I recently upgraded my 2001 discovery 2 to a 4 inch lift from 2 with 6 degree castor corrected radius arms and 33s. It may matter later but while test driving after that another car almost hit me and I ended up panicking and knocked it into reverse while it was moving forward at about 10 mph stalling the engine. At first everything seemed fine but when I got onto some faster roads I noticed a vibration that started around 30 mph and just got worse. They only seem to occur when accelerating and disappear as soon as I let off the gas. My first thought was driveshaft angles so I called up Tom Woods and they recommended a multiple double cardan driveshaft to deal with the new geometry. This did not fix the problem. I did notice while installing it though that I had torn motor mounts. So I replaced all of those. This did not work. So I found some play in the ball joints and replaced those. Again the vibration is still there. The vibration seems to go away with the front driveshaft off and the CDL locked although I am a bit wary of going fast with the CDL engaged. And it defiantly goes away off the gas. Does anyone have any idea what could be causing all this vibration? Could be related to my panicked reverse? It had no vibrations before the lift but I don't think it's that at this point I think something is broken. I'm at a loss. Thanks.

 

Was your panic reverse before or after you lifted?

Did you only notice the vibration after your panic reverse?

If yes, did you notice it immediately after your panic reverse?

The short answer is, going into reverse while moving forward at speed is going to cause *some* amount of damage. It could be as minor as some excess clutch wear that you'll never notice, or as major as broken hard parts in the transmission.

If you only noticed the issue after the incident, then I would guess transmission damage is the culprit. However that's only a guess and further diagnostic is necessary.

Have you noticed any new noises that accompany the vibration?

 

I haven't got any experience with lifting a Disco but I can offer some insight about the vibration. The output bearing of the transfer case is a verified source of vibration and removing the front driveshaft and having it go away is one test to confirm it (assuming your driveshaft itself is confirmed balanced). It could be that the increased angle of the driveshaft due to the lift could be loading the bearing differently and creating the vibration. I can't imagine jamming the trans into reverse could cause a vibration like you describe. I think you'd likely have other issues rather than a vibration, and I really don't think that any potential damage would go away by removing the front driveshaft and isolating the front diff. A trans expert might have a different opinion but to me that seems like a critical detail. Unfortunately I'm not sure of an easy way to test my theory but I thought it was worth mentioning.

 

The major thing that's throwing me off is the vibrations only happen under load and only with the front DS in from what I can tell. Unfortunately I cannot tell if it's damage from my panic reverse or something related to the lift that is causing the issue as the reverse happened before I had managed to get it up to the speed the vibrations occur at. Really any list of things that could cause front drive line vibrations under acceleration that aren't the driveshaft would be helpful.

 

Just because the driveshaft is new that doesn't mean that it is balanced...if you take the drive shaft out and the vibration goes away then the options are limited to the driveshaft, output flange on the t-case or the input on the diff. Also you can drive however fast you want with the CDL engaged so long as the diff is in HI range...I drove across country with the front shaft removed..

 

I have tried 2 different driveshafts. But would the driveshaft being unbalanced cause vibrations only while accelerating and not coasting?

 

I can attest to this. Had a vibration issue as well and tried 2 different shafts - one that I had balanced twice. Finally took it to a driveshaft expert and had it high speed balanced. As soon as I put it on vibration was gone. This is on a 3 inch lift btw.

 

if you only have vibration under load and not just coating i would think something is out of balance in your tranny,

 

I would also check the front transfer case bearing. Take the front driveshaft off and see if there is any play on the transfer case output shaft.

 

If it were the front driveshaft out of balance, it would vibrate regardless of load.

If it were the front Tcase output, it would mostly vibrate in sort of a mid load scenario. Neither when coasting, nor when under load, but sort of between the two.