Overdrive Front Poblems

[The-Blacksheep]

Hey guys got a question for ya, just did a little research and came up with all the information i could want, but absolutely nothing i needed so time to post up and find out.

I installed overdive gears in my front axles last night and it seems to turn fine, but i noticed that with the driveshaft off and i pushed in on the axle output it would start to catch and eventually lock up the axle where it wouldnt turn, keep in mind without putting pressure on it , this didnt happen, so i put it back together thinking it would be fine.... well guess what, it wasnt, i ran it for abot 20 minutes tonight continuasly checking the motor for it building heat, incase of a binding issue, and it didnt et hot immediately but it did over time get hot "Hotter than it should have got" so my question is how do i fix this problem, i used the 36/14 overdive gears from axial, and the only difference i could notice is that on the back of the ring gear where on the stock one had to nubs to locate it in the locker case, the overdrive ring gear did not..... any help would be much apreciated, maybe im missing a step or something heck i dont know.... thanks guys, if this has been covered, a link to this would be appreciated instead of bashing, however i did seach.....

[Big Daddy]

Mine did the same thing, but when I assembled it, it seemed to run fine. I did notice my runtime went way down but I figured that was from the gearing itself. I figured I'd run it a few times and pull it apart to check for any signs of wear. It's about time to do that...

[The-Blacksheep]

yea well i can tell its not good for the motor, let me know what you find when u tear it apart, anyone elese have any other idea or suggestions? im in the process of takin it apart now, to see what i can figure out........

[Szczerba]

I've always had to shim the pinion shafts from the outside with the bevel gear sets. The pinion shaft gear is a little shorter than the stock pinion gear. When you have the driveshaft connected, can you push the pinion/driveshaft towards the diff gear a bit? IF so, add some washers/shims to keep it from moving back towards the diff gear.


Edit. Picture of what I am talking about here. On a HPI mini trophy truck but same concept. 3rd picture down.
Shane's HPI Mini-Trophy Desert Truck

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[The-Blacksheep]

i tried what you said and i can push it in a little and thats when u can feel it binding...... ill try the washer trick if i cant shim it internally thanks alot that helps has anyone else had this problem and fixed it another way then has been descriped so far?

[Big Daddy]

Seems like the washer would push it in the direction that makes it bind..? I did consider putting a small spring between the drive shaft and the bearing but there isn't enough room once it's assembled.

[meatmonkey]

You need to have enough shims so that their isn't any in/out play in the pinion shaft.

I've put together four underdrive gearsets and they all required 3 or 4 shims on the outside of the axle housing between the outer pinion bearing and the driveshaft yolk. A total of about 1 to 1.5mm of shims will typically be required.

Putting shims inside the axle housing will effect ring/pinion contact. The only gears I've installed that required the pinion being shimmed in was two sets of the stock ring/pinion. Both had way to much backlash for me to trust. A single shim under the pinion head and it reduced the backlash by about half.

The helically cut HD gears are designed to run at a certain pinion depth, and as you've all discovered running them further in or out than from their sweet spot will result in reduced effeciency, bearing life, increased drivetrain noise, and premature gear wear.

I wish I knew the proper distance between the pinion bearings to make a "solid pinion bearing spacer" so that both bearings would have to equally split the in and out force on the pinion, hopefully leading to longer bearing life.

And does anyone else's HD gears have a reduced diameter right under the pinion head? When I saw that I was like WTF? No issues yet, but it doesn't even look right.

[The-Blacksheep]

thanks guys i got it fixed, i had to use 1 shim between the outside pinion bearing and driveshaft, works like a charm now, got it put together, all buttoned up, turned it on to test it around the house and the stock servo finally went out, it lasted quite a while tho, so i guess its time for a replacement, just my luck tho!

[Big Daddy]

Ahhh I was thinking they were saying to put the shim on the inside between the gear and bearing. Makes much more sense between the driveshaft. I'll have to take another look at it and see if I can get things working a bit better.

[Szczerba]

Originally Posted by Big Daddy

Ahhh I was thinking they were saying to put the shim on the inside between the gear and bearing. Makes much more sense between the driveshaft. I'll have to take another look at it and see if I can get things working a bit better.

I posted a link to what I was referring to. It's on a HPI MTDT but is the same idea.

Originally Posted by The-Blacksheep

thanks guys i got it fixed, i had to use 1 shim between the outside pinion bearing and driveshaft, works like a charm now, got it put together, all buttoned up, turned it on to test it around the house and the stock servo finally went out, it lasted quite a while tho, so i guess its time for a replacement, just my luck tho!

Good deal on the shims working. Glad you got it fixed.
Sucks about the servo though!

[jshull]

where are you guys getting shims?