why not a wide ratio 2-speed???

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big worm

big worm

Well-Known Member
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prince edward island, canada
ok seems to me that these 3 speed trannys are a lot of headches...tuning..not actually changing the ratios as much as claimed etc....
well how bout this for an idea? the original savage transmission and gears were designed for a .21 engine well todays engines are hp/torque monsters compared to those old .21s but because of the nature of the larger displacement of these .28+ engines they typicaly do not like to rev as high... and therefore run out or rpm before they run out of power..... so hows about a WIDE RATIO 2-speed i think that second gear in the 3 speed is really not needed .keep the fisrt gear ratio as is in the 2 speed and give us a taller 2nd gear (maybe the same as the regular 3rd or even like the new high speed 3rd) I personaly think a .28 would have enuf power for this....I mean traxxas did this for the revo when the 3.3 came out (3 avail ratios..close,std,and wide ratios)so you can set it up the way you like!!! immagine the high ratio of the new 3sp gears but without the extra rotating mass of the extra parts robbing power!!!!!! if only i had the machines to do this kind of work i would build a prototype
 
Thats a good idea, I would definitely get me one......

Have to wait and see what happens
 
can you immagine adding like 10 mph (from the combination of the ratio and the weight savings in rotating mass from a 3speed) without ANY loss of bottom end power at all and just for like $20 bux or so me thinks it would be the best bang for buck speed upgrade there is..... think bottom end like a 14t cb and the top end of a 18t !!!!!!!!!!!!!!!!!!!! or something like that
 
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Could you take the new high speed 3rd gear and just replace the current 2nd speed gear with it in the current X tranny?
 
dunno i have never compared the parts..... maybe if somone in here has 3 spd and a 2spd kickin round they could compare the parts........ lol i don't mind if someone else is the first to try the idea ...... i just hope that if someone does figure out a way to do it that i get credit for the idea...lol
 
that is a killer idea worm. I hope hpi or some after market parts place see's this and tries it. It better be cheap who ever dose it
 
It sounds like an ok idea, (it is a pain to tune it) just I don't think you would get much speed from the weight, of the 2nd gear, I don't know or have any idea about the movement and mech's of having the extra gear inside or if it robbs much power. but the weight wont do much.

I say this about the weight because I have 2 savy's one with the F4.6 and the other with the K4.6, the K is on a truck that is mostly stock, no ALU, the other is on a truck with all alu it weighs about 3.5 pounds more. (that's befrore I put 7" tires on it) At first I thought the weight was slowing it down a lot, fact was I didnt even run it long enough to tune it before deciding I didnt like it. Now Ive had it a while and run it quite a bit and with a good tune on it iI can hardly tell the difference between the 2 trucks, still have a problem keeping the front end down on both of them, bigger difference comes in slowing the heavy one down.

I do have a 2 sppeed around here and a high speed set, I will check it out, I kind of doubt it will work without at least some mods or I think they would advertise it for the 2 speed trany too.

I do also agree 100% that they could have or should at least design a better trany for the larger motors, I like the idea of a 3 speed that has a better choice of gears in it. Eventually something is going to have to be done, think about all the wasted power with the new k5.6 comming out.
 
i was not talkin about the overall weight of t he truck..... i was talking about ther rotating mass INSIDE the transmission......and anyone who knows anything about physics and how it appiles to things mechanical would know that the lower amount of rotating would be more efficient (less power waisted turning that weight) meaning more power to the wheels........ie guys who race small block chevys will shave up to 80lbs. off the weight of the crankshaft alone to lower the amount of rotating mass in the engine to allow for quicker revving of the engine(i don't mean overall top rpm , i do mean how quickly it get to that rpm) and less power loss from the weight..and they spend thousands to do this lightening of the crank!!!!!!!where as they could siply take out the carpet in the car and make the same weight savings...but with NOWHERE near the performance gains....... don't believe me well go out and put 100lbs in the box of a pickup truck and see how much that effects performance... probably not at all... now take that same 100 pounds and strap it to the driveshaft and tell me how much it kills the performance !!!!!
 
I do understand what your saying. I do not know how that extras gear movement effects things.

Take the difference between the 2 speed ans 3 speed trany's, Not much difference, I believe it is the 3rd gear that doesn't do much in the 3 speed (according to Doesgo's calculations less than 1% top speed) and about 7% better take off (first gear) so basically it is the 3rd gear that is almost useless. Prob ally where the new HS set comes in.

If you read Bruce's (Doesgo) thread he works out the calculations for both 2 and 3 speed (I don't know much about it ether way and am going by what I read in his thread) He does mention the extra rotating mass in the 3 speed and mentions it makes very slight difference.

Here's the thread I am going by (the 7th post is where he goes into a lot of detail on his calculations)https://www.hpisavageforum.com/forums/showthread.php?t=3550

I have very little understanding of how these transmissions work. I was thinking the gears, not engaged by the clutch don't turn anyway, but as I said I am not sure.
 
I was thinking about this, For a way to build your idea, instead of installing the HS set in the modified 2 speed trany. Take a three speed trany and install the HS set, then remove the extra gear you don't want (2nd speed gear) and make spacers like the plastic one that comes with the 3 speed trany kit (the one that is modled into the middle of the plastic gear, you have to snap the spacer out of the midle of) and use the spacer where the missing gear is.

actually I think you would need to make spacers for both the top and middle shaft cause you would want to remove both 2nd gear pair. I think that might work and would be easier than modding a 2 speed trany. the clutch would of course have to be adjusted for this.

????
 
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Wister thats what I was talking about with the 2 speed tranny. I haven't messed with the tranny too much yet so I'm not sure. But cant you pull the gears off the shafts on the 2 speed? If so then replace those gears with the 1st and 3rd gears from the 3 speed and just adjust the shift point. Again I'm just guessing. Until I take the tranny apart and look at it I'm not sure.
Also, slightly off topic, but what are the "bump" messages? Ive seen them on other boards too.
 
Wister said:
I was thinking about this, For a way to build your idea, instead of installing the HS set in the modified 2 speed trany. Take a three speed trany and install the HS set, then remove the extra gear you don't want (2nd speed gear) and make spacers like the plastic one that comes with the 3 speed trany kit (the one that is modled into the middle of the plastic gear, you have to snap the spacer out of the midle of) and use the spacer where the missing gear is.

actually I think you would need to make spacers for both the top and middle shaft cause you would want to remove both 2nd gear pair. I think that might work and would be easier than modding a 2 speed trany. the clutch would of course have to be adjusted for this.

????
Click to expand...

that idea just may work........anyone wanna experiment ?????
 
Keithv said:
Wister thats what I was talking about with the 2 speed tranny. I haven't messed with the tranny too much yet so I'm not sure. But cant you pull the gears off the shafts on the 2 speed? If so then replace those gears with the 1st and 3rd gears from the 3 speed and just adjust the shift point. Again I'm just guessing. Until I take the tranny apart and look at it I'm not sure.
Also, slightly off topic, but what are the "bump" messages? Ive seen them on other boards too.
Click to expand...

ya keith your idea is a lot closer to what i had in mind........even just changing out second gear........but i have no idea if the 3rd gear set would fit in place of 2nd in the 2speed.......but to someone with cad and a cnc mill it would be childs play to design and build a prototype of a set of gears that would have the same ratio as the new high speed 3rd but fit in place of 2nd in a 2 speed...AHEMM AHEMMM you listening hpi.... or robinson racing...and with the resources of a company like hpi... well I'm sure they could do it and sell it for around the same money as the high speed set for the 3speed.... and probably have it on the market within months.......and hey id even be willin to test out a prototype set lol
and as for the bump messages they are to keep a thread high on the list (as in the front page)
 
Ahh ok gotcha.
As for your gear idea. Have you tried emailing HPI directly? I know the supposedly like feed back from customers. Give it a shot. Whats the worse that can happen, they say no?
 
yup good idea... i think i will do so tomorrow... and maybe even pitch the idea to robinson racing products as well i mean they make internal tranny parts for other trucks and this may be righgt up their ally
 
I have been thinking about how they work, ok the top shaft (I don't have one open right now so I am doing this from memory) the top shaft has 3 gears on it they all spin all the time and are attached to the shaft, there are pins going through all three gears that lock them together.

the middle shaft has one gear locked to the shaft, its on the end, it drives the lower shaft which goes to the diff's, then there are 3 gears other than that on the middle shaft, not exactly sure about this part cause there is only 2 clutches, but I think they mesh with the gears on the top shaft and spinn all the time too, when a clutch engages it locks the spinning gear onto the shaft which causes the drive gear to spin on the middle and lower shaft.

Soo, for what I was talking about is on the top shaft you would have to remove the middle gear and have a spacer that would fit still allowing the pins to go from 1st to 3rd gear (this part could be trickyest) or just leave the middle gear on.

then on the middle shaft just remove the clutch and middle gear and add a spacer.

Next tim I pull mine apart I will look at it and see if it works how I am thinking, It will be as soon as the replacement parts for the bad HS set come. I should have one on the way now. (I did get the 3 speed installed with a small mod, and have yet to test it)

You know if it works, or any mod like this workks, there would be a good use for all those HS gears that are too thick 🙂 you would just have to make the spacer a bit shorter for the thicker gear.

EDIT-- I think I know why there is only 2 clutches, because the 1st speed gear is next to the drive gear, so they must use some other method to engage the 1st speed gear to the drive gear. and it must disengage when the drive gear gets going faster than it. ???
 
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