Heng long T-90 strange issue with drive sprocket.

[CSsync]

Hello there I hope you are doing well, I could not find any info on this specific problem online or on the forum so I thought I would see if anyone had the same issue and if so, how did you fix it? I recently purchased the TK 7.0 Heng long T-90 with the metal gear box and suspension arms and plastic everything else and I ran it for a few days stock without any issues then I did what I have done with all of my previous Heng long tanks and upgraded the dive sprockets and idlers to steel with anti slip rings. After this a couple of days using it with this upgrade applied it started not tracking straight so I decided to strip it down and I removed one of the drive sprockets without issue but when I tried to remove the one that was on the side that the tank was moving to it would not budge! I noticed there was some debris behind it and that it was sticking out far more than it should have been and the tracks were rubbing on the side skirts. So I thought it had to be the debris so I got a baiting needle which I use for carp fishing and went around the inside of the sprocket from behind and pulled out a small forest from back there and I thought that I would now be able get the sprocket off but it still would not budge and is still sticking out further than it should be and the tank is still not tracking straight (I pulled very hard to get it off but it did not move). I should also add that the tank still runs with this issue with the sprocket but does not track straight. I'm completely stumped and have never had this issue before but I'm fairly sure that the tank not tracking straight has something to do with this odd problem with the sprocket. If anyone knows how I could get the sprocket off or disassemble it in some way whilst it is still on the tank I would appreciate any advice that you can give. Thanks in advance.

[Herr Dr. Professor]

I'm puzzled, too. I wish I could help. Obviously you know the right way to pull off the sprocket, for you already switched out to a metal sprocket. There are lots of RCTW members with far more experience with HengLong tanks than I have, as I mostly stick with Taigen/Torro or others. My only suggestion--and it strikes me as rather simplistic--is to split and remove the tracks to see if the sprocket will come off more readily. The chances are that you have done so already (twice), but that's the best I can come up with. Someone should chime in here soon, but if not, I will see if I can have a look at my T-90 (new in box for the past, what six or seven years?) and offer anything better.

[CSsync]

Thank you so much for your reply, I have already tried what you suggested but thank you for trying to help anyway hopefully someone can figure out what is going on with it because I'm very puzzled too I had another go at today but still could not get it to budge I tried a couple more things such as running the tank with the tracks off and seeing if that might coax the sprocket out but so far nothing I have tried has worked. Again the reply was much appreciated, have a good day/night.

[Jofaur86]

just an idea like this
Good morning,
it's not easy from a distance and without a photo? but if I understood correctly glass worriesc? the pinion seems to have slipped on its axis? and come and rub on the skirts? have you tried with penetrating oil, like WD40, let it act, then try to turn it from right to left, by pulling on it, or gently, with a hub puller? taking care to insert two pieces of metal, between pinion and chassis, without guarantee that it will not break?

[tankme]

Had it happen with certain tanks where the sprockets are hard to get off. I just pry, pull, and twist until they come off. Eventually the do.

[HERMAN BIX]

Taking the upper hull off the lower will give you a better shot at it too.
Try very large flat blade screwdrivers -2 of them- and lever the sprocket out carefully.
If you bust the sprocket, unlikely but possible, I have several spare ones that I could send you one for nothing.
Once its off, dress the output shaft with a file or good sandpaper to remove any burr that may have contributed to this problem.

[tankme]

I've done it the way Herman describes. I've also used a large electrician type side cutter and used it as a lever between the sprocket and the hull.

[Herr Dr. Professor]

Definitely separate the lower and upper hulls if you haven't done so already." And when you do get the sprocket off, as you will, I agree that you should "...dress the output shaft...to remove any burr...". I had a burr on the tractor PTO shaft. After two of us old guys used coffee and significant linguistic prowess trying to get the shaft back on, we went carefully at the PTO spline with an angle grinder (a big Dremel tool) and then the shaft went on "like budder."

[CSsync]

Thank you guys so much for all of the replies I will try all of this stuff today and let you know if I manage to get it off. Have a fantastic day everybody.

[CSsync]

Hello all, hope you are doing well. Today I tried to remove the sprocket by oiling it, letting that soak in and then using two large flat head screwdrivers as leverage to pull the sprocket off of the tank. I saw it lifting and thought that it was coming off however what I did not realise was that instead of the sprocket coming off it was the whole shaft that connects it to the gearbox with the sprocket still attached to it. So the first thing I did was oil the sprocket some more wait a little bit, put it in a vice and tried to pull it off using a large pair of pliers. This still did not work so I kept trying and eventually it popped off however before that happened the sprocket fell apart into multiple pieces but luckily they fit back together quite easily. I inspected that sprocket mount arm (I'm not sure if this is actually what it is called but you probably know what I'm referring to) whilst it was out of the tank and saw no damage, rust or anything so I'm still confused as to how the sprocket even got so stuck in the first place. Anyway I tried to get the sprocket mount arm into the gearbox again but with no luck I decided to take the gearbox out and have a look and on closer inspection the washers and stops holding the arm in place had slipped out and its going to be a pain to get them back in. I was struggling to fit the arm back into the gearbox so I decided to leave it there and revisit it with hopefully some advice on how to fit it back tomorrow. Thanks for all of your help so far and thanks in advance for any help to come. Hope your all doing well.