# Traxxas Slash Differential Repair



## RCRocco (Jun 3, 2013)

I'm new to RC and fairly mechanical, is there a manual that can be purchased to help me repair my RC truck? Was driving it at the track yesterday and it suddenly acted like it lost drive, the guy at the hobby shop said it was probably a "loose differential", what's the best way to get to it? Help please!


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## nutz4rc (Oct 14, 2003)

All manuals for all Traxxas products are on the Traxxas.com website. Also there are tips for maintenance as well as racers forums where you can get info. 

To get to the diff you must remove the tranny and then take out the bolts that hold the tranny case together. Pull the case apart and the diff is in the lower part of the tranny below the idler gear. 

The Traxxas Slash normally have a geared diff so it can't get loose; if loose, it would be broken. Could he have meant the slipper was loose? If you have a ball diff replacement in the Traxxas tranny, then it could become loose; but can be tightened.

Other things that could cause this loss of power could be a cross pin in a rear wheel lost or the hex loose due to wheel nut backing off. A broken outdrive from the tranny output shaft could do it as well. Before taking anything apart, I would inspect the wheel nuts, hexes, cross pins, and check to see the outdrives are both working correctly and actually driving the wheels. If all this is OK, time to dig deeper.


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## RCRocco (Jun 3, 2013)

OK, so I've started to work through the issues. The symptom is that the truck drives slow in forward and almost not at all in reverse. It is not in "training" mode. I swapped out the motor and so I know it is not a motor problem. The gear that connects directly to the motor gear appears to be properly tightened so that when I just run the wheels without any resistance (not on the ground) it seems fine but when I try to drive the truck it just doesn't have much power. So does this help on troubleshooting? Thanks!


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## nutz4rc (Oct 14, 2003)

Let's try a few more tests. If you turn the spur gear (one that attaches to the tranny) by hand do the wheels both turn? If not there is a problem with the diff. Hold spur gear and turn a wheel does the other wheel turn. If not there is a problem with the diff. Set the truck on a stand with the wheels off the ground and pull the throttle from low speed to high speed, do the motor and wheels spin at high speed. If not there is an issue in the ESC (speed control) giving full speed signal to the motor. Are you certain the batt is fully charged and delivering proper power? Have you checked to see that the cross pins are in the hubs in the rear wheels. Without a cross pin, the truck will inch along but never reach any speed because an axle is not driving the wheel where the pin is gone.


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## RCRocco (Jun 3, 2013)

OK, so I now know it's a differential problem. I have started to tear down the Slash to get to the differential and I have everything (I think) done except that the two halves of the case won't pull apart. I can work it around and see daylight everywhere so I know there isn't a screw remaining, but I'm afraid to pull too hard and damage something. Is there a trick or a catch to getting the two halves of the case apart? Thanks for your help!


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## nutz4rc (Oct 14, 2003)

Double post


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## nutz4rc (Oct 14, 2003)

Have you gone to Traxxas.com and downloaded the exploded view of the truck tranny? This will help you see where everything is and how it is fits.


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## nutz4rc (Oct 14, 2003)

Have you removed the outdrives from the diff shafts that exit both sides of the tranny? If not, you may not be able to pull case apart depending on the age of the truck. Older outdrives attach with a phillips screw into the outdrive and then threaded into the shafts from the diff. Newer models have a cross pin that threads through the outdrive and through a hole in the shaft from the diff. 

You said this tranny has a ball diff. What type is it, who installed it? The tranny would have to have been opened to install the diff, hopefully they didn't do something inside the case.


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## nutz4rc (Oct 14, 2003)

If this is a ball diff, and it is installed in the tranny backwards; you will see exactly the problem you mentioned. When in backwards, as you run the truck the diff nut will loosen and then you lose all diff action which results in little and finally no movement of the outdrives and rear wheels.


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