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Replacing TRW steering box (DIY). Any hints?


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Hi all,

FINALLY, I got the Monaco Watts system purchased and installed (front watts link, rear watts link, rear cross bars). Fantastic results. Completely doable by a weekend wrench turner like me once I figured out which tie rod ends went on which parts (the location of the Zerk fittings - back or side) makes a big difference. Make Hughes responded to my questions over the weekend. Talk about customer support.... 🙂

AND, the existing TRW steering box has been adjusted by someone who actually knows what he is doing (evidently not me). 

BUT, the old TRW box, even when fully adjusted still has *way* too much lash in the upper shaft (ie. input shaft turns, but no corresponding output). Summary: it is shot and needs replacing.

SO, I ordered a reman unit from Weller Trucking (thanks again Brent and Scott for all your help). It will be here Wednesday  or Thursday of this week.

PROBLEM: I have to drive the beast early next week across the country, and getting the steering box swapped out at a shop is a problem (booked everywhere).

QUESTION:  As a DIY job, any hints?  

LIMITATIONS: No lift, no pit, so climb under after putting up jack stands.

  1. New TRW steering box is a TAS 4007 (weighs about 45lbs according to Scott at Weller)
  2. The bolts look like 3/4", so find big socket, and helper to hold up unit.
  3. Not sure of the torque specs, but might be fun (not) removing and then torquing the bolts. Hints? Torque specs?
  4. Disconnecting and reconnecting the hydraulic hoses: hints?
  5. Removing and replacing the pitman arm: Mark the location on the output shaft, then use a puller on the arm, put back in the same place? Or something more complicated? I was going to leave the drag link connected - the ends seem to be in good shape (69K miles, 20 years old). Hints?
  6. Disconnecting and reconnecting the upper shaft (to the steering wheel). Tricks or hints?
  7. Setting the poppets "appears" straight forward.  My experience - things that "appear" easy often need hints.
  8. Refilling the power steering fluid and removing any air: Where, how, hints?  (I know how to do it in a car)

What else should I have asked but didn't know to ask?

As always, thanks.

- John

2000 Monaco Diplomat

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You've thought through it well. Raise the coach all the way up on the air suspension. Then use jack stands just in case.  

 I use a small floor jack to hold the steering box up in place. 

Spray some PB Blaster on the nuts and bolts the day before.  

This is a link to several if not hundreds of swaps.  Most of these are swapping from a Sheppard steering box, but the principal is the same.

Steering Box Play- Sheppard M100 SHIM or Swap for a TRW ? - iRV2 Forums 

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Not bad. Just did with help. I believe the poppets were pretty much preset, the paperwork that came from Weller I think said they were anyway. 
 

I had to get a Torque multiplier. The one nut was I think 500 ft lbs. Amazon had one for $140 so picked it up. 
 

Messy, drained the oil as best we could before tackling the box. 
 

I can’t remember If we downloaded instructions or they come from Weller, but they were taken straight from a thread 

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John, read the last entry I posted here a couple of days ago.  It summarizes most of what you must be careful with.  I think it might be easier to disconnect the drag link.  You don't need a puller.  Just loosen the nut on the tie rod end, hold a heavy hammer on one side of the knuckle where the tie rod end stud is and whack it sharply with another hammer from the opposite side.  The momentary, microscopic distortion of the knuckle's tapered bore will free the taper.  Works every time.

Most common mistake is turning the steering box to get the drag link to align.  You MUST adjust the drag link overall length when the steering box is at mid-position (marks aligned) and wheels are dead ahead.

Just for edification, check that the witness lines on the steering box output shaft and the corresponding witness line on the steering box casting are aligned after you remove the Pittman arm and before moving the steering box locating bolts (front wheels dead ahead).  Any steering gear can wear out, but it's rare and would surely be unusual with the low mileage you have on it.  If, when the coach is driving in a straight line, you are not at the point where the steering gear is at its midpoint, there is lost motion (by design) to either side of center.

Having to reposition the splines in the input shafts under the steering wheel to get the steering wheel perfectly centered is common after a procedure like this.  It DOES NOT mean you need an alignment. 

It's not a ten-minute job, but entirely doable by anyone mechanically inclined.

Van

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  • 3 weeks later...

Hi Van,

Full Monaco watts setup (front watts, rear watts, crossbars) - update on results

The full (front, back, cross bars) Monaco watts setup is magnificent!

TRW steering box: Had local mechanic try to replace TRW box with new reman unit from Weller. He had trouble removing it without a torque multiplier, so he adjusted it as best he count. The slotted adjustment bolt was frozen to the jam nut. Yes, He did know how to adjust it properly, just could not get any more play out of it. After replacing it in Alabama (see below) And examining it on the ground, the internals seem to need a rebuild - I believe someone long ago screwed it up, and tried everything  EXCEPT replacing it to get the coach to drive nice, which it did not.

Drove from Colorado Springs to Fairhope Alabama. Lots of lash, but the Monaco watts setup was great. Went to help out my rapidly aging parents for a month or so.

Found a mobile big rig mechanic in Fairhope to install the TRW box (i brought it with me). The existing setup, Pittman arm, and steering column were all off.  He removed everything, installed the new TRW box, reset up everything properly (except that the steering wheel is off, but we ran out of daylight, so...)

Drove my Dad (88 and recovering from hernia surgery, so no flying) from Fairhope Alabama to Grand Rapids Michigan to say goodbye to his brother (90 - only about a month left). Drove back yesterday. Drives much better than the trip out here, BUT still has some play in the steering.

QUESTION: there is still a bit of lash in the input shaft (narrowed it down with the mechanic before leaving). He said “There will always be a little. Don’t tighten it any more or it will bind” . Note: Scott at Weller also said “You really can’t get all of the play out”

It would drive perfectly if I could remove the last bit of input shaft lash. For reference, while looking at the actual steering input shaft, a sharpie mark on the ~2” shaft tube moves about 1/4 of an inch.      Is it possible and advisable to tighten it up a bit more (lining it up properly, of course)?

Opinions?

Thanks,

John

2000 Monaco Diplomat

 

 

Edited by StellaTariche
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John, when measured at the rim of the steering wheel, what does the lash measure?

The steering wheel not being centered after the installation is normal.  It does NOT indicate alignment is needed, just that the splined joint beneath the steering wheel has to be repositioned.

When the dead straight-ahead position of the wheels coincides with the exact midpoint of the crown in the internal rack gear of the steering gear, it can be adjusted to zero lash.  That is the function of the witness line on the gear housing and gear output shaft.  When those two lines are aligned, you are at the midpoint of the crown of the rack gear.  It is still very common for even experienced mechanics to get this part wrong.  In that case, the straight-ahead position of the gear is to either side of the highest crown on the rack gear, and if in that position, if you adjust the steering gear to zero lash, there will be a slight binding when you "cross centerpoint" of the crowned rack gear.

Bottom line is that you should be able to adjust to zero play at the center position.

I'll give you a call this afternoon.  I have some appointments today until about 4:30 EST.

Van

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Hi Van,

I measure about 1/2" of lash on the outside of the 22" steering wheel.

Seeing the witness lines and the exact midpoint of the crow is tricky (mirror needed, but I have).  I'm traveling without a complete complement of tools, but I have a pair of vice grips and a 3/4" socket (1/2 drive) + a big flat blade screw driver, so I can probably get it un-torqued, adjusted, and tightened.

  Many thanks for the call (I'm on Central this week).

Best,

- John

Edited by StellaTariche
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13 hours ago, StellaTariche said:

Hi Van,

I measure about 1/2" of lash on the outside of the 22" steering wheel.

Seeing the witness lines and the exact midpoint of the crow is tricky (mirror needed, but I have).  I'm traveling without a complete complement of tools, but I have a pair of vice grips and a 3/4" socket (1/2 drive) + a big flat blade screw driver, so I can probably get it un-torqued, adjusted, and tightened.

  Many thanks for the call (I'm on Central this week).

Best,

- John

John, I am not sure you are fully comprehending what Van is trying to get across to you. The TRW has a high spot on the gear that is connected to the steering wheel and when you adjust the TRW that high spot must correspond with the wheels being pointed straight ahead. When you move the steering wheel left or right the gear moves off of that high spot and there is slop in the steering by design. You do not notice it because you are applying force since you are in a turn. When you move the steering wheel back straight again you should be back on that high spot with zero dead motion in the steering. A common mistake is folks replace the Shepard with a TRW and do not adjust the length of the drag link to reattach it to the Pitman arm. They move the steering wheel to get the drag link back on and that means when the wheels of the coach are pointing straight ahead you are no longer on the high spot of the TRW and will have dead motion in the steering. Ask me how I know this🙂. I suspect there is nothing wrong with your TRW and you do not need to replace it. You just need to make sure the mark on the output spline shaft is aligned with the mark on the body of the TRW. You must have the drag link disconnected when you do this and the wheels must be pointing straight ahead. Then you adjust the TRW. Next you must be careful not to move the steering wheel or the front wheels and if the drag link does not align with the Pitman arm you must adjust the tie rod end on the drag-link.

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  • 10 months later...
On 6/2/2021 at 6:29 AM, StellaTariche said:

... Drives much better than the trip out here, BUT still has some play in the steering.

QUESTION: there is still a bit of lash in the input shaft (narrowed it down with the mechanic before leaving). He said “There will always be a little. Don’t tighten it any more or it will bind” . Note: Scott at Weller also said “You really can’t get all of the play out”

It would drive perfectly if I could remove the last bit of input shaft lash. For reference, while looking at the actual steering input shaft, a sharpie mark on the ~2” shaft tube moves about 1/4 of an inch.      Is it possible and advisable to tighten it up a bit more (lining it up properly, of course)?

Hi John,

Were you able to get all the lash out on the input shaft? I have a TRW TAS65028A on our Windsor, actually this is our second one. The first one, TRW as well, I could not get all the lash out, so I've replaced it with a Weller reman one. After replacement, everything centered, adjustment screw tightened all the way, and still about 3/4" play on the wheel, so the same problem. I called Weller, they did not have any suggestions, and they did not confirm that its possible to get all the lash our -like you said. 

So, I am thinking we might have an older TRW model which can only be adjusted only to certain degree, but not to zero lash.  

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Hi Ali,

I had the mechanic who installed it and re-attached the drag link (correctly this time - it was upside down) re-adjust the drag link and pitman arm as outlined below.  Almost perfect (almost), so I asked him to tighten the adjustment screw a "slight" bit more. He had the touch.

No lash at all now.  Slight-ly tighter on the "return to center" and takes a slight bit more effort to turn - and I do mean *very* slight.  If it were a trigger on a pistol, *slightly" would be 1 pound pull increase.

Final adjustment to get the last bit of lash out was (maybe) 1/8 of a turn of the adjustment screw. You can always back it off if it binds too much.

Keys to success:

  1. spray everything with lubricant the night before.
  2. Front wheels perfectly straight (later, rinse, repeat). Straight, as in "when I'm driving on a typical highway, the steering wheel is here" position. Mark it with respect to your dash board.
  3. No play in drag link ends or tie rod ends
  4. No play in steering column (vice grips and a helper to check)
  5. Drag link installed correctly, and adjusted.  How?
  6. (a) Remove the pitman arm from the steering box (lots fun. not).  Removing and re-installing was the key.
  7. (b) Loosen the drag link (front adjustable part) (also not fun).  It spins and then clamps on the original.
  8. (c) If the drag link ends, or tie rod ends, have play, you will NEVER get it right.  Tie rod ends are easy - any big truck mechanic can replace.  Drag link - have a machine shop mod your existing one to accept a standard adjustable end (about $200).  Or pay $1100 for a custom built replacement.
  9. (d) Without moving the front wheels or steering wheel (helper holds it in place), use the drag link adjustment to adjust the pitman arm mark with the steering box mark. The pitman arm should slip on - no pushing or pulling the pitman arm, steering wheel, or front wheels. (I needed to cut a hole in my electrical bay to see it - sealed afterwards). One spline off on the steering box WILL make a difference.
  10. Finally Tighten everything.  Adjust steering box until no play (on a new or rebuilt box). No need to gorilla it, but the last 1/8 turn will be firm. Make sure nothing moves when you tighten the jam nut.
  11. Re-center steering wheel (easy). Drive a few miles. Re-adjust. Might move a spline or two to get it to taste.
  12. Lots of phone help from Van Williams

Worth it - I hate lash.

With that final steering box fix (TRW rebuilt box), a full Monaco Watts kit (front, rear, rear cross bars), it drives like a dream.  One handed driving.  Drive all day without fatigue.  Jersey barriers no longer freak me out. Winds across the southwest US are no longer an issue.

Good luck.  

- John

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