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Discussion Starter · #1 ·
Ok I have a 4" block below the f350 stock rear block for my rear lift, Since I installed this I have had a take off shudder, but no problems at highway speed.

The block is a 5* taper, tilting the front of the diff up, I also installed a pro comp carrier bearing drop (2pc drive shaft) I have played around with the shims for the carrier bearing drop and was only able to get a 2* difference between the pinion and driveshaft (pinion @ 10*, ds @ 12*) but I was still getting the shudder so I got a 3* shim pack and installed that now I have a 5* difference between pinion and driveshaft but still have the shudder, I haven't had a chance to play with all the shim combo's yet but I wanted to know if anyone had suggestions on what angle the pinion and ds should be at to eliminate shudder on take off?

Or is the pinion just raising so much that it can't be controlled without traction bars?

I'm not really interested in the adjustable carrier bearing drop brackets at the moment because I can simulate that with all the shim combo's without spending $150, and it's not a bolt in solution you still have to know where to align it to eliminate the shudder.
 

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BRING DA AMBALAMPS
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you're likely getting some axle wrap. when you accelerate, especially with a lift, there is a lot of stress put on the u joint and it tries to rotate up on itself. that increased angle due to the wrap will cause some vibration issues. traction bars are supposed to help a ton. i'm in the process of ordering parts to fab up a set myself.
 

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:popcorn:
 

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Discussion Starter · #4 ·
I've had people watch the front of the pinion when i'm accelerating and they say the front pinion raises about 2", but I'm wondering of this is something I can prevent by aligning my driveshaft to prepare for the rising pinion
 

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I had the same problem. you need to shim the carrier bearing down.
 

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Try to get it +or- one degree. So if your output flange on your transfer case is at 12 degrees try to get everything +or- one degree of that.
 

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Discussion Starter · #7 ·
I had the same problem. you need to shim the carrier bearing down.

I have the pro comp carrier bearing drop kit with the shims but it didn't help.
Did you use blocks in the rear for lift? Were they tapered blocks?


Try to get it +or- one degree. So if your output flange on your transfer case is at 12 degrees try to get everything +or- one degree of that.
It's a 2pc driveshaft so the output from the transfer case is angled up towards the carrier bearing then back down towards the pinion at 5* steeper angle then the pinion.
 

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What is your TC angle? The pinion needs to be down from the TC angle 2* so when you accelerate, the pinion rotates up and is in line with the TC. You want to have the front and rear portions of the rear driveshaft the same as if it's one.

There is alot of leaverage added with the blocks.

Your solution might have to be a properly built set of traction bars because they lock the pinion from rotating.

Billy T.
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Discussion Starter · #10 ·
driveshaft from transfer case to carrier bearing 10*

driveshaft from carrier bearing to pinion 12*

pinion angle 5*

before I added the 3* counter shim under the blocks I had the pinion @ 8* and the rear half of the driveshaft at 10* and it was the same as now...
 

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I just had a rear u-joint explode, it broke the axle free from the spring.



I was on the phone with several companies today, including superlift. I broke the U bolts and the 3" lift block. So while i was trying to find a lift block they (superlift) brought it to my attention that a 2 piece driveshaft is NOT supposed to have the tapered block. You ONLY shim the carrier.

There's my 2 cents, i currently have my whole rear end set-up disassembled waiting for parts.
 

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Discussion Starter · #13 ·


Then you have this:
High Angle Drivline-Call Jesse at 530-877-2875 - My Buildup

I am having this same issue. I really don't want to spend $700 for a driveshaft. I had the shudder but I have eliminated it but I have a slight vibration at 70mph.

Billy T.
[email protected]

Thanks for the info but none of that info has any insight on 2pc driveshafts, so I'm not sure how it can be applied


I just had a rear u-joint explode, it broke the axle free from the spring.



I was on the phone with several companies today, including superlift. I broke the U bolts and the 3" lift block. So while i was trying to find a lift block they (superlift) brought it to my attention that a 2 piece driveshaft is NOT supposed to have the tapered block. You ONLY shim the carrier.

There's my 2 cents, i currently have my whole rear end set-up disassembled waiting for parts.
thanks for the info about not using tapered blocks with a 2pc shaft that does make sense.
 

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Discussion Starter · #14 ·
Ok so I made the flat lift blocks (no taper) and I still get the same shudder on take off if not maybe even worse! I have had the carrier bearing shim kit since day one and I have played with the amount of shims, maybe I just need more shims???
 

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It is axle wrap and you need traction bars with those tall blocks as the taller they are the more leverage. If you watch a video you will see the axle rotating on acceleration and then once acceleration levels out its comes back down. I would think if you try to adjust for take off you will be out of align the rest of the time.
 

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Get rid of the stacked blocks on stock springs.

Your problem is axle wrap, due to the increased leverage of the stacked blocks on the stock springs. When you accelerate, your axle is moving forward and the pinion angle changes enough to cause the shudder.

To try to fix the problem, you can install some lift springs and maybe a small block. Or maybe look at some traction blocks from OUO.

Traction bars on your current setup might fix the mask the problem or possibly fix it, but I still don't like the idea of stacking blocks. I have seen people spit out blocks before and its not pretty. Look at the picture above.

Just changing the shims will not help with the axle wrap problem.
 

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:whs:........and if you look back, i said that 15 days ago...:poke:
 

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One Up Offroad The answer to your issues while looking good at the same time.
 

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Discussion Starter · #19 ·
I would rather build some traction bars myself

I don't really want to run the parrallel bars off each side of the axel for 2 reasons, 1- I have a side exhaust exhaust and I don't really want have to move it, and 2 it would limit the articulation of the truck.

I am planning on either comming off the sway bar mounts or make flange that bolts to the rear diff cover holes and comes over top of the diff and has a single center link that runs parrallel with the driveshaft and mounts around the carrier bearing, heim jointed on 1 end that would allow for maximum articulation and keep the axel from rotating
 

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Could you put up a sketch of what you are planning. BTW I am all for DIY trac bars. IMO one of the best suspension DIY projects out there.
 
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