Locker servo head-scratcher...

[high plains drifter]

As much as the trx4 locking servos have been discussed and despite my searching... had to post a new thread about this cause I still can't figure it out. And bear with me as this is my bud's truck and he's not on here... sorry.

Anyway- When we were crawling last week, he discovered that his front locker didn't seem to be fully engaging. Both wheels would spin but when he put a load on the drive side, it didn't seem like it was locking.

So he started poking around... checked the axles/ hubs/ differential gears and couldn't find any issues. Then he discovered that when the locker switch is in the "OFF" position, the servo arm is oriented in the center position. And when switching to the f/r locker position, it pushes the cable towards the front instead of pulling it to engage the locker mechanism.

Not sure if it's relevant but he just replaced the receiver recently. I told him to make sure that the tx/ rx is bound and he says that they are. I also told him to make sure that everything is wired to the new rx correctly. He confirmed that it's all good. I asked him if the servo saver is loose or damaged and whether the throw is smooth/ deliberate or chattering/ wonky. He said that the operation is smooth.

Any ideas? I'm going to take a look at it in the next day or two but until I get it in my hands, I'm just wondering if there's anything specific that y'all would suggest I inspect or if you can think of any reason that ( from what he described) the servo throw might have reversed itself. Sorry I don't have the truck in my hands right now but any advice or suggestions would be greatly appreciated.

[ScaleLifeNewbie]

Not sure if it’s the right way to do it, but I had a lot of problems with mine, so I just took the servo horns off , moved them to lock position, them screwed them back on. They do take a little bit of time to figure out, but it’s nice to have them

Hopefully this helps.


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[PFongemie]

What receiver did he upgrade to? On my DX5 Rugged there’s a setting for the aux channels for the servo swing. Either momentary, 2 position or 3 position. On mine buttons E & F run my lockers and the same thing happened to me. Switch them to 2 position and he’ll be good to go.

[amigaman]

Maybe it's just the channel reverse setting, it sounds like it.

TQi system or third party?
If TQI: Receiver bought used or brand new? Both may have different settings for the channels, they are model specific. Only a TRX4 receiver knows how the TRX4 channels work, all other may have reverse wrong.
Just set them either with the app or by blinking through the menu and you're good to go.

Or:
I did totally misunderstand you, and the locker does not lock at all (instead of "it reacts wrong but does work"):
Then you may have a problem with the servo saver or the servo itself. Either the saver is stuck (mud, dirt, rocks) or the servo has broken teeth.

[high plains drifter]

Original TQi tx and replacement 6533 rx bought brand new. I appreciate the replies. I'll go thru the settings and make sure that my bud has done that correctly and if that doesn't fix it then I'll take a look at the servo itself. From what he described, it doesn't sound fried but could be. We've been locking/ unlocking these trucks for a few years now lol. I personally think that he might've messed up something in the course of installing the new receiver or when he was doing something else with the axles/ hubs... maybe over-tightened something, I dunno.

In terms of the first suggestion, ScaleLife... Repositioning the servo arm to locked position or even re-centering the servo horn isn't going to address what the actual issue is... I do appreciate your input though.

Thanks very much, guys.

[HumboldtEF]

in the Traxxas Link (smart phone app) you can reverse the servo. At first I though maybe he had mixed up the front and rear and swapped the channels but they both operate in the same order from what I can see. So I'm not sure exactly why the channel has been reversed, it is odd.

It seems like the other half of the problem is the throw of the servo horn.
The servo seems happiest (least likely to strain and potentially fry) with around a 35-40 degree throw in each direction, and you can listen to the servo to see if its happy (just make sure the locker is engaged by giving it some throttle of manually spinning the wheels until its engaged).

Then you adjust the cable to ensure its locking and unlocking properly. I did some basic testing early on and found the cable that threads into the linkage can be shortened or lengthened to adjust the locker engagement (screw it in or out to adjust).

If the throw is really far off you may need to reposition the horn, just be very careful and hold onto the servo output spline with needle nose pliers while you loosed the screw holding the horn on, the gears will strip with ease if you dont hold onto this (ask me how I know).

[high plains drifter]

I really appreciate the insight, HumboldtEF. My first thought also was that he had maybe connected it to the wrong channel but all is good there and like you said... wouldn't matter anyway. I'll look into the other things you're suggesting.

[ScaleLifeNewbie]

Originally Posted by high plains drifter

Original TQi tx and replacement 6533 rx bought brand new. I appreciate the replies. I'll go thru the settings and make sure that my bud has done that correctly and if that doesn't fix it then I'll take a look at the servo itself. From what he described, it doesn't sound fried but could be. We've been locking/ unlocking these trucks for a few years now lol. I personally think that he might've messed up something in the course of installing the new receiver or when he was doing something else with the axles/ hubs... maybe over-tightened something, I dunno.

In terms of the first suggestion, ScaleLife... Repositioning the servo arm to locked position or even re-centering the servo horn isn't going to address what the actual issue is... I do appreciate your input though.

Thanks very much, guys.

Oh, sorry I misread! Now that I read again, my response what completely irrelevant.


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[high plains drifter]

We got it figured out! As suggested, I went ahead and set the tx to default mode ( page 31-32 of the trx4 manual). I dunno if it was the new rx itself or something that my bud accidentally did while installing it but it was definitely operating backwards. Rear locker servo operation was fine btw. Anyway... re-set the radio and voila... locker engaged smoothly with no issues/ rear still functioning normal as well. I did notice a slight binding of the front cable that was causing the servo-saver spring to uncoil more than normal. He confessed that he pulled it the other night and put it back on just off one tooth/ notch. We re-positioned the horn and fixed that too. Seems that all is well now. Thanks again, guys. The help was very much appreciated... ScaleLife too. Cheers!

[ScaleLifeNewbie]

Originally Posted by high plains drifter

We got it figured out! As suggested, I went ahead and set the tx to default mode ( page 31-32 of the trx4 manual). I dunno if it was the new rx itself or something that my bud accidentally did while installing it but it was definitely operating backwards. Rear locker servo operation was fine btw. Anyway... re-set the radio and voila... locker engaged smoothly with no issues/ rear still functioning normal as well. I did notice a slight binding of the front cable that was causing the servo-saver spring to uncoil more than normal. He confessed that he pulled it the other night and put it back on just off one tooth/ notch. We re-positioned the horn and fixed that too. Seems that all is well now. Thanks again, guys. The help was very much appreciated... ScaleLife too. Cheers!

Good to hear it’s all fixed!

Now you and your buddy, go have fun!


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[OnTheTrail]

Funny timing. I just picked up a used G500 and the way the diffs would be locked/unlocked based on the stock Tx switch was different then my Defender. After a bunch of experimenting, I found out the previous must have reversed the front locker servo somehow. Got that changed and now it's fine.

[high plains drifter]

Originally Posted by OnTheTrail

Funny timing. I just picked up a used G500 and the way the diffs would be locked/unlocked based on the stock Tx switch was different then my Defender. After a bunch of experimenting, I found out the previous must have reversed the front locker servo somehow. Got that changed and now it's fine.

While I was initially searching for additional information on the issue that my buddy was having, I found a lot of youtube videos out there ( as well as some threads here on RCC) with folks re-configuring the tx switch to engage the lockers differently. So yeah... I'm not surprised. The key words that kept bringing up that particular topic in searches was "reversing trx4 locker servo". I had to weed through a good deal of that info to eventually find what I was looking for which was the topic of simply resetting the radio settings. Glad you got yours figured out too.