Hey guys so I just installed my welded diff into my 92 ls400 and now it has a bad vibration starting at 35 mph. And seems to get worse the faster I go.I think I installed everything correctly but I just can't figure out the cause. From what I've been reading on forums I'm thinking it could be the bushing between the drive shaft and the diff? When the diff was out some grease dripped out of the axles, could that cause the vibration? Any help would be greatly appreciated!

 

welding a diff caused the vibration! it is very difficult to get the diff to balance correctly after adding metal in there. also yes you may be right also regarding the giubo bushing (flex disc) could be torn as well. who did the welding? it could have been installed incorrectly as well.

the grease you are seeing is from the axle boot themselves. this will just dry out your axles and will cause them to be unlubricated and eventually wear out.
don't confuse grease with diff fluid, as dripping diff fluid is also bad.

 

This is a funny one. The differential allows for variances. If one tire is a bit larger do to manufacture and air pressure or tread wear the differential slips to allow the difference in wheel speeds and of course turning corners, and like mentioned above anything that is rotating needs to be balanced though at 35 mph I don't think the rpms are enough to show up on that small carrier diameter as an imbalance that would induce much vibration. Its more likely one tire fighting the other on the road surface. Welded diffs are for certain racing and maybe for drifting, they are not for driving around town. So just be happy with it and go racing or drifting, if you want an everyday driver don't weld the diff or do other modifications to cause problems. Pretty simple stuff. I have cars that last for years and just need the normal stuff like oil changes and tires etc. The welded diff is going to knock out the CV joints pretty quick unless you have beefed them up with something better. Lots of new stresses on everything.

 

perfect example of a red neck project

 

If you look into any welded diff info online you will find that this is usually the result. Once you lock it up you reduce or completely remove its ability to adjust for variances in traction and balance.