Play in driveshaft / differential

[MrBlank]

About a month ago I broke the stock front driveshaft on my Sawback in the usual spot. I have a set of no name steel driveshafts coming through slowbay but they could take up to another month to get here... now onto the problem.

Backwhen the drive shaft broke I stopped by my LHS and picked up a nylon punisher shaft with steel yolks. Has been holding up good, but ive now noticed a ton of playin the front wheels. If I hold up the rear end and push lightly I can roll forward about an inch and a half before the wheels lock.

I've taken off the differential cover and can see that some of the play is in there, and I can move the output gear back and forth by pushing and pulling on the driveshaft. It also appears that the driveshaft itself (at the yolks) is partially to blame.

The rear end has some play as well, but only rolls about 5/8 of an inch in comparison.

Thoughts / solutions?

[Rathar3]

I have been doing a lot of reading on the sawback. something i have picked up on is the axle wrapping because of the soft springs. when you over torque the front axle the driveshaft rolls clockwise towards the ground. This changes the angle of the driveshaft causing problems like popping of shafts and can cause other issues.

Are you running anti wrap bars? This seems to affect the front more than the back due to the rear torquing up and bringing the rear shaft in line with the drive shaft.

I got most of this info from reading what others have posted all over the net

not sure if it will help

[MrBlank]

Yes, I have 2 anti wrap bars in the front and one in the rear, all home made - from servo mounts on pumpkin to the bolts holding the leafspring closest to the skid on either side.

I agree that torque twist was what originally caused the break, which I have now remidied - but I can notfigure out why I now have so much play in my axles / differentials / drive shafts - and what I can do to fix it.

Thank you for the reply though.

Originally Posted by Rathar3

I have been doing a lot of reading on the sawback. something i have picked up on is the axle wrapping because of the soft springs. when you over torque the front axle the driveshaft rolls clockwise towards the ground. This changes the angle of the driveshaft causing problems like popping of shafts and can cause other issues.

Are you running anti wrap bars? This seems to affect the front more than the back due to the rear torquing up and bringing the rear shaft in line with the drive shaft.

I got most of this info from reading what others have posted all over the net

not sure if it will help

[Natedog]

Double check all drivline set screws, screw pins, etc, re-tighten with blue Locitite. Diff gears may need shimmed to tighten up the gear mesh a little too.

[MrBlank]

Is there any particular shim kit (universal?) that you could recommend, that would fit the Sawback's differential? It appears that there is not one made specifically for the sawback (or I haven't been able to find it).

I had forgotten to respond to your reply, and have just been living with the problem is it doesnt seem to affect the way it drives.

Originally Posted by Natedog

Double check all drivline set screws, screw pins, etc, re-tighten with blue Locitite. Diff gears may need shimmed to tighten up the gear mesh a little too.

[Natedog]

Calandra Racing Concepts has the best selection of high quality steel shims in metric and standard!

https://www.teamcrc.com/crc/modules....category_id=79

[MrBlank]

I had continued to drive without the shims - I probably should have started another thread in the general or newbie section, asked at my LHS, etc...
But I didn't.

Then the weekend before last the front differential started slipping, and writhin minutes, the rear was slipping as well. Took it all apart last friday and discovered the gears were mostly stripped / deformed. I picked up some shims from the LHS and installed them (the difs dont skip so much now and it is somewhat drivable). Also ordered new gears for front and back from RCMart which should be here next week.

[MrBlank]

Thought I'd add a photo of the old "un-shimmed" gears that I pulled out last month when i got the replacements.

I cleaned most of the grease off - the damage was definitely due to play between the gears.

I do however wish that they had a hardened steel version available.

Sent from my SGH-I747M using Tapatalk

[steanlol]

I've had my sawback nearly 4yrs now and I've never touched the axles from the day I built them but the play in them is about as bad as you have had in yours .
I need to strip and rebuild them but I too cant understand why there isn't any uprated versions available to minimise all that slop but I guess I'll have to find some form of shims but over here in the Uk Lhs are very few and far between .

[thead]

i use traxxas 5x8 teflon coated shimms in mine.

[MrBlank]

Originally Posted by steanlol

I've had my sawback nearly 4yrs now and I've never touched the axles from the day I built them but the play in them is about as bad as you have had in yours .
I need to strip and rebuild them but I too cant understand why there isn't any uprated versions available to minimise all that slop but I guess I'll have to find some form of shims but over here in the Uk Lhs are very few and far between .

Order the shims online? I imagine you'll need to order the gears anyway.

I don't have a big issue with the slop / need for shims, although I wishthey were provided as with my Ascender kit. I do however wish they made hardened steel gears that could handle a bit of slop with out turning to powder - mine did not even last a year on a 7 cell NiMH.

Now that I new, properly shimmed gears, they aren't showing wear even with 3s lipo, no matter how rough I am on it.