vibration/clunking sound in rear when decelerating...

[SurfXJSnow]

any of you guys know what it could be if im having a slight vibration in the rear when taking my foot OFF the gas? this sound only happens when decelerating...

Just put a 3.5-4" kit on today... other than my steering wheel being way off and the clunking noise in the rear, im def happy with it.

shims? transfercase drop?

 

[logdog]

Sounds like drive shaft to me. SYE?

 

[SurfXJSnow]

no SYE... and trying everything in my power not to go that route. shims maybe? trans case droP? im going to take some pictures of my drive line angle and post them tomorrow morn... maybe that will give some insight to the problem.

 

[philip_g]

you can build a tcase drop really quick and cheap, might be worth a shot.

 

[Hypoid]

When you take your foot off the gas the axle has a tendency to roll forward tipping the pinion down...especially with a manual tranny.

Are the joints known to be good? Pump some fresh grease into them?

SYE has more to do with not letting the driveshaft fall out when a tire drops in a hole.

Square away the simple, cheap things first.

 

[SurfXJSnow]

When you take your foot off the gas the axle has a tendency to roll forward tipping the pinion down...especially with a manual tranny.

Are the joints known to be good? Pump some fresh grease into them?

SYE has more to do with not letting the driveshaft fall out when a tire drops in a hole.

Square away the simple, cheap things first.

i like your style "cheap things first"... im your average backyard/weekend mechanic... an SYE is well over my budget. im going to grease the bad boys tomorrow.

 

[Skully]

i like your style "cheap things first"... im your average backyard/weekend mechanic... an SYE is well over my budget. im going to grease the bad boys tomorrow.

You did a 3.5+ with out a transfer case drop? That is probably why........ Late model XJ's are more prone to vibration anyways. I have 5" in the rear and 4" in the front and got a little bit of vibs before dropping the T-Case.

Look up proper drive line angles on interwebby for a diagrams or here is one;

Pic
Standard 2 joint shaft Driveline angle

.....................you will see the output on the T-case and the pinion have to have a parallel line. If you look at yours by just glancing you can see if you are off or take a level and hold it up to get a quick eye on it.


Now if you had a CV shaft then the pinion needs to point straight at the output on the T-Case.

Like this;
CV style driveshaft SYE angle


Hope this helps...........:looney:

 

[SurfXJSnow]

You did a 3.5+ with out a transfer case drop? That is probably why........ Late model XJ's are more prone to vibration anyways. I have 5" in the rear and 4" in the front and got a little bit of vibs before dropping the T-Case.

Look up proper drive line angles on interwebby for a diagrams or here is one;

Pic
Standard 2 joint shaft Driveline angle

.....................you will see the output on the T-case and the pinion have to have a parallel line. If you look at yours by just glancing you can see if you are off or take a level and hold it up to get a quick eye on it.


Now if you had a CV shaft then the pinion needs to point straight at the output on the T-Case.

Like this;
CV style driveshaft SYE angle
Hope this helps...........:looney:

bear with me because im new to this whole pinion angle thing... but how do i know if i have a CV? thats the one in the front right? my rear looks alot like the first link/picture... only difference is my drive shaft is cocked a little bit more vertical. So T case drop you say?

 

[Skully]

bear with me because im new to this whole pinion angle thing... but how do i know if i have a CV? thats the one in the front right? my rear looks alot like the first link/picture... only difference is my drive shaft is cocked a little bit more vertical. So T case drop you say?

Your front does have a CV style shaft but odds for vibes are on the rear which if you have never none a SYE kit then you have the wonderfull standard 2 joint shaft and for that look at your rear shaft and draw and imaginary line from your axle to the t-case, it should match that first pic I posted. A lot of times when you put on a brand new lift it acutally nets you higher lift so you probably have 5" of lift right now. Check your angles and drive it allowing the springs to settle and that will help as well.

Most likely a simple t-case drop will eliminate any vibes, but for good measure look for play in your u-joints and grease em up good as Hypoid suggested.

Post a pic of your rear driveshaft showing your pinion and your output on the T-case.

 

[SurfXJSnow]

i just looked at some T case drop kits... how much should it be lowered at 4" lift? looks pretty simple to put on. just looks like a jack to support and a few spacers and bolts. heard getting the factory bolts out is a hell of a job though...

 

[Hypoid]

I don't know the magic number there. I took my home-made junk out after finding the real problem behind my vibes. I have a 1/2" drop just because I'm too lazy to remove it right now.

I'd offer you my leftovers but, I live 60 miles away. Hardly worth some scrap steel with holes drilled in it.

If you don't have this site bookmarked, you should:
http://go.jeep-xj.info/

 

[Skully]

I don't know the magic number there. I took my home-made junk out after finding the real problem behind my vibes. I have a 1/2" drop just because I'm too lazy to remove it right now.

I'd offer you my leftovers but, I live 60 miles away. Hardly worth some scrap steel with holes drilled in it.

For reference on my 90' POS 3.5" rear leafs, I have a 1" t-case drop and most of my vibes went away, then lifted the rear another 1.5" with shackles,(which in turn tilts the pinion angle up) and the minor vibes went away. ......now my tires are wearing funny and I have vibes from that ..........when you learn things never go away they just come back reincarnated as something else that is when you will be happy


Hypoid what kind of leftovers? Chinese, pizza, what?

If you don't have this site bookmarked, you should:
http://go.jeep-xj.info/

you are the link man!

 

[in4aride]

For reference on my 90' POS 3.5" rear leafs, I have a 1" t-case drop and most of my vibes went away, then lifted the rear another 1.5" with shackles,(which in turn tilts the pinion angle up) and the minor vibes went away. ......now my tires are wearing funny and I have vibes from that ..........when you learn things never go away they just come back reincarnated as something else that is when you will be happy


Hypoid what kind of leftovers? Chinese, pizza, what?



you are the link man!

x2 that site was awesome....
ive been wanting to redo the guages.....so hard to read...
AND put a light in the auto gear select indicator box thingy.....

sorry for jackin the thread randomly....
ill look with you when im up there tomorrow...
dunno if ill help much but we will try!

 

[Hypoid]

Hypoid what kind of leftovers? Chinese, pizza, what?

Just a couple spacers that I made, tried, and removed. One is 1/2" solid stock, the other is heavy wall tube like Gojeep used for his drop: http://go.jeep-xj.info/HowtoTCdrop.htm

One thing you have to remember is that the transfer case is at the end of an arc. If you drop the crossmember an inch, the transfer case hangs even lower. That is one of the reasons I stuck with just a 1/2" drop. The clincher was talking to a bud who helped his brother lift an XJ. They went to (I think) 4" with no SYE, no T-Case drop, and did not have the problems that some do. That challenged me to keep hunting down the real problem with our heep.

I found a pic of the XJ he was telling me about, pretty sweet:

 

[JohnJohn]

Pull the rear shaft and drive it around in 4wd. That will tell you if it's the shaft/need for SYE.

Go down to the hardware store. Take out one of the crossmember bolts. Buy 4 that are 1/2 longer. Also buy some steal washers. Make yourself a red-neck t-case drop.

If you want to go shims.

4" lift...assuming with a new leaf pack, not shackles and blocks. Go with 4 degree.

 

[in4aride]

Lower control arms are lookin good.....
im thinkin the small drop for the t case would be good

 

[SurfXJSnow]

Lower control arms are lookin good.....
im thinkin the small drop for the t case would be good

yeah dude, i owe you the world for the help on the LCA's. Screw the steering stabilizer noise... ill just wait for that bolt to fall out haha. T case drop on monday/tuesday? ill supply the beer and parts. those vibes need to GO.

 

[in4aride]

im fair game