U Joint

[99blkgs]

hey guys i was wondering does the 99 gs300 have a u joint connecting the differential to the driveshaft?

[TomWoodLexus]

Yes, however the never need replacement... damage?

[nc211]

Actually, no, not at the connector from the driveshaft to the differential, just something known as a "Flex Coupling", which is a 1 inch thick rubber connector between the driveshaft and the differential. The U joint is in the middle of the driveshaft, around the center bearing housing "A U shaped mount the drive shaft sits in".

I saw your other threads, and that you're being told the rear driveshaft needs to be replaced to address your vibration problems. I would not do this until you have tried a new flex coupling, a new transmission mount, and possibly a new U center bearing housing. The other possiblity is the rear differential mounts themselves could be torn. Do you have access to get under your car to look at these things? If so, here is what you're looking for:

The Differential mounts: from the rear of the differential, along the cross bar support of the car, you will see to circular rubber mounts, with bolts in the middle of them. They're actually set within circular cutouts of the cross member. Those can tear with too much hotrodding.

Flex coupling: At the front of the differential, look for a 5 (or 6 can't remember) bolt "star" like pattern. It's right where the driveshaft ends, and the differential begins. You'll see the black rubber coupling between the two.

The center bearing: Just follow the driveshaft to the middle part of the entire part. You'll see the U joint and the U clamp, that's your area to look for.

Most likely, it's one of these three items.

For the record, I had to replace my driveshaft on my 95LS400 too, after a very very long struggle to figure out what was wobbling. If you search for "wobble" on here, you'll probably find the thread. It's long....but I posted up the end result at the first thread. The dealership approach was to replace the whole driveshaft, as it "appeared" the rear section at the U joint connector was "sticking". It looked a bit notchy in operation, but honestly, I think the center bearing mount was what was bad. I had already replaced the flex couplings, the transmisison mount, and the rear differntial mounts. But, I will say, once that driveshaft had been replaced "and center bearing support", the car was freakin' glass smooth. Smoothest car I have ever driven. I do recall the senior tech who had built a history with the car saying "normally we don't have to replace the driveshafts, but every now and then one does go bad". It was a $1k repair though.

[99blkgs]

Actually, no, not at the connector from the driveshaft to the differential, just something known as a "Flex Coupling", which is a 1 inch thick rubber connector between the driveshaft and the differential. The U joint is in the middle of the driveshaft, around the center bearing housing "A U shaped mount the drive shaft sits in".

I saw your other threads, and that you're being told the rear driveshaft needs to be replaced to address your vibration problems. I would not do this until you have tried a new flex coupling, a new transmission mount, and possibly a new U center bearing housing. The other possiblity is the rear differential mounts themselves could be torn. Do you have access to get under your car to look at these things? If so, here is what you're looking for:

The Differential mounts: from the rear of the differential, along the cross bar support of the car, you will see to circular rubber mounts, with bolts in the middle of them. They're actually set within circular cutouts of the cross member. Those can tear with too much hotrodding.

Flex coupling: At the front of the differential, look for a 5 (or 6 can't remember) bolt "star" like pattern. It's right where the driveshaft ends, and the differential begins. You'll see the black rubber coupling between the two.

The center bearing: Just follow the driveshaft to the middle part of the entire part. You'll see the U joint and the U clamp, that's your area to look for.

Most likely, it's one of these three items.

For the record, I had to replace my driveshaft on my 95LS400 too, after a very very long struggle to figure out what was wobbling. If you search for "wobble" on here, you'll probably find the thread. It's long....but I posted up the end result at the first thread. The dealership approach was to replace the whole driveshaft, as it "appeared" the rear section at the U joint connector was "sticking". It looked a bit notchy in operation, but honestly, I think the center bearing mount was what was bad. I had already replaced the flex couplings, the transmisison mount, and the rear differntial mounts. But, I will say, once that driveshaft had been replaced "and center bearing support", the car was freakin' glass smooth. Smoothest car I have ever driven. I do recall the senior tech who had built a history with the car saying "normally we don't have to replace the driveshafts, but every now and then one does go bad". It was a $1k repair though.

yea when i had the car up and i moved the back tire left to right the driveshaft felt like it was loose it just had alot of wobble in it.