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Max lift on YJ with no sye/cv modifications?

36K views 51 replies 38 participants last post by  AmmitOsiris 
#1 ·
I've got an '88 YJ with stock suspension/rims/tires. I'm looking to install a suspension lift and 32"x11.50" to 33"x12.50" tires with 15"x10" rims with 4.0" backspacing. I want to lift it with a 4" suspension lift, but how big of a suspension lift can I get away with before I'd have to go with an sye and/or cv drive shaft? (I specifically want to add a Rubicon 4" suspension lift with M.T. Baja ATZ Radial Plus 33"x12.50" tires on Crager 365 V5 Black steel 15"x10" rims with 4.0" backspacing. Is this doable with no other modifications?)
 
#4 ·
A factory YJ comes from the factory with some driveline vibes. That should tell you something.

If you havent driven in a stock YJ with a SYE and longer driveshaft, you won't know just how smooth the YJ can really run. Most people never experience this so have no basis for comparison.
 
#5 ·
A factory YJ comes from the factory with some driveline vibes. That should tell you something.

If you havent driven in a stock YJ with a SYE and longer driveshaft, you won't know just how smooth the YJ can really run. Most people never experience this so have no basis for comparison.
Uhhh... no it doesn't. That makes no sense. It's like wiping before you poop.
 
#7 ·
Every jeep is different. There will be some jeeps that have a 4" lift that need a sye and other 4" ones that dont. Then there is people that have sye on jeeps lifted 2.5" because of drive line vibes. Only way to tell is lift it the way you want it and if it needs a sye put in on there. You don't want to make the drive shaft angle to steep because i have read about them popping off and doing more damage then it worth then getting a sye. You can ruin you t case, trans, exhaust and other parts of your jeep if your drive shaft isnt right.
 
#8 ·
Sorry but you are in error. All AMC Jeeps came with driveline vibs. It was an inevitable engineering compromise of the short wheelbase design. When Chrysler redesigned the CJ and came out with the YJ, the redesign was another engineering compromise. Direct from one of the original engineers. The driveline does have vibs and as I posted earlier, if you do not have the experience of driving in a stock YJ with an extended driveline, you will not realize the extent of the vibs. A lift... any lift, aggravates the vibs. Nothing more, nothing less.
 
#10 ·
I just put my 4" RE lift on a few days ago. I have a little vibration when I decelerate. But not enough to bug me. I do have the TC drop kit but have not put it in yet. But like people have said it all depends on the jeep I guess.
 
#12 ·
i do not have the details, but i just picked up a 88 with a 6 inch lift, no sye and not a whole heck of alot of vibes. i was amazed when i realized there was no sye. i assume they lifted the motor and dropped the tranny, so it would all line up.
 
#13 ·
well i have two YJ's on a 4 inch rc lift and 31's no case drop and then a bds 5 in on 33's with drop and have no vibes that are not the typical JY vibes and meaty tires.like they said its a slight gamble lift it then see where you are i say make sure to install the tc drop kit youll be fine.
 
#16 ·
Most of the time depends on how well the drive shafts are balanced. You have to remember they mass produce the drive shafts for the OME. They used a very wide tolerance. Them know most people where not looking for the smoothest ride in a jeep. If you find the you have drive shaft vibes and after you have checked the rest of the driveline out for bad u joints or a bad yoke ( rusted or bent ) or play on the slip joint. Then tak the drive shaft in and have it checked balance.
 
#17 ·
Will vibes do any damage to the vehicle and driveline if they aren't like to the point of shaking the whole vehicle? What would be the long term effects of driving around with driveline vibes aggravated by a 4" or so lift? I realize that every vehicle will be different but just an average amount of vibration over a 10 year time frame or whatever, what damage is gonna result from that?
 
#19 ·
I installed a RC 2.5" lift and had this with my DS....


I know it will settle but I did not want to chance it so I bought a JB conversion SYE and an XJ front DS from the local pick and pull. A shop near me will cut and balance it for $60. So long story short...

SYE $217.00 delivered
xj DS $25.00
Cut and balanced $60.00

For $302.00 I won't have to try MML or TC drop and see IF they work. Once I get my rear pinion angle correct it will work.
 
#21 ·
That's what I figured. Thanks.
So when you install a SYE where is the play in the driveshaft? Would you then have no slip at all between your pinion and transfer case? Is that ok? Is there still a slip joint on the pinion/differential end?
 
#24 ·
I have an XJ shaft all ready to shorten but I was just thinkin that when you shorten it, you're gonna lose your slip. Do you just cut it down at the CV end? I think I get it now.
 
#26 ·
Is that with a transfer case drop or what? No SYE or CV right? I didn't see any of that in your specs but just wanted to make sure.
 
#28 ·
alright. Gotcha. I'm gonna have to check you profile for a pic with the drop. thanks.
 
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