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Need new motors? Grind a gearbox? Adding teeth to a pinion?
User avatar
By taz11
#24015
(Edit 4/28/2016) Clarification of #7 vs #7r gearboxes - Thank You Taz!

The newest 7Rs are coming through with white gears. The best way to tell at a glance would be the plastic clips that hold the case together. The #7 has clips and screws, the 7R just has screws. Also, the #7 driver has flat spots inside it and the 7R has a driver that is round on the OD and ID.

The #7and 7R have the same gears inside(Ratio) for all pinions however there are 4 different types of gears depending on production date. The 7R gears only work in 7R boxes. The #7 gears came in 3 versions. The newest had blue colored center gears and they will only work in boxes with blue gears. The all white gears in the #7 come in two versions: New (coarse tooth) and old (Fine tooth) They are all interchangeable as long as they are changed as a set. The final ratios in ALL cases are the same. Ratios are changed by the pinion count only.

PHEW! :roll: :lol: .......easy right? :lol: :lol: :lol:
********************************

The truth of the matter is, there is NO info on the 7R gearboxes in the gearbox thread. We,as a group, know very little about them.


It just so happened that I came across a 16t 7R today! :D :D :D

THE 16T PINIONS ARE THE SAME! 32p. The difference seems to be the plastic collar that centers the motor. It has a different diameter.

The case is similar but does not have the plastic latches. Thay are not numbered anymore.....completely anyway. They are broken down into groups by a dimple on the case (like the old MF gbs) 13-14, 15-16-17,18-19-20, and 21-22-23.

7R 001.jpg
7R 002.jpg


Not sure if they change gear sizes inside to make the 3 pinion sizes fit one case. I only have 1 16t to work with. I can tell you for a fact that the 4 gears inside are different that the old #7. The pin sizes and tooth sizes have been changed. Hopefully more will surface and we can finally get some 7R inside info in the FAQ
Last edited by taz11 on Tue Jun 14, 2011 4:57 pm, edited 1 time in total.
By Ironhanddale
#24538
Does this site or any other have anything along the lines of a gearbox cross reference. Something along the lines of if you have this model of jeep and this model of car the gb's are interchangeable. Be a nice thing for tires also.
User avatar
By chozian
#24555
Ironhanddale wrote:Does this site or any other have anything along the lines of a gearbox cross reference. Something along the lines of if you have this model of jeep and this model of car the gb's are interchangeable. Be a nice thing for tires also.


There is the FAQ Definitive Gearbox Thread at viewtopic.php?f=41&t=103.
By PWDoc
#24834
I have tried and I can tell you that the 16T pinions on the No.7 gearbox DO NOT work in the No.7R 16T gearbox. It will just chew up the plastic gear.
User avatar
By hootienchyna
#24846
PWDoc wrote:I have tried and I can tell you that the 16T pinions on the No.7 gearbox DO NOT work in the No.7R 16T gearbox. It will just chew up the plastic gear.



thank you, i have been saying that they cannot be used with each other but there are some that do not understand what will happen.
User avatar
By taz11
#24855
I had 2 side by side. They are identicle except for the "16" stamp. Mirror image on the teeth. I cannot speak for the other pinion counts, I have not seen them.
By PWDoc
#24858
I have done some further investigation into the No.7R gearbox.

If you have a 16T 7R gearbox you will notice on the case and cover there are a series of numbers "15-16-17" which then has a raised line coming from the center of them pointing at the dimple that was discussed in the first post.

What this means is that the gearbox will accept at 15, 16 or 17 tooth pinion without a problem. This is not done by changing any of the internal plastic gears. All of the internal gears are the same in all of the 7R gearboxes.

The difference comes from the amount of teeth on the pinion, the diameter of the pinion, and the motor location changes BUT only for the 4 different pinion groupings.

The No.7R seems to be much stronger than the No.7 but the 7R uses smaller diameter steel pins than the 7.
By PWDoc
#24860
I know the No.7 and 7R pinions look similar besides the stamp but they are not swappable. The 1st gear will be destroyed if you try to mix up the No.7 and No.7R pinions. I have done it.
User avatar
By taz11
#24862
PWDoc wrote:I know the No.7 and 7R pinions look similar besides the stamp but they are not swappable. The 1st gear will be destroyed if you try to mix up the No.7 and No.7R pinions. I have done it.



Not trying to be a non-believer, but I have matched them up myself. This is one of those things I am going to have to try myself before I believe. I see no reason they will not work. No disrespect intended, just not buyin' it. I tend to be stubborn that way.
User avatar
By taz11
#25791
Well, I can't leave this alone. the curiousity wont let me. I spent the last few days trying to figure how this would not work.


Here is my theory:

If PW now uses three different pinions in one case, the three pinions have to change in some way. I suspect that about 1/3 of the pinion sizes will interchange with the old #7 32 pitch gear, the others will not. I am positive (in my mind) that the 15-16-17 7R will accept a 32 pitch 16t pinion. There is only one way to tell.

The goal here is not to disprove anything about stock motors. If you are using stock motors.... USE THE PROPER MOTOR AND GEAR! There is no reason not to. The purpose of this experiment is to determine when and if we can use aftermarket motors and pinions in a 7R gearbox. And......if so, which ones. It is only a matter of time and #7s will be hard to find....like the MF gearbox of today. We have to figure out how to work with the new stuff. Honestly, the 7R looks like a much better GB than the 7.
User avatar
By taz11
#25792
Here is the test vehicle. I searched my active duty sheds and decided this was the best choice.

7R EXP 002.jpg


I will be removing the 21ts and putting back a stock 16t #7 and a 15-16-17 7R fitted with a #7 motor w/16t gear (32p)
I will be adding 6 volts to get the speed back.

7R EXP 001.jpg
Last edited by taz11 on Tue Jun 14, 2011 5:28 pm, edited 1 time in total.
User avatar
By dozer
#25800
taz11 wrote:
PWDoc wrote:I know the No.7 and 7R pinions look similar besides the stamp but they are not swappable. The 1st gear will be destroyed if you try to mix up the No.7 and No.7R pinions. I have done it.



Not trying to be a non-believer, but I have matched them up myself. This is one of those things I am going to have to try myself before I believe. I see no reason they will not work. No disrespect intended, just not buyin' it. I tend to be stubborn that way.


I know what you mean. when visually looking at it part of your head is saying "they didn't try it right, my way will work."
but more often than not ......
User avatar
By taz11
#25810
Dozer....you may be 100% correct....... I can't imagine a plastic gearcase being completely acurate to start with. If it matches visually...it should work. I wish I could show you guys a pic.........my camera just goes to BLURRRRR on close-ups. The 16t is the same gear....... :?:
User avatar
By taz11
#25826
They're in.........

Runs like a champ......all we can do now is wait and see what happens. :? :? :?

7R EXP 005.jpg
User avatar
By taz11
#26470
Update...... A few hours of run time in the books.....so far so good. No funny noises or indications of pending failure. I will update this post as new info becomes available.
User avatar
By dozer
#26777
taz11 wrote:Dozer....you may be 100% correct....... I can't imagine a plastic gearcase being completely acurate to start with. If it matches visually...it should work. I wish I could show you guys a pic.........my camera just goes to BLURRRRR on close-ups. The 16t is the same gear....... :?:


Ha ha I was kind of making fun of guys like us. We just have to try it our way. But sometimes they other guy did miss something.
User avatar
By sprintracer53
#27461
Any updates on the testing?

My son has an Artic Cat (Monster Traction with 17T) that he rides in the yard. I upgraded it to 18V and one of the motors burnt up. This weekend I installed 2 new HPI GT550's with heatsinks and fans. It ran great for about 20 minutes until one of the gearboxes melted down. The small shaft which holds the spur gear driven by the pinion gear was spinning. This caused the cases to melt around the shaft and the hole in the spur gear also melted.

I read that the Jeep Huricane has lots of problems with the gearboxes and I was wondering if the Artic Cat uses the same ones? I was hoping to buy 2 new 7R gearboxes (17T) and install the GT550's, with aftermarket 32 pitch metal pinions. I did read that the plastic spacer that centers the motor is different for the 7R vs. the 7, but I have the means to fabricate the spacers.
User avatar
By Hobbymasters
#27491
I can tell you that so far we have NOT HAD ONE SINGLE 7R GEARBOX FAILURE come through our facility. Besides the gears being beafier, you can also see that the white plastic that used to grab the driver hub has been replaced by an orange plastic one twice as thick (pictured above). This means no more stripped out driver hubs / inner rims. If you destroy an old gearbox you will absolutely want to invest in a 7R and matching 7R motor, especially if you are modding. BTW - the final drive ratio of the 7 and 7R gearboxes are the same.
User avatar
By taz11
#27550
I don't know about the 17T. The 16t is still running strong with no issues. If my theory is correct (I feel strongly that it is) the 32p 17t pinion will not work but the 16t will.
User avatar
By sprintracer53
#27587
taz11 wrote:I don't know about the 17T. The 16t is still running strong with no issues. If my theory is correct (I feel strongly that it is) the 32p 17t pinion will not work but the 16t will.

So if I understand you correctly, your thought is that the diameter of the plastic spacer that goes on the motor changes the position of the motor to account for the different pinion sizes (15, 16,17) with the gearbox?

However, if you are confident that a 16 tooth 32 pitch pinion works, can we assume then that the gearboxes are 32 pitch?
User avatar
By taz11
#27595
sprintracer53 wrote:
taz11 wrote:I don't know about the 17T. The 16t is still running strong with no issues. If my theory is correct (I feel strongly that it is) the 32p 17t pinion will not work but the 16t will.

So if I understand you correctly, your thought is that the diameter of the plastic spacer that goes on the motor changes the position of the motor to account for the different pinion sizes (15, 16,17) with the gearbox?

However, if you are confident that a 16 tooth 32 pitch pinion works, can we assume then that the gearboxes are 32 pitch?



Not exactly. The ring is a different size to prevent someone from installing the motor in the wrong case. I don't use those rings with aftermarket motors since they dont fit on most of them. If the bolt holes are tight they are not nessasary. The rings are "idiot proofing".

The theory is that the middle tooth count in each gearbox "group" is 32p. The high and low tooth gears must be altered in someway to make the diameter of the gear the same on all 3 since the motor does not move. I may have a few "borrowed" 7Rs lined up for inspection to prove or disprove this shortly. For now all I can say 100% is that the 16t is a 32p gear and it has been working flawlessly since installed.
User avatar
By sprintracer53
#28368
Thanks Taz11. Your answer regarding changing of the pitch size to compensate for the pinion sized explained the issue.

Does anyone know about the 18-19-20 gearboxes? Is the 19T 32 pitch also like the 16T? So my 3 options are:
1. Buy the original #7, 17T gearboxes and blow them up again.
2. Buy a new 7R grearbox, but in 16T instead of 17T. How much difference will it make?
3. Buy the new 7R gearbox in 17T, along with stock 17T motors and try to take the pinion off the stock motors to put on the GT550's. Anyone have any luck with this?
Sorry, not trying to hijack this thread, but I'm trying to get the P.W. fixed and back on the road for my son.
User avatar
By taz11
#28371
Yes, this can be done...but it takes a little skill and patience. You would need to file a flat spot on the gear towards one side. Then drill and tap it for a set screw. Its not hard but you need to be cautious not to take away to much of the gear teeth and you need to be somewhat precise on your drilling.
User avatar
By taz11
#28855
It has been a rough week for playdates....kids are out of school and I swear they all live here during the day. As of this morning I have 4 vehicles in "sick bay". 3 with bad gearboxes and one peg that lost all forward speeds :evil: .

Well today the #7R test car went BANG! Catastrophic gearbox failure.......

Here is the kicker...........The #7 blew up! The "won't work" 7R with the #7 pinion is still going strong with no funny noises. When I change the other GB I will pull the motor out of the 7R and inspect the first gear.


As for the "loner" gearboxes.......I was able to briefly inspect the pinions the other night before I had to return the vehicles. The are proving my theroy so far. I looked at a 15t from a Brute Force and a 17T from an Artic Cat. Since you can't see a dang thing in my attempted close up shots I will decribe them the best I can.

The 15T is most definately a different pitch. I would say it is very similar in appearance to the #3 pinions. No doubt in my mind that this will NOT work with a 32p 15t pinion.

The 17T is interesting. It looks like a 32p pinion that someone stuck on a grinding wheel and ground off 1/32 of an inch all the way around to make it smaller. The OD edges of the teeth are actually flat. It still appears to be 32p. I would have to say that a 17t 32p gear could work in a used gearbox, but would probably bind in a new GB with no slop in the gears.


For now we will leave it at
13t...NO
14T...Unknown
15T...NO
16T...YES
17T...NO
18T...Unknown
19T...YES
20T...Unknown
21T...Unknown
22T...Unknown
23T...Unknown
Last edited by taz11 on Sun Jun 17, 2012 7:18 am, edited 4 times in total.
User avatar
By taz11
#29035
I got the old #7 swapped out last night......Yikes! The first gear, pin and case where fused together :shock: :o :? I think bricklayer99 cursed me after I told him I had never had that happen before.....LOL

Anyway....The 7R with the #7 16T pinion looks good. I put in a replacement #7 and the test continues.
User avatar
By taz11
#29039
hootienchyna wrote:how many volts ya got running taz


18volts
By Jeffreykdc
#29044
Theory:

If the 16t 32p pinion works in the 15-16-17 7R gb then...
the 19t 32p pinion will work in the 18-19-20 7R gb and..
the 22t 32p pinion will work in the 21-22-23 7R gb

there is a system or code to be broken here and it is not going to be too complex because complexity equals added manufacturing costs.

I believe that it is cheaper for them to produce fewer different gearboxes and to slightly modify the pinion gears.
User avatar
By taz11
#29045
Jeffreykdc wrote:Theory:

If the 16t 32p pinion works in the 15-16-17 7R gb then...
the 19t 32p pinion will work in the 18-19-20 7R gb and..
the 22t 32p pinion will work in the 21-22-23 7R gb

there is a system or code to be broken here and it is not going to be too complex because complexity equals added manufacturing costs.

I believe that it is cheaper for them to produce fewer different gearboxes and to slightly modify the pinion gears.



That's what i'm thinking.
By treebeme
#29089
That just doesn't sound right. The number of teeth is somewhat irrelevent. It's the diameter of the pinion that really matters. The tooth count just allows us to do some math to calculate gearing within a specific pitch. So whether the pinion had 15,16 or 17 teeth, it would have to be roughly the same diameter to reach the first gear in the gearbox and result in the same gearing no matter how they manipulated the pinion gear.
User avatar
By hootienchyna
#29095
treebeme wrote:That just doesn't sound right. The number of teeth is somewhat irrelevent. It's the diameter of the pinion that really matters. The tooth count just allows us to do some math to calculate gearing within a specific pitch. So whether the pinion had 15,16 or 17 teeth, it would have to be roughly the same diameter to reach the first gear in the gearbox and result in the same gearing no matter how they manipulated the pinion gear.


if you take a 7r that uses 15,16 and 17t pinions the motors all mount in the same place, all they did was change the diameter of the pinions to be all the same and kept the same pitch.

which means that of the 3 the 16 matches up using a 32p, the 15 and 17 are different diameters than the #7 motor pinion.
this is why you can use 1 gearbox for 3 tooth counts.

it doesnt matter if the pinion is an inch or 5 inches in diameter the pitch will stay the same just deeper or shorter grooves
By bricklayer99
#29107
The motors on the old 7 are all in the same place no matter the pinion count. They molded the hole for for the first gear in in different spots to correspond to The pinion being used. Look at the picture at the beginning of the post. The pinion groups have lines showing where the center lines where the pin for that group will be. So they only have to produce four different cases instead of twelve.
Last edited by bricklayer99 on Mon Jul 11, 2011 4:23 pm, edited 1 time in total.
User avatar
By hootienchyna
#29116
bricklayer99 wrote:The motors on the old 7 are all in the same place no matter the pinion count. They molded the hole for for the first gear in in different spots to correspond to The pinion being used. Look at the picture at the beginning of the post. The pinion groups have lines showing where the center lines where the pin for that group will be. So they only have to produce four different cases instead of twelve.



all those lines tell you on the 7r is the tooth count for that gearbox, has nothing to do with the pin that holds the gear. i can show you a pic of that pin hole that does not change in the 15,16,17 gearbox
Last edited by hootienchyna on Mon Jul 11, 2011 5:00 pm, edited 1 time in total.
User avatar
By taz11
#29121
It is motor position that changes. If you ever look at the inside of the case you will see that the motor bolts pass through an oblong block. The block is oblong so they could drill the motor holes where ever they needed. I suspect there is only one case. They put it in a jig to determine the drill location and the motor hole and bolt holes get drilled at the same time by a fancy drill press.



Treebeme.... I hear ya....but not totally true. If it where a pulley or a wheel you would be 100% correct. the diameter would determine the speed. In the case of the gear the diameter only determines how the tooth meshes. It still runs one tooth to one tooth so the number of teeth determins speed no matter how big or small the gear.

This shows us how much tolerance there is in these gbs.
By bricklayer99
#29124
ive gotta disagree. i just layed out a 15, 16, 19 and a 21. all 4 the motor is in the same spot, the first gear in is different. The pin on the 7 r won't change in that group of three(15-16-17) but I bet its farther away for (18-19-20) or closer for (13-14-15)
Last edited by bricklayer99 on Mon Jul 11, 2011 6:10 pm, edited 1 time in total.
User avatar
By taz11
#29144
bricklayer99 wrote:ive gotta disagree. i just layed out a 15, 16, 19 and a 21. all 4 the motor is in the same spot, the first gear in is different. The pin on the 7 r won't change in that group of three(15-16-17) but I bet its farther away for (18-19-20) or closer for (13-14-15)



You know...it's almost 11 and your going to make me go out and look aren't you........LOL
User avatar
By taz11
#29146
Hey guys... I think bricklayer is right. I just pulled a 15t 16t and 21t cases out of the bin. It sure looks like the first pin is moved. I stand corrected......I guess that will teach me to look instead of taking someones word for it :oops: Bricklayer comes through again....i'm going to have to step asside soon....LOL. :P


Nice catch.


If and when I find some 7Rs in those counts I will check. (Yes...I will use my eyes this time) :oops:
Last edited by taz11 on Mon Jul 11, 2011 9:06 pm, edited 1 time in total.
User avatar
By taz11
#34157
I blew up a motor in the 7R yesterday. I swapped in another #7 motor to continue the test. The first gear looks fine.



I also got to compare a 19T 7R pinion to a 32p pinion. It looks Identical.........Looks like my theory may be correct. I have not tested this gear but going by the appearance of the gear and the success of the 16T test. I'd say it is safe to use a 32p pinion in a 19T 7R.
User avatar
By taz11
#38580
Updated the chart and copied it here for easier reference:

For now we will leave it at
13t...NO
14T...Unknown
15T...NO
16T...YES
17T...NO
18T...Unknown
19T...YES
20T...Unknown
21T...Unknown
22T...Unknown
23T...Unknown

The 13T is by far a no go!......Hopefully that means a 14T will work :? ;)
Last edited by taz11 on Sun Jun 17, 2012 7:18 am, edited 1 time in total.
By surlyboy
#44646
Hey All,
Been reading the research (thanks guys) and was wondering if anyone has tried the 7R 19t GB with an aftermarket motor and 19T pinion yet? As that is what Im looking at for our Extreme Machine. We need more speed. I know Taz thinks the 19t would work but would like to be sure before I pay for shipping to Oz.

Traxxas Titan 550 Motor 21T
Traxxas Titan 550 Reverse Rotation Motor
Traxxas Pinion Gear 32P 19T

I know I could stick with the 16tooth setup easily but dont know if the increase in speed would be enough to satisfy my Evil Kneivel 4yr old who wants to keep up with a Gaucho Grande.

Also from what I've read would this # 7R Gearbox (15 Tooth Black) Part Number: 00968-2819
accept a 16t pinion? They're half the price of the 16t ones (that have the same part No. 00968-2819)
Cheers
Andy
User avatar
By taz11
#44651
surlyboy wrote:Ok scratch that last question... just found the question answered in another thread! Basically no chance! No wonder they're half price!



Yes....

I'm not sure about the part number I'll have to check.

anyway...a 15t, 16t, and 17t 7R uses the same gearbox. So a 16t 32p pinion will work in all 3

As for the 19t ....I have compared the pinion gears and they are identical. I have not tested the 19t in a vehicle but it matches the 32p gear just like the 16t that I am testing. That is still going strong BTW.

Do you have a link to the page with the price difference?
Last edited by taz11 on Sat Nov 19, 2011 8:14 am, edited 2 times in total.
By surlyboy
#44736
That's what I originally understood from the discussion, but was hoping to hear anyway... thanks! I will be ordering some of these then if you think they will accept a 16t pinion. http://www.ereplacementparts.com/-7r-gearbox-p-628555.html
Its a bit tricky down here in Oz as our EM model no. doesnt show up anywhere 74794 9564 so I have been going off the US parts diagrams for the 74790 or 74793. I already have 16t GBs Im just hoping I will see a decent increase in speed with the 550's and maybe 18volts.
User avatar
By taz11
#44737
I would grab them real quick. They are not supposed to be selling them to the public. If PW finds out, they will put the Kabosh on it real quick!
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