HELP! Drivetrain issues, back and fourth jolting

Greetings fellow Toyota people, I am nearly finished the process of completely restoring a 2001 Tacoma 4wd but am having two main problems. One being when driving at around 30-45mph and in 3 or 4th gear at aprox. Half throttle I am having a violent “coming from the rear” back and fourth jolting. Not up and down like it’s skipping and not a vibration. The truck feels like it’s having a fast forward misfire of letting off and picking back up but very quickly. It only does it at those specific times, it goes away when floored or let off. It doesn’t do it at low speeds either and only seems to do it under load. FYI I replaced almost everything on the truck, new leaf spring packs, new shackles which lifted it 2.5”, new brakes which is eliminated via pinching line thinking they might have contributed. New carrier bear for the second time and all new fluids. The U-joints are extremely tight and have been replaced recently and the only play in the rear driveshaft is the rear axle when trying to move it back and fourth. I stuck a camera right next to the drivshaft and drove it, it appeared that the carrier bearing was the problem but I have already installed a new one for the second time and it didn’t change. This is a TRQ brand bearing with a LT warranty. I had the rough country carrier bearing spacers in combo with their 2.5 lift. I removed them thinking it may help and it didn’t change. I’m very lost on a cause since there isn’t much to it. I know it’s not the clutch since it’s not doing it all the time and the engine runs great with no codes appearing. I would really appreciate some sort of help with this because I have no freakin clue, thanks.

 

Do you ever lube the driveshaft zerks?

 

the u joints need to move freely
if the driveshaft is out of phase that will cause a problem too.
if the drive shaft angle(s) are too great that will cause a problem as the driveshaft speeds up and slows down. You might have to shim the rear axle. There are many posts on this forum related to your issues.

 

Make sure your driveshaft is properly phased before doing anything else. Follow the steps in this video. I fought some pretty violent driveshaft vibes for a long time, usually just eyeballing the phasing, and now it's smooth as glass after following the steps in this video.
https://youtu.be/dt69zYAcXME

 

“Slander” I know mine is not correct because I had it completely apart a few times. I am going to go try it right now but I find it very hard to believe that has any effect. I’m not doubting it just seems goofy. I let you know how it goes and thanks for the response!

 

best explanation I can find...

https://www.youtube.com/watch?v=gmV4qwLfOMY

 

My transmission would violently shake like it was going to fly out from under the truck.

 

After recently replacing my leaf packs and I ended up with a driveline vibration- Same model springs, etc... ended up with a touch more ride height (as the old springs had settled over the years). I had to go through the whole drive line angle measurement process and shim the axle. It's a process, but don't ignore it.

 

Andy, can you explain more about what you did so I can get an idea?

 

There is a thread around here, which I can't find at the moment... which details out the process, it has a spread sheet.. etc..

However, what it all boiled down to for me, was to put the angle finder on the slip yoke, and zero it, then put it on the axle housing, that difference will determine the angle of shims that you need. The thread I mentioned had some other calculations (which are probably important), and the OP mentioned that he had to go with shims at a certain percentage different than the angle he measured (ie, he measure 3 degrees, installed a 1 degree shim, and it corrected to 0). I found the opposite, if I inserted a 1 degree shim, it changed 1 degree.