Hey all, as I have been attempting to track down a phantom drivetrain vibration, I'm leading myself to believe that I received a faulty or unbalanced propshaft from LK8 and just need some insight.

The vibration is always around 40-45mph when accelerating, uphill is worse, and sometimes if I'm trying to accelerate in that range to maintain momentum I'll feel it pretty noticeably. I've had two totally different sets of tires on it with the same result, both with alignments and balancing.

I replaced the driveshaft first thing when I bought the rig with a greasable shaft. I figured the vibration must be from somewhere else because that didn't relieve it. I grease the joints and yoke monthly as well as the rear shaft, which I have also recently replaced with the 4 bolt flange conversion.

No check engine codes, no amigos or other present issues. I've driven the rig 20,000 miles like this (I know, I know.. hard times for a poor man and his daily driver) and it's the only problem I have left to tackle.

Diffs filled, t-case filled, tranny filled, oil full.

There is a small amount of play when pushing the front shaft up and pulling down at the double cardan joint. It would make sense that there might be a little bit of play here but I don't remember it when I installed the shaft.

I'll include a video later today but I was hoping to gather some thoughts.

 

So, you had this same issue before driveshaft change and tire change. Was the transfer case full of oil when you bought it? I'd check output shaft, front, on transfer case for any unusual movement, in or out, up or down. I'd not consider the tires, since normally an unbalanced tire will usually appear at higher speeds...not during acceleration. Did you check your rear driveshaft joints and coupler? Do you have excessive play in axle yokes, back and forth, while turning driveshaft by hand?

 

When I bought the truck it had no front driveshaft and I had put a donor in very briefly but I can't recall it doing the 40-45 vibration, it's possible I was too focused on the other issues happening at the time, that was over a year ago regardless.

I replaced the rear drive shaft and couplings last week, I don't know if my mind is playing tricks on me because I thought it felt slightly better but now I feel like it is slightly worse, the vibration that is. I'll check the output shaft later today. The previous rear shaft couplings also seemed fine.

The transfer case fluid was not low. The diffs were full of water, mainly the front, maybe that's a sign?

 

Today I replaced the bolts at the front of the front driveshaft since I found that they were not able to be tightened to spec as I rounded them when installed it about a year and a half ago. I also found three things of issue regarding my repairs of the rear shaft/rotoflex delete and I am paying for it.

Firstly, only one single guide indicted that I may need a driveshaft spacer after a 1"+ lift. Well I have a 2" lift in back and a 3" lift in front and after 300 miles the splines had traveled enough after moderate offroading to pop the rubber gaiter/boot off its seat. Driving in town I have not had the same issue, just my familiar 40-45 vibe. I will also be replacing the pinion seal as I knackered it originally by forgetting the put the spacer in the right place so I've developed a diff leak at the seal.

Most importantly, somebody PLEASE tell me, after a rotoflex delete / 3 bolt flange - to - 4 bolt flange conversion what is the proper torque setting for a 2000 Discovery 2 with a BOLT fitting vs the nut fitting? The Atlantic British website says 90 ft lbs, the paper I received with the conversion kit says 74 ft lbs but I found play in the rear shaft today so I tightened it as tight as my torque wrench would go then a little bit further (I have an inch pounds torque wrench and it goes to 960 inch pounds so about 120 inch pounds short) and that reduced a little play but really I thing I ruined the pinion seal sadly.

I will follow up in a couple weeks when I have the parts and can confirm it's not the rear shaft. That conversion was a bear of an endeavor and I don't recommend it despite many posts saying otherwise. Just replace the rotoflex....

 

Hey Guys I'd like add that I had a similar vibration situation. I just installed a new Front Prop Shaft from British Parts of Utah ( https://www.bputah.com/Disco2%20Part...rive_Shaft.htm ) due to a terrible vibration (or clunking really) at all speeds... The stock height truck never did it before i put in the Lucky8 Terra Firma 3" lift kit ( https://lucky8llc.com/products/terrafirma-3-lift-kit ) so i assumed the shaft was the culprit. And yes putting in the new on did quiet it substantially, but i still have this smaller vibration on acceleration. Kind of annoying vibe...
Now I'm thinking would the lift angle still may have an affect this new longer travel HD Shaft? I only bough this one on recommendation by a Member here that said they had issue with the Tom Woods. The stock rear shaft angle really doesn't appear to be that substantial and that the stock shaft may be at fault here... The vibration to me still feels up front. Any Suggestions to look at?