
if i do have to take the engine out( i think i probrably will) is there any mods i should do while its out??
Thanks
Toby

 

[jpblue1000]

Also how do you check alignment.
Justin

 

[atom3624]

Also how do you check alignment.
Justin

I was searching the Forum for one of the 'textbook' answers - this is 'one of those questions' and I've seen mention of it quite a lot.
Lack of link means I didn't find a suitable answer.

You basically must have the motor straight such that the layshaft / diff gears are aligned as well as the Spur / Pinion.
You should be able to 'tightly fit a business card' between the gears - this should permit adequate 'play' without too much - mustn't be too loose either as this will aggrevate stress on the transmission.
SOME GEARS MAY NOT BE ROUND!!

Sounds stupid, but it's true, so don't gap the gears too closely and check all over several revolutions.

Hope that helps!
Al.

 

[jpblue1000]

Al,
I figured that much but how do you measure parallel between layshaft and diff. there si so much inthe way to get a tool in ther. is by sight and feel adequate or is there a trick.
cheers anyway.

Justin

 

[atom3624]

Al,
I figured that much but how do you measure parallel between layshaft and diff. there si so much inthe way to get a tool in ther. is by sight and feel adequate or is there a trick.
cheers anyway.

Justin

That's what I do mate !!

Al.

 

[Tobermory]

Right, i took the rc car apart last night and the only thing i could find was that the diff gear and the one that goes onto that were out of alignment and the drive cups are fairly severly worn.oh yeah and the bearing that holds the layshaft i think it is??(the gear that connects the diff to the spur gear) has abit of play in it,it wobbles up and down.is this supposed to be like this??
ive had abit of hastle in the past with my diff (lesking, screws coming out and bent gear) and i was wondering if this may be the problem, there is no grinding noise when in turn the wheels the opposite direction btw.
if i do need to replace the diff is it compatable with an fg one?? and i also think i may have to replace the blocks that hold it as i have stripped the plastic thread on one of them,so is this also compatable.
sorry for the really long post
Thanks
Toby

 

[atom3624]

Right, i took the rc car apart last night and the only thing i could find was that the diff gear and the one that goes onto that were out of alignment and the drive cups are fairly severly worn.oh yeah and the bearing that holds the layshaft i think it is??(the gear that connects the diff to the spur gear) has abit of play in it,it wobbles up and down.is this supposed to be like this??
ive had abit of hastle in the past with my diff (lesking, screws coming out and bent gear) and i was wondering if this may be the problem, there is no grinding noise when in turn the wheels the opposite direction btw.
if i do need to replace the diff is it compatable with an fg one?? and i also think i may have to replace the blocks that hold it as i have stripped the plastic thread on one of them,so is this also compatable.
sorry for the really long post
Thanks
Toby

Hi Toby,
Not certain on XTM, but from what I've seen, Carson is 'the same' as FG - let's see what others say.
Definitely program to replace the worn parts, and get the gears lined up, then it should run nice and smoothly.
Al.

 

[Tobermory]

Thanks for the replies Atom,
i just took it out earlier and it was still doing the noise. so i put it up against a wall and revved it to see what gears were moving, after this run it is quite clear that the gear on the layshaft is worn considerably.there also isnt a very good mesh between the gear on the diff itself.another problem i noticed is that the diff moves slightly up and back when it starts to rotate. so after all of that i think that it is time for a fairly big rebuild
If anyone can tell me if the diff mounts of the fg marder are compatible it would be a great help..also are alloy ones much better than plastic
Much appreciated
Toby

 

[atom3624]

Thanks for the replies Atom,
i just took it out earlier and it was still doing the noise. so i put it up against a wall and revved it to see what gears were moving, after this run it is quite clear that the gear on the layshaft is worn considerably.there also isnt a very good mesh between the gear on the diff itself.another problem i noticed is that the diff moves slightly up and back when it starts to rotate. so after all of that i think that it is time for a fairly big rebuild
If anyone can tell me if the diff mounts of the fg marder are compatible it would be a great help..also are alloy ones much better than plastic
Much appreciated
Toby

Hi Toby,

I THINK the answer is YES - BUT PLEASE CHECK FIRST.
Second, alloy mounts will not FLEX as much - LESS impact absorbance, but less affect on the gears.
Overall, BETTER I think for guarding the gears.
My 2 are all alloy, but several very experienced members prefer plastic - cheap and 'no problems'. Just a matter of good maintenance they say - probably right.
I WOULD SAY CHANGE TO ALLOY.
Engine mounts.
Diff mounts.
Gear mounts.
Radio tray.
Al.

 

[dwarfy]

The grinding noise is definitely the layshaft gear slipping. The most common cause is the screws work loose in the engine mounts allowing it to twist out of line under acceleration. Things you need to do:

Check / replace all worn bearings to layshaft and diff carrier
Replace layshaft gear
Check condition of engine mounts and make sure screws can still be tightened down otherwise replace
Make sure retaining screws to diff ring gear are tight (advisable to use blue loctite)
Replace worn diff carrier

When you re-assemble, put the screws in the engine mounts and nip them up enough so you can still move the engine to align the layshaft & diff gears. Once the gears are aligned correctly (as Al says in post above), carefully tighten the engine mount screws to avoid letting the engine slip out of position. When all engine mount screws are tight, remove 1 screw only, add blue loctite and tighten down fully. Do each screw in turn.

If you feel the diff is worn you can replace it with a stock FG diff. Also if the drive cups are worn you can swap them round LH cups with RH cups so they are driving on the good side again. Obviously sort these out before you go to the trouble of meshing the gears!!

 

[Tobermory]

The grinding noise is definitely the layshaft gear slipping. The most common cause is the screws work loose in the engine mounts allowing it to twist out of line under acceleration. Things you need to do:

Check / replace all worn bearings to layshaft and diff carrier
Replace layshaft gear
Check condition of engine mounts and make sure screws can still be tightened down otherwise replace
Make sure retaining screws to diff ring gear are tight (advisable to use blue loctite)
Replace worn diff carrier

When you re-assemble, put the screws in the engine mounts and nip them up enough so you can still move the engine to align the layshaft & diff gears. Once the gears are aligned correctly (as Al says in post above), carefully tighten the engine mount screws to avoid letting the engine slip out of position. When all engine mount screws are tight, remove 1 screw only, add blue loctite and tighten down fully. Do each screw in turn.

If you feel the diff is worn you can replace it with a stock FG diff. Also if the drive cups are worn you can swap them round LH cups with RH cups so they are driving on the good side again. Obviously sort these out before you go to the trouble of meshing the gears!!

Thanks dwarfy,
some very helpful information there!!
the only reason i was really thinking about replacing the diff was that it seems to leak grease (slightly) and the outside ring (the bit the gear screws onto) is warped,i kindoff want the diff to be alot more aggressive than it is so would there be any advantage to getting a new diff if all i had to do was put thicker grease in it??
thanks
Toby

 

[hyper 78]

Thanks dwarfy,
some very helpful information there!!
the only reason i was really thinking about replacing the diff was that it seems to leak grease (slightly) and the outside ring (the bit the gear screws onto) is warped,i kindoff want the diff to be alot more aggressive than it is so would there be any advantage to getting a new diff if all i had to do was put thicker grease in it??
thanks
Toby

my mate has the same problem with his xtm(same)
with a 16 lay it would only just touch,had to buy new black bone gears. he got a 17 lay which is better.also the screws in the diff mount kept coming loose resulting in movement between the diff and lay!

 

[Tobermory]

my mate has the same problem with his xtm(same)
with a 16 lay it would only just touch,had to buy new black bone gears. he got a 17 lay which is better.also the screws in the diff mount kept coming loose resulting in movement between the diff and lay!

just wondering if i got a 17 tooth gear as you say would that increase or decrease the top speed??
Thanks
Toby

 

[Trebor]

toby you just seem to be throwing money at your ride and not getting any where with it
a suggestion would be to sell it before it costs you more, and to buy a new
german quality FG

K....

 

[atom3624]

toby you just seem to be throwing money at your ride and not getting any where with it
a suggestion would be to sell it before it costs you more, and to buy a new
german quality FG

K....

One of those 'harsh but fair' comments.
Must admit I've no experience with Sheng Qi, but as Keith's saying, it's looking like you're modifying it, and not even giving yourself a clone, but rebuilding into an FG.
There are plenty of good ones on Fleabay from time to time.

Your call.

Al.

 

[Tobermory]

Yeah i know what you mean,a few months ago (probably about 6:loli was going to sell it,but i decided not to.then as i bought new stuff for it i kinda want to keep it more and more.the problem is that because ive spent so much money on it i know if i did sell it i wouldnt get half of that back,and because its still a "Clone" i wouldnt get much for it at all
i know what you mean about throwing money at it..time to consider mabee selling it again,its a hard decision though
Toby

 

[atom3624]

Yeah i know what you mean,a few months ago (probably about 6:loli was going to sell it,but i decided not to.then as i bought new stuff for it i kinda want to keep it more and more.the problem is that because ive spent so much money on it i know if i did sell it i wouldnt get half of that back,and because its still a "Clone" i wouldnt get much for it at all
i know what you mean about throwing money at it..time to consider mabee selling it again,its a hard decision though
Toby

The other side of the coin, is the exact opposite.
If by replacing selected parts with better quality ones, it becomes reliable, and able to be bashed as you like, and as you see others of us on here, then what's wrong with that?
It doesn't have to be perfect. It has to be something you like .....

Al.