Slight issue after lift...

[BIGdaddy]

Very specific issue

entered costco driveway, steep hill with sizable swale at bottom, doing like 5 mph...continued on, and started hearing what sounds like very light "thuds"

they were rotational, and happened like this: thud-thud....thud-thud.

I recreated it once more on my drive home when I went up anther steep driveway/entrance to a gas station.

did not feel it from costco to gas station...

I'm thinking rear dshaft ujoints, but I'm not sure.

thoughts? I'm thinking about pulling my shaft and having a shop replace both ujoints, since they probably have worn themselves to be where they "want" to be.

truck is in sig, and lift was around 2"-3".

I greased up both ujoints, and they actually took quite a bit of grease before it squeezed out near the cap/needle bearings. maybe that was it?

 

[jsolorza]

If you suspect the rear driveshaft u-joints, remove the driveshaft and drive with front wheels to replicate the symptom. But sounds like suspension noise.

 

[BIGdaddy]

driving was on flat ground going straight with no compression/unloading of suspension, and it happened about once per tire revolution...

It happened after the driveway was used.

 

[comrad_zeelaagee]

specs on lift? other changes to stock form... am assuming you're talking about your XJ.

 

[BIGdaddy]

specs on lift? other changes to stock form... am assuming you're talking about your XJ.

Haha...yeah. 1992 xj 4wd- 4.0l/auto/np231/d35

The lift is very simple, 2" coil spacers in the front and refreshed/hybrid leaf pack in the rear. In the back i went from 16" hub to fender lip to 19".(2" over standard 17" ride height)

The front was the same, 17 to about 19. I greased both ujoints last night till the old grease oozed out of the cup. It took a surprising amount to do it, though. I wonder if the joints are/ were just dry. Not sure if freeway driving is good-to-go or not?

Never really felt anything on my commute yesterday. No vibrating or pulling, etc...weird that it only happens when the driveline is loaded a certain way

 

[BIGdaddy]

Oh and the slip joint only moved out maybe. 1/4 to 1/2, so i think it still has more than enough spline engagement.

 

[alosix]

That looks ok, I know some XJs came with a pretty restrictive slip yoke on them that didn't like much angle at all on the shaft.

Can you recreate the thud while standing on the breaks from about 30mph? That will rotate the axle pinion down a bit and lift the rear a little. I've found that test normally lets me know if an XJ needs a different slip yoke on it or not.

Jason

 

[BIGdaddy]

That looks ok, I know some XJs came with a pretty restrictive slip yoke on them that didn't like much angle at all on the shaft.

Can you recreate the thud while standing on the breaks from about 30mph? That will rotate the axle pinion down a bit and lift the rear a little. I've found that test normally lets me know if an XJ needs a different slip yoke on it or not.

Jason

thats a good test, I'll do that...

 

[alosix]

yeah.. and if it does act up for that this would be the fix:

http://www.rubiconexpress.com/jeepparts/Product.aspx?folder=JPSYE&part=RE1822

 

[comrad_zeelaagee]

hmmmm- that's not a major lift. the one lingering issue i have from doing my lift is a squeal from my front ds ujoints... but this sounds like it's different from that.

have you double checked all your bolts and nuts that were worked on? maybe there's a loose nut on your yolk/ujoint?

is the noise a hard thus or soft thud? is it coming from far rear, mddle, or front?

 

[BIGdaddy]

hmmmm- that's not a major lift. the one lingering issue i have from doing my lift is a squeal from my front ds ujoints... but this sounds like it's different from that.

have you double checked all your bolts and nuts that were worked on? maybe there's a loose nut on your yolk/ujoint?

is the noise a hard thus or soft thud? is it coming from far rear, mddle, or front?

yeah, not what I'd consider major lift, either, 2" is well within the limits of needing a sye, and it doesn't vibrate at all (more than it did before the lift, anyways..haha!). I've checked most of the nuts and bolts, but it couldn't hurt to give it a "once over", again. Good idea.

Most decidedly a "soft thud", like a muffled, gentle "bump-bump". I've had cars with blown CV joints before, and thats a very distinctive, "snap-crack,snap-crack"...a lot more high pitched. This is more like some tapping the frame-rail with a rubber mallet, on a steady 4-4 beat, while its doing it.

Honestly, I can't tell where it feels like its from, but if I had to say, it feels like its below me or to the rear...I'd suspect the front axle ujoints, but it doesn't change or act up at all, when I'm hard over left or right, and I don't feel it in the steering wheel at all.

 

[BIGdaddy]

Drove it to work today, was careful about getting on it too hard, and I listened/felt for it when I slowed on offramps/onramps/stoplights and didn't feel it do it again at all.

Follows suit, I guess, since I only felt it when the truck went up those two driveways.

Weird!!

thanks for the help, y'all, love to hear any more idea's. I'm hoping that the joints just needed to get lubed.

 

[The Adam Blaster]

Usually you don't need a SYE until you go MORE than 3" on a lift.
When I went to a Skyjacker 3" everything was fine, the ujoints wore out sooner because of the angle, but not really that big of an issue, the joints should still last around 2 years depending on how many miles you drive. And loading it up with extra weight actually helps the angle because you compress the springs a bit.

 

[BIGdaddy]

Usually you don't need a SYE until you go MORE than 3" on a lift.
When I went to a Skyjacker 3" everything was fine, the ujoints wore out sooner because of the angle, but not really that big of an issue, the joints should still last around 2 years depending on how many miles you drive. And loading it up with extra weight actually helps the angle because you compress the springs a bit.

yeah, thats my understanding, too, and the reason i chose to stay below 3". I might just replace the ujoints with some nice new spicer units, to rule them out, since spitting a dshaft on a trip would be a BAD thing...:coffeedrink:

El cajon driveshaft can press in two new joints for about $75 bucks parts and labor (and thats with $28.00 per joint cost), in about an hour.

Very cheap!

 

[Purple People Eater]

Is it mainly a thud you can hear, or is it something you can feel? I had maybe a similar problem with mine, and it turned out to be the transmission mount. See if you can grab the rear of the transmission and wiggle it. If it moves at all, that maybe the source. Just a little suggestion you may want to try...