JRX2 Differential

[RCveteran]

If you're looking for a regular LRM differential, I have a nice smooth one just rebuilt with new balls that you can have, shoot me a PM.

[slow_jun]

Thanks Guys, going back again to my roots... hehehehe... i started with Jrx2 and regret selling my x2 oh well..... thanks to you guys and this was made possible here in this Great Forum..... thanks for the help and support.

Jun.

[RCveteran]

This is the LRM, low rotating mass transmission. The slipper clutch is an upgrade and would not have come with an X2 originally.

The next two are the retrofit transmission.

I like the LRM, I like the diff in the middle with the access hole for easy adjustment, I think it was pretty innovative.

[slow_jun]

Thanks for the Info RCVeteran, now im slowly digesting the info for the Jrx tranny retro thingy, i was searching yesterday and was able to find this site. containing http://www.wheelspinmodels.co.uk/car/category/Other-Losi-Spares__2d2/3/100/0/XX (bottom most parts), and saw that the whole retro tranny is somewhat very expensive? is this correct, and if i buy piece by piece i think i will not arrive with that amount.....


hmmm....

[JK Racing]

sorry jun, my parts are all for the 2.61 truck tranny, none for the 2.19 buggy.

[slow_jun]

Actually what i got is a Pro truck (conversion). Will be sending you a PM.

[JK Racing]

PM back at ya...

[slow_jun]

Already have a Losa3020 Diff, but you know this hobby, its a never ending upgrade so i will most probably be doing a retrofit tranny.

replied back

thanks Joey.

Jun.

[Lothsahn]

I've got a Junior two, and I stripped the diff gear in my trans. I couldn't find a replacement one ANYWHERE, but I found the retrofit trans set on ebay and bought it.

At this point, I've got all the parts for the retrofit trans and have it assembled, however I'd really like to keep using the LRM if possible. I'm interested in the prospect of being able to run brushless systems with the LRM, but I thought that wouldn't be possible. Is it reasonable to run brushless systems if you're using the aluminum diff, or will other parts of the LRM tranny still be too weak? Except for the diff gear, I've got a lot of LRM tranny spare parts too.

Finally, what is the A-3020 set everyone's talking about? Anyone have a picture of it? Does it require the thinner bearings or the "regular" thickness ones?

[shirochanwrx]

A well-built and maintained LRM can handle modern brushless power just about as well as the early retrofit / XX tranny's and almost as well as a vintage Stealth, IMO.

The LRM is not as efficient as the latter transmissions, so there will be somewhat more drag in the system, which means more heat. But not so much more that it would be a limiting factor. The LRM is one of the first truly modern transmissions.

[Lothsahn]

Shiro:

Does that assume an aluminum diff gear or stock parts? I found it was rather easy to strip the diff gear (using a 13T brushed motor). However, I didn't have a slipper setup at the time (which I now have for my car).

Other than regreasing the diff in the tranny and oiling the bearings, what other maintenance should I be doing?

[shirochanwrx]

I ran a Speedworks 14x4 and 15x2 for a long time in a JRX2 without any problems using the stock composite gears; no slipper BITD ... I think that using aluminum differential gears can just shift stress to a different part of the transmission, so I have never felt compelled to used them. You can still pick up the stock differential gear if you need one.

With a slipper, you should have even more cushion.

In terms of maintainence, I really meant to the diff itself. Build the diff according to the instructions, use high quality lubricants (e.g. Associated Stealth, others), and clean out the bearings a couple times a season with motor spray and re-oil after letting them dry overnight. Use carbide diff balls and new rings on rebuilds once a year, more often with non-carbide balls, or less with ceramic. The advent of the slipper clutch has really made differential rebuilds less frequent because it only has to operate as a diff, not as a combination diff/torque limiter.

Most importantly, don't let that diff slip more than a couple feet when you punch it on asphalt (with high traction tires) and the slipper locked. Excess slippage in the diff = heat. Where does all the energy not getting to wheels go in a slipping diff? Heat. And that heat means that the diff gear will soften (which accelerates wear), or outright melt if it gets hot enough. You are much better off running a diff a little tight than a little loose longevity-wise.

[Lothsahn]

You can still pick up the stock differential gear if you need one.

Do you know where? Horizon hobbies doesn't carry them anymore and I can't find them on ebay. Every place I see them is sold out:
http://www.ehobbies.com/losa3006.html

Basically, my entire LRM is in great condition--no dirt or grime or anything, but the central diff gear is stripped in one spot.

[shirochanwrx]

eBay. I've picked up 2 in the last month or so. One new, and one in a parts lot.

Parts lots are a good spot to look for transmission bits.