I am having a problem with my 2004 screwcab. I have 6 inches of procomp lift and a 2 inch leveling kit. The truck rides on 20x10 inch wheels that are wrapped around by toyo 37x13.50x20 tires. Before having the leveling kit and the 37 inch tires installed, the truck rode on 35 inch tires with no problems. Now, I am experiencing some viberations that seem to be coming from the rearend ( feels like the truck rim or tire is out of round ) I have had several shops balance the tires and check my rims and everything is fine, but the viberations are still there. I took it to a 4x4 shop here in town and the guy has tired everything, he even installed street tires and found the same viberations. And notice the rearend whinning. Can all this have anything to do with the angle of my drive shaft when i added the extra 2 inches with he 37 inch tires? Because, I really didn't notice anything before with the 35's. I have 1000 miles left before my warranty expires and I am headed to ford tomorrow morning.

 

There is almost nothing more beautiful than good looking lifted truck or SUV.

Many problems can arise when lifting a vehicle. The most common seems to be the driveline angularity. As a certified driveline technician, I have seen many abortions over the years. Yes, one was in a movie a few years back (cant remember the name of the movie).

The main concern on driveling angularity is the difference in operating angle of u-joint "A" and u-joint "B". How do I find this out and how to correct it?

Attain a spirit filled (liquid) protractor (usually available at Sears, Wal-Mart, or the local hardware). Put it on the D/S & measure the angle of the tubing at 12 o' clock (toward the vehicle floor board). Next measure the degree angle of each yoke on the flat (clock d/s to have flat ear of the yoke towards the floorboard of the vehicle).

Next: take the d/s tubing angle minus the u-joint angle "A" and then d/s tubing angle minus "B". the difference is the operating angle between u-joint "A" & "B".

For example: Let's say your reading @ the tran. is -3 deg., the angle at the diff. is +3 degrees and the angle on the tubing was 8 degrees. 8-3=0 and 8-3=0. You're difference in operating angle of the u-joints would be zero (don't worry about negatives and positives, they cancel out).

Zero difference in operating angle on u-joints is bad; it will brinnell the cross (trunion) of the u-joint. More than 2 degrees will generally destroy many components in the vehicle driveline, cab, and body, due to the vibration. Ideally, you want a minimum of 1/2 degree and no more than 1.5 degree difference in operating angle of u-joint "A" and u-joint 'B".

To obtain the correct operating angle, you may have to loosen the spring mountings and slide wedge shims under the axle mounting pads, retorque the springs. Checking and readjusting is usually required several times to get the assembly within tolerance.

 

Gearman thanks for the information. I have already taken my truck to ford and they could not find anything, i had brand new tires put on and nothing I even replaced my rims with new ones and again nothing. I will try the angular way. Is there an actual shop I could take my truck that specialize in this stuff?? The shop that put my lifts and all my gear just says thats the way some trucks ride. I think they're full of it. But again, thanks for the advise.

 

Which part of the world do you live in? I have a few contact across North America.

One thing I failed to tell you; have the vehicle on a level surface before doing the angles on the driveshaft.

 

I live in Florida, like the Jacksonville area. I would rather have someone that knows what they are doing like yourself than trying it myself and messing it up. I have spoken to several installers that install lifts and they assure me that the viberations have nothing to do with the angles. Again thanks for the response.

 

I was hoping you would say you lived in IN, S. CA, or OK. I don't have any excellent light vehicle driveline expert contacts near Jacksonville.

The reason why the lift installers are saying that driveline angles have nothing to do with vibrations: either they don't have a clue (buyer beware here), or they are trying to avoid the liability of what incorrectly lifting a vehicle can result in.

Some advise, visit you're local driveline jobbers that do the d/s repairs (balancing, re-tubing, and fabrication) for the larrger vehicle and get some advise on who in you're area has a good reputation for doing light truck and SUV lifts the correct way.

 

I appreciate all the information. I took my truck to a local 4x4 shop in town and he called me back and said my drive shaft was 5 of 6 degree off and that he had ordered some shims for it and he should have it ready tomorrow for a test drive. Unfortunately all that was chinese to me, I really do even know if the shaft should be reading zero degree or what, and a shim is that a small rat? Anyway thanks for the information at least someone found something and it might solve the problem.

 

Please keep us informed if resetting the d/s angles fixes you're problem.

 

Gearman

Update: Picked up my truck friday the guy tells me the truck was off 6 degrees and they at least put I back closer to 3 degree with the shims. The truck rides the same! No different. So, now I am thinking I should take it to an actual drive shaft shop in jacksonville Fla( Drive line) that's all they do. I figuire if the shaft is off they should put it back to the proper adjustment wouldn't they? I mean what ever the degrees. And I guess they will me able to check the u joints and the other components that go alone with the drive train. I was also told it could be my front end that is all out of wack. But, after getting the tires i had it all aligned. Well, i guess I will start tomorrow again and see what someone else tells me. I'm thinking if I can not get it fix within the 1500 dollar range, I am going to get rid of it.

 

You indicate the guy said you're rear D/S was off 6 degreees and he put it back to 3 degrees. You are getting closer if the guy is actually figuiring the difference in operating angle of the u-joint assembly. If so, you will still have noise / vibration at 3 degrees difference.

You need to get the difference in u-joint operating angle down to 1/2 to 1 degree difference. Can the guy install larger shims to tip the nose of the rear diff. upward?

If the pinion on the rear diff. is elevated upward; you may also want to increase the lube level in the diff. by installing a street elbow in the filler hole. What I am trying to say here: as you elevate the pinion upward you stand a greater chance of not getting enough lube to the outer pinion bearing cup and cone. Lube starvation to that would mean an early failure.

I am not familiar with the leveling system that you had installed? Is it air leveling? If so, there may be an easier way to get results.

Keep us posted, gearman

 

Again, thanks! Its not an air leveling system. Its a 2 inch leveling system that gave me another 2 inches to the front and rear of the truck attaches to the front springs and adds an add a leaf to the rear giving me a total of 8 inches of lift. The guy that did my truck said the 3 degree is to specs and he is going to get some sort of piece equipment that he can some how attach to different areas of the truck that will show where the viberation is coming from. After he does this and nothing is worked out I am taking it to an actual drive train shop to make sure it can't be better.