Emaxx 3908 Needs Better Bulkheads and Rear Diff. Strong Options?
05-26-2015, 06:53 PM
#46
Tech Adept
The silver ones would be ok, if there was not flex in the arms.
So having just that little bit extra, makes all the difference.
So having just that little bit extra, makes all the difference.
05-27-2015, 07:17 AM
#47
I just hope there isn't too much flex in my new setup with using one aluminum and one plastic control arm set on the front and rear. The RPM stuff holds together up to 4s power, but after that, their arms flex way too much which causes it to veer hard to the left under heavy throttle. Anyways, I really need to start putting this thing back together!
05-27-2015, 06:04 PM
#48
OK, I need some advice or a link to some sort of video on how to properly shim these Ofna 7 diff's inside these FLM Hybrid bulks. The pinion is set fine, but the side to side movement in the case is what is of concern. I already placed two .2 mm shims between the main bearings and it did tighten it up some. However, I'm not certain if it is messing correctly against the pinion gear.
Also, since I had to switch to the 1/8th output shafts, these shafts move in and out of the carrier about 2mm on each side. Not even sure how to shim that since there are no shims for these axles. These would need to be shimmed between the output drive cups and the outside of the carrier bearings. The original Ofna 7 drive cups/ axles installed in the original plastic housing had no in and out play on either side. Is this a concern?
Also, since I had to switch to the 1/8th output shafts, these shafts move in and out of the carrier about 2mm on each side. Not even sure how to shim that since there are no shims for these axles. These would need to be shimmed between the output drive cups and the outside of the carrier bearings. The original Ofna 7 drive cups/ axles installed in the original plastic housing had no in and out play on either side. Is this a concern?
05-28-2015, 02:27 AM
#49
Tech Adept
OK, I need some advice or a link to some sort of video on how to properly shim these Ofna 7 diff's inside these FLM Hybrid bulks. The pinion is set fine, but the side to side movement in the case is what is of concern. I already placed two .2 mm shims between the main bearings and it did tighten it up some. However, I'm not certain if it is messing correctly against the pinion gear.
Also, since I had to switch to the 1/8th output shafts, these shafts move in and out of the carrier about 2mm on each side. Not even sure how to shim that since there are no shims for these axles. These would need to be shimmed between the output drive cups and the outside of the carrier bearings. The original Ofna 7 drive cups/ axles installed in the original plastic housing had no in and out play on either side. Is this a concern?
Also, since I had to switch to the 1/8th output shafts, these shafts move in and out of the carrier about 2mm on each side. Not even sure how to shim that since there are no shims for these axles. These would need to be shimmed between the output drive cups and the outside of the carrier bearings. The original Ofna 7 drive cups/ axles installed in the original plastic housing had no in and out play on either side. Is this a concern?
The first thing you need to do is, check for side to side play.
To do this, assemble the bulks with the diff inside (without the pinion).
Now check how much side to side play there is. If there's lots of play (say about 2mm), you will need to use about 10 .2mm shims.
The shims go between the diffs output bearings, and bulks/diff case.
It doesn't mater if its the ring gear side or the other side, because there is no pinion installed yet.
When you've put the shims in, assemble the 2 bulk halves, and test for side to side play.
Repeat this step, until all the side to side play is removed.
Count how many shims you used to stop the side to side play. Lets say there's 10 shims.
Place 2 of them shims inside the bulk half that has the tapped thread holes in it (the 3 holes used to screw the bulk halves together).
Then insert the ring gear, with the gears of the ring gear facing up.
Put 2 bearings on the pinion shaft and place the pinion and bearings so they sit into there locations. Now look at the how the gear mesh lines up on the ring and pinion.
If the pinion has a lot of, in out play. You can place a shim or 2 in-between the pinion gear and inner bearing.
But adding to many shims to the pinion, can make the pinion gear rub up against the diff cup. If your at this point where you cant add more shims to the pinion, but you still have a lot of play. You will need to add another shim between the bulk half, and diff bearing (under the ring gear).
When you have eliminated the play in the pinion.
You can add the other 7 shims to the other bulk half, and re assemble it.
Check to make sure everything spins nice and free, but with minimal play.
Once your happy with it, disassemble it, and apply a light coat of synthetic grease over the ring and pinion gears. Then reassemble it, and fit it to your truck.
You can used 6mm shims between the drive cup and output shaft, to eliminate play from that area. Glow plug washes are 6mm and work good for taking up any play that's more then 1mm. I have used them between the wheel hex and axle carrier.
I did do a little video to show that the trophy diff fit. But i didn't really do a complete step by step tutorial. But it might help a little bit.
| + YouTube Video | |
05-28-2015, 08:13 AM
#50
You need to assemble and disassemble the diff several times, while checking for play in each part of the diff.
The first thing you need to do is, check for side to side play.
To do this, assemble the bulks with the diff inside (without the pinion).
Now check how much side to side play there is. If there's lots of play (say about 2mm), you will need to use about 10 .2mm shims.
The shims go between the diffs output bearings, and bulks/diff case.
It doesn't mater if its the ring gear side or the other side, because there is no pinion installed yet.
When you've put the shims in, assemble the 2 bulk halves, and test for side to side play.
Repeat this step, until all the side to side play is removed.
Count how many shims you used to stop the side to side play. Lets say there's 10 shims.
Place 2 of them shims inside the bulk half that has the tapped thread holes in it (the 3 holes used to screw the bulk halves together).
Then insert the ring gear, with the gears of the ring gear facing up.
Put 2 bearings on the pinion shaft and place the pinion and bearings so they sit into there locations. Now look at the how the gear mesh lines up on the ring and pinion.
If the pinion has a lot of, in out play. You can place a shim or 2 in-between the pinion gear and inner bearing.
But adding to many shims to the pinion, can make the pinion gear rub up against the diff cup. If your at this point where you cant add more shims to the pinion, but you still have a lot of play. You will need to add another shim between the bulk half, and diff bearing (under the ring gear).
When you have eliminated the play in the pinion.
You can add the other 7 shims to the other bulk half, and re assemble it.
Check to make sure everything spins nice and free, but with minimal play.
Once your happy with it, disassemble it, and apply a light coat of synthetic grease over the ring and pinion gears. Then reassemble it, and fit it to your truck.
You can used 6mm shims between the drive cup and output shaft, to eliminate play from that area. Glow plug washes are 6mm and work good for taking up any play that's more then 1mm. I have used them between the wheel hex and axle carrier.
I did do a little video to show that the trophy diff fit. But i didn't really do a complete step by step tutorial. But it might help a little bit.
The first thing you need to do is, check for side to side play.
To do this, assemble the bulks with the diff inside (without the pinion).
Now check how much side to side play there is. If there's lots of play (say about 2mm), you will need to use about 10 .2mm shims.
The shims go between the diffs output bearings, and bulks/diff case.
It doesn't mater if its the ring gear side or the other side, because there is no pinion installed yet.
When you've put the shims in, assemble the 2 bulk halves, and test for side to side play.
Repeat this step, until all the side to side play is removed.
Count how many shims you used to stop the side to side play. Lets say there's 10 shims.
Place 2 of them shims inside the bulk half that has the tapped thread holes in it (the 3 holes used to screw the bulk halves together).
Then insert the ring gear, with the gears of the ring gear facing up.
Put 2 bearings on the pinion shaft and place the pinion and bearings so they sit into there locations. Now look at the how the gear mesh lines up on the ring and pinion.
If the pinion has a lot of, in out play. You can place a shim or 2 in-between the pinion gear and inner bearing.
But adding to many shims to the pinion, can make the pinion gear rub up against the diff cup. If your at this point where you cant add more shims to the pinion, but you still have a lot of play. You will need to add another shim between the bulk half, and diff bearing (under the ring gear).
When you have eliminated the play in the pinion.
You can add the other 7 shims to the other bulk half, and re assemble it.
Check to make sure everything spins nice and free, but with minimal play.
Once your happy with it, disassemble it, and apply a light coat of synthetic grease over the ring and pinion gears. Then reassemble it, and fit it to your truck.
You can used 6mm shims between the drive cup and output shaft, to eliminate play from that area. Glow plug washes are 6mm and work good for taking up any play that's more then 1mm. I have used them between the wheel hex and axle carrier.
I did do a little video to show that the trophy diff fit. But i didn't really do a complete step by step tutorial. But it might help a little bit.
| + YouTube Video | |
The movement I have is the in and out axle play coming from within the carrier. I didn't know if this was common or needed to be addressed. At this time I do not have any shims for this size of shaft. You would need a shim to fit the axle diameter and the shim's shear size would need to closely match the drive cups size.
Are these shims available to purchase that I am describing or do you have to improvise? I find it odd that no one seems to mention this during any build video I have watched. If the drive cups had a set screw mount type, this would be easily fixed without the use of shims.
Also, how much ring to pinion gear mesh do you want or don't want?
05-28-2015, 09:50 AM
#51
Yes you should shim the pinion to eliminate any in and out movement as this movement will alter the mesh with the ring gear. As ausprime said you put some between the pinion and first bearing to set the pinion depth. Then if there's still in and out movement put some shims behind the drive cup until there isn't any movement.
You may have to adjust the pinion depth a little if you can't get the mesh right with the shims for the ring gear. Proper mesh has no play between the ring and pinion while also being as smooth as possible but sometimes you have to compromise a little. If there is some slight notchiness that is ok as the gears will wear in but it should be as little as possible. Slight notchiness is better than play between the gears.
Shims are available in sizes to shim any part of the diff even the spider gears. Shims in 10x8x.2mm should be perfect for shimming the pinion as they will only contact the inner race of the bearing and not hit the bearing's shielding. I'm not sure of the size for the spider gears but Ofna does have them. If you're referring to the in and out movement of the diff output, shimming the spider gears won't really help eliminate it. Also this movement doesn't really effect the mesh of the spider gears so it's not something to be too concerned with.
You may have to adjust the pinion depth a little if you can't get the mesh right with the shims for the ring gear. Proper mesh has no play between the ring and pinion while also being as smooth as possible but sometimes you have to compromise a little. If there is some slight notchiness that is ok as the gears will wear in but it should be as little as possible. Slight notchiness is better than play between the gears.
Shims are available in sizes to shim any part of the diff even the spider gears. Shims in 10x8x.2mm should be perfect for shimming the pinion as they will only contact the inner race of the bearing and not hit the bearing's shielding. I'm not sure of the size for the spider gears but Ofna does have them. If you're referring to the in and out movement of the diff output, shimming the spider gears won't really help eliminate it. Also this movement doesn't really effect the mesh of the spider gears so it's not something to be too concerned with.
05-28-2015, 04:03 PM
#52
Yes you should shim the pinion to eliminate any in and out movement as this movement will alter the mesh with the ring gear. As ausprime said you put some between the pinion and first bearing to set the pinion depth. Then if there's still in and out movement put some shims behind the drive cup until there isn't any movement.
You may have to adjust the pinion depth a little if you can't get the mesh right with the shims for the ring gear. Proper mesh has no play between the ring and pinion while also being as smooth as possible but sometimes you have to compromise a little. If there is some slight notchiness that is ok as the gears will wear in but it should be as little as possible. Slight notchiness is better than play between the gears.
Shims are available in sizes to shim any part of the diff even the spider gears. Shims in 10x8x.2mm should be perfect for shimming the pinion as they will only contact the inner race of the bearing and not hit the bearing's shielding. I'm not sure of the size for the spider gears but Ofna does have them. If you're referring to the in and out movement of the diff output, shimming the spider gears won't really help eliminate it. Also this movement doesn't really effect the mesh of the spider gears so it's not something to be too concerned with.
You may have to adjust the pinion depth a little if you can't get the mesh right with the shims for the ring gear. Proper mesh has no play between the ring and pinion while also being as smooth as possible but sometimes you have to compromise a little. If there is some slight notchiness that is ok as the gears will wear in but it should be as little as possible. Slight notchiness is better than play between the gears.
Shims are available in sizes to shim any part of the diff even the spider gears. Shims in 10x8x.2mm should be perfect for shimming the pinion as they will only contact the inner race of the bearing and not hit the bearing's shielding. I'm not sure of the size for the spider gears but Ofna does have them. If you're referring to the in and out movement of the diff output, shimming the spider gears won't really help eliminate it. Also this movement doesn't really effect the mesh of the spider gears so it's not something to be too concerned with.
05-28-2015, 06:05 PM
#53
Tech Adept
The output shafts are 6mm
so any 6mm shims will eliminate the in out play.
http://www.amain.com/rc-cars/calandr...cln4736/p48945
The 6mm shims will go on the output shafts, before the drive cups.
So they will sit up against the diff bearing, and drive cup.
so any 6mm shims will eliminate the in out play.
http://www.amain.com/rc-cars/calandr...cln4736/p48945
The 6mm shims will go on the output shafts, before the drive cups.
So they will sit up against the diff bearing, and drive cup.
05-28-2015, 06:41 PM
#54
Tech Regular
The in and out movement I believe he is referring to is inside the cup. You will have to open the diff and possibly shim the spider gears closer. And what I mean is not the set of 4 spiders on the steel rods, shim the two gears on either side of the cup that the output shaft spins with. You'll have to remove that gear and pin to shim behind it. I had to do this on one of my hyper diff's. I added a few inside and then shimmed the MIP drive cup away from the bearing to eliminate rest of the play. Be careful shimming spider gears as you'll get them too tight and cause abnormal or quick ware on the gears.
The last hyper diff I did I just added a lot of shims on the outside between the cup and bearing. Actually went to home depot and they are more like washers then shims....lol just really thick. Was to lazy to open the diff cup and shim the spider gears. This is on the front and haven't notice any issues yet and it's been running 5s and now have a cc 1717 xo-1 motor in it running stout.
The last hyper diff I did I just added a lot of shims on the outside between the cup and bearing. Actually went to home depot and they are more like washers then shims....lol just really thick. Was to lazy to open the diff cup and shim the spider gears. This is on the front and haven't notice any issues yet and it's been running 5s and now have a cc 1717 xo-1 motor in it running stout.
05-28-2015, 07:05 PM
#55
Tech Adept
The in and out movement I believe he is referring to is inside the cup. You will have to open the diff and possibly shim the spider gears closer. And what I mean is not the set of 4 spiders on the steel rods, shim the two gears on either side of the cup that the output shaft spins with. You'll have to remove that gear and pin to shim behind it. I had to do this on one of my hyper diff's. I added a few inside and then shimmed the MIP drive cup away from the bearing to eliminate rest of the play. Be careful shimming spider gears as you'll get them too tight and cause abnormal or quick ware on the gears.
The last hyper diff I did I just added a lot of shims on the outside between the cup and bearing. Actually went to home depot and they are more like washers then shims....lol just really thick. Was to lazy to open the diff cup and shim the spider gears. This is on the front and haven't notice any issues yet and it's been running 5s and now have a cc 1717 xo-1 motor in it running stout.
The last hyper diff I did I just added a lot of shims on the outside between the cup and bearing. Actually went to home depot and they are more like washers then shims....lol just really thick. Was to lazy to open the diff cup and shim the spider gears. This is on the front and haven't notice any issues yet and it's been running 5s and now have a cc 1717 xo-1 motor in it running stout.
This will eliminate slop in the spider gears.
Its basically a easier way of shimming the sun gears.
05-28-2015, 08:34 PM
#56
There is no gasket like that in these diff's you are referring to. The gasket between the ring gear and diff cup is an orange O ring. No other gaskets other than the axle shaft O rings.
05-28-2015, 09:46 PM
#57
Tech Adept
Oh okay, shimming the sun gears would probably be the only way to eliminate the play. But putting shims between the diff bearing and drive cup, will keep the output shaft from sliding in and out of the diff anyway.
05-30-2015, 06:27 PM
#58
The in and out movement I believe he is referring to is inside the cup. You will have to open the diff and possibly shim the spider gears closer. And what I mean is not the set of 4 spiders on the steel rods, shim the two gears on either side of the cup that the output shaft spins with. You'll have to remove that gear and pin to shim behind it. I had to do this on one of my hyper diff's. I added a few inside and then shimmed the MIP drive cup away from the bearing to eliminate rest of the play. Be careful shimming spider gears as you'll get them too tight and cause abnormal or quick ware on the gears.
The last hyper diff I did I just added a lot of shims on the outside between the cup and bearing. Actually went to home depot and they are more like washers then shims....lol just really thick. Was to lazy to open the diff cup and shim the spider gears. This is on the front and haven't notice any issues yet and it's been running 5s and now have a cc 1717 xo-1 motor in it running stout.
The last hyper diff I did I just added a lot of shims on the outside between the cup and bearing. Actually went to home depot and they are more like washers then shims....lol just really thick. Was to lazy to open the diff cup and shim the spider gears. This is on the front and haven't notice any issues yet and it's been running 5s and now have a cc 1717 xo-1 motor in it running stout.
My main concern is that the ring and pinion gears are shimmed correctly.
I am thinking the further in the pinion gear is onto the ring gear the better. I just need to make sure the end of the pinion gear doesn't touch the ring gear cup. Then I will shim the ring gear up to the point I can feel too much resistance and then back off with moving the .01 mm shims to the other side until constant free play is felt.
Of course, I will first shim the carrier assembly in the hybrid housing without the pinion gear and bearings installed.
Tedious process, but I think my plan will workout in the end. What helps is, I do have the Ofna 7 diffs and housings to reference for ring and pinion gear mesh feel and pinion gear depth.
One other question, I have the diff fluid for the spider gears, but what lubrication do I need for the ring and pinion gears?
Thanks for all the continued help guys.
05-30-2015, 07:01 PM
#59
Tech Adept
mobil 1 synthetic grease
06-01-2015, 04:05 PM
#60
Progress on the shimming of the axles cups.
I used one steel 6mm shim against both outsides of the drive axles, then I used 2 nylon washers drilled out to 6mm on both sides as well. With the drive cups installed, they are a tad tighter than I want without any adjustment. Therefore, instead of just losing an entire nylon washer and stacking a bunch of the 6mm steel axle shims.
I really wasn't expecting it to tighten anything, but when I tried to rotate both axles in opposite directions, it had a lot of resistance.
I really don't want to take the chance, but I honestly think it would loosen up due to the nylon washers slightly wearing some.
Then again, the single inner plastic or nylon washer inside the diff might wear out and cause metal to metal damage.
Photos:
I used one steel 6mm shim against both outsides of the drive axles, then I used 2 nylon washers drilled out to 6mm on both sides as well. With the drive cups installed, they are a tad tighter than I want without any adjustment. Therefore, instead of just losing an entire nylon washer and stacking a bunch of the 6mm steel axle shims.
I really wasn't expecting it to tighten anything, but when I tried to rotate both axles in opposite directions, it had a lot of resistance.
I really don't want to take the chance, but I honestly think it would loosen up due to the nylon washers slightly wearing some.
Then again, the single inner plastic or nylon washer inside the diff might wear out and cause metal to metal damage.
Photos: