I am asking here, because this is a real gearhead question. I have some freeplay in my steering gear box, that translates into about one inch of freeplay at the steering wheel rim. It cannot be adjusted out with the sector adjustment screw. My question is "Is that normal?"
It is not in the steering column or u joints. The clamp is tight on the input shaft. I can lock down the input shaft and there is NO freeplay in the steering wheel.
For more info let me describe the lengths I have gone to in order to quantify this. First I mounted a dial indicator on the end of the pitman arm. I would have a helper move the steering wheel right then left until I detected 0.001 movement on the pitman. The helper would record the movement of the steering wheel. I loosened the sector adjustment screw until I knew the box was loose, I would tighten 1/16 of a turn and measure the movement in the steering wheel that produced detectable movement in the pitman arm. At a certain point additional tightening of the sector adjustment screw does not result in a further reduction of the steering play. I also know from on the road experiments that running the box too tight results in the steering sticking on small right and left movements.
I have also removed the drag link and adjusted the box according to the TRW manual. That is turning the sector adjustment screw in until no lash is detectable in the pitman.
You can laugh at my OCD recovering engineer behavior, but it turns out both methods of adjusting the sector screw have the sector screw at exactly the same place. So I am confident that is as good as it is going to get. Still, I have the inch of freeplay in the steering wheel that results in no movement at the pitman arm.
Is this normal?
You probably know the selector shaft lash is checked at the "center of travel" with the drag link removed checked by hand not using the steering wheel there should be no lash at the pitman arm if any it will translate to the free play on the steering wheel
Cliff, you are absolutely correct. There is NO lash at the center of steering, with the pitman disconnected.
The problem is 1 inch of rotation in the steering wheel before any movement detected at the pitman. No adjustment in sector screw remedies this.
I can't believe that is normal.
Quote from: RichardEntrekin on April 16, 2017, 09:08:05 AM
Cliff, you are absolutely correct. There is NO lash at the center of steering, with the pitman disconnected.
The problem is 1 inch of rotation in the steering wheel before any movement detected at the pitman. No adjustment in sector screw remedies this.
I can't believe that is normal.
No it's not normal you have something with play if you have no lash at the pitman arm the TAS 85 is a 0 lash sector,it could be the upper or lower mast bearings have a little play if the u joints are tight
It sounds to me like the worm and main gear are worn out and the freeplay is not adjustable. You need a new steering box, or take a chance on a rebuilt box. Some rebuilders don't put new gears in and you end up with a sloppy rebuilt box.
--Geoff
Thank you both. I have looked at the exploded drawings and tried to figure out where slop could occur.
If I interpret the rebuild manual correctly, TRW has a procedure for setting the preload on one of the mast bearings.
I am worried about a reman box for the very reason you said.
If I could find a local place with a box, I could check it before buying. There is one in Tampa according to the interweb. I guess I am headed to Tampa.
Both of you were a great help in answering the question. I didn't think it was normal, but with a sample size of one, how do you know ::)
Other than being annoying to you, it is well in the safety range for free play in the steering wheel according to the DOT rules
A DOT inspection, when I was doing them, excludes power steering play. The question I have is the 1" play with the engine running or with the engine stopped. With the engine stopped is the true test with PS. One inch play with the engine stopped with the lightest pressure on the steering wheel is under the 1.5" allowed. When the engine is running you can't get an accurate measurement.
And if you go look at the rebuilt box take a pair of large vice grips to compare the play on both shafts on either box. There should be no freeplay on either shaft.
--Geoff
PS is not excluded now on DOT inspections and they give you a mile of leeway for free play more than I like
I quit doing DOT inspections because of the possible liability. You never know who might have worked on the truck/bus after you inspect and pass it and if there is an accident they come after you as having passed it per DOT. Not worth the risk for a couple of hours of paid work.
--Geoff
Measured with engine off.
I talked with TRW tech. They say 1 inch or so on a 20 inch steering wheel is perfectly fine.
Annoying, yes that is accurate description.
I haven't given up. Finding a reman is challenging because the model number on the bottom is either missing or illegible. Newell can't tell me, and yeah I know they should be able to.
For your benefit I just checked my freeplay and moving the steering wheel one way and slowly letting it settle with no hand on it in both directions I got 7/8" of an inch.
When I bought my bus it was at the time DOT inspections did not include the PS freeplay, and I had 3-4 inches of freeplay along with worn king pins (another item DOT inspections missed), and worn radius rod bushings (dog bones) (yup, another missed DOT item). I was constantly correcting the steering when driving and it plain wore me out in 500 miles. All that stuff is fixed now and the steering has been aligned now so it is a pleasure to drive.
--Geoff
I am following up to report what I have learned, mostly the hard way, since I initially posted.
First, there has to be some inherent play in an integral steering gear box like the TAS series. To oversimplify, the input shaft is connected to a torsion shaft, the torsion shaft is connected on it's opposite end to the worm gear that moves the pitman arm when no hydraulics are present. When the torsion shaft twists, it starts to open ports which allow the hydraulics to step in. The key is that the shaft has to be able to twist a wee bit. Gearboxes come with different diameter torsion bars. Obviously the larger the diameter the less it will twist. The larger diameter will give a much better feel when dead on center, but you won't have very much power steering. It's a tradeoff.
TRW is not very forthcoming even when you have the serial numbers. They do not want individuals in that box.
So, after removing the box, and putting in new seals, and adjusting the sector gear to specifications. I had just over 1 degree of rotation of input shaft to produce detectable rotation the output shaft. Not too bad.
Two things of note. In the steering box, there are hard stops to prevent the torsion shaft from twisting too far. When we turn the wheel back and forth with engine off, we are feeling the steering hit those hard stops. Second, if you wish to quantify the amount of freeplay between the steering wheel and the pitman arm like I did, then the pitman must be disconnected or the front wheels off the ground. If not, you have the torsion shaft twisting. I didn't realize this until I took the box apart and noodled out how it works. So if the steering is loaded, the measurement is whacked.
But, I still had about 8 degrees (or 1 1/4 inches on a 20 inch wheel) of rotation at the steering wheel to produce detectable (0.002) motion at the pitman arm.
There is an intermediate shaft between the steering column and the box. I replaced the u joints which helped slightly but still had too much dead band in the steering. While playing with it I noticed the upper u joint "wobbled" when I moved the wheel back and forth. The lower bearing in the steering column was shot.
As you guys would know, both ends of the drive system have to firmly fixed for a double u joint system to be stable. That applies to driveshafts and also to steering intermediate shafts.
Newell used a tilt GM column, and it looks like the original bearing was crapola to begin with almost twenty years ago. So I am replacing with a higher quality bearing. If this one lasts another 20 years and 200k miles, I won't complain.
Thanks for all your help.
Even though my steering feels light and loose, on a straight road I can move the steering wheel 1/4" either way and the bus will move. I guess that means everything is tight. Good Luck, TomC
I cannot help but to repeat that if you have worn radius rod bushings it doesn't matter how tight you steering is up front your bus is going to wander and you will be constantly correcting the steering. The radius rod bushings keep the rear and tag axles from moving side to side. Up and down on the bushings is okay, but side to side play will make your bus wander. I just got a call from a friend of mine that is in the same boat I was in years ago-- everything was tight in the steering components and steering box but the bus still wandered. He is now having his radius rod bushings replaced.
--Geoff
Thanks Geoff and I agree with you. However in this case the front is IFS.
I will check the back and the bushings in the Panhard bar.
Quote from: RichardEntrekin on May 05, 2017, 04:37:40 PM
Thanks Geoff and I agree with you. However in this case the front is IFS.
I will check the back and the bushings in the Panhard bar.
I also have IFS. The RTS used IFS until GM sold the manufacturing to TMC (I believe that is who bought it first, it has been sold a few times). What I am warning you about has nothing to do with IFS. That is part of the front end work-- I am warning you about the radius rod bushings in the rear, and that applies to all buses.
--Geoff
Oh, you have a Newell. That isn't a bus chassis or a bus conversion. Check your "Panhard bar", we have "dogbones".
Sorry Geoff, I should have read your post more carefully. Yes, you clearly said rear.
Funny how the mind sees what it wants to see. My first Newell was straight axle in the front with radius rods. My head immediately went there.
The rear is a Ridewell suspension with radius arms and panhard.
So just how would one check for play in those bushings?
I suppose I could mount a dial indicator on them, point a remote camera, and go for drive.
I can't see wiggling the 50K lb coach by hand or pry bar.
I am at a complete loss here how does the rear radius or stabilizer bars bushings affect the free play in a steering wheel :o
Cliff--
You also missed the conversion. What I've been saying is that if your front end and steering box is tight and your bus still wanders, it is probably from worn out radius rod bushings. Richard-- I don't know any easy way to check for worn bushings, other than seeing if they are bulging out on the edges and just plain look old. It is more of a process of elimination of having a tight box and tight front end and still having wandering problems (or loose steering).
I had this problem-- everything was new up front but I was constantly correcting the steering. The rear end was dancing around from worn out radius rod bushings which kept me having to correct the steering to keep going straight.
--Geoff
I know about wander and radius rods bushings but Richard is working on steering wheel lash I thought.I never saw a heavy @$# Newell wonder my self like a bus will
Ahhh,
To get back on track, I never used the word wander in my original post. What I was trying to understand was some unwanted freeplay between turning the steering wheel and nothing moving at the pitman arm. It was a very disconcerting feeling to have deadband in the steering. It would feel the same as if the sector adjustment was too loose, but I was absolutely certain the sector gear was adjusted properly.
Did that result in wandering. Yes, most of the time on a dead flat road. The best driving was either on a heavily crowned road or a consistent side wind. Both conditions allowed me to just correct "one" side of the steering and let the crown or the wind move it back to center.
I think I found it when I discovered the bearing at the bottom of the steering column was worn out permitting the upper u joint in the intermediate steering shaft to wallow around. In my era coach, Newell used a tilt GM column.
A new bearing will be installed as soon as it gets here, and I will quantify and report the results.
I didn't mean to stir anything up, I just feel like that folks who post an issue should also post the resolution of the issue. Who knows when someone else may be dealing with a similar problem, and a search engine may find this post and help them.
I posted on this forum because I think a lot of it's members have tremendous knowledge about the systems which are common to commercial buses and to Newells.
Thank you for all your help.
Quote from: Geoff on May 05, 2017, 08:21:59 AM
I cannot help but to repeat that if you have worn radius rod bushings it doesn't matter how tight you steering is up front your bus is going to wander and you will be constantly correcting the steering. The radius rod bushings keep the rear and tag axles from moving side to side. Up and down on the bushings is okay, but side to side play will make your bus wander. I just got a call from a friend of mine that is in the same boat I was in years ago-- everything was tight in the steering components and steering box but the bus still wandered. He is now having his radius rod bushings replaced.
--Geoff
Yep.
Not much like following a bus when the driver believes he's totally within his lane but his back end isn't.
But his setup must be totally different from mine. The procedure for determining the play is different, but one of the emphasized points is the cam groove adjustment.
I have a small wheel, but the book allows for 2" ( or 10 degrees) play. That would drive me crazy.
I realize expanding steering box freeplay to radius rod bushings might be a jump for some people but people don't normally complain about freeplay unless they are fighting their bus wandering. As a 102" bus conversion driver I know first-hand that keeping a bus centered in your lane takes constant attention. Loose steering and a wandering bus wears you out!
--Geoff
Yep I drove a few MCI 8 and 9 that had the old power assist steering they will wear you out trying to keep one between the lines and the ditch how the drivers could drive one every day was a marvel to me
what year did the MC8 get upgraded steering from the factory?
The 8's were never upgrade from the factory the 9's were in about the mid 80's,the MCI have radius rods on the front axle also like all buses with a straight axle do.
Richard I am changing the mast bearings on my MCI too I have play there
MC9 got a proper steering box for the 1982 models I was familiar with.
The older ones, it's all about properly set-up and everything the way it's supposed to be.
Set up wrong, you're rowing your way down the highway...
happy coaching!
buswarrior
Woo Hoo!
I replaced the steering column lower bearing, replaced the u joints in the steering shaft, and tightened the pinch bolt where the upper u joint connects to the steering column.
I had 1 3/8 inches of play before the work. I now have 5/16.
I don't get to road test for two more days, but I am looking forward to the drive.
Nice!
Quote from: RichardEntrekin on May 09, 2017, 06:20:28 PM...
I had 1 3/8 inches of play before the work. I now have 5/16.
I don't get to road test for two more days, but I am looking forward to the drive.
Quote from: windtrader on May 09, 2017, 09:11:31 PMNice!
Yes, sounds very nice, indeed. Although, I have to say, when I read Richard's first post, my mind saw it as "had 1 3/8 inches of play before the work. I now have
*1* 5/16." My instinctive first reaction was "yeah, old buses, you work on 'em for days for very little improvement". I'm glad that it was just that I mis-read it!
I reality, it sounds as if you have made a very large improvement -- I hope that the numbers are borne out on your road test.