My Used Night Crawler with Gremlins (Stuttering and Stalling)

[MailManX]

I am very new at RC crawling. I decided to start with a couple of used rigs and learn on them. I knew they may have issues or break right away, and I’m OK with that, both because I got them for a good price and because it gives me the opportunity to learn.

I need your advice with my used (modified) Losi Night Crawler. The symptoms it exhibits in low speed crawling seem like stripped gears, yet I cannot find evidence of that. I certainly don’t mind tearing into it and replacing parts, but I’m not sure where to start. I don’t want to throw money at it needlessly. It’s quite sufficient to throw money at it with purpose!

I will tell you what it’s equipped with, then describe the symptoms, then provide link to a video I took so you can see and hear what it is. I know some of you have been in this hobby so long that you can probably diagnose it just by the sound!

My Losi Night Crawler came to me equipped with a Mamba Max Pro ESC, a Losi Xcelorin 21.5T crawler motor, with a CC BEC and a Hitec HS-5955TG servo. I don’t know if any of the gears have been upgraded.

THE SYMPTOMS: My Losi runs the best at full throttle, but even then you can hear a slight, rhythmic pulsing sound. However, at crawling speed, it hesitates and stumbles. If it gets in a semi-tight spot, it stalls out and just makes a growling sound.

I’d be honored if you’d take the time to watch this short video I posted. It starts with some actual crawling, then ends with the body off, mounted on a pedestal with some close-up shots of it running. At one point I grabbed a tire to stall it out to see if any gears were slipping. The “visible” gears were fine.

My Losi Night Crawler With Drivetrain Gremlins - YouTube

Your opinions and feedback are highly valued. Thanks!

[Olle P]

Seems like someshing is slipping, yes.
Check the grub screws at the drive shafts.
Also check the gears in the tranny. The final drive (LOSB3013) is turning the drive shaft by means of a pin. Check this pin.

[GrimJeeper91]

IMO, break down the axles and check the condition of the worms and make sure they have plenty of grease. Add grease ports while you have it apart.

[dentonmac]

Originally Posted by GrimJeeper91

IMO, break down the axles and check the condition of the worms and make sure they have plenty of grease. Add grease ports while you have it apart.

X2. I am suspecting the worms.

I would start with pulling the pinion and spinning the drive shaft to see if you feel anything grabbing or difficult to turn in the driveline. Then remove the driveshafts from the tranny and spin the worms (especially the front), again feeling for any grabs or spots. That will help narrow down where to start. But definitely break open the axle cases and get more grease and insure the worm shimming is correct. Also inspect the worm gear bearings, those little guys take a pounding.

Once you get that sorted out you will have a great little setup. I am partial to the Losi motors (don't see many of them any more). And the MMP is a great crawling ESC.

[MailManX]

Thanks for all the thoughtful responses. I'll tear this thing down and rebuild it. Gonna have some fun! I'll probably wait till the weekend. Gotta work for now. Seems I have some RC bills to pay!

[Tgreer]

X3 on the worm gears! Inspect both axles very closely also make sure all the bearings are good, especially the one on the worm gear. When you put the axle back together use some heavy grease like red & tacky. I could not tell from the vid, but does it have a bec running to the servo, if not you need one ASAP.

They are hard to find now, but get your hands on some HD losi gears and if your really lucky, get your hands on a dlux chomoly worm!

[MailManX]

Originally Posted by Tgreer

X3 on the worm gears! Inspect both axles very closely also make sure all the bearings are good, especially the one on the worm gear. When you put the axle back together use some heavy grease like red & tacky. I could not tell from the vid, but does it have a bec running to the servo, if not you need one ASAP.

They are hard to find now, but get your hands on some HD losi gears and if your really lucky, get your hands on a dlux chomoly worm!

Yes, it does have a Castle 10a BEC, although I'm not certain that it's wired correctly because the servo powers up the instant I plug in the batteries BEFORE I turn on the power switch to the ESC. That is not critical to me for now, but I will definitely address it along the way.

I'm surprised that the HD Losi gears are getting hard to find. I thought the Losi was still a pretty popular crawler. Anyway, I'll have a look around since I defintely want to get those. I'm hoping to overdrive the front slighly.

[Tgreer]

Yes your servo will power up when you plug in the battery, because the bec is bypassing your on/off switch in the esc.

Also look into the tranny flip mod. It straightens out your driveline creating less friction and better performance!

[MailManX]

Originally Posted by Tgreer

Yes your servo will power up when you plug in the battery, because the bec is bypassing your on/off switch in the esc.

Also look into the tranny flip mod. It straightens out your driveline creating less friction and better performance!

Good to know that the servo power up is not a wiring problem.

In all the reading I've done so far, I've not come across the tranny flip mod, so I'll check it out. Sounds intriguing. Thanks!

[anuthabubba]

bryco13 (a few threads down - Back to my roots) just got a set of HD worms from Horizon within the past week or so!

[MailManX]

Originally Posted by anuthabubba

bryco13 (a few threads down - Back to my roots) just got a set of HD worms from Horizon within the past week or so!

Yup - I saw that Horizon has them in stock (LOSA3187). However, they seemed a bit pricey. I did spend some time trying to find Dlux Chromoly, but that wasn't meant to be. I finally found a seller with a new HD set for $29 shipped. It's on order.

[Tgreer]

Originally Posted by MailManX

Yup - I saw that Horizon has them in stock (LOSA3187). However, they seemed a bit pricey. I did spend some time trying to find Dlux Chromoly, but that wasn't meant to be. I finally found a seller with a new HD set for $29 shipped. It's on order.

At this point a dlux chomoly is about like a unicorn! The people that have them are not going to let it go.

[4everyoung]

mine did the same thing when i got it, motors got eaten up in 15 mins. took axles apart put a well amount of grease to the worms. havent had an issue since

[MailManX]

Originally Posted by 4everyoung

mine did the same thing when i got it, motors got eaten up in 15 mins. took axles apart put a well amount of grease to the worms. havent had an issue since

Thanks! That's good to know. I just received my new HD Worm Gear Set this weekend and plan to replace the original gears. I'll use the grease that came with the HD set.

I also ordered some new bearings from Avid. I ordered several different bearings for three different rigs I own in order to get to the free shipping level of $40. Turns out that I overshot that a bit. Therefore, I went back to my order and changed the Losi spool and pinion bearings to ceramic. It sure is hard to beat Avid's $5 price for ceramics! I managed to get my order just over $80 and qualified for the free "Priority" shipping. I hope to receive the bearings Tuesday. After that, I'll rebuild the axles plus make some other recommended changes. I have high hopes for great results.

[Olle P]

Originally Posted by MailManX

... received my new HD Worm Gear Set this weekend and plan to replace the original gears.

Replace only the front drive with HD!
Use the best original drive in the rear, and keep the rest for spares.

That way you get some front axle overdrive which helps reduce total friction and improves performance and handling in general.

[MailManX]

Originally Posted by Olle P

Replace only the front drive with HD!
Use the best original drive in the rear, and keep the rest for spares.

That way you get some front axle overdrive which helps reduce total friction and improves performance and handling in general.

That's a terrific idea! Thanks!