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Leaf Springs too soft???

M

Matt99XJ

NAXJA Forum User
Location
Ringgold, GA
Has anyone ever had a problem with their leaf springs being to soft?

I think that might be my problem. I think that they are letting the pinion rotate up too much and is causing my high sped vibes.

What is a good stiffer leaf spring? Rubicon Express?

Can I pull a leaf out of these and add a stiffer one?
 
This might cause vibes when accelerating, but once you are up to speed, the pinion will settle back to static height.

CRASH
 
Well it only does it after 60 mph. But, it only does it when I am on the gas. if I am coasting then it stops until I hit the gas again.
 
Are your axle u-bolts tight?

How is the pinion angle?

CRASH
 
I think you may need to drop the pinion down 1 or 2 degrees. When you're on the gas,the pinion wants to twist upward from the rotational force,as in when you're on the gas,and the harder you're on the gas,the more it wants to twist. You need the pinion angle to be the same as the tailshaft's,only the pinion should point downward 1-2 degrees to compensate for the acceleration "twist". Do you have a slip yoke eliminator? If you do,the pinion should be pointed straight at the tailshaft,again,down 1-2 degrees. I'd try to fix it that way instead of making the rig's ride more harsh by stiffening it up. HTH :D
 
The U-bolts are tight and the pinion angle is about 2.5* below the DS. Yeas I have a SYE.
 
When was the last time you balanced your tires?
 
What axle and SYE kit are we talking about.This was the problem with my 8.25" and a hack-n-tap kit!
 
Mike do you think that will help even though it only does it under acceleration. It seems like that will make it worse. I have some shims sitting in the garage that i could use if I think that is it.

My SYE is the Currie. It is basically the hack and tap but Currie cut and tapped it. It is a D44 rear with 4.56's
 
Well,I don't have an SYE kit on mine,and I ran mine for a while W/O shims and I had pretty harsh vibes under hard accelleration. I installed 2.5* shims and it moved the vibes upward in the speed range,enough so that they don't become an issue until around 70-75 MPH. I'm thinking about trying a set of 1-1.5* shims instead to see if it will totally eliminate them. It may help,it may not,but it's worth a shot,especially if you've got shims laying around,all it will cost is 30 minutes of your time to find out :)
 
Mike is yours a humming/droning type noise at 70+? Does it get worse the faster you go?
 
Last edited:
Bingo!Thats what I was talking about!The NP231(particularly the late models) dont seem to like high lifts without problems.I think the HD SYE kits add about another 3" of driveshaft length!Thats alot when it comes to driveshaft angles and bearing support!
 
Well,it's kinda hard to tell if it's humming or droaning with Swampers :D I've really just gotten used to it and haven't really paid it that much attention here lately. I'll go for a ride sometime this weekend in it and I'll try to see a pattern to it.
 
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