1ofmyfuns

As some of you know I am in the proccess of repairing my new Backdraft 3.5 due to a busted pionion gear in the rear diff. so Billy @RedcatRacing.com has made contact with me and hopefully we are in the proccess now of getting this gear replaced.

Nowfor the idea I had onpossibly helping to prevent this pinion gear from breaking as easyat it's weakest point where the cross pin seats into the backside of the gear, this looks tobe the thinnest area of the gear and not a real sturdy way ofdriving the diff unit in my opinion.

Is therea way to take the bulk of the pressure off ofthe reccessedcross pin seatingarea of this gear?

I think I have a simple solution that could help secure the gear better.....( RED Loctite ) NOTBLUE but RED,this will secure the gear very good to the diffsinput shaft andcause the shaft to apply torque to the gearas if it were press fitted onto the shaft instead of the cross pin applying 90% or more of thepressure only to the back portion of the gearat thegears thinnest and weakest point.

Some may say REDLoctite will make it very hard to remove and replace that gear, my answer is DREMEL TOOLand thin cutoff disc and it will beoff in a jiffy, or justa littleheat from a propane torch, personally I would do the Dremel.

What doya thank about this?

1ofmyfuns

Just sitting here looking at how the gear fits the shaft when I take the 2 pieces of the broken gear and position them back on the shaft, I noticed that on each side of the break there is a gap and no matter how hard I try I cant close this gap in the break, this make sme think of another possiblity of maybe why these gears may be breaking.

If the bore inside the gear itself is just slightly under size for the shaft or if the shaft it goes on is slightly over sized for the bore in the gear, this is gonna cause the gear to need to be forced onto the shaft in a way that would put a lot of extra stress on the gear which could also be a reason for it snapping into at it's weakest point as soon as a little extra pressure is applied, a cast gear like this shouldnt need to be driven onto a shaft like this under very much force since it is such a thin casting, so another idea here is that these gears could be failing because of a improper size either of the shaft or of the inside bore of the gear itself.

Just another though on this. 

billymare

Your going to find that you have to press that gear onto the shaft. make sure you use the correct amount of shims as this is pretty much a 1 shot deal. Check out catbob007's fix....

c54fun

This is what I used to press on my pinion. Works great. Around $50 at Harbor freight. Works great for removing the gear also.

1ofmyfuns

OK now i see things clearer, I didnt realize this was a press fit situation but now that I do Ican see easily how a faulty casting where the material may not be right wouldcause this failure.

just a simple bench vise should be a good tool for pressing this gear on the shaft.

How do I find the fix by catbob007 you mentioned, I can't seem to find it by searching?

By the way thanks for the info. this is my first experience with this so I'm learning as I go here.

1ofmyfuns

Ok billymare never mind I found the upgrade post you had mentioned by catbob007 very interesting I will keep this in mind

1ofmyfuns

yeah I've looked at the arbor presses at Harbor Freight a couple times, and yes that would be a very good tool for the job.
Thanks for the input