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Weird vibrations when coasting..

5K views 19 replies 8 participants last post by  thecarpilot 
#1 ·
I have a 1994 4.0 5sp with a 2.5 RC suspension lift that's really more like 3". No TC drop, SYE or anything else.. Just the suspension kit. I've read a bunch of threads about vibrations due to lack of tc drop or sye but most of the posts describe a wierd vib on acceleration. Mine is more when I let off and just coast. Still happens around the same speed though (30-45mph). Could the vibrations be due to something else? or is this still a driveline angle issue? Thanks in advance
 
#3 ·
Cheap & easy first. Check all your driveshaft U-joints, rear and front.

Then a TC drop and after that maybe a motor mount lift.

I would jump right to the certain cure if it were my Jeep. Shortest Slip Yoke Eliminator I could find. Naturally, it is the most expensive option.

Let us know what works for you.

Good Luck, L.M.
 
#4 ·
OK so I checked the u joints. They are fine. I believe a tc drop/sye is good...Heres the issue:

So this 2.5" lift was put on by the PO. I want to go to 4". always have, before I even owned a YJ. I know that I will def do it some time in my life. If I do it now, I can sell my 2.5 lift easily since its pretty much new. However, my parents tell me that I need to not spend so much money on unimportant things. Can someone please give me advice?? Is my head too high in the clouds? or is getting a 4" kit actually a good idea?

BTW, it will be the 4" rough country since that will come with everything I need..tc drop, brake line relocation, etc. So the issues from this lift should be mostly solved, and the remaining ones if any will be better to pinpoint.
 
#7 ·
It doesn't really look as bad in the pic as it does in real life.. my driveway is a ridiculous incline, so it was hard to get the angle right. But I have still seen way worse angles on other Jeeps which is why I'm wondering if it may be something else. My dad says it could be the gears..does that sound possible?
 
#8 ·
It already has a 2.5 lift on it now right? Does it have any spacers between the tc skid plate at all? I put a 2.5 lift on my 95 and without adding any drop to the tc the vibes were terrible. So i added 3/4 drop bars to skid and it helped it considerably. Does it vibe when you press the clutch in and coast?
 
#9 ·
Like I said before, I only have the Rough country 2.5" kit, which just comes with springs, shocks, U bolts and hardware. no tc skid spacers or anything extra. I'm pretty sure I should do something about the drive line angle, whether its sye or tc drop (probably the latter), but my parents tell me otherwise. That is why I'm here to get advice on how necessary this may be..or if there is any other possibility of what the issue ma be
 
#12 ·
Yeah, if anything, Ill do that..I just figured might as well get a 4" kit since i want that height and WILL get it some day, so why not now, while this current lift is new and I can sell it for good money instead of letting it waste away...I dont even have a warranty on it.
 
#13 ·
It sounds like you REALLY want the 4 inch lift. Ask yourself why? First, it isn't that cool. Second, your parents know your situation better than anyone. Third, your new 2.5 inch lift won't be wasted away, you'll still have a blast, it's a jeep! My 2 cents: go with the transfer case drop.
 
#14 ·
It sounds like you REALLY want the 4 inch lift. Ask yourself why? First, it isn't that cool.
I know, running 33s isn't cool at all :D
 
#15 ·
Mah.... He wants the 4" and is willing to work hard and save his clams to get it... I say bravo. More than I can say for 75% of the younger generation I hire, many dont have the work ethic to even receive minimum wage (let alone what my company pays!) , scares the hell out of me to be honest. I always try to hire military folk, I get better luck.

I applaud his determination, but ya 31's on a 2" lift can still be loads of fun. Hell a stock jeep is still loads of fun.... Just find some sweet trails and do some exploring and enjoy the Jeep

Sent from my LG-D959 using Tapatalk
 
#16 ·
Actually "he" is a she lol :) and here are the reasons I want 4:

- I want more flex

-when I take super duper tight turns, my 31s rub and I hate that

-I want a ride height and feel that is very different from my dads stock jeep (but not too insane just yet)

- I like the look of 4" way better (least important)

-I believe I can afford it, especially if I make money off of selling the old parts

So ya...I may be stubborn, or overly ambitious..but theres my reasoning. If I do end up keeping the 2.5, I'll still be okay..I mean getting upset over something like this is just not appropriate. I simply want advice from people who have more experience than me. So tell me what you think ppl? stay, or go higher? I'll follow the majority. And thanks for all the input so far everyone!
 
#17 ·
My many years of many jeeps has taught me that the 2.5" lift is optimal.

Your driveshaft angle is incorrect and the cause of the vibration. Its to much on top and not enough on the bottom. You need to drop you t-case skid, and maybe you need a small angle shim under the rear axle perch to tilt the pinion down.

Drop the skid first and see if you lose the vibe.

Going to a 4 inch lift begins a cascade of mods to Band-Aid successive maladies and will rob you blind.

If your 31s rub, just adjust the knuckle stop bolts so it doesn't turn so far as to rub.
 
#18 ·
That advice is very well put. Thanks. Now I feel a bit better about staying at my height. I have a question for future though, when I do lift it higher, which will probably not be for a long time, but doesn't hurt to ask now..

Instead of ordering a custom driveshaft like most people recommend for a lift, are there any vehicles with the needed length rear driveshaft that you can just take and use instead? Just wondering..
 
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