# F250 SD Won't Track Straight



## quillpig (Nov 13, 2004)

My father-in-law bought a 4WD 2001 F250 SD last month, and it has never wanted to track straight down the road. We had a Fisher 8-foot plow put on it, but (he reports) it did this on the test drive before the plow was installed. He figured it was normal for a big 4x4, since the biggest thing he'd ever driven was a Camry.

We had the front end aligned, but the shop reported that it was pretty much in alignment before they started, and it didn't change the behaviour.

It doesn't pull to one side or the other; instead it wanders off to either side. It isn't very noticable at low speed (not at all noticable at plowing speed), but you've got to have pretty good reflexes to drive it at highway speeds.

What should we be looking for?

Quillpig


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## Tarkus (Nov 19, 2004)

It is not unusual for some 4x4's with solid axles front and rear to dog track some going down the road. A little bit will not effect handling or stabilty at speed. Run a tape measure accurately between like points on front and reare axle between LF and RR and RF and LR wheels and see what you come up with for starters. (Pick a point near wheel on axle the is constitant to measure from.


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## grotecguy (Feb 8, 2004)

If it has ever had collision damage the frame could be bent. It could have a conditioned known as "diamond". Diamond is when one frame rail is pushed back compared to the other rail. This is usually caused by getting hit right on the end of the rail. This causes the rear axel housing to be misaligned, making the truck to "dog track".
The easiest way to check for diamond is with a tape measure. You have to find 2 spots on each rail that are symetrical and do a cross measurement. Usually under the cab. The measurement should be within 1/4 inch or less.

Diamond it the toughest condition to fix. It also sometimes goes undetected by a frame shop.

Good luck,
Mark K


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## Tarkus (Nov 19, 2004)

grotecguy said:


> The easiest way to check for diamond is with a tape measure. You have to find 2 spots on each rail that are symetrical and do a cross measurement. Usually under the cab. The measurement should be within 1/4 inch or less.
> 
> Diamond it the toughest condition to fix. It also sometimes goes undetected by a frame shop.


Never heard it called "Diamond", new one on me. As to hard it is to fix, it depends and how much it is off. It is usually caused in produceing not by frame bending but variation on hole centers in frame rails for spring hardware on it spings themselves to with the location of centering bolt in them cause a over all axle misalignment. A 1/4 inch here and there goes a long way in creating this problem.


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## grotecguy (Feb 8, 2004)

Diamond is a term used in collision repair shops to describe an out of square condition of the center section of a trucks frame. The center section is the section of frame under the cab. It includes the rails, crossmembers and cab mounting points.

During a collision one frame rail can be pushed back compared to the other rail. If it stays like that, the center section crossmembers bend around the rivits or welds, making that section "out of square".

Diamond is difficult to correct. The side that has not moved has to be tied down tight to the frame rack. The other rail has to be pulled beyond where it originally was. Sometimes it has to be pulled 2 inches past square so when the pressure is released it returns to being square. Sometimes heating and stress relieving is necessary. Diamond is very time consuming to correct.

Cross measuring the underside of the frame is a quick check. The points being measured have to be the same on each side. If the points aren't the same it will not measure out at all. If a quick check with a tape measure is much more that 1/4 inch off, you may want to have it looked at by a body shop with some form of laser measuring system. That will be the only true way of knowing if the frame is bent. The shop should be able to give a printout of their measurments.

Another thing to look at, maybe the rear axle housing has just shifted on the springs or the centering bolt.

Just a thought,
Mark K


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## tuna (Nov 2, 2002)

just an observation on diamond,when this occurs it would seem to me that the whole frame would also get narrower so this would throw a lot of things out of whack.


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## ciapek (Sep 14, 2003)

*tires*

Also check the tires load range at least d-class, a must. Rear axle could be off. It could be caused by big tread on soft tires.


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## Tarkus (Nov 19, 2004)

tuna said:


> just an observation on diamond,when this occurs it would seem to me that the whole frame would also get narrower so this would throw a lot of things out of whack.


Only if it is bent alot. If does not take much to make one dog track some. I have seen very few 4x4's that actually track perfectly straight. One way to tell for sure is check tracks in snow closely seen how front a rear axles are tracking when driven in a straight line.


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## ptllandscapeIL (Jan 15, 2004)

ON A f250 i wouldnt ride anything under a e class tire


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## Tarkus (Nov 19, 2004)

ptllandscapeIL said:


> ON A f250 i wouldnt ride anything under a e class tire


Depends on the tire size too because a 285D can carry about as much as a 245E


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## ptllandscapeIL (Jan 15, 2004)

good call thanks for the facts...the info people put up is always useful


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## quillpig (Nov 13, 2004)

Well,we found the problem. The truck started bleeding all over the snow last week. The "blood" was ATF, coming from the steering box. One new steering box later, and she tracks straight and true. No idea what killed the box in the first place.

QP


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