Hi guys. I have an older 811E. I bought it used about 8 years ago and haven't used it much until recently. For various reasons, I converted it to 2S by taking out the Tekin 1900kv motor and replacing it with a tekin 4300kv motor and I rewired the two batteries to be in parallel. It makes gobs of power but the rear-end fishtails badly without steering input. I have been advised to perhaps reduce the viscoity of the oil in the center diff. In all this time, I've never even checked the oil in the diffs let alone try to tune them. So I have some questions. I don't think my 811 came with a setup sheet. It may be defalut or may not be. I tried to go on the Serpent site and find the standard or defalut setup. It looks like they call for 5000/5000/3000 CST front/center/rear but I'd like to confirm that if possible. So questions:
Is there a way to check the actual version or model of my buggy? Like is it stamped on the frame somewhere?
What is the stock diff setup?
What are you guys actually running? Our track is dry, very hard dirt that gets a layer of very fine powder.
If I start with new 5000 in the center diff and I still get fishtailing , how much lower should I go to see if lighter oil helps the fishtailing?
What is the easiest way to get the diffs out to redo the oil?

I am open to other methods to get the ample power more controllable.

There are many changes that can be made to make the rear end more stable, but my suggestion would be to rebuild the whole car with the base setup. This way you will know what is in the car when you want to change anything, and you will know that nothing is bent or broken. After that, I suggest you talk to some racers at your track to figure out what tires people are using. Having the right tire is the most important part of the setup, and can transform how the car drives.

There is no quick way to know exactly what version you have, but if you post a picture people should be able to help you out.

I would not go below 5k in the center diff. As far as diff access, take a look at the manual. It may take some trial and error, but a good learning experience regardless.

all good suggestions. I understand that a full rebuild is a good idea but probably won't do that. In the meantime, I have removed and changed oil in all three diffs. It made a world of difference. I went with 7000 in the front, 5000 in the center, and 3000 in the rear.
In doing that work, i found that a lot of the screws aare metal going into tapped plastic. I'm not a big fan of that although i guess it is fairly prevlent in RC cars. I get screws coming out of the front end (mostlt steering) and the manual does not call out thread lock. I am using a thread lock rated for plastic called VC3.

I am pretty sure the version is the original 2011 ersion but maybe not. Here are some photos

My old Serpent 811be.