Steering issue when end points nearing maxed out

[high plains drifter]

On my Capra I have SSD disk brake rotors for looks and Vitavon brass portal covers for weight. Wheels are SSD 1.9 Trail with Proline Flat Iron XL tires if that matters... Pretty wide stance.

When I begin to max out the steering trim and turn the wheels left or right, the vehicle does this "lurching" thing. I don't see any binding of parts but the vehicle sort of lurches ( for lack of a better description) It does this with the wheels in the air and on the ground.

Is it an axle shaft issue? Is it an ackermann issue? I need to get this corrected but not sure how to address it.

Thanks for any assistance.

 

[Fallen]

Did your servo take a hard hit recently? Dead servos do weird things to vehicles and cause several types of unexpected behavior.

If your servo is just maxed out maybe it's displaying similar behavior to a bad servo. But if it didn't used to do that, and now it does I would suspect a bad servo.

Do you have any spare servos you can swap in for troubleshooting?

 

[high plains drifter]

It's definitely not a servo issue. Strong servo with no issues.. doesn't glitch and has full smooth travel lock to lock. Just installed and calibrated a HW1080. I never noticed this lurching issue prior to installing the new ESC ( at least not as prevalent although it might have already existed, I just don't recall) but it seems to be related to something with the axle-shafts or something related to the steering linkage when turning up the steering rate.

 

[JatoTheRipper]

Do you have a video?

Are you turning more than the maximum angle of the CVDs?

 

[bgredjeep]

I agree on a video to show what's going on.

If you are talking about the wheels "pulsing" under power while turning sharp, that's just the way u-joint style shafts work. Totally normal.

 

[high plains drifter]

Unfortunately I don't have the ability to share video atm. It may indeed be an issue with the u-joint shafts but I've had this Capra for a few years and never had this issue before... at least not this prominently or noticeably.

Regarding what Jato is suggesting, it starts lurching ( jumping) long before maxing out the steering rate. If I were to set the steering rate to where the lurching doesn't happen, the vehicle would have only very minimum steering. FWIW The issue happens in a very regular interval as the wheels(s) rotate... not random like if it was due to an electronics glitch.

While I had this Capra on the bench for maintenance and to install the new ESC, I did open up and grease the f&r diffs. I'm wondering if maybe I didn't get the shafts re-seated properly or something along those lines.

To kind of re-describe the issue... It's as if there is something making contact with the wheel once or twice every rotation... like something rubbing the wheel and causing it to not rotate freely. But I'm not seeing anything making any contact.

 

[ferp420]

unhook the servo and see if the problem happens when steering the wheels by hand then run the servo and see if it happens with out a load on it that would narrow the problem down a little
also you could find any binding if there is any and you could still be Browning out of the servo is pushing past a brown out

i had a new set of knuckles and chubs that where loose when straight but the more you turn them the stiffer they got they would bind long before the universals bound up
nothing a little time with a file dident fix
just a thought

 

[bgredjeep]

Any chance it looks like this? Lmk if the link doesn't work and I can change the permissions.

https://imgur.com/a/R1jKlvD

 

[high plains drifter]

Very similar if not exactly like in the video link ( I really appreciate you sharing that). I didn't see any comments though. But yep... just like that and when on the ground, it kind of lurches due to whatever contact or pressure causing whatever parts to "seize then release". Whether minimum throttle or more... still does it. Speed doesn't seem to be causing anything although obviously the more I pull the trigger, the more obvious the issue is.

Regarding what ferp has said- I disconnected the servo and it still happens so I don't think it's electrical. It's a good quality 3bros servo that I've never had any issues with and I set the BEC setting on the ESC to only 6v so there shouldn't be any issues on that end.

Regarding also the filing- I would take a Dremel to the u-joints but I honestly can't see where they might be binding aside from the typical drag that u-joints experience when at too much of an angle.

I could understand if this was happening towards the max full-lock end points but like I said, if I dial out the steering rate to where it doesn't do this lurching deal, then I'd have hardly any steering at all.

I've spun the driveshafts and rear wheels with suspension unloaded as well as compressed and I don't feel or hear any issues there. I keep looking for any rubbed areas all around the axles, hex hubs, portal covers, etc... just not seeing anything suspect.

 

[bgredjeep]

The pulsing I showed in my video is normal. It's just how u-joints work. This video about driveline troubleshooting demonstrates it (starting around 1:40). In the video, they are showing the constant rpm being delivered at the end like a driveshaft, and the pulse effect in the center of the driveshaft. In the case of the steering axle, consider that constant rpm is sent to the center shaft, so the outside (the tires) will pulse. To avoid this, you would have to swap to CV (constant velocity) shafts. CV shafts will run smooth, but also limit steering angle to about 45-50° usually.

https://youtu.be/DDmz0tibVGM?si=gqMDdD51C5CDtkoX

 

[high plains drifter]

Yeah... I'm definitely aware of u-joints vs CVD's in RC as well as 1:1. I actually replaced the OEM joints in my Jeep with Reid Racing CVD's.

It's more that I never noticed this extreme limitation in my Capra before now. And I feel that there has to be something else at play here because I'm only able to steer side to side maybe 45-50% before it starts doing this... leaving me with VERY little unaffected steering throw. I have to be able to get closer to full lock left/ right than where I'm at now.

I appreciate the link to the video though. Reminded me to check my drive shafts to ensure they're in phase.

I also put the factory wheels/ tires back on ( as these SSD wheels and XL Flat Irons give a pretty wide stance from stock). Still has the issue but not as bad. I'm wondering if scrub is maybe playing into this issue too.. dunno.

I guess at this point I'm going to have to tear into the front end and inspect all drive-line components, maybe clean and lube/ graphite some parts and take some measurements with my calipers.

Still interested to hear any other input. To those that have tried to help here, I really appreciate it. Thank you, guys.

 

[Timmahh]

I would put my pennies on the issue being the dogbones/cup style drive shaft setup. The CVDs don't lobe over like the dogbone/cup shafts do.
MY stock v1 capra has a little of this I can see just on the bench turning things around. not ran it yet. Planned on CVDs for it, but its been 'benched' since I got the Promotos.

 

[high plains drifter]

Do you have a part number or name of what I should be looking at regarding a cvd style. I've seen some stuff on amazon and at amain but it's all Axial entire units or F9, TRX4, SCX10, Vanquish, etc... I also see the Axial UTB18 Universal. Not sure what I should be looking at that's compatible with OEM links and stuff.

 

[Bertman82]

Something else to consider, since you said you recently took the differential apart and put it back together, is you may have got the driveshaft phasing incorrect. There are pins in the end joints of the driveshafts, if the pins are not pointing in the same direction, that can cause slight binding in the rotation which can cause similar surging that you are describing. I had this happen to me and took a bunch of research pinpoint.

I found the video below that explains it gooder than I can via text. It's an easy fix to pull one end of the driveshaft off, separate the shafts from the center, align the pins and put it all back together.

https://www.youtube.com/watch?v=70POekJ0whQ

 

[high plains drifter]

Something else to consider, since you said you recently took the differential apart and put it back together, is you may have got the driveshaft phasing incorrect. There are pins in the end joints of the driveshafts, if the pins are not pointing in the same direction, that can cause slight binding in the rotation which can cause similar surging that you are describing. I had this happen to me and took a bunch of research pinpoint.

I found the video below that explains it gooder than I can via text. It's an easy fix to pull one end of the driveshaft off, separate the shafts from the center, align the pins and put it all back together.

https://www.youtube.com/watch?v=70POekJ0whQ

Yep. That was one of the first things I checked. Driveshafts are in phase so that's not a contributing factor. Thank you.

 

[Fallen]

Bertman's option brings up an interesting scab to pick at. Do both front wheels exhibit the same behavior? What if you remove one of the wheels, or one of the axle shafts? Does the other wheel still exhibit the problem?

My next step would be remove each wheel, one at a time and test if the other wheel still exhibits the problem. If yes, then remove both wheels to see if the problem is in the axle shafts. If the problem still persists, maybe it's in the steering linkage somewhere.

 

[high plains drifter]

Bertman's option brings up an interesting scab to pick at. Do both front wheels exhibit the same behavior? What if you remove one of the wheels, or one of the axle shafts? Does the other wheel still exhibit the problem?

My next step would be remove each wheel, one at a time and test if the other wheel still exhibits the problem. If yes, then remove both wheels to see if the problem is in the axle shafts. If the problem still persists, maybe it's in the steering linkage somewhere.

Both wheels seem to be exhibiting the same behavior but I say "seem" because I haven't done yet what you suggest.. I haven't pulled one to see if it's one or the other that's at issue... or neither.

I've inspected and rotated the rear wheels, rear driveshafts, front driveshafts, and transmission/ t-case and all looks and feels and sounds good there so I am mainly zeroing in on the front axle-shaft(s) at this point... just not sure exactly where the issue lies... maybe something going on in the diff or at the joints themselves.

I know that u-joints don't typically rotate freely as the angle between the axle-shaft and the stub-shaft become more angled, but like I said previously, it seems somehow much worse than it was before. This Capra didn't lurch like this last time I ran it... before the new ESC, greasing the diffs, pulling the shafts, pulling the transmission, etc.

I also thought that maybe I messed something up or torqued something down too tightly regarding the transmission but again... that all feels good. I may need to take that all apart again too though because maybe I'm just not feeling something that's actually faulty.

 

[nightcrawler48]

This is kind of a long shot. Berman82's comment about driveshafts being out of phase triggered a thought from something I had happen years ago. The truck was an Axial SCX10 OG and I broke a dogbone pin so had to put in a new shaft and new cup. Next time I ran it I had a similar issue. Took a bit of checking but finally found I'd put the new axle in out of phase with the axle on the other side. Once I corrected that, everything sorted itself out. Why? Don't know. I understand driveshaft phasing but I didn't think it made a difference on an axle. Ever since then I've always put steering axles "in phase".

Maybe this helps, at least it's one more thing to eliminate as a possible source of the problem.

 

[high plains drifter]

This is kind of a long shot. Berman82's comment about driveshafts being out of phase triggered a thought from something I had happen years ago. The truck was an Axial SCX10 OG and I broke a dogbone pin so had to put in a new shaft and new cup. Next time I ran it I had a similar issue. Took a bit of checking but finally found I'd put the new axle in out of phase with the axle on the other side. Once I corrected that, everything sorted itself out. Why? Don't know. I understand driveshaft phasing but I didn't think it made a difference on an axle. Ever since then I've always put steering axles "in phase".

Maybe this helps, at least it's one more thing to eliminate as a possible source of the problem.

It helps in more ways than one. I was actually wondering just this very thing but thought it was too dumb to even ask about... regarding the axle-shafts being in phase. I haven't checked them yet but I sure did wonder if that might be an issue as well. You sort of confirmed that it can be so I'll check those too. Very much appreciate you mentioning this and I don't feel quite so dumb wondering if it could be a potential problem. Thanks.

 

[bgredjeep]

You can't install the axle shafts out of phase with the locker. They only go in 2 ways, and always in phase either way.

I'm not sure how anyone can offer any more options of what might be going on without seeing it. You are looking right at it and can't tell. Post a video to Instagram or something so we can see what it's doing.

Based on everything posted so far I'm pretty sure it's normal and you just never noticed before.