Diff shimming 101

[Jeremy]

scroll down a bit and there is a good guide to shimming your diffs!!!

Source: http://ashburg.com/?cat=8

How to Rebuild, Shim, Strengthen and Race Lube an HPI Savage X Differential
by admin @ 10:14 pm. Filed under Gear Ratio Tips, RC Events in South Carolina, HPI Savage X, HPI HellFire

Stop the presses…since writing this up, I have learned a great deal about shimming savage differentials. I learned, for one, that the procedure described below is INcorrect. The small shims shown do absolutely nothing for the issue at hand, which is to #1) tighten up the play inside the diff cup and #2) tighten up the play with the crown gear and the pinion gear.

I highly recommend that you check out this article for the proper procedure on how to shim savage differentials: Here is the link to the article

Just keep that in mind when you read this…

How to Rebuild, Shim, Strengthen and Race Lube a Savage X Differential - Using an Aluminum Differential Housing, axle Shims, O rings, and the Differential Lube of your choice…

If you don’t want to end up like I did last weekend, busted up with a stripped out spider gears in the rear end differential, you might want to strengthen up your differential. Here’s How I did it…

Here’s My Savage X after 10 minutes on a nice mud track - the stock, plastic differential coupled with a bad gear mesh did a real number on the rear end and left me with no truck to race…
http://www.ashburg.com/images/IMGP4994.JPG

This is the culprit that brought down my Savage:
http://www.ashburg.com/images/IMGP5028.JPG
The first thing I did when I got home was to get on the computer and start ordering parts. I was determined that this would not happen again. If it does happen again, I’m going to an Ofna Rear End, which is apparently very very strong.

Here is a list of the parts that you will need:

1) HPI Savage 4-Gear Differential Gear Set (you’ll need one cup for front, one for rear)

2) Nova 7075 Aluminum Alloy Differential Cup for Savage

3) Mugen 5,000wt Silicone Differential Lube (for Rear differential)

4) Mugen 7,000wt Silicone Differential Lube (for Front differential)

5) Mugen 50,000wt Silicone Differential Lube (for coating the outside of the differential assembly)

6) BRP Axle Shim .250x.309x.014″ (get 2 sets)

7) HPI O-Ring 5×8x1.5mm Savage 21 (6) (get 2 sets)

8) HPI O-Ring 6×9.5×2mm Black Savage 21 (8) (for the cups where the dogbone goes in, for cushion)

9) Great Planes Pro Threadlocker

10) For Differential Gaskets, I just used the old gasket, putting a thin layer of Permatex Silicone Gasket Maker there. If you need to replace your differential gaskets, Ofna makes a compatible set - Diff Gaskets

Below are some pictures of the assembly. Also, here are 2 videos showing you the point of all this:

1) The fact that the stock plastic differential flexes under load and
2) What is meant by “shimming” the differential (I know it doesnt work right now, fixing it)

Here’s that stock plastic differential cup:
http://www.ashburg.com/images/IMGP5033.JPG

http://www.ashburg.com/images/IMGP5133.JPGhttp://www.ashburg.com/images/IMGP5132.JPGhttp://www.ashburg.com/images/IMGP5131.JPG
http://www.ashburg.com/images/IMGP5129.JPGhttp://www.ashburg.com/images/IMGP5128.JPGhttp://www.ashburg.com/images/IMGP5126.JPG
http://www.ashburg.com/images/IMGP5125.JPGhttp://www.ashburg.com/images/IMGP5124.JPGhttp://www.ashburg.com/images/IMGP5122.JPG
http://www.ashburg.com/images/IMGP5121.JPGhttp://www.ashburg.com/images/IMGP5120.JPGhttp://www.ashburg.com/images/IMGP5118.JPG
http://www.ashburg.com/images/IMGP5117.JPGhttp://www.ashburg.com/images/IMGP5116.JPGhttp://www.ashburg.com/images/IMGP5115.JPG
http://www.ashburg.com/images/IMGP5114.JPGhttp://www.ashburg.com/images/IMGP5113.JPGhttp://www.ashburg.com/images/IMGP5112.JPG

A few Notes on assembly:

On the Savage X, the differential is very easy to remove. All you have to do is remove 6 screws, the lower hinge pins, and pull off the differential cover. After you have the diff out, spray it down and clean it up some with some carburetor cleaner. Take it apart, noting how it goes back together!

Once you have it apart, clean up the inside, again, using carburetor cleaner or whatever works for you. Remove all cleaner residue before you go to put this back together, it might break down your diff lube if you don’t.

Take the diff access set looking screw out of the side of your stock plastic diff cup, it’s on the side of the cup. Transfer that screw to the new alloy aluminum diff cup AFTER you put the shims and the inside retainer pin on the shaft. Replace the inside o ring with a new one. Remove the old bearing from the stock plastic diff cup and transfer it to the new aluminum diff cup.

Put the entire gear assembly together DRY a few times, noting any play in the shafts going into the differential. You want a few thousandths of an inch play there. You want a Little play, but want to avoid too much. You are trying to get those spider gears inside to mesh as good as possible. Shim up any play with the tiny axle shims you bought.

When the play is all shimmed up right, put in your hex screw (set screw looking screw) into the side of the new aluminum diff housing. Pour your differential lube into the cup and remember that the bevel gear will displace some of that lube…leave some room at the top.

Put the whole assembly together, locktight the 4 screws, and cinch it down. Note: you can’t use the stock 4 screws, you will be using 4 diff cup screws that come with the aluminum diff cup.

Coat the outside of the assembly with 50,000 weight Lock Lube to catch dust. Also, put some 50k lube around and near the bearings to catch any dust and dirt that would want to enter into the assembly. You will be servicing this differential after every gallon of fuel. Put the entire assembly back into the housing, throw your 6 screws and 2 hinge pins back in and get ready to LIGHT UP THE TIRES because you’re going to be transferring all of that torque to the wheels WAY more effectively now.

FYI, RTR, out of the box, there is virtually NO lube in the differentials…

[]-[0pa]0ng]

Guys when you come across and find a great thread be sure to 1 Rate it and 2 leave a Rep for them. Who knows someone may do the same for you.


What I did and learned from. I just rebuilt my diffs filled them up w/ 7 in the front and 10 in the rear. I few days later they leaked and bad. What I didn't change out was the old O-rings. Bad mistake. Always change them out for a new set. I didn't shim the diff axles and noticed there was some play, too much play when they slide back and forth. So I will buy more o-rings and 4 new diff axles. They diff axles I have are around 4 yrs old. Plus the BRP shims will take care of the slop w/ the axles.

The one thing I didn't see in the Article was using Ofna diff shims behind ea. spyder gear in the Nova cups. That much I did and seems to fit perfectly. That part number is listed below. I will also be using the 50 thous as mentioned in the article.

SMF diff shims (http://www.smfstore.com/product_info.php?cPath=31_91&products_id=1287)

SMF diff gaskets (http://www.smfstore.com/product_info.php?cPath=31_91&products_id=1071)

[Jeremy]

Thanks you for the links to the gaskets and shimms !!!! didn't think of posting that....

Hop bye O-rings do u meen the o ring in the 43 tooth ring gear ? I overlook replaceing that should I ? (it never looks bad I dont think)

[]-[0pa]0ng]

If an O-ring isn't flexable or feels hard not as plyable time to replace. Good chance that they will leak. Mine just so happend to leak fast enough that I caught it in time prior to closing it all up in the gearbox. Plus I think my axles have seen a few miles. SJ- Yes replace the one in the 43 th gear and the one inside the diff cup.

[X25]

thanks for the info SJ very good find

[Jeremy]

I noticed the link wasn't working so here is a differet one

DIFF SHIM!! (http://www.midmad.com/ek4/shim/ek4shim.html)

[ShiftPoint]

-[0pa]0ng;17416']Guys when you come across and find a great thread be sure to 1 Rate it and 2 leave a Rep for them. Who knows someone may do the same for you.


What I did and learned from. I just rebuilt my diffs filled them up w/ 7 in the front and 10 in the rear. I few days later they leaked and bad. What I didn't change out was the old O-rings. Bad mistake. Always change them out for a new set. I didn't shim the diff axles and noticed there was some play, too much play when they slide back and forth. So I will buy more o-rings and 4 new diff axles. They diff axles I have are around 4 yrs old. Plus the BRP shims will take care of the slop w/ the axles.

The one thing I didn't see in the Article was using Ofna diff shims behind ea. spyder gear in the Nova cups. That much I did and seems to fit perfectly. That part number is listed below. I will also be using the 50 thous as mentioned in the article.

SMF diff shims (http://www.smfstore.com/product_info.php?cPath=31_91&products_id=1287)

SMF diff gaskets (http://www.smfstore.com/product_info.php?cPath=31_91&products_id=1071)

Thank you, I had no idea about the rep points (i guess if I opened mt eyes and looked) I thought they were something the mod's gave. I owe a bunch of you guys some rep points, I will go back to the old threads and take care of it.
Thanks for the links too!

SJ, thanks for the info, here's another thing I had no idea about the diff shimming!

Slowly but surely I'll get the hang of it,


Thanks,

John

[Shaun]

Great Info Guys!! Real Easy To Understand!! And Yes Heres Some Reps!! I Always Give Out Reps To Whoever Helps Me Or Someone I Know! IM NOT A "NEWBIE" BUT I STILL FIND MYSELF GOING BACK TO THE OLD THREADS FOR HELP!! THANKS SJ

[Jeremy]

Thanks for any rep ... also Iam posting this link to another thread I have made .

It gives links to all the shims you need to shim those diffs


http://www.hpisavageforum.com/forums/showthread.php?t=3263

[ShiftPoint]

-[0pa]0ng;17416']Guys when you come across and find a great thread be sure to 1 Rate it and 2 leave a Rep for them. Who knows someone may do the same for you.


What I did and learned from. I just rebuilt my diffs filled them up w/ 7 in the front and 10 in the rear. I few days later they leaked and bad. What I didn't change out was the old O-rings. Bad mistake. Always change them out for a new set. I didn't shim the diff axles and noticed there was some play, too much play when they slide back and forth. So I will buy more o-rings and 4 new diff axles. They diff axles I have are around 4 yrs old. Plus the BRP shims will take care of the slop w/ the axles.

The one thing I didn't see in the Article was using Ofna diff shims behind ea. spyder gear in the Nova cups. That much I did and seems to fit perfectly. That part number is listed below. I will also be using the 50 thous as mentioned in the article.

SMF diff shims (http://www.smfstore.com/product_info.php?cPath=31_91&products_id=1287)

SMF diff gaskets (http://www.smfstore.com/product_info.php?cPath=31_91&products_id=1071)

hI,

thanks for the links, I have never done this before and am wondering if the washers and gaskets from the links , well if I buy one package of each is that enough to do one diff or do I need other parts too? Are is one package enough to do one truck or is that just one washer for one spot on 1 diff.

Thanks,

Jhn

[Jeremy]

The shims that }{op posted I think there are for the inside of the diff cup. (for bevel gears ) not sure but I think that's what they are for .. anyway there will be enough gaskets there for 3 (front and rear diff rebuilds)

But the links I posted were for outside of the diff cup .. IMO where you need it most ..

[ShiftPoint]

The shims that }{op posted I think there are for the inside of the diff cup. (for bevel gears ) not sure but I think that's what they are for .. anyway there will be enough gaskets there for 3 (front and rear diff rebuilds)

But the links I posted were for outside of the diff cup .. IMO where you need it most ..


Hi,

Thanks again, I didn't see that link cause someone knocked on the door right as I was posting asking about the links from Op,

Thanks again, I ve been worried about gettng that done since reading about it.

John

[dunerdog94]

Just so you guys know, the savage X has the plastic diff cups, but the 4.6 X has the alloy ones. Don't know if that will help.

-dunerdog94

[ikesavage]

Does anyone have a part number for the savage X stronger diffs I am checking all my diffs and other things and noticed that my duffs are plastic. Also grease or diff oil and if so what is the best weight and yes I did see that you used oil at the top of the page I just wanna get everyones input.

[GOLFVR6]

As far as I can see there is no repair here .You have shimmed the diff shafts , however the problem is the insufficient gear tooth contact in the diff between the diff gears 86023a ( large gears ) and 86032b ( small gears ).
This is a factory fault and HPI IS NOT TAKING RESPONSIBILITY TO REPAIR IT !!!!!!!!!
The Savage used to be the most populare monster where I come from but now everyone is racing Revo's and now I know why !!!

[Double-O-Zilch]

Blasphemy! I found following these methods to fix my diffs. I haven't had a problem with them since. May not be a "repair" but it definetly works.

[Crash]

As far as I can see there is no repair here .You have shimmed the diff shafts , however the problem is the insufficient gear toth contact in the diff between the diff gears 86023a ( large gears ) and 86032b ( small gears ).
This is a factory fault and HPI IS NOT TAKING RESPONSIBILITY TO REPAIR IT !!!!!!!!!
The Savage used to be the most populare monster where I come from but now everyone is racing Revo's and now I know why !!!

do some research and you will find the savage is the badest basher you can buy. Yes you do have to do some upgrades to make it bullet proof.

in ending, SILLY RABBIT TRAXXAS IS FOR KIDS!

[GOLFVR6]

I own 2 and if the diff packs up after 1 1/2 fuel tanks on a flat surface and whilst treating the vehicle with care as I am not yet used to its handling , it is a BABY !!!!!
I am most definitely not new to the Rc game , I have owned 4 GS RACING VEHICLES ( 2 BUGGIES AND 2 TRUGGY ).Never have I have a diff problem !!!

[GOLFVR6]

The Savage has the lowest selling rate where I come from .

[Jeremy]

The Savage has the lowest selling rate where I come from .

Did you join the forum to talk crap?
The savage in stock form is not a racer.. we all know that ..

[Crash]

The Savage has the lowest selling rate where I come from .

Thanks for the info.
now get some air to that head.
http://i216.photobucket.com/albums/cc280/wheelieking101/093020Head20of20Infinity20Broadcast.jpg

[Shaun]

As far as I can see there is no repair here .You have shimmed the diff shafts , however the problem is the insufficient gear toth contact in the diff between the diff gears 86023a ( large gears ) and 86032b ( small gears ).
This is a factory fault and HPI IS NOT TAKING RESPONSIBILITY TO REPAIR IT !!!!!!!!!
The Savage used to be the most populare monster where I come from but now everyone is racing Revo's and now I know why !!!

well thats something new to me as hpi has always stood behind there products when i first got my sav x it was one out of the old batch so it didnt have the alum diffs and stuff in the box as upgrades which the newer ones do so i emailed them and no lie less then 2 weeks later i got the upgrades FREE of charge and a spare spur gear (25 slipper) so all my dealings with hpi have been great!! and as far as racing i would probabally go with a revo too, savages were never made for racing really THERE BASHERS so comparing the two in racing makes no sense to me!!

[JohnH]

Hmmmm........ Well I beat the hell out of my Savage and sorry guys you got to do some work but you can make a Savage a racer. As far as shimming your diffs I have no clue what you are talking about but when you put the shims on the diff cup or the ring gear you are sliding the diff either closer to the pinion or away from it. This is called shimming a diff. The biggest reason for diffs failing are do to the fact of the bearing races separating. This in turn puts a lot of play on the diff under load. Then you get a clicking sound then the wheels don't load up......so on....so on.....so on............. When you do a diff shim you are adjusting where the diff sits do to how many shims you put on either side or in some cases both sides of the diff to make it stand off from the bearings. the bearings sit in the pockets and the diff is then unable to slide back and forth on the ******* that the bearings ride on. simple. But hell I don't know anything............................

[chrisw]

hey golf we all know the savage is not made for racing ,i have a 25 and blew my diff up ,i put alloy cups and 4 bevel gears in did a little shimming and i beat the crap out of it and put a gal of fuel so for and no problems ,i want to see a t maxx or revo get 10 to 15 feet of air land it and drive away,my friend has a t maxx and he is fixing it more then he drives it ,just remember a stock savage is not made for racing it is made to be driven hard

[Double-O-Zilch]

I own 2 and if the diff packs up after 1 1/2 fuel tanks on a flat surface and whilst treating the vehicle with care as I am not yet used to its handling , it is a BABY !!!!!
I am most definitely not new to the Rc game , I have owned 4 GS RACING VEHICLES ( 2 BUGGIES AND 2 TRUGGY ).Never have I have a diff problem !!!
Sounds to me like someone is blameing their wrenching ability on the savage. Have you even addressed the problem, or are you throwing parts at it and doing nothing?

[Jeremy]

Hmmmm........ Well I beat the hell out of my Savage and sorry guys you got to do some work but you can make a Savage a racer. As far as shimming your diffs I have no clue what you are talking about but when you put the shims on the diff cup or the ring gear you are sliding the diff either closer to the pinion or away from it. This is called shimming a diff. The biggest reason for diffs failing are do to the fact of the bearing races separating. This in turn puts a lot of play on the diff under load. Then you get a clicking sound then the wheels don't load up......so on....so on.....so on............. When you do a diff shim you are adjusting where the diff sits do to how many shims you put on either side or in some cases both sides of the diff to make it stand off from the bearings. the bearings sit in the pockets and the diff is then unable to slide back and forth on the ******* that the bearings ride on. simple. But hell I don't know anything............................

Thanks for the detailed info John :resp:

[GOLFVR6]

Thank you CHRIS ! At last someone has given me a solution . Replacing parts left right and centre does not make sense to me . Once again thank you CHRIS I will invest in some alloy diffs etc !

A solution to a problem at last ! Wonder why HPI could not give me this info ?

[JohnH]

"Once again thank you CHRIS I will invest in some alloy diffs etc !"
I think that was said several times. Just by putting alloy diff cups in will not solve the problem if you do not shim them. and depending who you go with if the inner race gets hot enough it will seize to the cup or the ring gear. Then you will have to carefully cut it off or replace the parts. That is why HPI makes a diff shim kit. HPI part # 86827
or HPI part #Z897

[Shaun]

If the Savage cannot be raced , why develope a 3 speed gearbox ( notice " speed " ) , why low the chassis height of the X and why advertise the 4.6 ss ( when it came out ) on a race track ( again notice" race track " ) .

Anyway I have put the Savage back together and as son as the weather permites I will take her out for a spin .

Well thanx for now .

funny, i dont remeber saying it CANT be raced i just sad they arent really made for racing as stock!! i wont argue the fact that theres savage racers but it takes a little time and effort to get them to race quality as there mainly bashers!! we were trying to help and all we get is attitude, u should of known coming to a HPI forum wasnt really a great place to shoot down the savage:duh: and your asking sj if he's learned how to read? have you learned how to show someone thats trying to help you the respect they deserve? I THINK NOT!!!!!!!

[chrisw]

I think i said the same thing as everyone else ,dont thank me thank everyone

[GOLFVR6]

Well Chris you where the only one that made sence to me .
What can I say ?
Flat out racing , ye !
Golf

[Jeremy]

Alloy diff cups and shimming the diffs are 2 different things .. We shim the diffs to eliminate slop between the ring and pinion gears.. The stock savage bearings are A HUGE cause to why the diffs need shimmed.. There not a quality bearing...

[Double-O-Zilch]

Try asking a question next time and showing a little respect. The people on here are awesome. I can say from personal experience that they will bend over backwards for all the members. If you did not intend to come off like a jerk, then say so. I do beleive you owe someone an apology.

[Crash]

well said, parker

[GOLFVR6]

I appologize .
Golf

[THE PIPER]

Alloy diff cups and shimming the diffs are 2 different things .. We shim the diffs to eliminate slop between the ring and pinion gears.. The stock savage bearings are A HUGE cause to why the diffs need shimmed.. There not a quality bearing...

Hi Jester, I'm in the midst of getting my cups from Nova and still trying to figer out how to shim. I've read all the posts and still cant picture it. I feel like a idiot. Do you have pictures on how to do it? Cheers!:cheers:

[Crash]

piper the first post has pics

[THE PIPER]

Also the extra parts that I need, you posted earlyer in the year. does it work for the savage 4.6? Cheers!

[THE PIPER]

piper the first post has pics

HI Crash. I was looking at that. I didn't see the shims. Now are they small looking Orings? where do we put them. In the picture all I saw is the cup and oil being added with the spider gears. I might just be blind. Looking left to right from the first post what picture is it? Cheers!!

[Jeremy]

I thought I would post some links to the proper diffs shimm sizes you need in shimming the diffs..

ofna 13x16 shims CLICK ME (http://www2.towerhobbies.com/cgi-bin/wti0001p?&W=000426515&I=LXCWP5&P=K)

These go on the 43tooth and diff cup





hpi 8x10x0.2 shims CLICK ME (http://www2.towerhobbies.com/cgi-bin/wti0001p?&W=001089434&I=LXGPC9&P=K)

These go on the pinion



I just order these shimms last night .. When I get them I will show everyone HOW I SHIMM DIFFS

[THE PIPER]

I just order these shimms last night .. When I get them I will show everyone HOW I SHIMM DIFFS

Excellent Cheers!!:cheers:

[f1n3sse]

Is there a rule when you should shim the diff? Im building a new sav x as we speak and I read somewhere on here you should not shim them until after 1 gallon...is this true? or should i shim them as i build?

[Jeremy]

No shimm them asap .. after a gallon .. WHAT ?

[f1n3sse]

yeah I dont know what post it was but i was reading a bunch last week and I read somewhere on here that you should wait to shim until after a gallon. thanks for the insight I will shim them asap. do i need different sizes of shims or are they all the same size?

[Jeremy]

Here ya go
http://www.hpisavageforum.com/forums/showthread.php?t=3263

[silvergs]

are there videos of this?

[turboit]

great thread!.. I have the 4.6 alloy diffs that are "pre shimmed" by hpi... should I re-shim them?

[Jeremy]

They are not per shimmed to unlimite side to side movement of the ring gear

[turboit]

ahh good info! Thanks Jeremy. I guess this will be getting done with the rest of build might as well while everything is apart still :duh:

[Seedster]

Here ya go
http://www.hpisavageforum.com/forums/showthread.php?t=3263

Is this method of shimming side to side still being used?

I thought it was pointless to put the shims between the bearing and the diff cups. Aren't you supposed to put them between the bearing and the outdrive cups?

[xll-SavageX-llx]

Great thread !

[maximusraylius]

good thread nice pictures im a gotta see it kinda guy so it works good for me .. good job..nicely detaild ..

[unicorn87]

I know again someone with hard head(more brain but ok):whipit:

I inspect my diffs and found some slope so i want to shim them,found a lot of ways to do it.But in many howtos they shim that shim is touching both races of ball bearing which i dislike.

So i am asking is this is rite to do.Puting 13x16x0.2 shims on the outside of ball bearing(betwen bb an bulkhead)i marked on pic with red where shim go?
And another question is it normal that outdrive cups on diff having mm or so, in and out movement,marked with black on pic?

http://www.shrani.si/t/27/ZS/JAD7vD3/diff.jpg (http://www.shrani.si/?27/ZS/JAD7vD3/diff.jpg)