Is this much spur gear/diff hub gap normal?

[flatspunout]

Six-gear transmission. Every spur I have is like this...a few og nylon and a bag full of Kimbroughs.

[juicedcoupe]

No, not normal.

That is an AE 32P spur gear but I have modern 48P Kimbrough gears that fit the same.

But you should be aware that there are spur gears with different hub diameters out there.

[flatspunout]

Thanks for the pic, mine mics at .366. Guess I left it in the dryer too long.

[juicedcoupe]

Assuming that both of our calipers are accurate, 0.002" isn't much.

But if you are sure that all your spur gears are standard (and still too large), you might can try a Traxxas gear. The center hub is slightly smaller.

[XLR8]

fwiw - I had a hub like yours bitd that was badly worn. I happened upon a short length of brass tube in one of my junk boxes that seemed to fit both parts perfectly so I cut it to proper length and CA-glued it to the hub and it's been doing fine ever since. Today it's in one of my frequent runners and it's still going strong. I reckon the brass is harder than the aluminum hub so maybe it has slightly improved the diff's efficiency.

Probably not much help to you but I thought I'd mention it anyway. I excel at relaying useless information.

[flatspunout]

My calipers are Harbor Freight specials, so the accuracy is always questionable.

I had a spare diff tube in the parts box (the bearing version by Losi) and all of my spurs fit that one fine.

I’ll check for some appropriately sized brass tubing the next time I make a trip to the hardware store, thanks for the tip!

[juicedcoupe]

As I said, you can try a Traxxas spur as well.

The center is close enough that it will still physically fit on a standard tube, but the fit is too tight for the diff to work.

[flatspunout]

My preference is to use the AE spurs, but I will keep the Traxxas option in my back pocket as a last resort. The Losi diff tube is in the car now and fabricating a brass spacer for the shrunken one will be easy enough.

[juicedcoupe]

I don't know who made AE spurs in the past but current one's are repackaged Kimbroughs. Oddly enough, they are cheaper through AE.

[XLR8]

Well, what's most important is that it's your car so build it your way. I can fully appreciate the desire to keep the car 100% "AE" but there's no shame in venturing outside the brand to resolve a problem. If the Traxxas spur will fit then, by all means, feel free to use it.

This is bizarre but I'm building a Kyosho Optima Mid runner car and last night I was searching through my selection of spur gears to find a suitable replacement for that odd pitch gear the Mid's came with - I only have one pinion in the box that fits the Mid's spur and it won't yield the ratio I need. Well, long story short, I landed upon a 87 tooth AE spur for my SC10 (B4 trans). However, the AE spur has a center hole slightly too large for the Mid's shaft (0.186" dia. vs 0.156"). So, I went back to that same junk box I mentioned before and found another brass tube that fits both parts. Except this time, the brass tube was actually the correct length and didn't need to be cut so it was a total drop-in solution to my problem. I think that little box of brass tubes dates back to my slot car days in the late 1960's.

Anyway, my friends and family often chuckle and scoff that I never throw anything away but sometimes it pays to keep that old junk.

[juicedcoupe]

Well, what's most important is that it's your car so build it your way. I can fully appreciate the desire to keep the car 100% "AE" but there's no shame in venturing outside the brand to resolve a problem. If the Traxxas spur will fit then, by all means, feel free to use it.

That is why I mentioned that current AE gears are actually Kimbrough. They even have "Kimbrough" molded in the gears, just a new package.

Some people have an aversion to all things Traxxas. However, Kimbrough also makes gears sized for the earlier Traxxas cars as well. So, you can technically get a gear that is the same brand as the AE gears but with a slightly smaller hub.

[XLR8]

Well, what's most important is that it's your car so build it your way. I can fully appreciate the desire to keep the car 100% "AE" but there's no shame in venturing outside the brand to resolve a problem. If the Traxxas spur will fit then, by all means, feel free to use it.

That is why I mentioned that current AE gears are actually Kimbrough. They even have "Kimbrough" molded in the gears, just a new package.

I never noticed that until recently but you're right. Anyway, keeping my vintage RC's genuine used to be important to me but these days I've stopped caring. If I have a part that fits, I use it no matter who made it because the genuine OEM part is discontinued, unavailable or scalpers are asking a ridiculous price.

Wow, I'm doing a lot of ranting today. I need a mood adjustment.

[juicedcoupe]

Following up on this.

I received a 6 gear transmission today and it had this very same problem.

Luckily, I kept all my old Traxxas spurs from when I removed the slipper from my Stampede. The Traxxas spur was a perfect fit.