After lifting my 2010 F350 Regular cab 6-speed I've experienced a vibration in the drive line.

Here are the stats on the configuration:

• BDS 4" lift, radius arm in front
• 4" spring lift and 2.5" tapered blocks in rear
• Installed at 10K miles
• 14K miles on truck now
• 35" Goodyear MT/Rs on 17 inch steel rims

And here are the conditions where I get the vibration:

• Speed greater than about 50 mph
• Zero to low load on driveline; basically going down a hill

I went back to the shop that installed the lift. They said I need ladder bars, which I thought was a bit ludicrous. There is no hopping at take-off, which is what ladder bars are for.

I took the truck to another shop and the guy checked out things underneath and said driveshaft, u-joints, yoke all looked good. He said there was a lot of play in the rubber mount at the tranny and that tightening this up might help, but it's damn near brand new so I'd probably be doing some custom work to increase the stability there.

I'd like to hear your thoughts on the vibration because I'm not convinced either shop is right yet.

 

Do you have any idea what the pinion angle is set at?

With the tapered blocks and such a short wheelbase, depending on the leaf spring manufacturer and center pin location, the pinion angle could be incorrect.

Does that 6 speed truck have a one or two piece driveshaft?

 

You are correct about the traction bars not being the correction to your problem.

Traction/Ladder bars help to prevent spring wrap, which is terrible on trucks with diesels. Big tires, gears, heavy loads, trailers, short wheelbases can exaggerate it as well.

Uncontrolled spring wrap produces 'shudder' from dead stops and if you stand in the throttle hard at low speed, but doesn't occur when the spring is at rest, such as decel.

If this problem manifested itself after the lift and no other changes, I would be paying close attention to the pinion angle, as previously stated, and the relation of the pinion to the angle of the driveshaft.

 

Thanks guys. The pinion angle was a question of mine as well... the second shop said they thought it was a long enough driveline that it wasn't a problem, but I still wonder.

It is a one-piece driveshaft.

I'm going to snap a couple pics of the driveline and postem up to see what you think.

Thanks again for the help.

 

Got some pics of the pinion angle:

 

not to go off topic but..... I WANT YOUR TRUCK SO BAD! If it were red i might come and steal it.

 

Well I just wanted to comment on this one thing. I could be wrong and unclear in remembering the info. But your said you have 2.5 " tapered blocks. I thought tapered blocks would be used if you had a two piece driveshaft.

Now I could be misinformed so do not all yell at me at once. It was just a thought and maybe a solution for the OP.

 

Did a little web search and a couple other forums state that the front and rear u-joints should be parallel to each other to avoid vibration (Mine aren't, obviously). Makes me wonder if I should try a set of non-tapered blocks to see what happens.

 

Could you post a photo of the transfer case to driveshaft? If you have a standard U-Joint at that location, the angle should match the driveshaft-to-Pumpkin angle. That angle difference might cause a vibration.

Are you sure that you do not see any shudder when taking off from a stop? The rear pinion pitches up when that happens. If there is no shudder or vibration on take-off, it is possible that you need a slightly larger shim to point the pumkin to the drive shaft.

Also make *very* sure that the U-Bolts holding the spring pack in place are properly torqued - the torque value is high, somewhere in the 165 ft-lb range. If the spring pack is not fully secured, it can 'rock' in relation to the axle.

Lou Braun

 

its gunna be a u-joint angle issue..

compounded by the fact you have a single peice driveshaft.

 

That thing has waaaaaayy too much pinion angle. The pinion should never be inline with the driveshaft like it is. You may not feel it, but when you clutch that torquey diesel off the line from a dead stop, the spring wrap will actually send the pinion over center (so it points upward, past the center line of the driveshaft).

This is obviously not good. You need to ditch the angled blocks, put in some that have minimal, or zero taper, and check the pinion angle with a magnetic protractor.

If the pinion angle is close to correct, the pinion will point down in relation to the center line of the driveshaft, rather than inline like it is in the pics.

 

SoCal - thanks for the reply. I ordered straight blocks this weekend and will have them in as soon as I get here and will report back on any changes.

Thanks again to everyone for your input and expertise.

Josh

 

No problem Josh!

 

I got the straight blocks in. The problem I had is completely gone! Also, it turns out that a lot of vibration that I had attributed to the large tires was also coming from the driveline and this vibration is also gone. You guys are worth your weight in gold. Thanks again!

 

A little fun after I got her fixed!