Center Diff question - running as RWD

[NinoS]

I have an Ofna Ultra LX, and it needs a new drivecup up front due to serious wear ovalling the shaft mounting area. So the part is coming in the mail.

I can lock the front brake with a zip tie to lock the front side of the diff, making the car temporarily 2wd with all power going to the rear.

Now the "should" part. Outside the lack of handling and the wear to the rear drivetrain from more power than usual, is there any other catostrophic damage awaiting me if i take the car for a drive like this? I envision more wear to rear drivetrain, but nothing more....am i missing anything?

 

[cbaker65]

I have an Ofna Ultra LX, and it needs a new drivecup up front due to serious wear ovalling the shaft mounting area. So the part is coming in the mail.

I can lock the front brake with a zip tie to lock the front side of the diff, making the car temporarily 2wd with all power going to the rear.

Now the "should" part. Outside the lack of handling and the wear to the rear drivetrain from more power than usual, is there any other catostrophic damage awaiting me if i take the car for a drive like this? I envision more wear to rear drivetrain, but nothing more....am i missing anything?

You shouldn't lock the front brake ,it put a strain on the center diff & engine clutch!
You should be ok just simply pulling the drive shaft out an removing the brake disc if you have to!..

 

[NinoS]

You shouldn't lock the front brake ,it put a strain on the center diff & engine clutch!
You should be ok just simply pulling the drive shaft out an removing the brake disc if you have to!..

Thanks for response..I've pulled the driveshaft but this doesn't prevent the diff from trying to send power to the front, hence needing a a way to stop the front side of the diff from spinning so power actually goes to rear. my crazy scheme for that is locking the brake (i realize if it starts slipping, that should be bad!)

Or I may be interpreting your post incorrectly

Best thing is to just wait for the part, but wheres the fun in that!

 

[cbaker65]

Thanks for response..I've pulled the driveshaft but this doesn't prevent the diff from trying to send power to the front, hence needing a a way to stop the front side of the diff from spinning so power actually goes to rear. my crazy scheme for that is locking the brake (i realize if it starts slipping, that should be bad!)

Or I may be interpreting your post incorrectly

Best thing is to just wait for the part, but wheres the fun in that!

I've ran rear drive before on a all wheel drive ,it doesn't make no difference on the out put shaft
if it just sits there an spin with out the drive shaft.
If you pull the drive shaft ,then you eliminate the front diff of power ,you do not lose any more
power to the rear if the output shaft is still spinning!

You will lose power if you force the brake on!

 

[NinoS]

I've ran rear drive before on a all wheel drive ,it doesn't make no difference on the out put shaft
if it just sits there an spin with out the drive shaft.
If you pull the drive shaft ,then you eliminate the front diff of power ,you do not lose any more
power to the rear if the output shaft is still spinning!

On a car with no center diff though, correct?,

Heres my observations on this car with a center diff: when the front drive cup fell off, leaving the front drive shaft spinning, the car barely moves, because the center diff is sending all the power to where the car has least traction --- which is obviously the now free spinning front shaft, or if i remove the front shaft, the front center diff cup by itself. Meanwhile back tires barely turn...unless you stop the front side of diff from moving (via brake, hold it, whatever), then power finally goes to rear. It seems unless i force the front side of center diff to stop moving.

 

[cbaker65]

On a car with no center diff though, correct?,

Heres my observations on this car with a center diff: when the front drive cup fell off, leaving the front drive shaft spinning, the car barely moves, because the center diff is sending all the power to where the car has least traction --- which is obviously the now free spinning front shaft, or if i remove the front shaft, the front center diff cup by itself. Meanwhile back tires barely turn...unless you stop the front side of diff from moving (via brake, hold it, whatever), then power finally goes to rear. It seems unless i force the front side of center diff to stop moving.

If that is the case ,then something else is wrong or loose!...
Check the other drive cups ,also make sure that all grub screws on each diff is tight !....MEANING THE OUTPUT CUPS ON THE REAR DIFF & FRONT
WHERE THE DRIVE AXLE COMES OUT!

The rear & front diffs output cups have set screws or what we call grub screws tend to loosing up ,make sure those are tight!...

I can show you detail pics to show you what I'm talking about if you like!...

Your car does not have a transmission ,it has what we call a center diff. ,then you have a front & rear diff.!

They all have a drive cup that is held on with a set screw ,those loosen up ,an have to be re-tighten every now & then ,...
If one does loosen up ,you can lose any drive!

 

[NinoS]

@cbaker i do appreciate all your help! The grub screw, or surrounding area on front input shaft was the reason all this started. The drivecup is out of round (worn into an oval) where it sits around the shaft, so even with a tight, loctite'd grub screw the cup will work itself off, hence needing a new drive cup up front. Meanwhile, i got this nutty idea to run 2wd by removing the front driveshaft - the rear drivetrain is still rock solid. When the front drivetrain is hooked up for 4wd, everything works as it should and the car handles great (meaning when that front drivecup was on there and working properly) .

There is some schism here in our conversation, as this center diff is working like any other open differential I have ever come across - you turn the input shaft (essentially the spur in this case), and power is distributed to the least resistance path - in this case the front drive cup since it's not hooked up to the front diff and wheels, therefore there is no resistance. works like any open differential i've ever seen - by your explanation i may be missing something, so i made a 30 second video to clarify what i'm on about....i've basically abandoned the original idea though, just going to get the part and have a full 4 wheel drive buggy - this is one of my favorites so no need to jack it up.

 

[cbaker65]

I fully understand what your talking about ,but you should not have to hold the front brake to make power to the rear!
That is a full time diff ,yet ,there is give inside the diff due to the gears....Its hard to explain if you don't know how the diff works ,

EXAMPLE Usually if you turn one side of an output one way ,the other side will turn the opposite way!
So there is some free way of the diffs!

 

[NinoS]

There's a happy ending, documented below, back to full 4wd......had to loctite the bejesus out of the new drive cup because the shaft itself that it mounts on with the set screw is also getting worn from previous slippage, so that will be the next parts order...in the meantime, running like a champ (except needing need to adjust my throttle linkage a little so it goes back to full idle off throttle, you can probably tell from video). This was my first nitro buggy, and still probably the most fun to drive off road.

 

[cbaker65]

Nice bashin!

Be careful with those curb hits ,those front arm hinge brackets will break!...

 

[NinoS]

Be careful with those curb hits ,those front arm hinge brackets will break!...

Thanks! Yup that was a nasty hit, was genuinely surprised my steering was still intact after that one....missed the "ramp"!! Some of my dumbest RC moments are while filming, because I'm not focused 100% on driving, rather the camera, staying out of way, slow mo button for super high FPS, etc...