savage only driving 2 wheels

[Badkitty]

my savage 25 is only driving the front wheels. i can pick up the truck and turn both back wheels in same direction and the fronts move with it, same with moving both fronts, the rear move. yet when i start the truck and hit the gas only the front wheels spin. If i pick up the front end and hit gas the rear do nothing, and while holding rear up the front wheel grab fine. what is wrong ? i thought it were gears in rear diff, as i have stripped them before and replaced, but they're fine now.

 

[Monkey Wrench]

May want to check the out drive cups on the transmission and the rear diff. Sometimes that set screw can back itself out. When you hit the gas, does the center, rear dogbone spin?

 

[Badkitty]

actually i think the rear diff gears are stripped AGAIN.. what would cuase these to go 2x? all i do is jump ramps and bash.

 

[SMaxxin]

Also check the wheels, the hubs might be stripped

 

[Badkitty]

i opened rear diff..the right side bevel gear..stripped 2 teeth 180degrees from each other..dont understand why it keeps breaking these.

oh and by the way..when i rebuild this..should i put some kind of diff oil in it ? would 50K be ok? and do i fill it up to a certain point? it did not have any oil in it when i first took it apart.

 

[bustedgears]

Lack of lubrication will definitly cause it to heat up and break.

Landing on the front or back is particularly bad on the diffs.

1. have you done the 4 spider gear mod
2. fill up till the fluid is just over the rods
3. 50k will be fine for the rear, but too thick for the front.

 

[Badkitty]

Landing on the front of back is particularly bad on the diffs.

what do you mean ? or front of back suppose to be front OR back

Do you have a link to the spider gear mod ?

here is a pic of it




here is a pic of it

and a pic of the gear i stripped

 

[bustedgears]

Front or back, my mistake.

As far as the gears go, buy an ofna shim kit and take out almost all the play from them as possible. Don't let the gears grind, but get them close. This will keep them from grenading on you like this here.

 

[Badkitty]

i got messed up when editing that last post...so i'll do a new one..

the picture in this https://www.rcnitrotalk.com/2004/savage-4-gear-differential-spider-mod/2/ show the diff with 2 gears after dissassembling, and installing 2 more new ones for 4. Do the newly produced savage 25 already come stock with this ? cause mine already had 4

 

[digger]

Nothing else will fit in yours. When they first came out, they only had 2 spider gears.

Check all of the gears. Check the housing where the pins sit. Make sure the screws are tight that bolt it together. They give you longer ones with the gear set? If they back out, the diff is trash pretty quick.

Damn, it's been a long time since I had mine apart......

 

[racin_38]

i have been told a cpl time that when rebuilding the savage diff to get either a new diff cup because the get oblonged due to stress and get the upgraded screws to it also they are fine threaded and hold much better then the course threaded and do not back out!
that may have been your problem right there ,your screws may have loosened and whammo blown diff ,been there done that bud

 

[Badkitty]

hmm...well my stock one is NOT oblong, but has fine thread screws. it wasn't anywhere NEAR loose when i first took it off. actually half way stripped one trying to break it loose. but we'll see

 

[Badkitty]

so i drove it today. OMG..and i thought this thing had some torque before. After putting 50K in the rear I'm pulling wheelies on stock tires on the street, not too mention the grass.

Now i have a new prob...before i got to changing the front diff out, i fried a gear in there as well. I only ran it for 5mins today, but i guess it went out the same way the rear did, it has no oil in it. looks like i got some more work to do

 

[redneckracer1979]

I would Go with all new gears and cups when you rebuild. Also the bearings that are on the diff are known to be weak and if a bearing goes bad it usualy takes out the ring and pinion. I have around 8 gallons on my stock diffs with the 4 spider mod and it still works perfectly.

 

[Badkitty]

k i got new cups and bearings...since i put 50Kwt in the rear..what should i put in the front? i remember someone saying 50k was too much.

 

[redneckracer1979]

I would try something like 10k and go from there.

 

[racin_38]

if you put anything lighter in the front it is not going to drive right ,all your power will more or less upload to the front wheels since you have thicher in the rear ,
a buggy with diffs front/center/rear the normal starting point is 7kfront/5kmiddle/1krear ,then the fronts are not working quicker then the rears and be basically running like a front wheel drive and just pulling with the fronts (if thicker in rear only)
make sense??
if you have to rebuild the fronts either replace it with the same thats in the rears or put a lighter fluid and swap the diffs

 

[redneckracer1979]

It will not unload to the front because the Savage doesn't have a center diff. Also you want to run a stiffer fluid in the front as opposed to the rear because when going around a corner and getting back on the throttle the front will unload easier then the rear.

 

[racin_38]

i was only using the center diff thing to make a point ,and like i said heavier in the front lighter in rear so the power goes to the rear and not the front

 

[redneckracer1979]

But what I am saying is that they run heavier in the front of a 3 diff setup because of the diffunloading forces when cornering. If you watch your rig when conering hard you will see the inside front tire comes off the ground and the heavier fluid in the front diff helps to keep that from unloading. With a Savage their is always equal power going to the front and rear of the truck.