Vibration under power 40-65 mph?

[Jeff Ward]

Hi All,

Just acquired a 2003 Discovery II, very tidy, but with a touch over 100K miles. Only difficulty seems to be nasty vibration from 40 mph to 65 mph, then it pretty much goes away. Prior owner has put on new shocks,some suspension items, new front prop shaft.

The vibration stops if I back off the throttle (i.e. coast). I have searched, the archives, but no clear trend or pattern in answers. Could the rear drive shaft do this?

Can you help me out? Thanks, Jeff

[Mjollnir]

I have a '99 DII with 105K, and the only advice I was given when I asked my Land Rover specialist what to look out for, was that if there is a vibration in the 30-50MPH range while accelerating, that would be the front prop shaft. It would also disappear when I took my foot off the gas.
However, in your case, the front prop shaft was replaced. The only advice I can give to you is that perhaps the prop shaft was aftermarket and not up to spec, out of round and/or balance, not installed properly, or a combination of these.
The reason the vibration goes away when you take your foot off the gas is because the prop shaft is slowing down and, most likely, the degree to which it is out of round is lessened as rotation is decreased. It can rotate slow enough or fast enough not to be noticible, but the 40-65MPH range is the sweet spot where it is noticible.
The only other cause could be either a bent rim or the other modifications were improperly installed and are getting knocked back and forth. That is all I can come up with.
An easy way to tell: get underneath the Disco and twist the front prop shaft. If you have significant play, there is something wrong. In either case, get to an LR specialist ASAP before it grenades itself and a whole other bunch of mechanicals.

[Jeff Ward]

Thanks Thor, figured it out

I just got back from sliding up under the Land Rover, and immediately figured out what was wrong- Hallelujah!

The rear prop shaft had been replaced, stickers still on it, handprints all over it with silver anti-seize. Apparently they forgot to tighten down the bolts going through the rubber doughnut. Two nuts where barely on the bolts, one was gone. It is miracle that I didn't have a failure on the road.

Thanks, Thor. You were on the right track it seems, I was confused on which shaft had been replaced.

Jeff

[Mjollnir]

I check the forum quite frequently, as I like to be proactive just in case an enthusiast has an issue that could affect me and my family. I'll check it out on my end just to make sure is doesn't exist, or to catch it before it gets progressively worse.
This was the first time where months of inquiring as to the possibility of something going wrong actually helped another enthusiast and prevented a grenading of, well, half the driveline and the loss of a perfectly good Disco II.
Glad to help, and thankfully you only have to get one new bolt. Make sure the bolts are tightened to torque spec- I don't know what that may be for the '03 Disco. More importantly, no one got hurt in the process.
If you have any other questions, I'll be glad to help. Have a great weekend.

[Jeff Ward]

Well, you have done your good deed

I check the forum quite frequently, as I like to be proactive just in case an enthusiast has an issue that could affect me and my family. I'll check it out on my end just to make sure is doesn't exist, or to catch it before it gets progressively worse.
This was the first time where months of inquiring as to the possibility of something going wrong actually helped another enthusiast and prevented a grenading of, well, half the driveline and the loss of a perfectly good Disco II.
Glad to help, and thankfully you only have to get one new bolt. Make sure the bolts are tightened to torque spec- I don't know what that may be for the '03 Disco. More importantly, no one got hurt in the process.
If you have any other questions, I'll be glad to help. Have a great weekend.

Thanks, Thor. You sure have helped me focus in so I could find the problem.
Now I just need to get the torque specifications for the rear prop shaft bolts, at the rubber doughnut end, and I'll be set to go.

Jeff

[Jeff Ward]

Problem solved

Wow, the Discovery is pretty smooth at highway speeds. I'm right impressed, (now that the drive shaft is installed correctly!).

Jeff