1995 80 series 4”lift vibration

[mhawk80series]

Hey everyone, I’m new here but I need help.

I’ve been chasing this driveline vibration for the better part of a year. I have a Dobinsons 4”lift, 37s, 5.29 gears, Ironman radius drop bracket for the radius arm, castor correction plates, upper and lower adjustable trailing arms along with front and rear adjustable pan hard bar a double cardan front drive shaft. I’m thinking of going with the delta radius arms to try and help with castor and pinion angle but I’m out of my depth and I’ve been chasing for a while now. Vibrations on deceleration, 65mph +

 

[efjayatee]

Did you get your casters measured at an alignment shop? Are your engine & tranny mounts original? Also how sure your tires are balanced.
Seems like you have all the boxes checked for ur 4" lift mod though.

 

[CruiserDave]

The boxes and plates are probably to much correction. I ran into this problem with boxes and arms. I removed the boxes and problem cleared but steering is a little lighter. Mine is on a "3 lift but my arms are superpro and don't correction as much as plates.

 

[mhawk80series]

Did you get your casters measured at an alignment shop? Are your engine & tranny mounts original? Also how sure your tires are balanced.
Seems like you have all the boxes checked for ur 4" lift mod though.

Not measured yet tires are balanced original engine mounts and transmission

 

[efjayatee]

See where your casters are when measured. That will eliminate one factor. Next is engine/tranny mounts....they are 30yrs old-might aswell.
And lastly the most important, check your wheel bearings by lifting your wheels off the ground and see any "wobble" when shaking. Check any cracks (hairline) where the steering box in mounted on the sub frame.

 

[mhawk80series]

Did you get your casters measured at an alignment shop? Are your engine & tranny mounts original? Also how sure your tires are balanced.
Seems like you have all the boxes checked for ur 4" lift mod though.

Not measured yet tires are balanced original engine mounts and transmission

The boxes and plates are probably too much correction. I ran into this problem with boxes and arms. I removed the boxes and problem cleared but steering is a little lighter. Mine is on a "3 lift but my arms are superpro and don't correction as much as plates.

so do I remove the castor correction plates? I’m at 4 inch lift

 

[efjayatee]

so do I remove the castor correction plates? I’m at 4 inch lift
[/QUOTE]

Unless you have superpro arms....

Remove your caster corrections snd get it measure. Once you know the casters:
A. Get caster correction bushings on the radius arms to compensate.
B. Get either Delta or Trail Tailer arms based on your casters
C. Get it remeasured to make sure ur casters are in spec

Once that's sorted out and still vibrates....look into other worn bushings like rear/upper control arms, engine/trans bushings, wheel bearings.

 

[CruiserDave]

I would remove the boxes first, since it's easy, and see how it drives. I know plates used to require modification to the radius arm mounts. Removing them would require work to replace removed material. So remove the drop boxes and try it out. It's free and only uses your time if you're doing the work.

 

[reklund5]

Are you certain it is tires or driveline? Have you removed the front shaft and locked the CDL and driven it to confirm? Then reinstalled front and removed rear to confirm? I spent a long time and a LOTTA money chasing it on mine, only to find the rear driveshaft was the culprit and what fixed it was a ~$450 OEM rear driveshaft..... Look for my thread on the matter.

 

[mhawk80series]

so do I remove the castor correction plates? I’m at 4 inch lift

Unless you have superpro arms....

Remove your caster corrections snd get it measure. Once you know the casters:
A. Get caster correction bushings on the radius arms to compensate.
B. Get either Delta or Trail Tailer arms based on your casters
C. Get it remeasured to make sure ur casters are in spec

Once that's sorted out and still vibrates....look into other worn bushings like rear/upper control arms, engine/trans bushings, wheel bearings.
[/QUOTE]
Ok I have trailing arms, I’m waiting on a response from delta to find out which arms are best.

 

[mhawk80series]

so do I remove the castor correction plates? I’m at 4 inch lift

Unless you have superpro arms....

Remove your caster corrections snd get it measure. Once you know the casters:
A. Get caster correction bushings on the radius arms to compensate.
B. Get either Delta or Trail Tailer arms based on your casters
C. Get it remeasured to make sure ur casters are in spec

Once that's sorted out and still vibrates....look into other worn bushings like rear/upper control arms, engine/trans bushings, wheel bearings.
[/QUOTE]
Ok I have trailing arms, I’m waiting on a response from delta to find out which arms are best

 

[efjayatee]

Either the 3L or the 4. The 3L pushes the F axle farther forward to help clear w/37s

 

[mhawk80series]

Are you certain it is tires or driveline? Have you removed the front shaft and locked the CDL and driven it to confirm? Then reinstalled front and removed rear to confirm? I spent a long time and a LOTTA money chasing it on mine, only to find the rear driveshaft was the culprit and what fixed it was a ~$450 OEM rear driveshaft..... Look for my thread on the matter.

The problem persisted after I removed the front drive shaft. Could it be the rear of it feels like the front of the vehicle?

 

[mhawk80series]

Are you certain it is tires or driveline? Have you removed the front shaft and locked the CDL and driven it to confirm? Then reinstalled front and removed rear to confirm? I spent a long time and a LOTTA money chasing it on mine, only to find the rear driveshaft was the culprit and what fixed it was a ~$450 OEM rear driveshaft..... Look for my thread on the matter.

Your in Carson city Nevada I’m in Vegas please help

 

[reklund5]

Your in Carson city Nevada I’m in Vegas please help

It could still be in the rear. You need to start systematically ruling things out. Try known good wheels and tires from another vehicle, reinstall the front shaft and try just the rear. Check engine and trans mounts, etc. I had to do both drivelines on mine to finally get it tolerable.

Yes, I'm up in Carson City. I'd love to help- but it's a 7hr drive....

 

[GW Nugget]

I've been chatting on Instagram with @mhawk80series
I suggested to replace the rear Ujoints for starters.
He also reported his hub to flare measuments are 26" meaning its a 6" lift. So 7" of correction isn't a over correcting caster issue in my opinion.
I'm adding here he also can try the 90° phasing trick on front driveline. It worked for me. With a front CV joint I'm not sure it would help but what I'm say is a 10 minute one shot in the dark. Give it a try.


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