Wandering steering-steering gear problem

[Bikeboy57]

I am posting this for archiving. Perhaps the moderater will also link it to the Freightliner forum.

I was not happy with the steering on my coach. I knew it should drive without that much work to keep it between the ditches. I also wanted to eliminate every possible cause before I threw a steering stabilizer at it. In my opinion, that would be masking the real root cause and not fixing the real problem.

I went through the ride height, alignment, tire pressure, proper weight, new shocks, check for worn components routine. The coach would track perfectly straight with no hands for about 300 hundred yards at 65 mph so I had no reason to continue to suspect alignment or loose components. This problem was strictly related to any steering correction input.

Nothing in the above list of addressed items made a significant improvement. Some previous posts and info indicated that the steering gear could be misadjusted.

Here is what I have learned through this experience. Too loose and too tight have very similar symptoms. Plus, a little adjustment goes a long way.

I got the manual on the TRW/Tass 85 gearbox on the TRW site. It shows a torque spec for the input shaft. However the box has to be isolated from all the other steering attachments to do this properly. On my IFS I could not remove the pitman arm without removing the gearbox, so I thought I would try the old trial and error to see what happens. If that failed I was going to disconnect the tie rod ends and the steering input shaft to isolate the box.

The steering gear adjustment on this box is also called the sector shaft adjustment. It is a 3/8" screw with locknut on the opposite side of the box from the output shaft.

The initial symptom was the coach would wander side to side. A relatively large input was required to get it to go the other way, but over all the steering seemed to have a mind of it's own. I now know that is too loose. I didn't know that when I started. My first move was to tighten the adjustment to "hand tight".
Well, that produced a symptom very similar to the first except for a subtle clue. It seemed that any movement in the steering wheel to get the coach to steer was almost always too much. During this 100 miles I learned to correct and immediately turn the wheel back the opposite direction just a tad. I now know that is too tight.

There was exactly 3/8 of one turn between these two conditions. I started making very slight adjustments and driving for ten miles. I became sensitized to too tight and too loose, and finally got it just right by turning the screw in 1/16 of a rotation increments.

The result......AHHHHHHHHHHHHHH. This is what it is supposed to be like. Now I can drive one handed and drink coffee without the bride having a coronary.

I hope this makes sense if you are chasing steering perfection like I was and you have been down the usual suspects checklist. I strongly suspect that the average technician is not going to take the time to adjust one that carefully. I am also not suggesting that you start monkeying with this adjustment if you don't have a problem.

I hope this post helps the next anal retentive engineer like me to solve his or her problem. You can P.M. me if you have specific questions. Sorry I don't have pictures.

[Bikeboy57]

I am posting this for archiving. Perhaps the moderater will also link it to the Freightliner forum.

I was not happy with the steering on my coach. I knew it should drive without that much work to keep it between the ditches. I also wanted to eliminate every possible cause before I threw a steering stabilizer at it. In my opinion, that would be masking the real root cause and not fixing the real problem.

I went through the ride height, alignment, tire pressure, proper weight, new shocks, check for worn components routine. The coach would track perfectly straight with no hands for about 300 hundred yards at 65 mph so I had no reason to continue to suspect alignment or loose components. This problem was strictly related to any steering correction input.

Nothing in the above list of addressed items made a significant improvement. Some previous posts and info indicated that the steering gear could be misadjusted.

Here is what I have learned through this experience. Too loose and too tight have very similar symptoms. Plus, a little adjustment goes a long way.

I got the manual on the TRW/Tass 85 gearbox on the TRW site. It shows a torque spec for the input shaft. However the box has to be isolated from all the other steering attachments to do this properly. On my IFS I could not remove the pitman arm without removing the gearbox, so I thought I would try the old trial and error to see what happens. If that failed I was going to disconnect the tie rod ends and the steering input shaft to isolate the box.

The steering gear adjustment on this box is also called the sector shaft adjustment. It is a 3/8" screw with locknut on the opposite side of the box from the output shaft.

The initial symptom was the coach would wander side to side. A relatively large input was required to get it to go the other way, but over all the steering seemed to have a mind of it's own. I now know that is too loose. I didn't know that when I started. My first move was to tighten the adjustment to "hand tight".
Well, that produced a symptom very similar to the first except for a subtle clue. It seemed that any movement in the steering wheel to get the coach to steer was almost always too much. During this 100 miles I learned to correct and immediately turn the wheel back the opposite direction just a tad. I now know that is too tight.

There was exactly 3/8 of one turn between these two conditions. I started making very slight adjustments and driving for ten miles. I became sensitized to too tight and too loose, and finally got it just right by turning the screw in 1/16 of a rotation increments.

The result......AHHHHHHHHHHHHHH. This is what it is supposed to be like. Now I can drive one handed and drink coffee without the bride having a coronary.

I hope this makes sense if you are chasing steering perfection like I was and you have been down the usual suspects checklist. I strongly suspect that the average technician is not going to take the time to adjust one that carefully. I am also not suggesting that you start monkeying with this adjustment if you don't have a problem.

I hope this post helps the next anal retentive engineer like me to solve his or her problem. You can P.M. me if you have specific questions. Sorry I don't have pictures.

[Dav5942]

Got the exact same issue but have not tried any fixes as yet, was waiting to go to Spartan but after reading your thread they probably would not be of much help. Fortunately we have spent the first 10k miles on winding roads where the handling is absolutely superb, but with what little time on the straight-aways we have seen the same symptoms you describe. Tomorrow will be on a small ferry(60 ft. long) crossing the Yukon River-will see how it handles.