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LST2 vs. LST XXL transmission gearing question

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Old 07-31-2015, 12:34 PM
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mark102780
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Default LST2 vs. LST XXL transmission gearing question

Hey guys i just picked up an LST2 and now own both of these monsters. I've read that the gearing is a little better in the XXL tranny. Can someone explain this a little more. I know they got rid of the hi/low feature, but which gears exactly got changed and with what result? My goal is to re-gear my LST2 to XXL standards if possible, if not, i may try to find an XXL or XXL 2 transmission to put in the LST2.
Thanks! Mark

Last edited by mark102780; 07-31-2015 at 12:41 PM.
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Old 08-01-2015, 05:03 AM
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I think they added a tooth or two to the gears in the XXL transmission and even a couple more in the brushless conversion kit. I have two LST2s and have the FOC in both. One has the gear flip mod, the other doesn't. The gear flip mod is essentially what the XXL is setup for I believe. Correct me if I'm wrong. The gear flip swaps the input gear and output gear in the transmission setup for FOC and hi/low delete. Look at the trans gear part numbers between the LST2, XXL, and the BL conversion kit. In respective order, it's basically fast, faster, fastest. I'm not sure if the BL kit gears fit the standard LST2 transmission or if the cases are different.
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Old 08-04-2015, 03:55 AM
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All LST transmissions use the same case, although Losi updated the case with the LST2 it wasn't for fitting different gears or in a different configuration. No matter what case you have doing the "gear swap/flip" requires a little grinding on the case. The gear swap involves the gear on the input shaft and the gear on the intermediate shaft swapping places. This can only be done on a FOC equipped trans. The bevel gears on the output shaft cannot be swapped.

Internal trans gear ratios have have changed and that was done by changing the bevel gears on the output of the trans. Losi has never done the "gear flip/swap" or anything like that. There are 3 ratios (that I know of), LST/LST2/Aftershock at 2.09:1, XXL at 1.89:1 and Losi electric conversion at about 1.70:1. I forget the exact ratio (I calculated it once years ago) of the Losi electric conversion bevel gears and I do not know what ratio gears the XXL2 or XXL2e uses but I believe them to be one of the three listed above not a new ratio.

These are only the internal trans ratios. Losi also made changes to the spur gears over the years and the clutchbell tooth count with the XXL and XXL2. I'm not familiar with the exact changes in tooth count for either of those though.

Last edited by Maj_Overdrive; 08-04-2015 at 03:59 AM.
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Old 08-04-2015, 06:43 PM
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The gear flip involves flipping the input shaft gear and counter-shaft gears in the trans case and yes, the case needs to be modified to fit the 23t gear where the 22t gear usually sits. I did not mean to infer that any of the Losi trucks come with the "gear flip" mod factory, but that the output ratio is similar. I didn't have the part numbers or ratios handy at the time and forgot to do some reading to find the proper information. Below is what little info I could find with specific gear counts and such. The usual method for more speed on top is to go smaller on the spur gear and larger on the pinion. Vice versa for better wheelies and low speed torque. Here's another thread I found on the subject. http://www.rcnitrotalk.com/forum/thr...r-ratio.49965/

LST2 stock transmission bevel gears are 15/30 (LOSB3118)

LST XXL FOC Kit is the same as the LST2 Kit - input gear is 22t and counter shaft gear is 23t.
XXL bevel gears inside transmission are 16/29 teeth (LOSB3119). Option gear set is 15/30 for transmission. (LOSB3118)
XXL uses same spur gear tooth counts (63/70) as LST2
All LST trucks use the same diff gears, stock XXL clutchbell/pinion is 19/26, and from what I see, all use the same spur gears standard. There are optional pinions for the threaded clutchbell and corresponding spur gears but only available or the LST2 2-speed hub.

XXL2 (CDI Gas engine) uses same trans gearing as LST2.

LST Brushless Electric conversion kit:
Trans bevel gears: 17/28 (LOSB3120)


XXL Manual and parts list: http://www.overdriverc.com/pdf/LST%20XXL%20Manual.pdf
LST2 Parts list: http://www.overdriverc.com/pdf/LST2%20exploded.pdf
XXL2 Manual and parts list: http://www.horizonhobby.com/pdf/LOS04002-Manual_EN.pdf
LST Electric Conversion kit manual and parts list: http://www.losi.com/ProdInfo/Files/LOSB0017_Manual.pdf

Last edited by 1QwkSport2.5r; 08-05-2015 at 12:29 AM. Reason: Fixed clutch spec
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Old 08-04-2015, 09:24 PM
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I read your post again and I see what you meant about the gear flip. I missed that but regardless I was actually just trying to be clear and concise with the info in my post though, not correct or go against your post in any way. In your last post though you say 18/25 is standard for the clutchbell on all LST's. I've never had the stock clutchbell on my XXL (got it as a roller and converted it to brushless) but have read many, many times the XXL is 1 or 2 teeth higher than LST2 so I believe it's true. I once bought a used LST1 I thought was all stock but I guess it had the high speed kit since it had a 64t 2nd gear spur instead of 63t. I converted to brushless for my nephew so I didn't pay any attention to 1st gear or the clutchbell.

I actually have the trans ratios in my head from doing gear calcs to answer brushless conversion questions so many times. But I never got the bevel gear tooth counts straight. That info always leaks out of my head so thanks for posting that and the XXL2 bevel gears. Hopefully the info will stay in there this time. Now I just gotta find out what bevel gears the XXL2e uses.

Edit: Just for clear and consise info, the XXL does use a different clutchbell LOSB3342 19/26 according to the manual you posted. The consensus from what I've read is the larger 454 engine of the XXL doesn't rev as high as previous engines. But it is more powerful so they geared it up to regain the top speed lost, possibly gaining a few extra mph over the LST2 to boot.

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Old 08-04-2015, 09:56 PM
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Just for poop and giggles here's what effect the gear swap mod has on the trans ratios.
LST1/LST2/Aftershock/XXL2 goes from 2.09:1 to 1.91:1 with gear swap
XXL goes from 1.89:1 to 1.73:1
Losi brushless conversion goes from 1.70 to 1.56

Thanks to 1QwkSport2.5's posting of the Losi conversion bevel gear tooth count I actually calculated those ratios instead of going by hazy memory. Sadly enough the LST2 and XXL ratios with the gear swap were in my head, no calculating necessary.

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Old 08-05-2015, 12:32 AM
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Man... I combed those manuals for almost an hour making sure I got all the specs and part numbers right... I corrected my last post to reflect the correct info about the stock XXL clutchbell. Thanks for catching that. All of this as motivated me to get my modding hat on to do some work on one of my LST2s... One of them just *needs* to be different.. LOL.
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Old 08-05-2015, 01:22 PM
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Gonna try the 4 stroke you talked about awhile back?
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Old 08-05-2015, 02:31 PM
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Quote:
Originally Posted by Maj_Overdrive View Post
Gonna try the 4 stroke you talked about awhile back?
I would really like to, but my machinist buddy who I'd have to talk into making some of the parts is moving back to Texas.. So in short, not likely. I'd need to make an engine mount, find a clutch and flywheel to fit the 7mm shaft (which I cannot cut the crankshaft anyway), and whatever other mods to fit it to the chassis. Probably won't happen. I think I'm gonna gear-flip the trans in #2, install bigger pinions and spur gears, add the brushless transmission bevel gears, and maybe add Muggy towers and shock shafts. I've got some other projects going that I need to finish first, but I'm gonna find something to do with it anyway...

I think with those mods and my great running .28, that truck should do close to 45mph.
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Old 11-05-2015, 04:21 PM
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Just a heads up. I went to the hobby shop to order some parts for one of my LST2s only to find one part discontinued. I went with the plan to get the BL Conversion transmission bevel gears and the XXL clutchbell only to find the XXL clutchbell discontinued and unavailable. So my speed rig might need to get a 22t low gear pinion instead of the 18t stocker.
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Old 05-17-2016, 07:05 AM
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I'm reviving this thread with some findings... I recently put a modified Picco P3 .28 into one of my LST2 trucks. I used a stock long Losi manifold, Dynamite 086HS pipe, 20/11 fuel, and I installed the LOSB3120 brushless conversion bevel gears in the transmission. I broke the engine in 20/14 fuel for two quarts and then changed to 20/11 fuel. I noted the truck was quite a bit faster despite the engine running quite rich, but the engine did run hotter than I would like. So I swapped the stock LST2 transmission bevel gears in and ran it more. The engine ran cooler, but still not quite right. I then put a Novarossi 41016 conical manifold in and changed out the cheap Traxxas 3232x medium glow plug for a McCoy MC9 cold plug. Now the truck is an absolutely ridiculous beast. The engine just revs and revs! Now that I have a gallon through the engine, I need to fix some sticking 2-spd clutch shoes and after that is sorted, I'll reinstall the LOSB3120 brushless bevel gears for some speed runs to see just how fast it will go. With the stock bevel gears and output gear flip mod, the truck is easily 5mph faster if not more. The engine is setup on the mild side, but I may elect to go hotter on the mods to get more top end out of it.

So in short, if you have a stout engine with lots of power, the brushless bevel gears will wake up your LST based truck quite a bit on the top end, but don't expect any wheelies and expect the bottom end to feel a fair bit softer off the line due to the taller gearing.
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Old 05-17-2016, 08:18 AM
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If you have the threaded 2 speed clutch bell you can change the gears on it. RC-Monster has gears of all sizes available and I've read about others using them on the threaded LST clutchbell. Make your own XXL spec clutchbell or whatever number of teeth you like.

1st gear http://www.rc-monster.com/proddetail...speed_1st_gear

2nd gear http://www.rc-monster.com/proddetail...speed_2nd_gear
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Old 05-17-2016, 03:06 PM
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That clutchbell doesn't allow using the larger 5x13 bearing though... I am running some beastly engines, so the clutch needs as much help as it can. With that said, I'm okay with the stock gearing. In reality, it's plenty fast. If I gear it up too much it kills the low end. But it is good to know there are other pi jobs available for the threaded clutchbell. I have one on my other truck.
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Old 05-08-2017, 08:25 AM
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I did some speed runs last week with my Picco .28 LST2 truck experimenting with a couple different glow plugs too. P6TC gave a 43.1mph top speed fully peaked out and on P6TH I got 44.1mph fully peaked out. Stock transmission (no gear flip), stock sour and pinions, Novarossi 41016 manifold, Dynamite 086HS pipe, bald ATX stores, and 20% nitro 11% oil fuel. Next I'll test a Novarossi 41017 manifold (I suspect this may hinder top end some) and Novarossi 9886 pipe. Curious to see how fast a stock truck can go with a good engine...

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Old 05-08-2017, 10:55 AM
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Tried the 41017 Nova manifold with Nova 9886 pipe on the P6TH and best I could get was 43.2mph. Now to put the 41016 on the 9886 and test again. Given the high timing of the engine, I might gain a teeny but more with the 41015 short manifold, but probably not much. As I mentioned in my last post, this is with a stock FOC transmission. I'll do a manifold swap and then do the gear flip again. I think the engine has the power to push the extra gearing.

I would have have done more testing today, but the receiver battery got a bit low for my tastes.
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Old 06-24-2017, 04:12 AM
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I now have all three trans gear options for the LST trucks. I've done speed runs using stock gears (15/30)in my Picco .28 truck getting an all-out max speed of 44mph. I swapped in the XXL gears (16/29) and after breaking in the transmission gears, will do more speed runs. I also built a Fwd/Rev transmission with hi/Lo range. I have had the fed/rev transmission for a long time, but never messed with it because it was missing parts and I didn't care about reverse. Now I feel inclined to try it. Basically I built a go-faster and a go-slower transmission.. LoL.
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Old 06-24-2017, 06:46 AM
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Weight difference between a Forward Only transmission and the standard Fed/Rev/Hi/Low.. not as much as I expected to see; 202g (7.2oz) FOC versus 292g (10.4oz) standard trans.
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