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Discussion Starter #1
I'm running an 8" BDS lift kit (including t-case indexing ring) on my truck, 37" Toyo MT's. When I installed the lift kit I didn't have any issues with driveline vibrations (running the stock 3.73 gears). It was perfectly fine until I had the 4.56 gears installed. Since they were installed I've developed a driveline vibration that is pretty much only noticeable while coasting at highway speeds (at that point where you're feathering the throttle so that it's not slowing down from the engine but not under load either). My first thought was that it was the front driveshaft because of what I've read about getting it lengthened rather than running the spacer that came with the BDS kit. I figured because it was spinning faster now with the new gears it would make sense for that to be the problem. So this past weekend it took it out to see if that would solve the problem and no such luck... still there.

So at this point I'm a little stumped as to what it could be. The rear transmission-driveshaft-pinion angles are all good so that's not the problem. It's definitely not a gear howling noise as I know what that sounds like (plus I've had the shop who did the gear install recheck everything to see if there was an issue on their end). My only thought is that maybe it's the rear driveshaft. Maybe it's worth pulling it out and having it rebalanced? Just wondering if anyone else has had this problem or if anyone has any advice to fix it. I'm all ears.
 

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Maybe its just the set-up of the gears. Sounds like it only happens on the coast side not the acceleration side, so it could jut be the way the installer put your gear sets in.
 

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I'm no mechanic by any stretch of the imagination. I have read where the carrier bearing that connects the 2 drive shafts on a long bed truck can cause a vibration.

I see that all the work you have done, you may have thought of this already. Hope this helps.
 

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Discussion Starter #4
Maybe its just the set-up of the gears. Sounds like it only happens on the coast side not the acceleration side, so it could jut be the way the installer put your gear sets in.
I thought about that as well but if the coast side of the gears wasn't setup right you'd think it would have a problem during all of deceleration, not just coasting. Plus the shop who did my gears specifically does only differential work and has done a number of 1 ton Rams lately so I'm fairly confident they set it up right.

I'm no mechanic by any stretch of the imagination. I have read where the carrier bearing that connects the 2 drive shafts on a long bed truck can cause a vibration.

I see that all the work you have done, you may have thought of this already. Hope this helps.
Only long boxes and mega cabs have a carrier bearing. Mine has a 1 piece aluminum drive shaft. Thanks for the input though!
 

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Maybe ujoints. Mine seized at 34k had bad driveine vibration.maybe too simple but possiby overlooked?
 

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Discussion Starter #6
Maybe ujoints. Mine seized at 34k had bad driveine vibration.maybe too simple but possiby overlooked?
That could be. Did cross my mind as one of the options... Might have to get under there and check them out this weekend.
 

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That could be. Did cross my mind as one of the options... Might have to get under there and check them out this weekend.
And they might not have any play when you check them. Mine didn't but the caps were so dry
 
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