vibes

[drewclare25]

fellas,
i've had my 3 inch lift on for almost a year now, and its finally starting to vibrate. It starts to rattle the car when I'm accelerating from a very slow speed, and stops around 25 mph. The vibe sounds like its coming from somehwere near the passenger seat. My question is: driveshaft, or ujoint. Also, if one is bad, how will i know? Play in the driveshaft? anything?
Thanks,
Drew

[Disco Mike]

If you are lucky, it may only need to have the u-joints greased. If that makes it any better then you most like have a bad u-joint. How often do you grease them?
As for your lift, you are nearly in that hrey area where you may need to replace one or both drive shafts with some up-grade shafts.
Mike

[jhmover]

If you still have the rotoflex in the rear that's probably the problem. Look at rear driveshaft where it bolts to the differential yolk. If you have one you'll see what looks like a rubber donut sandwiched in between. It's probably cracking and this is causing your noise. Suggest you do some research and replace it with a regular u-joint driveshaft. I lifted my D1, rotoflexes don't last when they're lifted. Probably too much pressure on them and they're not designed to flex that much.

You can yank the rear driveshaft, put the cdl in 4 lock high then drive it. If there's no vibration then the rear driveshaft is probably the cause. If it doesn't go away you can put the rear back, then pull the front and see if it goes away.

Go here http://www.discoweb.org/index.html scroll left down to rotoflex to u-joint conversion, has pictures and instructions.

If you decide to to this you have many options.

1. They have a kit for this at Atlantic British.
2. You can take the driveshaft to a driveshaft shop. They can weld on the proper flange, put in new u-joints and balance it.
3. You can have a new driveshaft built.
4. You can order the fancy ones from Tom Woods or Great Basin Rovers.
5. You can find a good used D2 rear driveshaft, you still need to change the flange on the differential though and put the spacer in.
6. You can put in a new rotoflex, but I wouldn't expect it to last very long.

[drewclare25]

great thanks alot guys

[Disco Mike]

For what it is worth, I put 83,000 miles on my D2 with a 3" lift, held up just fine.
What ever you do, check out all the joints and replace as necessary be it the roto flex or u-joints, you may find a couple that are bad base3d on your trucks mileage and how often they were greased.
Good luck,
Mike

[jhmover]

Well just FYI I put about 70k on the first one, but the 2nd one after about 25k was already cracking. This is with only about a 2 inch lift. Since I bought a 3rd member with ARB and the u-joint flange I got lucky and got a D2 driveshaft that was newly rebuilt and never used.

The other thing I noticed was the pinion would growl when you left off the gas on the freeway. That went away when I put this 3rd member in. I have a theory (no proof at this time) that the rotoflex puts some pressure on the pinion bearing and eventually causes the growl. I can't see any problems with the gears in the 3rd member I removed (just looking at it), so I'm thinking the bearing, although you can't really feel any problem when you turn the yolk with it out of the truck.

Some day when I have time I'll yank the pinion bearing out and see if there's a problem. Could be backlash isn't right, too, but I kind of question that because I can't see any wierd wear on the gears.

[drewclare25]

i greased the driveshaft nd most of the u joints...(ran out of grease). So far it hasn't helped. I am going to try some more grease but if that doesn't work...is there anything else it could be? I don't want to get rid of my ds if they are perfectly fine.
Also i just noticed i messed up about the speed of the vibes earlier...it starts around 25 and leaves around 30 mph. if that makes any difference.