Grinding sound/vibration after 3.5 inch lift in 4H Auto mode at high speed

[DSJG]

Hi,

I have gladiator launch edition and recently upgraded the suspension. Have put Teraflex 3.5 inch coil spring base lift kit with Falcon 2.5-3.0 inch adjustable falcon shocks and teraflex front lower sport control arm kit (# 1253000). Running 315/70 R17 tires and have Mopar factor fitted dual tip catback exhaust.

After putting this lift, I have started experiencing grinding/vibration when I take my foot off the accelerator at speed of around 110 KPMH (~70 MPH) and above in 4H Auto mode. This does not happen when the truck is in 2H mode. While coasting at high speed even in 4H Auto mode, the truck drives very smooth without any issues.

Have shown the truck at the dealer but they did not find anything wrong (no clearance issue). Since it is not a mopar lift, they are not willing to diagnose it beyond a visual inspection.

I got the lift installed from a professional after-market modification shop and in their opinion this is normal with such a high lift and I should look at changing the drive shaft as the next upgrade.

Could it be the angle of front drive shaft that is causing the issue? Or anything else?

Any help will be highly appreciated.

Thank you all in advance.

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[Artsifrtsi]

Somebody correct me if I'm wrong, but 4hi "auto" (full time) did not come on the Launch edition (2020) but the next year. Do you have more than 2hi/4hi/N/4lo on your transfer case? If not, are you putting miles on hard surfaces in 4hi?

 

[Rusty PW]

Somebody correct me if I'm wrong, but 4hi "auto" (full time) did not come on the Launch edition (2020) but the next year. Do you have more than 2hi/4hi/N/4lo on your transfer case? If not, are you putting miles on hard surfaces in 4hi?

His is an export model. So they get the full time transfer case.

With that much lift. The front drive shaft should be changed. And a spacer add to the carrier bearing on the rear drive shaft.

 

[DSJG]

Somebody correct me if I'm wrong, but 4hi "auto" (full time) did not come on the Launch edition (2020) but the next year. Do you have more than 2hi/4hi/N/4lo on your transfer case? If not, are you putting miles on hard surfaces in 4hi?

Yes mine is the export model (UAE) and it had 4H Auto in the Launch Edition.

 

[DSJG]

His is an export model. So they get the full time transfer case.

With that much lift. The front drive shaft should be changed. And a spacer add to the carrier bearing on the rear drive shaft.

Yeah I thought so but its good to check with people who have experience. Thanks for your reply.

 

[FitfulGoat]

His is an export model. So they get the full time transfer case.

With that much lift. The front drive shaft should be changed. And a spacer add to the carrier bearing on the rear drive shaft.

This is where I would start as well. Anything over 3” and you really need to check driveline alignment with your drive shafts and carrier bearings. The excessive angle and shift in friction with deceleration could be the cause.

I would also add, a 3.5” lift can often result in a true 4”+ change in height only making the above comments on drive shaft etc. that much more applicable.

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