savage 25 rear diff weak ?

[Badkitty]

in the last 3 weeks i've gone thru 2 rear diffs and a drive gear. I am not bashing it that hard and this last time i started it up..and ran it down the street and noticed only the front wheels spun...DARNIT!!! could having 50K diff oil in it be causing this ? i broke 2 teeth off a spider gear this time.

 

[Monkey Wrench]

I don't know, man, but it sounds to me like you need to shim the slop out of it. I get the feeling there's too much backlash because you're chipping teeth off, versus grinding them down. Are you putting shims between the diff case and outdrives? I also grease the crown gear and pinion real good (not gobs, just a nice even coat) in addition to the diff lube.

 

[Badkitty]

Are you putting shims between the diff case and outdrives?

uh..no. How do i do this and with what?

 

[olds97_lss]

I agree with MW. Sounds like your diff cases are worn out and/or you need to shim the slop out.

Personally, I went with aluminum diff case/housing in the rear (not the internal cup) so I could shim it right where I wanted it. Over time, the plastic heats and warps which will throw off the mesh.

I've run 3 gallons through my savage since replaceing the rear diff case with AL and shimmed it properly. The ring/pinion still look like new.

You also might want to check all your bearings. The ones for the input/output shafts may be shot which will also alter mesh.


I "borrowed" this from savage central. The guy that did it took his time and took nice pictures of everything.

In place of the Kyosho Shims, you could use these instead OFNA 13X16 Shims:

10 Step How-To: Shim a Differential
Why do I need to shim the differential?
The Differential Housing cannot support the diff tight enough to keep the ring-and-pinion gear mesh constant. This can cause the failure of the pinion by breaking off some teeth or cause the ring-and-pinion to skip off each other grinding each gearsÎéÎ÷ teeth down.
What am I shimming?
You are shimming the differentials side bearings.

OK lets startÎíÎõ
Parts Needed:
-1 (or 2) completely disassembled differentials
-Kyosho Shims Part# BS53 (need 2 packs) 1 pack includes 4 shims

Step 1 (Differential Parts)
To start with you need to have both differentials completely disassembled

Step2 (Shims)
Remove the correct shims form the Kyosho shim packs

Step 3 (Side Bearings)
Now install the differential bearings on the diff cup and ring gear. Make sure you have the bearing on the diff cup pushed all the way on, it will take a little muscle to get it to slide down.

Step 4 (sicjÎéÎ÷s Tip) (Ring Gear Attachment)
The fastest way to find out how many shims you may need on each side of the diff, I attach the ring gear to the diff cup w/ the paper gasket.
The fastest way to do this is to use some 8mm Flathead machine screws.

Attach the ring gear with the two screws opposite of each other

Step 5 (Pinion Install)
Install the pinion in the front half of the housing (GPM/GH housings are cut side-side, stock housings are front-back.)

Step 6 (Diff install)
With the pinion teeth facing you, install the diff so the ring gear is on the left side of the pinion (For GPM/GH housings: install it on the right and those wheels will go in reverse :lol: )

Step 7 (Backlash test)
Install the back of the housing and slide the diff shafts into the diff (hold the entire unit together)

Now hold the diff shafts and move the diff side to side to feel the movement of the diff.

Step 7 (Ring Gear Shim)
Now take the diff out of the housing. Remove the diff shafts, and install 1 shim on the ring gear side bearing. Slide the diff shafts back into the diff and install in the housing.
(With GPM/GH housings just put the shim in the housing where the bearing will sit, then put the diff back in and check for the backlash)
Shim in housing

After you have put 1 shim on the ring gear bearing, put the diff back in the housing halves and check for the movement towards the ring gear. Push the diff away from the pinion, then push the diff towards the pinion. Then determine if you need to shim the ring gear closer to the pinion. If the ring-and-pinion mesh needs to be tighter, add 1 more shim.

Step 8 (Diff Cup Shim)
OK now that you have the ring gear shimmed into the pinion the way you want, itÎéÎ÷s time to shim the diff cup side bearing. You need to do this to prevent the ring gear from being pushed too hard into the pinion.

just follow the procedure for the ring gear, normally the diff cup side bearing will only need 1 shim.

Step 9 (Completion)
After you shimmed the diff cup side bearing, you have to take the diff all apart and build up the differential.
Remember that when it comes time to install the diff shaft(s) put the shim(s) on the diff shaft then slide it in. You cannot slide the shim over the diff shaft.

Step 10
After you diff(s) has been built you will have to line up the shims while you slide the two halves of the diff housing together, go slow and be careful, the shims will bend very easily.

 

[Monkey Wrench]

Look at this picture:

The part I circled is where you can add shims. You take the out drive off and add them until you cannot rock the out drive back-and-forth. You want to do this on both sides to make sure you take all the slop out.

I'd suggest replacing the bearings as Olds referred to as well. Cheaper than replacing gears all the time. I also like Olds' idea of using AL cases as well. Gonna have to do that when it comes time to rebuild the diff's.


EDIT: Darn it! Olds' is better! Follow his! Good stuff!

 

[olds97_lss]

Oh, I also used white lightning bicycle chain wax lube for the ring/pinion. It doesn't attract dirt like grease/oil.

 

[kurt_02f150]

dang. i think mine went kaput today.


1 tank

 

[tannera]

this just happened to me the rear diff wouldn't mesh atal, i think it's becasue my rear diff caseing has worn so i have brought new caseings and i will reshim the diff and hopfuly all should be well

 

[kurt_02f150]

mine ended up being a stripped hex.


time for the X conversion for yew.