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Old 03-26-2010, 09:50 AM   #1
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Default STRR /hot bodies ring pinion mod

Does anybody have any info on replacing the bevel and pinion gears of a STRR with hot bodies ? I was told there was info on the STRR thread but couldn't find it. I know shimming is crucial for the ring gears not to strip, I am just looking for alternatives, with proper shimming I went through 3 sets last season.
I bought a set the other day and they appear VERY similar. The teeth of the HB gears are cut deeper with a flat on the top verses the Kyosho being sharper. I have one report of this helping another driver, just looking for imput so I can get another season out of the old girl. Any help would be appreciated
(ps- please keep it constructive
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Old 03-26-2010, 09:54 AM   #2
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the diffs are a complete drop in, with the pinion gear,

my buddy who races a hot bodies d8t runs kyosho front universals,

he said no one makes a drive shaft like kyosho dose..

but yes COMPLETE diff drop in im going that way soon as i am starting to strip some stuff the more i go to bigger tracks.
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Old 03-26-2010, 10:05 AM   #3
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The hotbodies gears were used to replace the pot metal st-r gears they are not needed in the st-rr the strr gears are chromoly and stronger than the st-r gears when you strip a set of gears buy a new bulkhead don't use the old one and shin the gears till they are a little notchy and you should be fine
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Old 03-26-2010, 10:08 AM   #4
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Originally Posted by EugeneJohn View Post
Does anybody have any info on replacing the bevel and pinion gears of a STRR with hot bodies ? I was told there was info on the STRR thread but couldn't find it. I know shimming is crucial for the ring gears not to strip, I am just looking for alternatives, with proper shimming I went through 3 sets last season.
I bought a set the other day and they appear VERY similar. The teeth of the HB gears are cut deeper with a flat on the top verses the Kyosho being sharper. I have one report of this helping another driver, just looking for imput so I can get another season out of the old girl. Any help would be appreciated
(ps- please keep it constructive
or just have houston help you out !!


i will get you dialed in when we get the season going john , use IF112C bulkhead , IS101 and IS102 gears , properly shimmed !!
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Old 03-26-2010, 11:23 AM   #5
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or just have houston help you out !!


i will get you dialed in when we get the season going john , use IF112C bulkhead , IS101 and IS102 gears , properly shimmed !!
i striped a set of st-rr gears because of some huge on power landings at the nor-cal rc track and silver state.

didnt help that my front drive shaft was pretty slopy and the set screw was loose.

its got a completly new front end!
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Old 03-26-2010, 02:41 PM   #6
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Having raced the LSP then going to the ST-R, I do think that changing the entire diff to HB hardened internals and using their ring and pinion helped prolong the life of the diff. I liked the metal that HB used for their ring and pinion as well as the cuts. I pulled apart my old LSP that my g/f's son uses(my original LSP) and the gears were in great condition even through the years of use. If you are looking to extend the life a bit, go with the HB stuff for the diffs. You may have a harder time getting the input gear for the LSP/Lightning series of vehicles. The ones from the D8T will not work unless you change your ST-RR center drive shafts to something else because the D8/D8T input gear is cut down a bit where the Center drive shafts mates to it versus the LSP/Lightning ones. Good luck.
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Old 03-26-2010, 03:35 PM   #7
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Originally Posted by gotspeed_2000 View Post
Having raced the LSP then going to the ST-R, I do think that changing the entire diff to HB hardened internals and using their ring and pinion helped prolong the life of the diff. I liked the metal that HB used for their ring and pinion as well as the cuts. I pulled apart my old LSP that my g/f's son uses(my original LSP) and the gears were in great condition even through the years of use. If you are looking to extend the life a bit, go with the HB stuff for the diffs. You may have a harder time getting the input gear for the LSP/Lightning series of vehicles. The ones from the D8T will not work unless you change your ST-RR center drive shafts to something else because the D8/D8T input gear is cut down a bit where the Center drive shafts mates to it versus the LSP/Lightning ones. Good luck.
Thanks, thats exactly the kind of imput I was looking for, I too liked the machining/ cut of the HB gears, I'm sur I could get the Kyosho stuff to work fine, just a maintenence issue but the HB mod might be that extra bit of strength I'm looking for, the gears seem deeper, more material than the K gears. Has anyone swapped just the gears and still used the Kyosho diff cups or do you need to swap the entire assembly, cups ,spiders and all? it would be cool if you could just swap the bevel gear and leave the rest Kyosho but I doubt it would mesh since the cut of the gears is different.


I know I should do it your way Monte just lookinfor options
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Old 03-26-2010, 03:44 PM   #8
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Quote:
Originally Posted by EugeneJohn View Post
Thanks, thats exactly the kind of imput I was looking for, I too liked the machining/ cut of the HB gears, I'm sur I could get the Kyosho stuff to work fine, just a maintenence issue but the HB mod might be that extra bit of strength I'm looking for, the gears seem deeper, more material than the K gears. Has anyone swapped just the gears and still used the Kyosho diff cups or do you need to swap the entire assembly, cups ,spiders and all? it would be cool if you could just swap the bevel gear and leave the rest Kyosho but I doubt it would mesh since the cut of the gears is different.


I know I should do it your way Monte just lookinfor options
ive used kyosho diff cups in my hot bodies and it works fine. like you said though they problem might be with the input gear mesh.
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Old 03-26-2010, 03:54 PM   #9
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ive used kyosho diff cups in my hot bodies and it works fine. like you said though they problem might be with the input gear mesh.
+1 on the use of the kyosho cups. I've done it that way and it's worked. Also, you might want to consider the HB hardened internal bevel gears to prolong the life of the diff especailly if you are using lighter weight diff oils. If you are thinking about using the hardened gears, I'd just go HB all the way to be safe when it comes to the internal(cross pins, cups, outdrives). You can pick up the diffs from a few sellers on flea bay for around 20 bucks plus shipping per diff from the D8/D8T kits. The diff units themselves are the same, just not the input gears. Then all you gotta find is the input gear, but that's gonna run around 15 bucks or so per piece. Good luck.
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Old 03-26-2010, 04:02 PM   #10
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i use hot bodies spider gears in my strr diff cups without an issue. they are stronger and the almost the same weight as the kyoshos. i have used aftermarket jammin machined aluminum diff cups as well, works great but if you forget to threadlock the bolts, they will back out of the ring gear and make a mess. from what i have seen kyosho, jammin, and hot bodies use the same internals, just different materials. hot bodies out drives seem to wear out faster than the kyoshos. kyosho strr ring and pinions will last as long as shimmed properly and new bulkheads are used.
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Old 06-14-2010, 07:05 AM   #11
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Default ok, so to clarify......

Houston, you said:

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Originally Posted by houston View Post
or just have houston help you out !!


i will get you dialed in when we get the season going john , use IF112C bulkhead , IS101 and IS102 gears , properly shimmed !!
you mentioned the IF112C bulkhead specifically - how is this one different from the IF112B which seems to be teh original one wiith the st-rr?

If I were to go with the hot bodies ring/pinion gears, would I also need to replace the drive shafts going to the front/rear diffs? Someone said that the pinion is cut different, so I am not sure what that means.

Is it possible to just purchase the HB ring/pinion and go with just those two parts on my st-rr?

Also, how many shims are most people using on each side of the diff? I have the thick one and two thin ones on the ring side, and 1 thin on the other side. Does this sound about right?


Also, if I hear that clicking noise under heavy breaking, does that mean that my gears are shot and i should go with a new case,ring, pinion?

thanks for the help guys-
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Old 06-14-2010, 08:05 AM   #12
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You need the LSP pinion but it is too long. You need to cut the end that slides into the rear center driveshaft a few mm's to get a proper backlash setting. Also the HotBodies D8 diffs are not a direct drop in, yes they will drop in but the outdrive cups are too long. I found out the hard way. The HB outdrive cups are a little longer and contact the lower suspension arm when it's compressed. Thus killing your diffs...
Honestly, your best bet is all new housings and kyosho ring and pinions. You can not tell if everything is shimmed properly until you tighten every screw down. There is so much flex in these damn housings it's ridiculous. Also keep some high quality light weight oil on the ring and pinion. I use Royal Purple spray film on mine. It stays on the teeth great.
I went thru this already, all the hot bodies stuff was worse imo.
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Old 06-17-2010, 09:32 AM   #13
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Default Thanks - thats what I needed to know

It sounded like a better route to go HB, but you made some good points -

I'll just keep trying to get mine sorted out - new cases are on the way -

Can you tell me roughly ( i know it is always different for everyone) how many shims is to few or too many?

When you need to re-shim, does that usually mean you need to put another shim on the ring gear side?

I can't tell if I need to shim - if you grab the diff by the cups, the cups can move in and out a bit so you can't tell - you need to grab it by the diff case and wiggle it, but if you screw it down, you can't grab the diff housing

with the car assembled, someone told me that if you hold the diff cup still, then you should not be able to feel any slack when trying to wiggle the drive shaft attacehd to the pinion - is this right, or should there be a littel bit of slack?

Last edited by fixitfreddy; 06-23-2010 at 08:06 AM. Reason: my spell-checker was fired
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Old 06-17-2010, 03:04 PM   #14
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Just the tiniest amount of play possible. Also the pinion needs to be able to slide for and aft in the rear diff, otherwise it will overheat the bearings and melt thru the housing. This is the only r/c I have had be so sensitive to diff shimming. My Jammin truggy diffs were bulletproof.
The way I check it is to first figure out how many shims it needs to remove all side to side play. Then I go after the ring to pinion mesh. I use different size shims so telling you how many and which side to put them on is impossible. I set the mesh, tighten it all down and check for binding. Take it back apart....until it is right. I hold both outdrives with my finger and thumb, then rock the center drivershaft back and forth to feel the play. It's a pain but once you set it, you won't need to change the shim settings.
With new parts I would follow the manual to the letter. It's never lead me wrong. The rear diff for some odd reason is prone to overheating the pinion bearings if you butt the center driveshaft up on the pinion tight. I have to leave 1-2 mm of back and forth play as well as the ring and pinion play needed to make my diffs last. New diff housings do wonders, Kyosho or King Headz needs to make an Al. housing for this rig.
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Old 06-23-2010, 08:04 AM   #15
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Default Thats some good info!

The only part that confuses me a bit, is how you leave some slack in the pinion fore and aft. it seems that there will be some slack in the gear mesh with the pinion fore, and then less aft (or vice versa) which would make your mesh off either when you are accelerating or when you are breaking. you must be talking about a very small amount of slack I suppose.

Do you shim behind the pinion? I think i read pitpop saying that he puts a single shim behind the pinion.
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