Servo replacement trouble

[HTFU Defender]

I replaced the steering servo on my Traxxas TRX-4. The original was dead and wouldn't respond at all. I tried to place the horn on the new servo in the same position as the old servo. However, as you can see in the picture the front left wheel is pointing a little left when the servo is in it's natural position. It corrects a little when the transmitter is turned on and the trim pulls the wheels a little right. I have a pretty bad pull to the left when I am driving. Is my horn positioned wrong on the servo? Is there something else I have done improperly when installing this servo? Thanks.

 

[Jim85IROC]

It's easy enough to reposition the servo arm, so I'd try that first. Get it as close as you can doing that, and fix the rest of it with the steering trim on the remote.

The easiest way to get it as close as possible is to disconnect the servo arm, turn the truck & transmitter on with the transmitter steering trim set to "0" or "center". This will center the servo. Then with it still on, slide the arm on to the servo and see how close the wheel alignment is. Move the arm 1 tooth until it's as good as it gets, then screw it down. Use the transmitter's steering trim to get it the rest of the way.

Once things are properly aligned, don't forget to set your end points for the new servo using the dual rate adjustment on the transmitter. This is a critical step because if the servo tries to turn farther than the steering can mechanically go, that's when you start burning up servos.

 

[HTFU Defender]

Thanks. I'll check all of these things.

Why does my left wheel look like it is turned further than the right wheel? Is that just the suspension design?

 

[Jim85IROC]

The tie rod is what connects the two front knuckles. If the links on that tie rod aren't tightened all the way, it will add toe-out. I'm not familiar with the TRX4, but some vehicles have multiple tie rod mounting holes in the knuckles, and it's possible that one or both of the ends is in the wrong hole if that vehicle has multiple holes.

 

[HTFU Defender]

I think I got it all straightened out. Thanks for eveyone’s input.

 

[LSXGMC]

You should post what it was that was causing your issue, so others who have similar issues can use this thread as a reference in the future.

 

[HTFU Defender]

Ha, I would if I knew exactly what I did. I followed the advice given but each time I tried to position the horn on the servo it seemed it would only go on at an angle. Finally I got it to mount at a mostly 90 angle to the servo. I'm not sure if I was just missing that middle spot in all of my previous attempts to mount the horn or if I've worn it out taking it on and off so many times. I guess we'll know as soon as I'm able to get a little driving in.

You should post what it was that was causing your issue, so others who have similar issues can use this thread as a reference in the future.

 

[LSXGMC]

Ha, I would if I knew exactly what I did. I followed the advice given but each time I tried to position the horn on the servo it seemed it would only go on at an angle. Finally I got it to mount at a mostly 90 angle to the servo. I'm not sure if I was just missing that middle spot in all of my previous attempts to mount the horn or if I've worn it out taking it on and off so many times. I guess we'll know as soon as I'm able to get a little driving in.

You typically won’t get it perfectly centred with a new servo, that’s where the trim settings on the radio come into play. Those allow you to fine-tune the steering centre position so the truck tracks straight.