Question for those running HP Dana 30s on 2000/2001 XJs

Now that my caster angle has been fixed on my '01 (lengthened my LCAs by 1/4"), I'm getting noticeably more driveline vibrations from the front DS between 10 and 30 MPH... I can tolerate it, however, I think it's nearing the time for me to finish cleaning up and building up my HP30 that has been sitting idle for damn near a year.

My understanding is that the exhaust manifold and pre-cats on 2000 and 2001 XJs will likely interfere with the driveshaft when running a high-pinion front axle... I'm running an RE 3.5" lift (truly 4.5" though) - how likely is it that I'll run into this issue? Is it curable by bump stops or should I consider a reworking of the exhaust system?

It shouldn't be a problem at that lift if you are bump-stopped correctly.Your front shaft probably has some wear on it also,what did you set your castor at,Im at 6" of lift on my 2000 and don't have any issues(been lifted since mile 36)!

Honestly, I didn't even measure... I knew it was too steep based on how twitchy the steering was and due to wandering issues on the highway, and realized my LCAs were set properly for 3.5" of lift rather than 4.5"... I just extended them 1/4" and called it a day. I assume it's set correctly because highway road manners and ride quality are now damned near as good as they were at stock height.

Are you still running the low-pinion D30? If so, I'd assume you've got a transfer case drop?

I have a 2001 with the precats, a 1996 HP30 front axle, and stock springs with a 2" coil spacer. I still run the stock bump stops and in full flex the driveshaft does not contact anything.

Yeah, ive got those coils, with a HP pinion out of a 90 Xj, on my 01. No issues to date.

I have terrible front vibes, but I think its the double cardan joint on the driveline.

anthrax323 said:

Are you still running the low-pinion D30? If so, I'd assume you've got a transfer case drop?

Click to expand...

Yes,Im still running my LP D30. No,I dont have a T-case drop as that makes the front driveline angles even worse!

anthrax323 said:

Now that my caster angle has been fixed on my '01 (lengthened my LCAs by 1/4"), I'm getting noticeably more driveline vibrations from the front DS between 10 and 30 MPH... I can tolerate it, however, I think it's nearing the time for me to finish cleaning up and building up my HP30 that has been sitting idle for damn near a year.

My understanding is that the exhaust manifold and pre-cats on 2000 and 2001 XJs will likely interfere with the driveshaft when running a high-pinion front axle... I'm running an RE 3.5" lift (truly 4.5" though) - how likely is it that I'll run into this issue? Is it curable by bump stops or should I consider a reworking of the exhaust system?

Click to expand...

If you plan on installing the HP D30 and want to improve the caster issue, then you need to rotate your knuckles too. Any more lift than 4-4.5" and you will be fighting the complex battle of driveline angle/vibes VS good steering/insufficient negative caster.

I swapped a HP D30 into my 2000, which is a daily driver that sees about 45 miles per day freeway, plus 15-20 in town on weekdays. After about 6 months of driving, I took a step backwards and tore it down, rotated the knuckles back 4 degrees to net a caster angle that worked well with my 6" lift setup.

It's not that hard to do and well worth the effort....... here's my write-up, gusset the knuckles and housing while you're at it. http://www.naxja.org/forum/showthread.php?t=913774&page=10

Note: If you rotate the knuckles back more than 4 degrees, you will likely need to relocate the spring perches as well, to prevent the coils from bowing, FWIW.