torque converter shutter or axle wrap

[john6200]

I have searched already and and I can't find an answer to my question.

My truck: 2003 F250, 7.3 auto, crew cab short box, Tuff country level kit in front, One 4 inch tall block in the rear and a set of BDS add a leafs in the rear. 315/75-16 Kelly safari tsr


My problem: I get vibration/shudder from the rear when accelerating from a stop until 15mph. no matter how fast or slow I accelerate. there is NO shudder when stopping or when accelerating at any speed other then from a stop. also it did not happen right after I lifted the truck.


What I have done: the carrier bearing is shimmed down 1-1/4 inches and the two pieces of the drive shaft are .8 degrees different from each other. The u joints are less then a year old along with the trans from jasper. I just greased the slip joints and changed the rear diff fluid and added a container of friction modifier. The trans is full and the fluid is bright red and smells like brand new.

Questions: Torque converter shudder or axle wrap? How can I tell the difference?

 

[powerboatr]

my bet would be the rear axle is wrapping up from the torque.
might need a stabilizer tube to control the twist.
250 springs are soft and long to begin with, adding a 4" block only enhances the flexibility.

has it always done this, or just since you added the lift?
15 mph the tq isnt locking so its not shuddering, at that speed its still a fluid to fluid connection.
may have to put it on rollers and see how and what is moving on the suspension,
or ....mount a small camera under and shoot some video as you drive, laugh now...but that's how i found a coolant leak on my generator in the rv.

 

[john6200]

I did the leveling kit a while ago and that's when I replaced the factory f250 blocks "2.75inches" with 4 inch ones from ready lift. either I don't remember it shuddering then or it didn't do it.

Recently I added the BDS add a leafs so it wouldn't sag with my ATV in the back. I would think that with a block the same height at a stock f350 and the add a leafs in there the springs should be pretty close to a DRW f350 set up.

 

[powerboatr]

I did the leveling kit a while ago and that's when I replaced the factory f250 blocks "2.75inches" with 4 inch ones from ready lift. either I don't remember it shuddering then or it didn't do it.

Recently I added the BDS add a leafs so it wouldn't sag with my ATV in the back. I would think that with a block the same height at a stock f350 and the add a leafs in there the springs should be pretty close to a DRW f350 set up.

being the same height as a 350 or any other truck is really not the important thing. if you removed the blocks and used leaves to gain back your height the torq load would be less pronounced, and absorbed more by the springs
its not the height. its the added fulcrum from a 4 " block
big tires don't want to move, therefore we have tq to get em rolling,

just like using a cheater bar gives you an added twisting leverage, the blocks do the same thing to the axle and let it roll more than without the added fulcrum lenght.
anti tq rods or ladder bars across the top of the spring to a fixed point near the front end of the spring would let the tq or twist be transmitted to the tube and not let the axle roll or twist as much
axle wrap has always been an issue in everything. but its engineered to be minimized by the engineers. adding a new lever just negates the previous work.
if its only at low speed might not be a biggie.....
however if your at low speed and you need power to the wheels whilst off roading...then the twist could be a huge factor
I am surprised at lifts and sets that do not include an added piece to limit or put axle twist back to a stock amount
using a 350 block, without 350 springs would also defeat the engineered setup.
best course would be to load it and get a video of whats going on so you can have a good ride and limit the axle twist that will eventually leave you stranded when you need the ummph

one more note
if the shudder is recent....i would retorque all the bolts you touched doing the bds leaves,
i pic would help to as i am having a hard time getting my brain around how tall the tires are...
sounds like you are doing it right...checking everything

 

[john6200]

The tires are 35 inches tall and 12.5 inches wide. I dont't wanna go all spring lift because I don't like hauling with lift leafs. I checked all the bolts in the rear all are torqued corretly. I guess its time to look for trac bars or some sort.

 

[Dogman]

Or you could for testing only is put your 2.75 blocks back in the rear and see if it still does it. Wont cost you anything but time. If not then you will know you need ladder bars for the 4" blocks.
The other thing to is you could do is have the spring rearched. As spring age they will get week and you will get axle wrap too. Check with you local dealer for spring packs prices. I got some for my 04 F350 and it was just over 100.00buck each for new.

 

[powerboatr]

The tires are 35 inches tall and 12.5 inches wide. I dont't wanna go all spring lift because I don't like hauling with lift leafs. I checked all the bolts in the rear all are torqued corretly. I guess its time to look for trac bars or some sort.

yup thats a lot of rubber
track bars would help
and.....good shocks will to an extent
agree all spring lifts can ride harsh, i had a 92 250 TTB front end, with leaves all around ouch ouch i think the springs were just there to hold the axle inline

 

[john6200]

I might try just springs no blocks and take the shims out of the carrier bearing. If it doesn't shudder then I'll start looking at anti-wrap devices.

 

[BJS]

I truly doubt that you're getting axle wrap. and here's my thinking 3.5" blocks were standard on F350 4wd trucks. the 35" tires while taller are not outside the realm of normal. I'm running the exact same size tire on mine with no problems with no lift. The Add-a-leaf on the rear is going to have stiffened up the rear suspension to compensate for the lighter rated springs from the F250. Combine the above with your statement that it does it no matter how fast or slow you accelerate tells me that you're not twisting your suspension, and definitely not enough to cause drive shaft binding

Jasper is not known for using the highest quality of parts and something may be off in the trans or your converter.

 

[john6200]

I should clarify about it happening at any speed. If I baby it from a stop I can still feel the shudder but it's not so bad as to make the rear end hop like when I lay into it a bit. I also have heard nothing but good things about jasper products.

After a weekend full of reading fourms and talking with people it is a pretty common thing for F250 crew cab short boxes on 35s to have axle wrap. In fact one guy I talked to had axle wrap on his stock f350 when hauling his cattle trailer. Ford shimmed his carier bearing and suggested caltracs.

I am going to tape a web cam underneath My truck tonight and if I can see the axle wrap with my own eyes I buyin a set of one up offroad track bars